1 /*
   2  * Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciMethodData.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "libadt/vectset.hpp"
  31 #include "memory/allocation.inline.hpp"
  32 #include "memory/resourceArea.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/arraycopynode.hpp"
  35 #include "opto/callnode.hpp"
  36 #include "opto/compile.inline.hpp"
  37 #include "opto/connode.hpp"
  38 #include "opto/convertnode.hpp"
  39 #include "opto/divnode.hpp"
  40 #include "opto/idealGraphPrinter.hpp"
  41 #include "opto/loopnode.hpp"
  42 #include "opto/movenode.hpp"
  43 #include "opto/mulnode.hpp"
  44 #include "opto/rootnode.hpp"
  45 #include "opto/superword.hpp"
  46 #include "utilities/powerOfTwo.hpp"
  47 
  48 //=============================================================================
  49 //--------------------------is_cloop_ind_var-----------------------------------
  50 // Determine if a node is a counted loop induction variable.
  51 // NOTE: The method is declared in "node.hpp".
  52 bool Node::is_cloop_ind_var() const {
  53   return (is_Phi() && !as_Phi()->is_copy() &&
  54           as_Phi()->region()->is_CountedLoop() &&
  55           as_Phi()->region()->as_CountedLoop()->phi() == this);
  56 }
  57 
  58 //=============================================================================
  59 //------------------------------dump_spec--------------------------------------
  60 // Dump special per-node info
  61 #ifndef PRODUCT
  62 void LoopNode::dump_spec(outputStream *st) const {
  63   if (is_inner_loop()) st->print( "inner " );
  64   if (is_partial_peel_loop()) st->print( "partial_peel " );
  65   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  66 }
  67 #endif
  68 
  69 //------------------------------is_valid_counted_loop-------------------------
  70 bool LoopNode::is_valid_counted_loop() const {
  71   if (is_CountedLoop()) {
  72     CountedLoopNode*    l  = as_CountedLoop();
  73     CountedLoopEndNode* le = l->loopexit_or_null();
  74     if (le != NULL &&
  75         le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  76       Node* phi  = l->phi();
  77       Node* exit = le->proj_out_or_null(0 /* false */);
  78       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  79           phi != NULL && phi->is_Phi() &&
  80           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  81           le->loopnode() == l && le->stride_is_con()) {
  82         return true;
  83       }
  84     }
  85   }
  86   return false;
  87 }
  88 
  89 //------------------------------get_early_ctrl---------------------------------
  90 // Compute earliest legal control
  91 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  92   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  93   uint i;
  94   Node *early;
  95   if (n->in(0) && !n->is_expensive()) {
  96     early = n->in(0);
  97     if (!early->is_CFG()) // Might be a non-CFG multi-def
  98       early = get_ctrl(early);        // So treat input as a straight data input
  99     i = 1;
 100   } else {
 101     early = get_ctrl(n->in(1));
 102     i = 2;
 103   }
 104   uint e_d = dom_depth(early);
 105   assert( early, "" );
 106   for (; i < n->req(); i++) {
 107     Node *cin = get_ctrl(n->in(i));
 108     assert( cin, "" );
 109     // Keep deepest dominator depth
 110     uint c_d = dom_depth(cin);
 111     if (c_d > e_d) {           // Deeper guy?
 112       early = cin;              // Keep deepest found so far
 113       e_d = c_d;
 114     } else if (c_d == e_d &&    // Same depth?
 115                early != cin) { // If not equal, must use slower algorithm
 116       // If same depth but not equal, one _must_ dominate the other
 117       // and we want the deeper (i.e., dominated) guy.
 118       Node *n1 = early;
 119       Node *n2 = cin;
 120       while (1) {
 121         n1 = idom(n1);          // Walk up until break cycle
 122         n2 = idom(n2);
 123         if (n1 == cin ||        // Walked early up to cin
 124             dom_depth(n2) < c_d)
 125           break;                // early is deeper; keep him
 126         if (n2 == early ||      // Walked cin up to early
 127             dom_depth(n1) < c_d) {
 128           early = cin;          // cin is deeper; keep him
 129           break;
 130         }
 131       }
 132       e_d = dom_depth(early);   // Reset depth register cache
 133     }
 134   }
 135 
 136   // Return earliest legal location
 137   assert(early == find_non_split_ctrl(early), "unexpected early control");
 138 
 139   if (n->is_expensive() && !_verify_only && !_verify_me) {
 140     assert(n->in(0), "should have control input");
 141     early = get_early_ctrl_for_expensive(n, early);
 142   }
 143 
 144   return early;
 145 }
 146 
 147 //------------------------------get_early_ctrl_for_expensive---------------------------------
 148 // Move node up the dominator tree as high as legal while still beneficial
 149 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 150   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 151   assert(OptimizeExpensiveOps, "optimization off?");
 152 
 153   Node* ctl = n->in(0);
 154   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 155   uint min_dom_depth = dom_depth(earliest);
 156 #ifdef ASSERT
 157   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 158     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 159     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 160   }
 161 #endif
 162   if (dom_depth(ctl) < min_dom_depth) {
 163     return earliest;
 164   }
 165 
 166   while (1) {
 167     Node *next = ctl;
 168     // Moving the node out of a loop on the projection of a If
 169     // confuses loop predication. So once we hit a Loop in a If branch
 170     // that doesn't branch to an UNC, we stop. The code that process
 171     // expensive nodes will notice the loop and skip over it to try to
 172     // move the node further up.
 173     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 174       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 175         break;
 176       }
 177       next = idom(ctl->in(1)->in(0));
 178     } else if (ctl->is_Proj()) {
 179       // We only move it up along a projection if the projection is
 180       // the single control projection for its parent: same code path,
 181       // if it's a If with UNC or fallthrough of a call.
 182       Node* parent_ctl = ctl->in(0);
 183       if (parent_ctl == NULL) {
 184         break;
 185       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 186         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 187       } else if (parent_ctl->is_If()) {
 188         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 189           break;
 190         }
 191         assert(idom(ctl) == parent_ctl, "strange");
 192         next = idom(parent_ctl);
 193       } else if (ctl->is_CatchProj()) {
 194         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 195           break;
 196         }
 197         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 198         next = parent_ctl->in(0)->in(0)->in(0);
 199       } else {
 200         // Check if parent control has a single projection (this
 201         // control is the only possible successor of the parent
 202         // control). If so, we can try to move the node above the
 203         // parent control.
 204         int nb_ctl_proj = 0;
 205         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 206           Node *p = parent_ctl->fast_out(i);
 207           if (p->is_Proj() && p->is_CFG()) {
 208             nb_ctl_proj++;
 209             if (nb_ctl_proj > 1) {
 210               break;
 211             }
 212           }
 213         }
 214 
 215         if (nb_ctl_proj > 1) {
 216           break;
 217         }
 218         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
 219                BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
 220         assert(idom(ctl) == parent_ctl, "strange");
 221         next = idom(parent_ctl);
 222       }
 223     } else {
 224       next = idom(ctl);
 225     }
 226     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 227       break;
 228     }
 229     ctl = next;
 230   }
 231 
 232   if (ctl != n->in(0)) {
 233     _igvn.replace_input_of(n, 0, ctl);
 234     _igvn.hash_insert(n);
 235   }
 236 
 237   return ctl;
 238 }
 239 
 240 
 241 //------------------------------set_early_ctrl---------------------------------
 242 // Set earliest legal control
 243 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 244   Node *early = get_early_ctrl(n);
 245 
 246   // Record earliest legal location
 247   set_ctrl(n, early);
 248 }
 249 
 250 //------------------------------set_subtree_ctrl-------------------------------
 251 // set missing _ctrl entries on new nodes
 252 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 253   // Already set?  Get out.
 254   if( _nodes[n->_idx] ) return;
 255   // Recursively set _nodes array to indicate where the Node goes
 256   uint i;
 257   for( i = 0; i < n->req(); ++i ) {
 258     Node *m = n->in(i);
 259     if( m && m != C->root() )
 260       set_subtree_ctrl( m );
 261   }
 262 
 263   // Fixup self
 264   set_early_ctrl( n );
 265 }
 266 
 267 // Create a skeleton strip mined outer loop: a Loop head before the
 268 // inner strip mined loop, a safepoint and an exit condition guarded
 269 // by an opaque node after the inner strip mined loop with a backedge
 270 // to the loop head. The inner strip mined loop is left as it is. Only
 271 // once loop optimizations are over, do we adjust the inner loop exit
 272 // condition to limit its number of iterations, set the outer loop
 273 // exit condition and add Phis to the outer loop head. Some loop
 274 // optimizations that operate on the inner strip mined loop need to be
 275 // aware of the outer strip mined loop: loop unswitching needs to
 276 // clone the outer loop as well as the inner, unrolling needs to only
 277 // clone the inner loop etc. No optimizations need to change the outer
 278 // strip mined loop as it is only a skeleton.
 279 IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
 280                                                              IdealLoopTree* loop, float cl_prob, float le_fcnt,
 281                                                              Node*& entry_control, Node*& iffalse) {
 282   Node* outer_test = _igvn.intcon(0);
 283   set_ctrl(outer_test, C->root());
 284   Node *orig = iffalse;
 285   iffalse = iffalse->clone();
 286   _igvn.register_new_node_with_optimizer(iffalse);
 287   set_idom(iffalse, idom(orig), dom_depth(orig));
 288 
 289   IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
 290   Node *outer_ift = new IfTrueNode (outer_le);
 291   Node* outer_iff = orig;
 292   _igvn.replace_input_of(outer_iff, 0, outer_le);
 293 
 294   LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
 295   entry_control = outer_l;
 296 
 297   IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
 298   IdealLoopTree* parent = loop->_parent;
 299   IdealLoopTree* sibling = parent->_child;
 300   if (sibling == loop) {
 301     parent->_child = outer_ilt;
 302   } else {
 303     while (sibling->_next != loop) {
 304       sibling = sibling->_next;
 305     }
 306     sibling->_next = outer_ilt;
 307   }
 308   outer_ilt->_next = loop->_next;
 309   outer_ilt->_parent = parent;
 310   outer_ilt->_child = loop;
 311   outer_ilt->_nest = loop->_nest;
 312   loop->_parent = outer_ilt;
 313   loop->_next = NULL;
 314   loop->_nest++;
 315 
 316   set_loop(iffalse, outer_ilt);
 317   register_control(outer_le, outer_ilt, iffalse);
 318   register_control(outer_ift, outer_ilt, outer_le);
 319   set_idom(outer_iff, outer_le, dom_depth(outer_le));
 320   _igvn.register_new_node_with_optimizer(outer_l);
 321   set_loop(outer_l, outer_ilt);
 322   set_idom(outer_l, init_control, dom_depth(init_control)+1);
 323 
 324   return outer_ilt;
 325 }
 326 
 327 void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) {
 328   Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL,
 329                                                          Deoptimization::Reason_loop_limit_check,
 330                                                          Op_If);
 331   Node* iff = new_predicate_proj->in(0);
 332   assert(iff->Opcode() == Op_If, "bad graph shape");
 333   Node* conv = iff->in(1);
 334   assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
 335   Node* opaq = conv->in(1);
 336   assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
 337   cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 338   bol = _igvn.register_new_node_with_optimizer(bol);
 339   set_subtree_ctrl(bol);
 340   _igvn.replace_input_of(iff, 1, bol);
 341 
 342 #ifndef PRODUCT
 343   // report that the loop predication has been actually performed
 344   // for this loop
 345   if (TraceLoopLimitCheck) {
 346     tty->print_cr("Counted Loop Limit Check generated:");
 347     debug_only( bol->dump(2); )
 348   }
 349 #endif
 350 }
 351 
 352 //------------------------------is_counted_loop--------------------------------
 353 bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) {
 354   PhaseGVN *gvn = &_igvn;
 355 
 356   // Counted loop head must be a good RegionNode with only 3 not NULL
 357   // control input edges: Self, Entry, LoopBack.
 358   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 359     return false;
 360   }
 361   Node *init_control = x->in(LoopNode::EntryControl);
 362   Node *back_control = x->in(LoopNode::LoopBackControl);
 363   if (init_control == NULL || back_control == NULL)    // Partially dead
 364     return false;
 365   // Must also check for TOP when looking for a dead loop
 366   if (init_control->is_top() || back_control->is_top())
 367     return false;
 368 
 369   // Allow funny placement of Safepoint
 370   if (back_control->Opcode() == Op_SafePoint) {
 371     if (LoopStripMiningIter != 0) {
 372       // Leaving the safepoint on the backedge and creating a
 373       // CountedLoop will confuse optimizations. We can't move the
 374       // safepoint around because its jvm state wouldn't match a new
 375       // location. Give up on that loop.
 376       return false;
 377     }
 378     back_control = back_control->in(TypeFunc::Control);
 379   }
 380 
 381   // Controlling test for loop
 382   Node *iftrue = back_control;
 383   uint iftrue_op = iftrue->Opcode();
 384   if (iftrue_op != Op_IfTrue &&
 385       iftrue_op != Op_IfFalse)
 386     // I have a weird back-control.  Probably the loop-exit test is in
 387     // the middle of the loop and I am looking at some trailing control-flow
 388     // merge point.  To fix this I would have to partially peel the loop.
 389     return false; // Obscure back-control
 390 
 391   // Get boolean guarding loop-back test
 392   Node *iff = iftrue->in(0);
 393   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 394     return false;
 395   BoolNode *test = iff->in(1)->as_Bool();
 396   BoolTest::mask bt = test->_test._test;
 397   float cl_prob = iff->as_If()->_prob;
 398   if (iftrue_op == Op_IfFalse) {
 399     bt = BoolTest(bt).negate();
 400     cl_prob = 1.0 - cl_prob;
 401   }
 402   // Get backedge compare
 403   Node *cmp = test->in(1);
 404   int cmp_op = cmp->Opcode();
 405   if (cmp_op != Op_CmpI)
 406     return false;                // Avoid pointer & float compares
 407 
 408   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 409   Node *incr  = cmp->in(1);
 410   Node *limit = cmp->in(2);
 411 
 412   // ---------
 413   // need 'loop()' test to tell if limit is loop invariant
 414   // ---------
 415 
 416   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 417     Node *tmp = incr;            // Then reverse order into the CmpI
 418     incr = limit;
 419     limit = tmp;
 420     bt = BoolTest(bt).commute(); // And commute the exit test
 421   }
 422   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 423     return false;
 424   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 425     return false;
 426 
 427   Node* phi_incr = NULL;
 428   // Trip-counter increment must be commutative & associative.
 429   if (incr->Opcode() == Op_CastII) {
 430     incr = incr->in(1);
 431   }
 432   if (incr->is_Phi()) {
 433     if (incr->as_Phi()->region() != x || incr->req() != 3)
 434       return false; // Not simple trip counter expression
 435     phi_incr = incr;
 436     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 437     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 438       return false;
 439   }
 440 
 441   Node* trunc1 = NULL;
 442   Node* trunc2 = NULL;
 443   const TypeInt* iv_trunc_t = NULL;
 444   Node* orig_incr = incr;
 445   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 446     return false; // Funny increment opcode
 447   }
 448   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 449 
 450   const TypeInt* limit_t = gvn->type(limit)->is_int();
 451   if (trunc1 != NULL) {
 452     // When there is a truncation, we must be sure that after the truncation
 453     // the trip counter will end up higher than the limit, otherwise we are looking
 454     // at an endless loop. Can happen with range checks.
 455 
 456     // Example:
 457     // int i = 0;
 458     // while (true)
 459     //    sum + = array[i];
 460     //    i++;
 461     //    i = i && 0x7fff;
 462     //  }
 463     //
 464     // If the array is shorter than 0x8000 this exits through a AIOOB
 465     //  - Counted loop transformation is ok
 466     // If the array is longer then this is an endless loop
 467     //  - No transformation can be done.
 468 
 469     const TypeInt* incr_t = gvn->type(orig_incr)->is_int();
 470     if (limit_t->_hi > incr_t->_hi) {
 471       // if the limit can have a higher value than the increment (before the phi)
 472       return false;
 473     }
 474   }
 475 
 476   // Get merge point
 477   Node *xphi = incr->in(1);
 478   Node *stride = incr->in(2);
 479   if (!stride->is_Con()) {     // Oops, swap these
 480     if (!xphi->is_Con())       // Is the other guy a constant?
 481       return false;             // Nope, unknown stride, bail out
 482     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 483     xphi = stride;
 484     stride = tmp;
 485   }
 486   if (xphi->Opcode() == Op_CastII) {
 487     xphi = xphi->in(1);
 488   }
 489   // Stride must be constant
 490   int stride_con = stride->get_int();
 491   if (stride_con == 0)
 492     return false; // missed some peephole opt
 493 
 494   if (!xphi->is_Phi())
 495     return false; // Too much math on the trip counter
 496   if (phi_incr != NULL && phi_incr != xphi)
 497     return false;
 498   PhiNode *phi = xphi->as_Phi();
 499 
 500   // Phi must be of loop header; backedge must wrap to increment
 501   if (phi->region() != x)
 502     return false;
 503   if ((trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) ||
 504       (trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) {
 505     return false;
 506   }
 507   Node *init_trip = phi->in(LoopNode::EntryControl);
 508 
 509   // If iv trunc type is smaller than int, check for possible wrap.
 510   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 511     assert(trunc1 != NULL, "must have found some truncation");
 512 
 513     // Get a better type for the phi (filtered thru if's)
 514     const TypeInt* phi_ft = filtered_type(phi);
 515 
 516     // Can iv take on a value that will wrap?
 517     //
 518     // Ensure iv's limit is not within "stride" of the wrap value.
 519     //
 520     // Example for "short" type
 521     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 522     //    If the stride is +10, then the last value of the induction
 523     //    variable before the increment (phi_ft->_hi) must be
 524     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 525     //    ensure no truncation occurs after the increment.
 526 
 527     if (stride_con > 0) {
 528       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 529           iv_trunc_t->_lo > phi_ft->_lo) {
 530         return false;  // truncation may occur
 531       }
 532     } else if (stride_con < 0) {
 533       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 534           iv_trunc_t->_hi < phi_ft->_hi) {
 535         return false;  // truncation may occur
 536       }
 537     }
 538     // No possibility of wrap so truncation can be discarded
 539     // Promote iv type to Int
 540   } else {
 541     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 542   }
 543 
 544   // If the condition is inverted and we will be rolling
 545   // through MININT to MAXINT, then bail out.
 546   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 547       // Odd stride
 548       (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
 549       // Count down loop rolls through MAXINT
 550       ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
 551       // Count up loop rolls through MININT
 552       ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
 553     return false; // Bail out
 554   }
 555 
 556   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 557 
 558   if (stride_con > 0) {
 559     jlong init_p = (jlong)init_t->_lo + stride_con;
 560     if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
 561       return false; // cyclic loop or this loop trips only once
 562   } else {
 563     jlong init_p = (jlong)init_t->_hi + stride_con;
 564     if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
 565       return false; // cyclic loop or this loop trips only once
 566   }
 567 
 568   if (phi_incr != NULL && bt != BoolTest::ne) {
 569     // check if there is a possiblity of IV overflowing after the first increment
 570     if (stride_con > 0) {
 571       if (init_t->_hi > max_jint - stride_con) {
 572         return false;
 573       }
 574     } else {
 575       if (init_t->_lo < min_jint - stride_con) {
 576         return false;
 577       }
 578     }
 579   }
 580 
 581   // =================================================
 582   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 583   //
 584   assert(x->Opcode() == Op_Loop, "regular loops only");
 585   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 586 
 587   Node *hook = new Node(6);
 588 
 589   // ===================================================
 590   // Generate loop limit check to avoid integer overflow
 591   // in cases like next (cyclic loops):
 592   //
 593   // for (i=0; i <= max_jint; i++) {}
 594   // for (i=0; i <  max_jint; i+=2) {}
 595   //
 596   //
 597   // Limit check predicate depends on the loop test:
 598   //
 599   // for(;i != limit; i++)       --> limit <= (max_jint)
 600   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 601   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 602   //
 603 
 604   // Check if limit is excluded to do more precise int overflow check.
 605   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 606   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 607 
 608   // If compare points directly to the phi we need to adjust
 609   // the compare so that it points to the incr. Limit have
 610   // to be adjusted to keep trip count the same and the
 611   // adjusted limit should be checked for int overflow.
 612   if (phi_incr != NULL) {
 613     stride_m  += stride_con;
 614   }
 615 
 616   if (limit->is_Con()) {
 617     int limit_con = limit->get_int();
 618     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 619         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 620       // Bailout: it could be integer overflow.
 621       return false;
 622     }
 623   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 624              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 625       // Limit's type may satisfy the condition, for example,
 626       // when it is an array length.
 627   } else {
 628     // Generate loop's limit check.
 629     // Loop limit check predicate should be near the loop.
 630     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 631     if (!limit_check_proj) {
 632       // The limit check predicate is not generated if this method trapped here before.
 633 #ifdef ASSERT
 634       if (TraceLoopLimitCheck) {
 635         tty->print("missing loop limit check:");
 636         loop->dump_head();
 637         x->dump(1);
 638       }
 639 #endif
 640       return false;
 641     }
 642 
 643     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 644 
 645     if (!is_dominator(get_ctrl(limit), check_iff->in(0))) {
 646       return false;
 647     }
 648 
 649     Node* cmp_limit;
 650     Node* bol;
 651 
 652     if (stride_con > 0) {
 653       cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 654       bol = new BoolNode(cmp_limit, BoolTest::le);
 655     } else {
 656       cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 657       bol = new BoolNode(cmp_limit, BoolTest::ge);
 658     }
 659 
 660     insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 661   }
 662 
 663   // Now we need to canonicalize loop condition.
 664   if (bt == BoolTest::ne) {
 665     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 666     if (stride_con > 0 && init_t->_hi < limit_t->_lo) {
 667       // 'ne' can be replaced with 'lt' only when init < limit.
 668       bt = BoolTest::lt;
 669     } else if (stride_con < 0 && init_t->_lo > limit_t->_hi) {
 670       // 'ne' can be replaced with 'gt' only when init > limit.
 671       bt = BoolTest::gt;
 672     } else {
 673       ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 674       if (!limit_check_proj) {
 675         // The limit check predicate is not generated if this method trapped here before.
 676 #ifdef ASSERT
 677         if (TraceLoopLimitCheck) {
 678           tty->print("missing loop limit check:");
 679           loop->dump_head();
 680           x->dump(1);
 681         }
 682 #endif
 683         return false;
 684       }
 685       IfNode* check_iff = limit_check_proj->in(0)->as_If();
 686 
 687       if (!is_dominator(get_ctrl(limit), check_iff->in(0)) ||
 688           !is_dominator(get_ctrl(init_trip), check_iff->in(0))) {
 689         return false;
 690       }
 691 
 692       Node* cmp_limit;
 693       Node* bol;
 694 
 695       if (stride_con > 0) {
 696         cmp_limit = new CmpINode(init_trip, limit);
 697         bol = new BoolNode(cmp_limit, BoolTest::lt);
 698       } else {
 699         cmp_limit = new CmpINode(init_trip, limit);
 700         bol = new BoolNode(cmp_limit, BoolTest::gt);
 701       }
 702 
 703       insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 704 
 705       if (stride_con > 0) {
 706         // 'ne' can be replaced with 'lt' only when init < limit.
 707         bt = BoolTest::lt;
 708       } else if (stride_con < 0) {
 709         // 'ne' can be replaced with 'gt' only when init > limit.
 710         bt = BoolTest::gt;
 711       }
 712     }
 713   }
 714 
 715   if (phi_incr != NULL) {
 716     // If compare points directly to the phi we need to adjust
 717     // the compare so that it points to the incr. Limit have
 718     // to be adjusted to keep trip count the same and we
 719     // should avoid int overflow.
 720     //
 721     //   i = init; do {} while(i++ < limit);
 722     // is converted to
 723     //   i = init; do {} while(++i < limit+1);
 724     //
 725     limit = gvn->transform(new AddINode(limit, stride));
 726   }
 727 
 728   if (incl_limit) {
 729     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 730     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 731     //
 732     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 733     limit = gvn->transform(new AddINode(limit, one));
 734     if (bt == BoolTest::le)
 735       bt = BoolTest::lt;
 736     else if (bt == BoolTest::ge)
 737       bt = BoolTest::gt;
 738     else
 739       ShouldNotReachHere();
 740   }
 741   set_subtree_ctrl( limit );
 742 
 743   if (LoopStripMiningIter == 0) {
 744     // Check for SafePoint on backedge and remove
 745     Node *sfpt = x->in(LoopNode::LoopBackControl);
 746     if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 747       lazy_replace( sfpt, iftrue );
 748       if (loop->_safepts != NULL) {
 749         loop->_safepts->yank(sfpt);
 750       }
 751       loop->_tail = iftrue;
 752     }
 753   }
 754 
 755   // Build a canonical trip test.
 756   // Clone code, as old values may be in use.
 757   incr = incr->clone();
 758   incr->set_req(1,phi);
 759   incr->set_req(2,stride);
 760   incr = _igvn.register_new_node_with_optimizer(incr);
 761   set_early_ctrl( incr );
 762   _igvn.rehash_node_delayed(phi);
 763   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 764 
 765   // If phi type is more restrictive than Int, raise to
 766   // Int to prevent (almost) infinite recursion in igvn
 767   // which can only handle integer types for constants or minint..maxint.
 768   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 769     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 770     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 771     nphi = _igvn.register_new_node_with_optimizer(nphi);
 772     set_ctrl(nphi, get_ctrl(phi));
 773     _igvn.replace_node(phi, nphi);
 774     phi = nphi->as_Phi();
 775   }
 776   cmp = cmp->clone();
 777   cmp->set_req(1,incr);
 778   cmp->set_req(2,limit);
 779   cmp = _igvn.register_new_node_with_optimizer(cmp);
 780   set_ctrl(cmp, iff->in(0));
 781 
 782   test = test->clone()->as_Bool();
 783   (*(BoolTest*)&test->_test)._test = bt;
 784   test->set_req(1,cmp);
 785   _igvn.register_new_node_with_optimizer(test);
 786   set_ctrl(test, iff->in(0));
 787 
 788   // Replace the old IfNode with a new LoopEndNode
 789   Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 790   IfNode *le = lex->as_If();
 791   uint dd = dom_depth(iff);
 792   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 793   set_loop(le, loop);
 794 
 795   // Get the loop-exit control
 796   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 797 
 798   // Need to swap loop-exit and loop-back control?
 799   if (iftrue_op == Op_IfFalse) {
 800     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
 801     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
 802 
 803     loop->_tail = back_control = ift2;
 804     set_loop(ift2, loop);
 805     set_loop(iff2, get_loop(iffalse));
 806 
 807     // Lazy update of 'get_ctrl' mechanism.
 808     lazy_replace(iffalse, iff2);
 809     lazy_replace(iftrue,  ift2);
 810 
 811     // Swap names
 812     iffalse = iff2;
 813     iftrue  = ift2;
 814   } else {
 815     _igvn.rehash_node_delayed(iffalse);
 816     _igvn.rehash_node_delayed(iftrue);
 817     iffalse->set_req_X( 0, le, &_igvn );
 818     iftrue ->set_req_X( 0, le, &_igvn );
 819   }
 820 
 821   set_idom(iftrue,  le, dd+1);
 822   set_idom(iffalse, le, dd+1);
 823   assert(iff->outcnt() == 0, "should be dead now");
 824   lazy_replace( iff, le ); // fix 'get_ctrl'
 825 
 826   Node *sfpt2 = le->in(0);
 827 
 828   Node* entry_control = init_control;
 829   bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL &&
 830     sfpt2->Opcode() == Op_SafePoint && !loop->_has_call;
 831   IdealLoopTree* outer_ilt = NULL;
 832   if (strip_mine_loop) {
 833     outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
 834                                               cl_prob, le->_fcnt, entry_control,
 835                                               iffalse);
 836   }
 837 
 838   // Now setup a new CountedLoopNode to replace the existing LoopNode
 839   CountedLoopNode *l = new CountedLoopNode(entry_control, back_control);
 840   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 841   // The following assert is approximately true, and defines the intention
 842   // of can_be_counted_loop.  It fails, however, because phase->type
 843   // is not yet initialized for this loop and its parts.
 844   //assert(l->can_be_counted_loop(this), "sanity");
 845   _igvn.register_new_node_with_optimizer(l);
 846   set_loop(l, loop);
 847   loop->_head = l;
 848   // Fix all data nodes placed at the old loop head.
 849   // Uses the lazy-update mechanism of 'get_ctrl'.
 850   lazy_replace( x, l );
 851   set_idom(l, entry_control, dom_depth(entry_control) + 1);
 852 
 853   if (LoopStripMiningIter == 0 || strip_mine_loop) {
 854     // Check for immediately preceding SafePoint and remove
 855     if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) {
 856       if (strip_mine_loop) {
 857         Node* outer_le = outer_ilt->_tail->in(0);
 858         Node* sfpt = sfpt2->clone();
 859         sfpt->set_req(0, iffalse);
 860         outer_le->set_req(0, sfpt);
 861         register_control(sfpt, outer_ilt, iffalse);
 862         set_idom(outer_le, sfpt, dom_depth(sfpt));
 863       }
 864       lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 865       if (loop->_safepts != NULL) {
 866         loop->_safepts->yank(sfpt2);
 867       }
 868     }
 869   }
 870 
 871   // Free up intermediate goo
 872   _igvn.remove_dead_node(hook);
 873 
 874 #ifdef ASSERT
 875   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 876   assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
 877 #endif
 878 #ifndef PRODUCT
 879   if (TraceLoopOpts) {
 880     tty->print("Counted      ");
 881     loop->dump_head();
 882   }
 883 #endif
 884 
 885   C->print_method(PHASE_AFTER_CLOOPS, 3);
 886 
 887   // Capture bounds of the loop in the induction variable Phi before
 888   // subsequent transformation (iteration splitting) obscures the
 889   // bounds
 890   l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
 891 
 892   if (strip_mine_loop) {
 893     l->mark_strip_mined();
 894     l->verify_strip_mined(1);
 895     outer_ilt->_head->as_Loop()->verify_strip_mined(1);
 896     loop = outer_ilt;
 897   }
 898 
 899   return true;
 900 }
 901 
 902 //----------------------exact_limit-------------------------------------------
 903 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 904   assert(loop->_head->is_CountedLoop(), "");
 905   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 906   assert(cl->is_valid_counted_loop(), "");
 907 
 908   if (ABS(cl->stride_con()) == 1 ||
 909       cl->limit()->Opcode() == Op_LoopLimit) {
 910     // Old code has exact limit (it could be incorrect in case of int overflow).
 911     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 912     return cl->limit();
 913   }
 914   Node *limit = NULL;
 915 #ifdef ASSERT
 916   BoolTest::mask bt = cl->loopexit()->test_trip();
 917   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 918 #endif
 919   if (cl->has_exact_trip_count()) {
 920     // Simple case: loop has constant boundaries.
 921     // Use jlongs to avoid integer overflow.
 922     int stride_con = cl->stride_con();
 923     jlong  init_con = cl->init_trip()->get_int();
 924     jlong limit_con = cl->limit()->get_int();
 925     julong trip_cnt = cl->trip_count();
 926     jlong final_con = init_con + trip_cnt*stride_con;
 927     int final_int = (int)final_con;
 928     // The final value should be in integer range since the loop
 929     // is counted and the limit was checked for overflow.
 930     assert(final_con == (jlong)final_int, "final value should be integer");
 931     limit = _igvn.intcon(final_int);
 932   } else {
 933     // Create new LoopLimit node to get exact limit (final iv value).
 934     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 935     register_new_node(limit, cl->in(LoopNode::EntryControl));
 936   }
 937   assert(limit != NULL, "sanity");
 938   return limit;
 939 }
 940 
 941 //------------------------------Ideal------------------------------------------
 942 // Return a node which is more "ideal" than the current node.
 943 // Attempt to convert into a counted-loop.
 944 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 945   if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
 946     phase->C->set_major_progress();
 947   }
 948   return RegionNode::Ideal(phase, can_reshape);
 949 }
 950 
 951 #ifdef ASSERT
 952 void LoopNode::verify_strip_mined(int expect_skeleton) const {
 953   const OuterStripMinedLoopNode* outer = NULL;
 954   const CountedLoopNode* inner = NULL;
 955   if (is_strip_mined()) {
 956     if (!is_valid_counted_loop()) {
 957       return; // Skip malformed counted loop
 958     }
 959     assert(is_CountedLoop(), "no Loop should be marked strip mined");
 960     inner = as_CountedLoop();
 961     outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
 962   } else if (is_OuterStripMinedLoop()) {
 963     outer = this->as_OuterStripMinedLoop();
 964     inner = outer->unique_ctrl_out()->as_CountedLoop();
 965     assert(inner->is_valid_counted_loop() && inner->is_strip_mined(), "OuterStripMinedLoop should have been removed");
 966     assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
 967   }
 968   if (inner != NULL || outer != NULL) {
 969     assert(inner != NULL && outer != NULL, "missing loop in strip mined nest");
 970     Node* outer_tail = outer->in(LoopNode::LoopBackControl);
 971     Node* outer_le = outer_tail->in(0);
 972     assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
 973     Node* sfpt = outer_le->in(0);
 974     assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
 975     Node* inner_out = sfpt->in(0);
 976     if (inner_out->outcnt() != 1) {
 977       ResourceMark rm;
 978       Unique_Node_List wq;
 979 
 980       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
 981         Node* u = inner_out->fast_out(i);
 982         if (u == sfpt) {
 983           continue;
 984         }
 985         wq.clear();
 986         wq.push(u);
 987         bool found_sfpt = false;
 988         for (uint next = 0; next < wq.size() && !found_sfpt; next++) {
 989           Node* n = wq.at(next);
 990           for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) {
 991             Node* u = n->fast_out(i);
 992             if (u == sfpt) {
 993               found_sfpt = true;
 994             }
 995             if (!u->is_CFG()) {
 996               wq.push(u);
 997             }
 998           }
 999         }
1000         assert(found_sfpt, "no node in loop that's not input to safepoint");
1001       }
1002     }
1003 
1004     CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
1005     assert(cle == inner->loopexit_or_null(), "mismatch");
1006     bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
1007     if (has_skeleton) {
1008       assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
1009       assert(outer->outcnt() == 2, "only phis");
1010     } else {
1011       assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
1012       uint phis = 0;
1013       for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
1014         Node* u = inner->fast_out(i);
1015         if (u->is_Phi()) {
1016           phis++;
1017         }
1018       }
1019       for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
1020         Node* u = outer->fast_out(i);
1021         assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
1022       }
1023       uint stores = 0;
1024       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
1025         Node* u = inner_out->fast_out(i);
1026         if (u->is_Store()) {
1027           stores++;
1028         }
1029       }
1030       assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
1031     }
1032     assert(sfpt->outcnt() == 1, "no data node");
1033     assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
1034   }
1035 }
1036 #endif
1037 
1038 //=============================================================================
1039 //------------------------------Ideal------------------------------------------
1040 // Return a node which is more "ideal" than the current node.
1041 // Attempt to convert into a counted-loop.
1042 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1043   return RegionNode::Ideal(phase, can_reshape);
1044 }
1045 
1046 //------------------------------dump_spec--------------------------------------
1047 // Dump special per-node info
1048 #ifndef PRODUCT
1049 void CountedLoopNode::dump_spec(outputStream *st) const {
1050   LoopNode::dump_spec(st);
1051   if (stride_is_con()) {
1052     st->print("stride: %d ",stride_con());
1053   }
1054   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
1055   if (is_main_loop()) st->print("main of N%d", _idx);
1056   if (is_post_loop()) st->print("post of N%d", _main_idx);
1057   if (is_strip_mined()) st->print(" strip mined");
1058 }
1059 #endif
1060 
1061 //=============================================================================
1062 int CountedLoopEndNode::stride_con() const {
1063   return stride()->bottom_type()->is_int()->get_con();
1064 }
1065 
1066 //=============================================================================
1067 //------------------------------Value-----------------------------------------
1068 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
1069   const Type* init_t   = phase->type(in(Init));
1070   const Type* limit_t  = phase->type(in(Limit));
1071   const Type* stride_t = phase->type(in(Stride));
1072   // Either input is TOP ==> the result is TOP
1073   if (init_t   == Type::TOP) return Type::TOP;
1074   if (limit_t  == Type::TOP) return Type::TOP;
1075   if (stride_t == Type::TOP) return Type::TOP;
1076 
1077   int stride_con = stride_t->is_int()->get_con();
1078   if (stride_con == 1)
1079     return NULL;  // Identity
1080 
1081   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
1082     // Use jlongs to avoid integer overflow.
1083     jlong init_con   =  init_t->is_int()->get_con();
1084     jlong limit_con  = limit_t->is_int()->get_con();
1085     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
1086     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
1087     jlong final_con  = init_con + stride_con*trip_count;
1088     int final_int = (int)final_con;
1089     // The final value should be in integer range since the loop
1090     // is counted and the limit was checked for overflow.
1091     assert(final_con == (jlong)final_int, "final value should be integer");
1092     return TypeInt::make(final_int);
1093   }
1094 
1095   return bottom_type(); // TypeInt::INT
1096 }
1097 
1098 //------------------------------Ideal------------------------------------------
1099 // Return a node which is more "ideal" than the current node.
1100 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1101   if (phase->type(in(Init))   == Type::TOP ||
1102       phase->type(in(Limit))  == Type::TOP ||
1103       phase->type(in(Stride)) == Type::TOP)
1104     return NULL;  // Dead
1105 
1106   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1107   if (stride_con == 1)
1108     return NULL;  // Identity
1109 
1110   if (in(Init)->is_Con() && in(Limit)->is_Con())
1111     return NULL;  // Value
1112 
1113   // Delay following optimizations until all loop optimizations
1114   // done to keep Ideal graph simple.
1115   if (!can_reshape || phase->C->major_progress())
1116     return NULL;
1117 
1118   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
1119   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
1120   int stride_p;
1121   jlong lim, ini;
1122   julong max;
1123   if (stride_con > 0) {
1124     stride_p = stride_con;
1125     lim = limit_t->_hi;
1126     ini = init_t->_lo;
1127     max = (julong)max_jint;
1128   } else {
1129     stride_p = -stride_con;
1130     lim = init_t->_hi;
1131     ini = limit_t->_lo;
1132     max = (julong)min_jint;
1133   }
1134   julong range = lim - ini + stride_p;
1135   if (range <= max) {
1136     // Convert to integer expression if it is not overflow.
1137     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
1138     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
1139     Node *bias  = phase->transform(new AddINode(range, stride_m));
1140     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
1141     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
1142     return new AddINode(span, in(Init)); // exact limit
1143   }
1144 
1145   if (is_power_of_2(stride_p) ||                // divisor is 2^n
1146       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
1147     // Convert to long expression to avoid integer overflow
1148     // and let igvn optimizer convert this division.
1149     //
1150     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
1151     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
1152     Node* stride   = phase->longcon(stride_con);
1153     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
1154 
1155     Node *range = phase->transform(new SubLNode(limit, init));
1156     Node *bias  = phase->transform(new AddLNode(range, stride_m));
1157     Node *span;
1158     if (stride_con > 0 && is_power_of_2(stride_p)) {
1159       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
1160       // and avoid generating rounding for division. Zero trip guard should
1161       // guarantee that init < limit but sometimes the guard is missing and
1162       // we can get situation when init > limit. Note, for the empty loop
1163       // optimization zero trip guard is generated explicitly which leaves
1164       // only RCE predicate where exact limit is used and the predicate
1165       // will simply fail forcing recompilation.
1166       Node* neg_stride   = phase->longcon(-stride_con);
1167       span = phase->transform(new AndLNode(bias, neg_stride));
1168     } else {
1169       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
1170       span = phase->transform(new MulLNode(trip, stride));
1171     }
1172     // Convert back to int
1173     Node *span_int = phase->transform(new ConvL2INode(span));
1174     return new AddINode(span_int, in(Init)); // exact limit
1175   }
1176 
1177   return NULL;    // No progress
1178 }
1179 
1180 //------------------------------Identity---------------------------------------
1181 // If stride == 1 return limit node.
1182 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1183   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1184   if (stride_con == 1 || stride_con == -1)
1185     return in(Limit);
1186   return this;
1187 }
1188 
1189 //=============================================================================
1190 //----------------------match_incr_with_optional_truncation--------------------
1191 // Match increment with optional truncation:
1192 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1193 // Return NULL for failure. Success returns the increment node.
1194 Node* CountedLoopNode::match_incr_with_optional_truncation(
1195                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1196   // Quick cutouts:
1197   if (expr == NULL || expr->req() != 3)  return NULL;
1198 
1199   Node *t1 = NULL;
1200   Node *t2 = NULL;
1201   const TypeInt* trunc_t = TypeInt::INT;
1202   Node* n1 = expr;
1203   int   n1op = n1->Opcode();
1204 
1205   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1206   if (n1op == Op_AndI &&
1207       n1->in(2)->is_Con() &&
1208       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1209     // %%% This check should match any mask of 2**K-1.
1210     t1 = n1;
1211     n1 = t1->in(1);
1212     n1op = n1->Opcode();
1213     trunc_t = TypeInt::CHAR;
1214   } else if (n1op == Op_RShiftI &&
1215              n1->in(1) != NULL &&
1216              n1->in(1)->Opcode() == Op_LShiftI &&
1217              n1->in(2) == n1->in(1)->in(2) &&
1218              n1->in(2)->is_Con()) {
1219     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1220     // %%% This check should match any shift in [1..31].
1221     if (shift == 16 || shift == 8) {
1222       t1 = n1;
1223       t2 = t1->in(1);
1224       n1 = t2->in(1);
1225       n1op = n1->Opcode();
1226       if (shift == 16) {
1227         trunc_t = TypeInt::SHORT;
1228       } else if (shift == 8) {
1229         trunc_t = TypeInt::BYTE;
1230       }
1231     }
1232   }
1233 
1234   // If (maybe after stripping) it is an AddI, we won:
1235   if (n1op == Op_AddI) {
1236     *trunc1 = t1;
1237     *trunc2 = t2;
1238     *trunc_type = trunc_t;
1239     return n1;
1240   }
1241 
1242   // failed
1243   return NULL;
1244 }
1245 
1246 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
1247   if (is_strip_mined() && is_valid_counted_loop()) {
1248     verify_strip_mined(expect_skeleton);
1249     return in(EntryControl)->as_Loop();
1250   }
1251   return this;
1252 }
1253 
1254 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
1255   assert(is_strip_mined(), "not a strip mined loop");
1256   Node* c = in(EntryControl);
1257   if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) {
1258     return NULL;
1259   }
1260   return c->as_OuterStripMinedLoop();
1261 }
1262 
1263 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
1264   Node* c = in(LoopBackControl);
1265   if (c == NULL || c->is_top()) {
1266     return NULL;
1267   }
1268   return c->as_IfTrue();
1269 }
1270 
1271 IfTrueNode* CountedLoopNode::outer_loop_tail() const {
1272   LoopNode* l = outer_loop();
1273   if (l == NULL) {
1274     return NULL;
1275   }
1276   return l->outer_loop_tail();
1277 }
1278 
1279 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
1280   IfTrueNode* proj = outer_loop_tail();
1281   if (proj == NULL) {
1282     return NULL;
1283   }
1284   Node* c = proj->in(0);
1285   if (c == NULL || c->is_top() || c->outcnt() != 2) {
1286     return NULL;
1287   }
1288   return c->as_OuterStripMinedLoopEnd();
1289 }
1290 
1291 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
1292   LoopNode* l = outer_loop();
1293   if (l == NULL) {
1294     return NULL;
1295   }
1296   return l->outer_loop_end();
1297 }
1298 
1299 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
1300   IfNode* le = outer_loop_end();
1301   if (le == NULL) {
1302     return NULL;
1303   }
1304   Node* c = le->proj_out_or_null(false);
1305   if (c == NULL) {
1306     return NULL;
1307   }
1308   return c->as_IfFalse();
1309 }
1310 
1311 IfFalseNode* CountedLoopNode::outer_loop_exit() const {
1312   LoopNode* l = outer_loop();
1313   if (l == NULL) {
1314     return NULL;
1315   }
1316   return l->outer_loop_exit();
1317 }
1318 
1319 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
1320   IfNode* le = outer_loop_end();
1321   if (le == NULL) {
1322     return NULL;
1323   }
1324   Node* c = le->in(0);
1325   if (c == NULL || c->is_top()) {
1326     return NULL;
1327   }
1328   assert(c->Opcode() == Op_SafePoint, "broken outer loop");
1329   return c->as_SafePoint();
1330 }
1331 
1332 SafePointNode* CountedLoopNode::outer_safepoint() const {
1333   LoopNode* l = outer_loop();
1334   if (l == NULL) {
1335     return NULL;
1336   }
1337   return l->outer_safepoint();
1338 }
1339 
1340 Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
1341     while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() &&
1342            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
1343            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) {
1344       ctrl = ctrl->in(0)->in(0);
1345     }
1346 
1347     return ctrl;
1348   }
1349 
1350 Node* CountedLoopNode::skip_predicates() {
1351   if (is_main_loop()) {
1352     Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
1353 
1354     return skip_predicates_from_entry(ctrl);
1355   }
1356   return in(LoopNode::EntryControl);
1357 }
1358 
1359 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
1360   // Look for the outer & inner strip mined loop, reduce number of
1361   // iterations of the inner loop, set exit condition of outer loop,
1362   // construct required phi nodes for outer loop.
1363   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
1364   assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
1365   Node* inner_iv_phi = inner_cl->phi();
1366   if (inner_iv_phi == NULL) {
1367     IfNode* outer_le = outer_loop_end();
1368     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1369     igvn->replace_node(outer_le, iff);
1370     inner_cl->clear_strip_mined();
1371     return;
1372   }
1373   CountedLoopEndNode* inner_cle = inner_cl->loopexit();
1374 
1375   int stride = inner_cl->stride_con();
1376   jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
1377   int scaled_iters = (int)scaled_iters_long;
1378   int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
1379   const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
1380   jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
1381   assert(iter_estimate > 0, "broken");
1382   if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
1383     // Remove outer loop and safepoint (too few iterations)
1384     Node* outer_sfpt = outer_safepoint();
1385     Node* outer_out = outer_loop_exit();
1386     igvn->replace_node(outer_out, outer_sfpt->in(0));
1387     igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
1388     inner_cl->clear_strip_mined();
1389     return;
1390   }
1391   if (iter_estimate <= scaled_iters_long) {
1392     // We would only go through one iteration of
1393     // the outer loop: drop the outer loop but
1394     // keep the safepoint so we don't run for
1395     // too long without a safepoint
1396     IfNode* outer_le = outer_loop_end();
1397     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1398     igvn->replace_node(outer_le, iff);
1399     inner_cl->clear_strip_mined();
1400     return;
1401   }
1402 
1403   Node* cle_tail = inner_cle->proj_out(true);
1404   ResourceMark rm;
1405   Node_List old_new;
1406   if (cle_tail->outcnt() > 1) {
1407     // Look for nodes on backedge of inner loop and clone them
1408     Unique_Node_List backedge_nodes;
1409     for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
1410       Node* u = cle_tail->fast_out(i);
1411       if (u != inner_cl) {
1412         assert(!u->is_CFG(), "control flow on the backedge?");
1413         backedge_nodes.push(u);
1414       }
1415     }
1416     uint last = igvn->C->unique();
1417     for (uint next = 0; next < backedge_nodes.size(); next++) {
1418       Node* n = backedge_nodes.at(next);
1419       old_new.map(n->_idx, n->clone());
1420       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1421         Node* u = n->fast_out(i);
1422         assert(!u->is_CFG(), "broken");
1423         if (u->_idx >= last) {
1424           continue;
1425         }
1426         if (!u->is_Phi()) {
1427           backedge_nodes.push(u);
1428         } else {
1429           assert(u->in(0) == inner_cl, "strange phi on the backedge");
1430         }
1431       }
1432     }
1433     // Put the clones on the outer loop backedge
1434     Node* le_tail = outer_loop_tail();
1435     for (uint next = 0; next < backedge_nodes.size(); next++) {
1436       Node *n = old_new[backedge_nodes.at(next)->_idx];
1437       for (uint i = 1; i < n->req(); i++) {
1438         if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) {
1439           n->set_req(i, old_new[n->in(i)->_idx]);
1440         }
1441       }
1442       if (n->in(0) != NULL && n->in(0) == cle_tail) {
1443         n->set_req(0, le_tail);
1444       }
1445       igvn->register_new_node_with_optimizer(n);
1446     }
1447   }
1448 
1449   Node* iv_phi = NULL;
1450   // Make a clone of each phi in the inner loop
1451   // for the outer loop
1452   for (uint i = 0; i < inner_cl->outcnt(); i++) {
1453     Node* u = inner_cl->raw_out(i);
1454     if (u->is_Phi()) {
1455       assert(u->in(0) == inner_cl, "inconsistent");
1456       Node* phi = u->clone();
1457       phi->set_req(0, this);
1458       Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
1459       if (be != NULL) {
1460         phi->set_req(LoopNode::LoopBackControl, be);
1461       }
1462       phi = igvn->transform(phi);
1463       igvn->replace_input_of(u, LoopNode::EntryControl, phi);
1464       if (u == inner_iv_phi) {
1465         iv_phi = phi;
1466       }
1467     }
1468   }
1469   Node* cle_out = inner_cle->proj_out(false);
1470   if (cle_out->outcnt() > 1) {
1471     // Look for chains of stores that were sunk
1472     // out of the inner loop and are in the outer loop
1473     for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
1474       Node* u = cle_out->fast_out(i);
1475       if (u->is_Store()) {
1476         Node* first = u;
1477         for(;;) {
1478           Node* next = first->in(MemNode::Memory);
1479           if (!next->is_Store() || next->in(0) != cle_out) {
1480             break;
1481           }
1482           first = next;
1483         }
1484         Node* last = u;
1485         for(;;) {
1486           Node* next = NULL;
1487           for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
1488             Node* uu = last->fast_out(j);
1489             if (uu->is_Store() && uu->in(0) == cle_out) {
1490               assert(next == NULL, "only one in the outer loop");
1491               next = uu;
1492             }
1493           }
1494           if (next == NULL) {
1495             break;
1496           }
1497           last = next;
1498         }
1499         Node* phi = NULL;
1500         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1501           Node* uu = fast_out(j);
1502           if (uu->is_Phi()) {
1503             Node* be = uu->in(LoopNode::LoopBackControl);
1504             if (be->is_Store() && old_new[be->_idx] != NULL) {
1505               assert(false, "store on the backedge + sunk stores: unsupported");
1506               // drop outer loop
1507               IfNode* outer_le = outer_loop_end();
1508               Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1509               igvn->replace_node(outer_le, iff);
1510               inner_cl->clear_strip_mined();
1511               return;
1512             }
1513             if (be == last || be == first->in(MemNode::Memory)) {
1514               assert(phi == NULL, "only one phi");
1515               phi = uu;
1516             }
1517           }
1518         }
1519 #ifdef ASSERT
1520         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1521           Node* uu = fast_out(j);
1522           if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
1523             if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
1524               assert(phi == uu, "what's that phi?");
1525             } else if (uu->adr_type() == TypePtr::BOTTOM) {
1526               Node* n = uu->in(LoopNode::LoopBackControl);
1527               uint limit = igvn->C->live_nodes();
1528               uint i = 0;
1529               while (n != uu) {
1530                 i++;
1531                 assert(i < limit, "infinite loop");
1532                 if (n->is_Proj()) {
1533                   n = n->in(0);
1534                 } else if (n->is_SafePoint() || n->is_MemBar()) {
1535                   n = n->in(TypeFunc::Memory);
1536                 } else if (n->is_Phi()) {
1537                   n = n->in(1);
1538                 } else if (n->is_MergeMem()) {
1539                   n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
1540                 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
1541                   n = n->in(MemNode::Memory);
1542                 } else {
1543                   n->dump();
1544                   ShouldNotReachHere();
1545                 }
1546               }
1547             }
1548           }
1549         }
1550 #endif
1551         if (phi == NULL) {
1552           // If the an entire chains was sunk, the
1553           // inner loop has no phi for that memory
1554           // slice, create one for the outer loop
1555           phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY,
1556                               igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
1557           phi->set_req(LoopNode::LoopBackControl, last);
1558           phi = igvn->transform(phi);
1559           igvn->replace_input_of(first, MemNode::Memory, phi);
1560         } else {
1561           // Or fix the outer loop fix to include
1562           // that chain of stores.
1563           Node* be = phi->in(LoopNode::LoopBackControl);
1564           assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported");
1565           if (be == first->in(MemNode::Memory)) {
1566             if (be == phi->in(LoopNode::LoopBackControl)) {
1567               igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
1568             } else {
1569               igvn->replace_input_of(be, MemNode::Memory, last);
1570             }
1571           } else {
1572 #ifdef ASSERT
1573             if (be == phi->in(LoopNode::LoopBackControl)) {
1574               assert(phi->in(LoopNode::LoopBackControl) == last, "");
1575             } else {
1576               assert(be->in(MemNode::Memory) == last, "");
1577             }
1578 #endif
1579           }
1580         }
1581       }
1582     }
1583   }
1584 
1585   if (iv_phi != NULL) {
1586     // Now adjust the inner loop's exit condition
1587     Node* limit = inner_cl->limit();
1588     Node* sub = NULL;
1589     if (stride > 0) {
1590       sub = igvn->transform(new SubINode(limit, iv_phi));
1591     } else {
1592       sub = igvn->transform(new SubINode(iv_phi, limit));
1593     }
1594     // sub is positive and can be larger than the max signed int
1595     // value. Use an unsigned min.
1596     Node* const_iters = igvn->intcon(scaled_iters);
1597     Node* cmp = igvn->transform(new CmpUNode(sub, const_iters));
1598     Node* bol = igvn->transform(new BoolNode(cmp, BoolTest::lt));
1599     Node* min = igvn->transform(new CMoveINode(bol, const_iters, sub, TypeInt::make(0, scaled_iters, Type::WidenMin)));
1600 
1601     Node* new_limit = NULL;
1602     if (stride > 0) {
1603       new_limit = igvn->transform(new AddINode(min, iv_phi));
1604     } else {
1605       new_limit = igvn->transform(new SubINode(iv_phi, min));
1606     }
1607     Node* inner_cmp = inner_cle->cmp_node();
1608     Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
1609     Node* outer_bol = inner_bol;
1610     // cmp node for inner loop may be shared
1611     inner_cmp = inner_cmp->clone();
1612     inner_cmp->set_req(2, new_limit);
1613     inner_bol = inner_bol->clone();
1614     inner_bol->set_req(1, igvn->transform(inner_cmp));
1615     igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
1616     // Set the outer loop's exit condition too
1617     igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
1618   } else {
1619     assert(false, "should be able to adjust outer loop");
1620     IfNode* outer_le = outer_loop_end();
1621     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1622     igvn->replace_node(outer_le, iff);
1623     inner_cl->clear_strip_mined();
1624   }
1625 }
1626 
1627 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
1628   if (!in(0)) return Type::TOP;
1629   if (phase->type(in(0)) == Type::TOP)
1630     return Type::TOP;
1631 
1632   return TypeTuple::IFBOTH;
1633 }
1634 
1635 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1636   if (remove_dead_region(phase, can_reshape))  return this;
1637 
1638   return NULL;
1639 }
1640 
1641 //------------------------------filtered_type--------------------------------
1642 // Return a type based on condition control flow
1643 // A successful return will be a type that is restricted due
1644 // to a series of dominating if-tests, such as:
1645 //    if (i < 10) {
1646 //       if (i > 0) {
1647 //          here: "i" type is [1..10)
1648 //       }
1649 //    }
1650 // or a control flow merge
1651 //    if (i < 10) {
1652 //       do {
1653 //          phi( , ) -- at top of loop type is [min_int..10)
1654 //         i = ?
1655 //       } while ( i < 10)
1656 //
1657 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1658   assert(n && n->bottom_type()->is_int(), "must be int");
1659   const TypeInt* filtered_t = NULL;
1660   if (!n->is_Phi()) {
1661     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1662     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1663 
1664   } else {
1665     Node* phi    = n->as_Phi();
1666     Node* region = phi->in(0);
1667     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1668     if (region && region != C->top()) {
1669       for (uint i = 1; i < phi->req(); i++) {
1670         Node* val   = phi->in(i);
1671         Node* use_c = region->in(i);
1672         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1673         if (val_t != NULL) {
1674           if (filtered_t == NULL) {
1675             filtered_t = val_t;
1676           } else {
1677             filtered_t = filtered_t->meet(val_t)->is_int();
1678           }
1679         }
1680       }
1681     }
1682   }
1683   const TypeInt* n_t = _igvn.type(n)->is_int();
1684   if (filtered_t != NULL) {
1685     n_t = n_t->join(filtered_t)->is_int();
1686   }
1687   return n_t;
1688 }
1689 
1690 
1691 //------------------------------filtered_type_from_dominators--------------------------------
1692 // Return a possibly more restrictive type for val based on condition control flow of dominators
1693 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1694   if (val->is_Con()) {
1695      return val->bottom_type()->is_int();
1696   }
1697   uint if_limit = 10; // Max number of dominating if's visited
1698   const TypeInt* rtn_t = NULL;
1699 
1700   if (use_ctrl && use_ctrl != C->top()) {
1701     Node* val_ctrl = get_ctrl(val);
1702     uint val_dom_depth = dom_depth(val_ctrl);
1703     Node* pred = use_ctrl;
1704     uint if_cnt = 0;
1705     while (if_cnt < if_limit) {
1706       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1707         if_cnt++;
1708         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1709         if (if_t != NULL) {
1710           if (rtn_t == NULL) {
1711             rtn_t = if_t;
1712           } else {
1713             rtn_t = rtn_t->join(if_t)->is_int();
1714           }
1715         }
1716       }
1717       pred = idom(pred);
1718       if (pred == NULL || pred == C->top()) {
1719         break;
1720       }
1721       // Stop if going beyond definition block of val
1722       if (dom_depth(pred) < val_dom_depth) {
1723         break;
1724       }
1725     }
1726   }
1727   return rtn_t;
1728 }
1729 
1730 
1731 //------------------------------dump_spec--------------------------------------
1732 // Dump special per-node info
1733 #ifndef PRODUCT
1734 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1735   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1736     BoolTest bt( test_trip()); // Added this for g++.
1737 
1738     st->print("[");
1739     bt.dump_on(st);
1740     st->print("]");
1741   }
1742   st->print(" ");
1743   IfNode::dump_spec(st);
1744 }
1745 #endif
1746 
1747 //=============================================================================
1748 //------------------------------is_member--------------------------------------
1749 // Is 'l' a member of 'this'?
1750 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1751   while( l->_nest > _nest ) l = l->_parent;
1752   return l == this;
1753 }
1754 
1755 //------------------------------set_nest---------------------------------------
1756 // Set loop tree nesting depth.  Accumulate _has_call bits.
1757 int IdealLoopTree::set_nest( uint depth ) {
1758   _nest = depth;
1759   int bits = _has_call;
1760   if( _child ) bits |= _child->set_nest(depth+1);
1761   if( bits ) _has_call = 1;
1762   if( _next  ) bits |= _next ->set_nest(depth  );
1763   return bits;
1764 }
1765 
1766 //------------------------------split_fall_in----------------------------------
1767 // Split out multiple fall-in edges from the loop header.  Move them to a
1768 // private RegionNode before the loop.  This becomes the loop landing pad.
1769 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1770   PhaseIterGVN &igvn = phase->_igvn;
1771   uint i;
1772 
1773   // Make a new RegionNode to be the landing pad.
1774   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1775   phase->set_loop(landing_pad,_parent);
1776   // Gather all the fall-in control paths into the landing pad
1777   uint icnt = fall_in_cnt;
1778   uint oreq = _head->req();
1779   for( i = oreq-1; i>0; i-- )
1780     if( !phase->is_member( this, _head->in(i) ) )
1781       landing_pad->set_req(icnt--,_head->in(i));
1782 
1783   // Peel off PhiNode edges as well
1784   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1785     Node *oj = _head->fast_out(j);
1786     if( oj->is_Phi() ) {
1787       PhiNode* old_phi = oj->as_Phi();
1788       assert( old_phi->region() == _head, "" );
1789       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1790       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1791       uint icnt = fall_in_cnt;
1792       for( i = oreq-1; i>0; i-- ) {
1793         if( !phase->is_member( this, _head->in(i) ) ) {
1794           p->init_req(icnt--, old_phi->in(i));
1795           // Go ahead and clean out old edges from old phi
1796           old_phi->del_req(i);
1797         }
1798       }
1799       // Search for CSE's here, because ZKM.jar does a lot of
1800       // loop hackery and we need to be a little incremental
1801       // with the CSE to avoid O(N^2) node blow-up.
1802       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1803       if( p2 ) {                // Found CSE
1804         p->destruct();          // Recover useless new node
1805         p = p2;                 // Use old node
1806       } else {
1807         igvn.register_new_node_with_optimizer(p, old_phi);
1808       }
1809       // Make old Phi refer to new Phi.
1810       old_phi->add_req(p);
1811       // Check for the special case of making the old phi useless and
1812       // disappear it.  In JavaGrande I have a case where this useless
1813       // Phi is the loop limit and prevents recognizing a CountedLoop
1814       // which in turn prevents removing an empty loop.
1815       Node *id_old_phi = old_phi->Identity(&igvn);
1816       if( id_old_phi != old_phi ) { // Found a simple identity?
1817         // Note that I cannot call 'replace_node' here, because
1818         // that will yank the edge from old_phi to the Region and
1819         // I'm mid-iteration over the Region's uses.
1820         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1821           Node* use = old_phi->last_out(i);
1822           igvn.rehash_node_delayed(use);
1823           uint uses_found = 0;
1824           for (uint j = 0; j < use->len(); j++) {
1825             if (use->in(j) == old_phi) {
1826               if (j < use->req()) use->set_req (j, id_old_phi);
1827               else                use->set_prec(j, id_old_phi);
1828               uses_found++;
1829             }
1830           }
1831           i -= uses_found;    // we deleted 1 or more copies of this edge
1832         }
1833       }
1834       igvn._worklist.push(old_phi);
1835     }
1836   }
1837   // Finally clean out the fall-in edges from the RegionNode
1838   for( i = oreq-1; i>0; i-- ) {
1839     if( !phase->is_member( this, _head->in(i) ) ) {
1840       _head->del_req(i);
1841     }
1842   }
1843   igvn.rehash_node_delayed(_head);
1844   // Transform landing pad
1845   igvn.register_new_node_with_optimizer(landing_pad, _head);
1846   // Insert landing pad into the header
1847   _head->add_req(landing_pad);
1848 }
1849 
1850 //------------------------------split_outer_loop-------------------------------
1851 // Split out the outermost loop from this shared header.
1852 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1853   PhaseIterGVN &igvn = phase->_igvn;
1854 
1855   // Find index of outermost loop; it should also be my tail.
1856   uint outer_idx = 1;
1857   while( _head->in(outer_idx) != _tail ) outer_idx++;
1858 
1859   // Make a LoopNode for the outermost loop.
1860   Node *ctl = _head->in(LoopNode::EntryControl);
1861   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1862   outer = igvn.register_new_node_with_optimizer(outer, _head);
1863   phase->set_created_loop_node();
1864 
1865   // Outermost loop falls into '_head' loop
1866   _head->set_req(LoopNode::EntryControl, outer);
1867   _head->del_req(outer_idx);
1868   // Split all the Phis up between '_head' loop and 'outer' loop.
1869   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1870     Node *out = _head->fast_out(j);
1871     if( out->is_Phi() ) {
1872       PhiNode *old_phi = out->as_Phi();
1873       assert( old_phi->region() == _head, "" );
1874       Node *phi = PhiNode::make_blank(outer, old_phi);
1875       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1876       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1877       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1878       // Make old Phi point to new Phi on the fall-in path
1879       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1880       old_phi->del_req(outer_idx);
1881     }
1882   }
1883 
1884   // Use the new loop head instead of the old shared one
1885   _head = outer;
1886   phase->set_loop(_head, this);
1887 }
1888 
1889 //------------------------------fix_parent-------------------------------------
1890 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1891   loop->_parent = parent;
1892   if( loop->_child ) fix_parent( loop->_child, loop   );
1893   if( loop->_next  ) fix_parent( loop->_next , parent );
1894 }
1895 
1896 //------------------------------estimate_path_freq-----------------------------
1897 static float estimate_path_freq( Node *n ) {
1898   // Try to extract some path frequency info
1899   IfNode *iff;
1900   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1901     uint nop = n->Opcode();
1902     if( nop == Op_SafePoint ) {   // Skip any safepoint
1903       n = n->in(0);
1904       continue;
1905     }
1906     if( nop == Op_CatchProj ) {   // Get count from a prior call
1907       // Assume call does not always throw exceptions: means the call-site
1908       // count is also the frequency of the fall-through path.
1909       assert( n->is_CatchProj(), "" );
1910       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1911         return 0.0f;            // Assume call exception path is rare
1912       Node *call = n->in(0)->in(0)->in(0);
1913       assert( call->is_Call(), "expect a call here" );
1914       const JVMState *jvms = ((CallNode*)call)->jvms();
1915       ciMethodData* methodData = jvms->method()->method_data();
1916       if (!methodData->is_mature())  return 0.0f; // No call-site data
1917       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1918       if ((data == NULL) || !data->is_CounterData()) {
1919         // no call profile available, try call's control input
1920         n = n->in(0);
1921         continue;
1922       }
1923       return data->as_CounterData()->count()/FreqCountInvocations;
1924     }
1925     // See if there's a gating IF test
1926     Node *n_c = n->in(0);
1927     if( !n_c->is_If() ) break;       // No estimate available
1928     iff = n_c->as_If();
1929     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1930       // Compute how much count comes on this path
1931       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1932     // Have no count info.  Skip dull uncommon-trap like branches.
1933     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1934         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1935       break;
1936     // Skip through never-taken branch; look for a real loop exit.
1937     n = iff->in(0);
1938   }
1939   return 0.0f;                  // No estimate available
1940 }
1941 
1942 //------------------------------merge_many_backedges---------------------------
1943 // Merge all the backedges from the shared header into a private Region.
1944 // Feed that region as the one backedge to this loop.
1945 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1946   uint i;
1947 
1948   // Scan for the top 2 hottest backedges
1949   float hotcnt = 0.0f;
1950   float warmcnt = 0.0f;
1951   uint hot_idx = 0;
1952   // Loop starts at 2 because slot 1 is the fall-in path
1953   for( i = 2; i < _head->req(); i++ ) {
1954     float cnt = estimate_path_freq(_head->in(i));
1955     if( cnt > hotcnt ) {       // Grab hottest path
1956       warmcnt = hotcnt;
1957       hotcnt = cnt;
1958       hot_idx = i;
1959     } else if( cnt > warmcnt ) { // And 2nd hottest path
1960       warmcnt = cnt;
1961     }
1962   }
1963 
1964   // See if the hottest backedge is worthy of being an inner loop
1965   // by being much hotter than the next hottest backedge.
1966   if( hotcnt <= 0.0001 ||
1967       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1968 
1969   // Peel out the backedges into a private merge point; peel
1970   // them all except optionally hot_idx.
1971   PhaseIterGVN &igvn = phase->_igvn;
1972 
1973   Node *hot_tail = NULL;
1974   // Make a Region for the merge point
1975   Node *r = new RegionNode(1);
1976   for( i = 2; i < _head->req(); i++ ) {
1977     if( i != hot_idx )
1978       r->add_req( _head->in(i) );
1979     else hot_tail = _head->in(i);
1980   }
1981   igvn.register_new_node_with_optimizer(r, _head);
1982   // Plug region into end of loop _head, followed by hot_tail
1983   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1984   igvn.replace_input_of(_head, 2, r);
1985   if( hot_idx ) _head->add_req(hot_tail);
1986 
1987   // Split all the Phis up between '_head' loop and the Region 'r'
1988   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1989     Node *out = _head->fast_out(j);
1990     if( out->is_Phi() ) {
1991       PhiNode* n = out->as_Phi();
1992       igvn.hash_delete(n);      // Delete from hash before hacking edges
1993       Node *hot_phi = NULL;
1994       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1995       // Check all inputs for the ones to peel out
1996       uint j = 1;
1997       for( uint i = 2; i < n->req(); i++ ) {
1998         if( i != hot_idx )
1999           phi->set_req( j++, n->in(i) );
2000         else hot_phi = n->in(i);
2001       }
2002       // Register the phi but do not transform until whole place transforms
2003       igvn.register_new_node_with_optimizer(phi, n);
2004       // Add the merge phi to the old Phi
2005       while( n->req() > 3 ) n->del_req( n->req()-1 );
2006       igvn.replace_input_of(n, 2, phi);
2007       if( hot_idx ) n->add_req(hot_phi);
2008     }
2009   }
2010 
2011 
2012   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
2013   // of self loop tree.  Turn self into a loop headed by _head and with
2014   // tail being the new merge point.
2015   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
2016   phase->set_loop(_tail,ilt);   // Adjust tail
2017   _tail = r;                    // Self's tail is new merge point
2018   phase->set_loop(r,this);
2019   ilt->_child = _child;         // New guy has my children
2020   _child = ilt;                 // Self has new guy as only child
2021   ilt->_parent = this;          // new guy has self for parent
2022   ilt->_nest = _nest;           // Same nesting depth (for now)
2023 
2024   // Starting with 'ilt', look for child loop trees using the same shared
2025   // header.  Flatten these out; they will no longer be loops in the end.
2026   IdealLoopTree **pilt = &_child;
2027   while( ilt ) {
2028     if( ilt->_head == _head ) {
2029       uint i;
2030       for( i = 2; i < _head->req(); i++ )
2031         if( _head->in(i) == ilt->_tail )
2032           break;                // Still a loop
2033       if( i == _head->req() ) { // No longer a loop
2034         // Flatten ilt.  Hang ilt's "_next" list from the end of
2035         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
2036         IdealLoopTree **cp = &ilt->_child;
2037         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
2038         *cp = ilt->_next;       // Hang next list at end of child list
2039         *pilt = ilt->_child;    // Move child up to replace ilt
2040         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
2041         ilt = ilt->_child;      // Repeat using new ilt
2042         continue;               // do not advance over ilt->_child
2043       }
2044       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
2045       phase->set_loop(_head,ilt);
2046     }
2047     pilt = &ilt->_child;        // Advance to next
2048     ilt = *pilt;
2049   }
2050 
2051   if( _child ) fix_parent( _child, this );
2052 }
2053 
2054 //------------------------------beautify_loops---------------------------------
2055 // Split shared headers and insert loop landing pads.
2056 // Insert a LoopNode to replace the RegionNode.
2057 // Return TRUE if loop tree is structurally changed.
2058 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
2059   bool result = false;
2060   // Cache parts in locals for easy
2061   PhaseIterGVN &igvn = phase->_igvn;
2062 
2063   igvn.hash_delete(_head);      // Yank from hash before hacking edges
2064 
2065   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
2066   int fall_in_cnt = 0;
2067   for( uint i = 1; i < _head->req(); i++ )
2068     if( !phase->is_member( this, _head->in(i) ) )
2069       fall_in_cnt++;
2070   assert( fall_in_cnt, "at least 1 fall-in path" );
2071   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
2072     split_fall_in( phase, fall_in_cnt );
2073 
2074   // Swap inputs to the _head and all Phis to move the fall-in edge to
2075   // the left.
2076   fall_in_cnt = 1;
2077   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
2078     fall_in_cnt++;
2079   if( fall_in_cnt > 1 ) {
2080     // Since I am just swapping inputs I do not need to update def-use info
2081     Node *tmp = _head->in(1);
2082     igvn.rehash_node_delayed(_head);
2083     _head->set_req( 1, _head->in(fall_in_cnt) );
2084     _head->set_req( fall_in_cnt, tmp );
2085     // Swap also all Phis
2086     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
2087       Node* phi = _head->fast_out(i);
2088       if( phi->is_Phi() ) {
2089         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
2090         tmp = phi->in(1);
2091         phi->set_req( 1, phi->in(fall_in_cnt) );
2092         phi->set_req( fall_in_cnt, tmp );
2093       }
2094     }
2095   }
2096   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
2097   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
2098 
2099   // If I am a shared header (multiple backedges), peel off the many
2100   // backedges into a private merge point and use the merge point as
2101   // the one true backedge.
2102   if (_head->req() > 3 && !_irreducible) {
2103     // Merge the many backedges into a single backedge but leave
2104     // the hottest backedge as separate edge for the following peel.
2105     merge_many_backedges( phase );
2106     result = true;
2107   }
2108 
2109   // If I have one hot backedge, peel off myself loop.
2110   // I better be the outermost loop.
2111   if (_head->req() > 3 && !_irreducible) {
2112     split_outer_loop( phase );
2113     result = true;
2114 
2115   } else if (!_head->is_Loop() && !_irreducible) {
2116     // Make a new LoopNode to replace the old loop head
2117     Node *l = new LoopNode( _head->in(1), _head->in(2) );
2118     l = igvn.register_new_node_with_optimizer(l, _head);
2119     phase->set_created_loop_node();
2120     // Go ahead and replace _head
2121     phase->_igvn.replace_node( _head, l );
2122     _head = l;
2123     phase->set_loop(_head, this);
2124   }
2125 
2126   // Now recursively beautify nested loops
2127   if( _child ) result |= _child->beautify_loops( phase );
2128   if( _next  ) result |= _next ->beautify_loops( phase );
2129   return result;
2130 }
2131 
2132 //------------------------------allpaths_check_safepts----------------------------
2133 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
2134 // encountered.  Helper for check_safepts.
2135 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
2136   assert(stack.size() == 0, "empty stack");
2137   stack.push(_tail);
2138   visited.clear();
2139   visited.set(_tail->_idx);
2140   while (stack.size() > 0) {
2141     Node* n = stack.pop();
2142     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2143       // Terminate this path
2144     } else if (n->Opcode() == Op_SafePoint) {
2145       if (_phase->get_loop(n) != this) {
2146         if (_required_safept == NULL) _required_safept = new Node_List();
2147         _required_safept->push(n);  // save the one closest to the tail
2148       }
2149       // Terminate this path
2150     } else {
2151       uint start = n->is_Region() ? 1 : 0;
2152       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
2153       for (uint i = start; i < end; i++) {
2154         Node* in = n->in(i);
2155         assert(in->is_CFG(), "must be");
2156         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
2157           stack.push(in);
2158         }
2159       }
2160     }
2161   }
2162 }
2163 
2164 //------------------------------check_safepts----------------------------
2165 // Given dominators, try to find loops with calls that must always be
2166 // executed (call dominates loop tail).  These loops do not need non-call
2167 // safepoints (ncsfpt).
2168 //
2169 // A complication is that a safepoint in a inner loop may be needed
2170 // by an outer loop. In the following, the inner loop sees it has a
2171 // call (block 3) on every path from the head (block 2) to the
2172 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
2173 // in block 2, _but_ this leaves the outer loop without a safepoint.
2174 //
2175 //          entry  0
2176 //                 |
2177 //                 v
2178 // outer 1,2    +->1
2179 //              |  |
2180 //              |  v
2181 //              |  2<---+  ncsfpt in 2
2182 //              |_/|\   |
2183 //                 | v  |
2184 // inner 2,3      /  3  |  call in 3
2185 //               /   |  |
2186 //              v    +--+
2187 //        exit  4
2188 //
2189 //
2190 // This method creates a list (_required_safept) of ncsfpt nodes that must
2191 // be protected is created for each loop. When a ncsfpt maybe deleted, it
2192 // is first looked for in the lists for the outer loops of the current loop.
2193 //
2194 // The insights into the problem:
2195 //  A) counted loops are okay
2196 //  B) innermost loops are okay (only an inner loop can delete
2197 //     a ncsfpt needed by an outer loop)
2198 //  C) a loop is immune from an inner loop deleting a safepoint
2199 //     if the loop has a call on the idom-path
2200 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
2201 //     idom-path that is not in a nested loop
2202 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
2203 //     loop needs to be prevented from deletion by an inner loop
2204 //
2205 // There are two analyses:
2206 //  1) The first, and cheaper one, scans the loop body from
2207 //     tail to head following the idom (immediate dominator)
2208 //     chain, looking for the cases (C,D,E) above.
2209 //     Since inner loops are scanned before outer loops, there is summary
2210 //     information about inner loops.  Inner loops can be skipped over
2211 //     when the tail of an inner loop is encountered.
2212 //
2213 //  2) The second, invoked if the first fails to find a call or ncsfpt on
2214 //     the idom path (which is rare), scans all predecessor control paths
2215 //     from the tail to the head, terminating a path when a call or sfpt
2216 //     is encountered, to find the ncsfpt's that are closest to the tail.
2217 //
2218 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
2219   // Bottom up traversal
2220   IdealLoopTree* ch = _child;
2221   if (_child) _child->check_safepts(visited, stack);
2222   if (_next)  _next ->check_safepts(visited, stack);
2223 
2224   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
2225     bool  has_call         = false; // call on dom-path
2226     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
2227     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
2228     // Scan the dom-path nodes from tail to head
2229     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
2230       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2231         has_call = true;
2232         _has_sfpt = 1;          // Then no need for a safept!
2233         break;
2234       } else if (n->Opcode() == Op_SafePoint) {
2235         if (_phase->get_loop(n) == this) {
2236           has_local_ncsfpt = true;
2237           break;
2238         }
2239         if (nonlocal_ncsfpt == NULL) {
2240           nonlocal_ncsfpt = n; // save the one closest to the tail
2241         }
2242       } else {
2243         IdealLoopTree* nlpt = _phase->get_loop(n);
2244         if (this != nlpt) {
2245           // If at an inner loop tail, see if the inner loop has already
2246           // recorded seeing a call on the dom-path (and stop.)  If not,
2247           // jump to the head of the inner loop.
2248           assert(is_member(nlpt), "nested loop");
2249           Node* tail = nlpt->_tail;
2250           if (tail->in(0)->is_If()) tail = tail->in(0);
2251           if (n == tail) {
2252             // If inner loop has call on dom-path, so does outer loop
2253             if (nlpt->_has_sfpt) {
2254               has_call = true;
2255               _has_sfpt = 1;
2256               break;
2257             }
2258             // Skip to head of inner loop
2259             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
2260             n = nlpt->_head;
2261           }
2262         }
2263       }
2264     }
2265     // Record safept's that this loop needs preserved when an
2266     // inner loop attempts to delete it's safepoints.
2267     if (_child != NULL && !has_call && !has_local_ncsfpt) {
2268       if (nonlocal_ncsfpt != NULL) {
2269         if (_required_safept == NULL) _required_safept = new Node_List();
2270         _required_safept->push(nonlocal_ncsfpt);
2271       } else {
2272         // Failed to find a suitable safept on the dom-path.  Now use
2273         // an all paths walk from tail to head, looking for safepoints to preserve.
2274         allpaths_check_safepts(visited, stack);
2275       }
2276     }
2277   }
2278 }
2279 
2280 //---------------------------is_deleteable_safept----------------------------
2281 // Is safept not required by an outer loop?
2282 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
2283   assert(sfpt->Opcode() == Op_SafePoint, "");
2284   IdealLoopTree* lp = get_loop(sfpt)->_parent;
2285   while (lp != NULL) {
2286     Node_List* sfpts = lp->_required_safept;
2287     if (sfpts != NULL) {
2288       for (uint i = 0; i < sfpts->size(); i++) {
2289         if (sfpt == sfpts->at(i))
2290           return false;
2291       }
2292     }
2293     lp = lp->_parent;
2294   }
2295   return true;
2296 }
2297 
2298 //---------------------------replace_parallel_iv-------------------------------
2299 // Replace parallel induction variable (parallel to trip counter)
2300 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
2301   assert(loop->_head->is_CountedLoop(), "");
2302   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2303   if (!cl->is_valid_counted_loop())
2304     return;         // skip malformed counted loop
2305   Node *incr = cl->incr();
2306   if (incr == NULL)
2307     return;         // Dead loop?
2308   Node *init = cl->init_trip();
2309   Node *phi  = cl->phi();
2310   int stride_con = cl->stride_con();
2311 
2312   // Visit all children, looking for Phis
2313   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
2314     Node *out = cl->out(i);
2315     // Look for other phis (secondary IVs). Skip dead ones
2316     if (!out->is_Phi() || out == phi || !has_node(out))
2317       continue;
2318     PhiNode* phi2 = out->as_Phi();
2319     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
2320     // Look for induction variables of the form:  X += constant
2321     if (phi2->region() != loop->_head ||
2322         incr2->req() != 3 ||
2323         incr2->in(1) != phi2 ||
2324         incr2 == incr ||
2325         incr2->Opcode() != Op_AddI ||
2326         !incr2->in(2)->is_Con())
2327       continue;
2328 
2329     // Check for parallel induction variable (parallel to trip counter)
2330     // via an affine function.  In particular, count-down loops with
2331     // count-up array indices are common. We only RCE references off
2332     // the trip-counter, so we need to convert all these to trip-counter
2333     // expressions.
2334     Node *init2 = phi2->in( LoopNode::EntryControl );
2335     int stride_con2 = incr2->in(2)->get_int();
2336 
2337     // The ratio of the two strides cannot be represented as an int
2338     // if stride_con2 is min_int and stride_con is -1.
2339     if (stride_con2 == min_jint && stride_con == -1) {
2340       continue;
2341     }
2342 
2343     // The general case here gets a little tricky.  We want to find the
2344     // GCD of all possible parallel IV's and make a new IV using this
2345     // GCD for the loop.  Then all possible IVs are simple multiples of
2346     // the GCD.  In practice, this will cover very few extra loops.
2347     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
2348     // where +/-1 is the common case, but other integer multiples are
2349     // also easy to handle.
2350     int ratio_con = stride_con2/stride_con;
2351 
2352     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
2353 #ifndef PRODUCT
2354       if (TraceLoopOpts) {
2355         tty->print("Parallel IV: %d ", phi2->_idx);
2356         loop->dump_head();
2357       }
2358 #endif
2359       // Convert to using the trip counter.  The parallel induction
2360       // variable differs from the trip counter by a loop-invariant
2361       // amount, the difference between their respective initial values.
2362       // It is scaled by the 'ratio_con'.
2363       Node* ratio = _igvn.intcon(ratio_con);
2364       set_ctrl(ratio, C->root());
2365       Node* ratio_init = new MulINode(init, ratio);
2366       _igvn.register_new_node_with_optimizer(ratio_init, init);
2367       set_early_ctrl(ratio_init);
2368       Node* diff = new SubINode(init2, ratio_init);
2369       _igvn.register_new_node_with_optimizer(diff, init2);
2370       set_early_ctrl(diff);
2371       Node* ratio_idx = new MulINode(phi, ratio);
2372       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
2373       set_ctrl(ratio_idx, cl);
2374       Node* add = new AddINode(ratio_idx, diff);
2375       _igvn.register_new_node_with_optimizer(add);
2376       set_ctrl(add, cl);
2377       _igvn.replace_node( phi2, add );
2378       // Sometimes an induction variable is unused
2379       if (add->outcnt() == 0) {
2380         _igvn.remove_dead_node(add);
2381       }
2382       --i; // deleted this phi; rescan starting with next position
2383       continue;
2384     }
2385   }
2386 }
2387 
2388 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
2389   Node* keep = NULL;
2390   if (keep_one) {
2391     // Look for a safepoint on the idom-path.
2392     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
2393       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
2394         keep = i;
2395         break; // Found one
2396       }
2397     }
2398   }
2399 
2400   // Don't remove any safepoints if it is requested to keep a single safepoint and
2401   // no safepoint was found on idom-path. It is not safe to remove any safepoint
2402   // in this case since there's no safepoint dominating all paths in the loop body.
2403   bool prune = !keep_one || keep != NULL;
2404 
2405   // Delete other safepoints in this loop.
2406   Node_List* sfpts = _safepts;
2407   if (prune && sfpts != NULL) {
2408     assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
2409     for (uint i = 0; i < sfpts->size(); i++) {
2410       Node* n = sfpts->at(i);
2411       assert(phase->get_loop(n) == this, "");
2412       if (n != keep && phase->is_deleteable_safept(n)) {
2413         phase->lazy_replace(n, n->in(TypeFunc::Control));
2414       }
2415     }
2416   }
2417 }
2418 
2419 //------------------------------counted_loop-----------------------------------
2420 // Convert to counted loops where possible
2421 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
2422 
2423   // For grins, set the inner-loop flag here
2424   if (!_child) {
2425     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
2426   }
2427 
2428   IdealLoopTree* loop = this;
2429   if (_head->is_CountedLoop() ||
2430       phase->is_counted_loop(_head, loop)) {
2431 
2432     if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) {
2433       // Indicate we do not need a safepoint here
2434       _has_sfpt = 1;
2435     }
2436 
2437     // Remove safepoints
2438     bool keep_one_sfpt = !(_has_call || _has_sfpt);
2439     remove_safepoints(phase, keep_one_sfpt);
2440 
2441     // Look for induction variables
2442     phase->replace_parallel_iv(this);
2443 
2444   } else if (_parent != NULL && !_irreducible) {
2445     // Not a counted loop. Keep one safepoint.
2446     bool keep_one_sfpt = true;
2447     remove_safepoints(phase, keep_one_sfpt);
2448   }
2449 
2450   // Recursively
2451   assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
2452   assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops");
2453   if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
2454   if (loop->_next)  loop->_next ->counted_loop(phase);
2455 }
2456 
2457 
2458 // The Estimated Loop Clone Size:
2459 //   CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
2460 // where  BC and  CC are  totally ad-hoc/magic  "body" and "clone" constants,
2461 // respectively, used to ensure that the node usage estimates made are on the
2462 // safe side, for the most part. The FanOutTerm is an attempt to estimate the
2463 // possible additional/excessive nodes generated due to data and control flow
2464 // merging, for edges reaching outside the loop.
2465 uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
2466 
2467   precond(0 < factor && factor < 16);
2468 
2469   uint const bc = 13;
2470   uint const cc = 17;
2471   uint const sz = _body.size() + (_body.size() + 7) / 8;
2472   uint estimate = factor * (sz + bc) + cc;
2473 
2474   assert((estimate - cc) / factor == sz + bc, "overflow");
2475 
2476   return estimate + est_loop_flow_merge_sz();
2477 }
2478 
2479 // The Estimated Loop (full-) Unroll Size:
2480 //   UnrollFactor * (~106% * BodySize) + CC + FanOutTerm,
2481 // where CC is a (totally) ad-hoc/magic "clone" constant, used to ensure that
2482 // node usage estimates made are on the safe side, for the most part. This is
2483 // a "light" version of the loop clone size calculation (above), based on the
2484 // assumption that most of the loop-construct overhead will be unraveled when
2485 // (fully) unrolled. Defined for unroll factors larger or equal to one (>=1),
2486 // including an overflow check and returning UINT_MAX in case of an overflow.
2487 uint IdealLoopTree::est_loop_unroll_sz(uint factor) const {
2488 
2489   precond(factor > 0);
2490 
2491   // Take into account that after unroll conjoined heads and tails will fold.
2492   uint const b0 = _body.size() - EMPTY_LOOP_SIZE;
2493   uint const cc = 7;
2494   uint const sz = b0 + (b0 + 15) / 16;
2495   uint estimate = factor * sz + cc;
2496 
2497   if ((estimate - cc) / factor != sz) {
2498     return UINT_MAX;
2499   }
2500 
2501   return estimate + est_loop_flow_merge_sz();
2502 }
2503 
2504 // Estimate the growth effect (in nodes) of merging control and data flow when
2505 // cloning a loop body, based on the amount of  control and data flow reaching
2506 // outside of the (current) loop body.
2507 uint IdealLoopTree::est_loop_flow_merge_sz() const {
2508 
2509   uint ctrl_edge_out_cnt = 0;
2510   uint data_edge_out_cnt = 0;
2511 
2512   for (uint i = 0; i < _body.size(); i++) {
2513     Node* node = _body.at(i);
2514     uint outcnt = node->outcnt();
2515 
2516     for (uint k = 0; k < outcnt; k++) {
2517       Node* out = node->raw_out(k);
2518       if (out == NULL) continue;
2519       if (out->is_CFG()) {
2520         if (!is_member(_phase->get_loop(out))) {
2521           ctrl_edge_out_cnt++;
2522         }
2523       } else if (_phase->has_ctrl(out)) {
2524         Node* ctrl = _phase->get_ctrl(out);
2525         assert(ctrl != NULL, "must be");
2526         assert(ctrl->is_CFG(), "must be");
2527         if (!is_member(_phase->get_loop(ctrl))) {
2528           data_edge_out_cnt++;
2529         }
2530       }
2531     }
2532   }
2533   // Use data and control count (x2.0) in estimate iff both are > 0. This is
2534   // a rather pessimistic estimate for the most part, in particular for some
2535   // complex loops, but still not enough to capture all loops.
2536   if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
2537     return 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
2538   }
2539   return 0;
2540 }
2541 
2542 #ifndef PRODUCT
2543 //------------------------------dump_head--------------------------------------
2544 // Dump 1 liner for loop header info
2545 void IdealLoopTree::dump_head() const {
2546   tty->sp(2 * _nest);
2547   tty->print("Loop: N%d/N%d ", _head->_idx, _tail->_idx);
2548   if (_irreducible) tty->print(" IRREDUCIBLE");
2549   Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl);
2550   Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
2551   if (predicate != NULL ) {
2552     tty->print(" limit_check");
2553     entry = PhaseIdealLoop::skip_loop_predicates(entry);
2554   }
2555   if (UseProfiledLoopPredicate) {
2556     predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
2557     if (predicate != NULL) {
2558       tty->print(" profile_predicated");
2559       entry = PhaseIdealLoop::skip_loop_predicates(entry);
2560     }
2561   }
2562   if (UseLoopPredicate) {
2563     predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2564     if (predicate != NULL) {
2565       tty->print(" predicated");
2566     }
2567   }
2568   if (_head->is_CountedLoop()) {
2569     CountedLoopNode *cl = _head->as_CountedLoop();
2570     tty->print(" counted");
2571 
2572     Node* init_n = cl->init_trip();
2573     if (init_n  != NULL &&  init_n->is_Con())
2574       tty->print(" [%d,", cl->init_trip()->get_int());
2575     else
2576       tty->print(" [int,");
2577     Node* limit_n = cl->limit();
2578     if (limit_n  != NULL &&  limit_n->is_Con())
2579       tty->print("%d),", cl->limit()->get_int());
2580     else
2581       tty->print("int),");
2582     int stride_con  = cl->stride_con();
2583     if (stride_con > 0) tty->print("+");
2584     tty->print("%d", stride_con);
2585 
2586     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
2587 
2588     if (cl->is_pre_loop ()) tty->print(" pre" );
2589     if (cl->is_main_loop()) tty->print(" main");
2590     if (cl->is_post_loop()) tty->print(" post");
2591     if (cl->is_vectorized_loop()) tty->print(" vector");
2592     if (cl->range_checks_present()) tty->print(" rc ");
2593     if (cl->is_multiversioned()) tty->print(" multi ");
2594   }
2595   if (_has_call) tty->print(" has_call");
2596   if (_has_sfpt) tty->print(" has_sfpt");
2597   if (_rce_candidate) tty->print(" rce");
2598   if (_safepts != NULL && _safepts->size() > 0) {
2599     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
2600   }
2601   if (_required_safept != NULL && _required_safept->size() > 0) {
2602     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
2603   }
2604   if (Verbose) {
2605     tty->print(" body={"); _body.dump_simple(); tty->print(" }");
2606   }
2607   if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
2608     tty->print(" strip_mined");
2609   }
2610   tty->cr();
2611 }
2612 
2613 //------------------------------dump-------------------------------------------
2614 // Dump loops by loop tree
2615 void IdealLoopTree::dump() const {
2616   dump_head();
2617   if (_child) _child->dump();
2618   if (_next)  _next ->dump();
2619 }
2620 
2621 #endif
2622 
2623 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
2624   if (loop == root) {
2625     if (loop->_child != NULL) {
2626       log->begin_head("loop_tree");
2627       log->end_head();
2628       if( loop->_child ) log_loop_tree(root, loop->_child, log);
2629       log->tail("loop_tree");
2630       assert(loop->_next == NULL, "what?");
2631     }
2632   } else {
2633     Node* head = loop->_head;
2634     log->begin_head("loop");
2635     log->print(" idx='%d' ", head->_idx);
2636     if (loop->_irreducible) log->print("irreducible='1' ");
2637     if (head->is_Loop()) {
2638       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
2639       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
2640     }
2641     if (head->is_CountedLoop()) {
2642       CountedLoopNode* cl = head->as_CountedLoop();
2643       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
2644       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
2645       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
2646     }
2647     log->end_head();
2648     if( loop->_child ) log_loop_tree(root, loop->_child, log);
2649     log->tail("loop");
2650     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
2651   }
2652 }
2653 
2654 //---------------------collect_potentially_useful_predicates-----------------------
2655 // Helper function to collect potentially useful predicates to prevent them from
2656 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
2657 void PhaseIdealLoop::collect_potentially_useful_predicates(
2658                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
2659   if (loop->_child) { // child
2660     collect_potentially_useful_predicates(loop->_child, useful_predicates);
2661   }
2662 
2663   // self (only loops that we can apply loop predication may use their predicates)
2664   if (loop->_head->is_Loop() &&
2665       !loop->_irreducible    &&
2666       !loop->tail()->is_top()) {
2667     LoopNode* lpn = loop->_head->as_Loop();
2668     Node* entry = lpn->in(LoopNode::EntryControl);
2669     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2670     if (predicate_proj != NULL) { // right pattern that can be used by loop predication
2671       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2672       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2673       entry = skip_loop_predicates(entry);
2674     }
2675     if (UseProfiledLoopPredicate) {
2676       predicate_proj = find_predicate(entry); // Predicate
2677       if (predicate_proj != NULL) {
2678         useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2679         entry = skip_loop_predicates(entry);
2680       }
2681     }
2682     predicate_proj = find_predicate(entry); // Predicate
2683     if (predicate_proj != NULL) {
2684       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2685     }
2686   }
2687 
2688   if (loop->_next) { // sibling
2689     collect_potentially_useful_predicates(loop->_next, useful_predicates);
2690   }
2691 }
2692 
2693 //------------------------eliminate_useless_predicates-----------------------------
2694 // Eliminate all inserted predicates if they could not be used by loop predication.
2695 // Note: it will also eliminates loop limits check predicate since it also uses
2696 // Opaque1 node (see Parse::add_predicate()).
2697 void PhaseIdealLoop::eliminate_useless_predicates() {
2698   if (C->predicate_count() == 0)
2699     return; // no predicate left
2700 
2701   Unique_Node_List useful_predicates; // to store useful predicates
2702   if (C->has_loops()) {
2703     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2704   }
2705 
2706   for (int i = C->predicate_count(); i > 0; i--) {
2707      Node * n = C->predicate_opaque1_node(i-1);
2708      assert(n->Opcode() == Op_Opaque1, "must be");
2709      if (!useful_predicates.member(n)) { // not in the useful list
2710        _igvn.replace_node(n, n->in(1));
2711      }
2712   }
2713 }
2714 
2715 //------------------------process_expensive_nodes-----------------------------
2716 // Expensive nodes have their control input set to prevent the GVN
2717 // from commoning them and as a result forcing the resulting node to
2718 // be in a more frequent path. Use CFG information here, to change the
2719 // control inputs so that some expensive nodes can be commoned while
2720 // not executed more frequently.
2721 bool PhaseIdealLoop::process_expensive_nodes() {
2722   assert(OptimizeExpensiveOps, "optimization off?");
2723 
2724   // Sort nodes to bring similar nodes together
2725   C->sort_expensive_nodes();
2726 
2727   bool progress = false;
2728 
2729   for (int i = 0; i < C->expensive_count(); ) {
2730     Node* n = C->expensive_node(i);
2731     int start = i;
2732     // Find nodes similar to n
2733     i++;
2734     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2735     int end = i;
2736     // And compare them two by two
2737     for (int j = start; j < end; j++) {
2738       Node* n1 = C->expensive_node(j);
2739       if (is_node_unreachable(n1)) {
2740         continue;
2741       }
2742       for (int k = j+1; k < end; k++) {
2743         Node* n2 = C->expensive_node(k);
2744         if (is_node_unreachable(n2)) {
2745           continue;
2746         }
2747 
2748         assert(n1 != n2, "should be pair of nodes");
2749 
2750         Node* c1 = n1->in(0);
2751         Node* c2 = n2->in(0);
2752 
2753         Node* parent_c1 = c1;
2754         Node* parent_c2 = c2;
2755 
2756         // The call to get_early_ctrl_for_expensive() moves the
2757         // expensive nodes up but stops at loops that are in a if
2758         // branch. See whether we can exit the loop and move above the
2759         // If.
2760         if (c1->is_Loop()) {
2761           parent_c1 = c1->in(1);
2762         }
2763         if (c2->is_Loop()) {
2764           parent_c2 = c2->in(1);
2765         }
2766 
2767         if (parent_c1 == parent_c2) {
2768           _igvn._worklist.push(n1);
2769           _igvn._worklist.push(n2);
2770           continue;
2771         }
2772 
2773         // Look for identical expensive node up the dominator chain.
2774         if (is_dominator(c1, c2)) {
2775           c2 = c1;
2776         } else if (is_dominator(c2, c1)) {
2777           c1 = c2;
2778         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2779                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2780           // Both branches have the same expensive node so move it up
2781           // before the if.
2782           c1 = c2 = idom(parent_c1->in(0));
2783         }
2784         // Do the actual moves
2785         if (n1->in(0) != c1) {
2786           _igvn.hash_delete(n1);
2787           n1->set_req(0, c1);
2788           _igvn.hash_insert(n1);
2789           _igvn._worklist.push(n1);
2790           progress = true;
2791         }
2792         if (n2->in(0) != c2) {
2793           _igvn.hash_delete(n2);
2794           n2->set_req(0, c2);
2795           _igvn.hash_insert(n2);
2796           _igvn._worklist.push(n2);
2797           progress = true;
2798         }
2799       }
2800     }
2801   }
2802 
2803   return progress;
2804 }
2805 
2806 
2807 //=============================================================================
2808 //----------------------------build_and_optimize-------------------------------
2809 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2810 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2811 void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) {
2812   bool do_split_ifs = (mode == LoopOptsDefault);
2813   bool skip_loop_opts = (mode == LoopOptsNone);
2814 
2815   int old_progress = C->major_progress();
2816   uint orig_worklist_size = _igvn._worklist.size();
2817 
2818   // Reset major-progress flag for the driver's heuristics
2819   C->clear_major_progress();
2820 
2821 #ifndef PRODUCT
2822   // Capture for later assert
2823   uint unique = C->unique();
2824   _loop_invokes++;
2825   _loop_work += unique;
2826 #endif
2827 
2828   // True if the method has at least 1 irreducible loop
2829   _has_irreducible_loops = false;
2830 
2831   _created_loop_node = false;
2832 
2833   Arena *a = Thread::current()->resource_area();
2834   VectorSet visited(a);
2835   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2836   _nodes.map(C->unique(), NULL);
2837   memset(_nodes.adr(), 0, wordSize * C->unique());
2838 
2839   // Pre-build the top-level outermost loop tree entry
2840   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2841   // Do not need a safepoint at the top level
2842   _ltree_root->_has_sfpt = 1;
2843 
2844   // Initialize Dominators.
2845   // Checked in clone_loop_predicate() during beautify_loops().
2846   _idom_size = 0;
2847   _idom      = NULL;
2848   _dom_depth = NULL;
2849   _dom_stk   = NULL;
2850 
2851   // Empty pre-order array
2852   allocate_preorders();
2853 
2854   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2855   // IdealLoopTree entries.  Data nodes are NOT walked.
2856   build_loop_tree();
2857   // Check for bailout, and return
2858   if (C->failing()) {
2859     return;
2860   }
2861 
2862   // No loops after all
2863   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2864 
2865   // There should always be an outer loop containing the Root and Return nodes.
2866   // If not, we have a degenerate empty program.  Bail out in this case.
2867   if (!has_node(C->root())) {
2868     if (!_verify_only) {
2869       C->clear_major_progress();
2870       C->record_method_not_compilable("empty program detected during loop optimization");
2871     }
2872     return;
2873   }
2874 
2875   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2876   // Nothing to do, so get out
2877   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only &&
2878     !bs->is_gc_specific_loop_opts_pass(mode);
2879   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2880   bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(mode);
2881   if (stop_early && !do_expensive_nodes) {
2882     _igvn.optimize();           // Cleanup NeverBranches
2883     return;
2884   }
2885 
2886   // Set loop nesting depth
2887   _ltree_root->set_nest( 0 );
2888 
2889   // Split shared headers and insert loop landing pads.
2890   // Do not bother doing this on the Root loop of course.
2891   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2892     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2893     if( _ltree_root->_child->beautify_loops( this ) ) {
2894       // Re-build loop tree!
2895       _ltree_root->_child = NULL;
2896       _nodes.clear();
2897       reallocate_preorders();
2898       build_loop_tree();
2899       // Check for bailout, and return
2900       if (C->failing()) {
2901         return;
2902       }
2903       // Reset loop nesting depth
2904       _ltree_root->set_nest( 0 );
2905 
2906       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2907     }
2908   }
2909 
2910   // Build Dominators for elision of NULL checks & loop finding.
2911   // Since nodes do not have a slot for immediate dominator, make
2912   // a persistent side array for that info indexed on node->_idx.
2913   _idom_size = C->unique();
2914   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2915   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2916   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2917   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2918 
2919   Dominators();
2920 
2921   if (!_verify_only) {
2922     // As a side effect, Dominators removed any unreachable CFG paths
2923     // into RegionNodes.  It doesn't do this test against Root, so
2924     // we do it here.
2925     for( uint i = 1; i < C->root()->req(); i++ ) {
2926       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2927         _igvn.delete_input_of(C->root(), i);
2928         i--;                      // Rerun same iteration on compressed edges
2929       }
2930     }
2931 
2932     // Given dominators, try to find inner loops with calls that must
2933     // always be executed (call dominates loop tail).  These loops do
2934     // not need a separate safepoint.
2935     Node_List cisstack(a);
2936     _ltree_root->check_safepts(visited, cisstack);
2937   }
2938 
2939   // Walk the DATA nodes and place into loops.  Find earliest control
2940   // node.  For CFG nodes, the _nodes array starts out and remains
2941   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2942   // _nodes array holds the earliest legal controlling CFG node.
2943 
2944   // Allocate stack with enough space to avoid frequent realloc
2945   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2946   Node_Stack nstack( a, stack_size );
2947 
2948   visited.clear();
2949   Node_List worklist(a);
2950   // Don't need C->root() on worklist since
2951   // it will be processed among C->top() inputs
2952   worklist.push(C->top());
2953   visited.set(C->top()->_idx); // Set C->top() as visited now
2954   build_loop_early( visited, worklist, nstack );
2955 
2956   // Given early legal placement, try finding counted loops.  This placement
2957   // is good enough to discover most loop invariants.
2958   if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
2959     _ltree_root->counted_loop( this );
2960   }
2961 
2962   // Find latest loop placement.  Find ideal loop placement.
2963   visited.clear();
2964   init_dom_lca_tags();
2965   // Need C->root() on worklist when processing outs
2966   worklist.push(C->root());
2967   NOT_PRODUCT( C->verify_graph_edges(); )
2968   worklist.push(C->top());
2969   build_loop_late( visited, worklist, nstack );
2970 
2971   if (_verify_only) {
2972     C->restore_major_progress(old_progress);
2973     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2974     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2975     return;
2976   }
2977 
2978   // clear out the dead code after build_loop_late
2979   while (_deadlist.size()) {
2980     _igvn.remove_globally_dead_node(_deadlist.pop());
2981   }
2982 
2983   if (stop_early) {
2984     assert(do_expensive_nodes, "why are we here?");
2985     if (process_expensive_nodes()) {
2986       // If we made some progress when processing expensive nodes then
2987       // the IGVN may modify the graph in a way that will allow us to
2988       // make some more progress: we need to try processing expensive
2989       // nodes again.
2990       C->set_major_progress();
2991     }
2992     _igvn.optimize();
2993     return;
2994   }
2995 
2996   // Some parser-inserted loop predicates could never be used by loop
2997   // predication or they were moved away from loop during some optimizations.
2998   // For example, peeling. Eliminate them before next loop optimizations.
2999   eliminate_useless_predicates();
3000 
3001 #ifndef PRODUCT
3002   C->verify_graph_edges();
3003   if (_verify_me) {             // Nested verify pass?
3004     // Check to see if the verify mode is broken
3005     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
3006     return;
3007   }
3008   if (VerifyLoopOptimizations) verify();
3009   if (TraceLoopOpts && C->has_loops()) {
3010     _ltree_root->dump();
3011   }
3012 #endif
3013 
3014   if (skip_loop_opts) {
3015     // restore major progress flag
3016     C->restore_major_progress(old_progress);
3017 
3018     // Cleanup any modified bits
3019     _igvn.optimize();
3020 
3021     if (C->log() != NULL) {
3022       log_loop_tree(_ltree_root, _ltree_root, C->log());
3023     }
3024     return;
3025   }
3026 
3027   if (mode == LoopOptsMaxUnroll) {
3028     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3029       IdealLoopTree* lpt = iter.current();
3030       if (lpt->is_innermost() && lpt->_allow_optimizations && !lpt->_has_call && lpt->is_counted()) {
3031         lpt->compute_trip_count(this);
3032         if (!lpt->do_one_iteration_loop(this) &&
3033             !lpt->do_remove_empty_loop(this)) {
3034           AutoNodeBudget node_budget(this);
3035           if (lpt->_head->as_CountedLoop()->is_normal_loop() &&
3036               lpt->policy_maximally_unroll(this)) {
3037             memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3038             do_maximally_unroll(lpt, worklist);
3039           }
3040         }
3041       }
3042     }
3043 
3044     C->restore_major_progress(old_progress);
3045 
3046     _igvn.optimize();
3047 
3048     if (C->log() != NULL) {
3049       log_loop_tree(_ltree_root, _ltree_root, C->log());
3050     }
3051     return;
3052   }
3053 
3054   if (bs->optimize_loops(this, mode, visited, nstack, worklist)) {
3055     _igvn.optimize();
3056     if (C->log() != NULL) {
3057       log_loop_tree(_ltree_root, _ltree_root, C->log());
3058     }
3059     return;
3060   }
3061 
3062   if (ReassociateInvariants) {
3063     // Reassociate invariants and prep for split_thru_phi
3064     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3065       IdealLoopTree* lpt = iter.current();
3066       bool is_counted = lpt->is_counted();
3067       if (!is_counted || !lpt->is_innermost()) continue;
3068 
3069       // check for vectorized loops, any reassociation of invariants was already done
3070       if (is_counted && lpt->_head->as_CountedLoop()->is_unroll_only()) {
3071         continue;
3072       } else {
3073         AutoNodeBudget node_budget(this);
3074         lpt->reassociate_invariants(this);
3075       }
3076       // Because RCE opportunities can be masked by split_thru_phi,
3077       // look for RCE candidates and inhibit split_thru_phi
3078       // on just their loop-phi's for this pass of loop opts
3079       if (SplitIfBlocks && do_split_ifs) {
3080         AutoNodeBudget node_budget(this, AutoNodeBudget::NO_BUDGET_CHECK);
3081         if (lpt->policy_range_check(this)) {
3082           lpt->_rce_candidate = 1; // = true
3083         }
3084       }
3085     }
3086   }
3087 
3088   // Check for aggressive application of split-if and other transforms
3089   // that require basic-block info (like cloning through Phi's)
3090   if( SplitIfBlocks && do_split_ifs ) {
3091     visited.clear();
3092     split_if_with_blocks( visited, nstack);
3093     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
3094   }
3095 
3096   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
3097     C->set_major_progress();
3098   }
3099 
3100   // Perform loop predication before iteration splitting
3101   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
3102     _ltree_root->_child->loop_predication(this);
3103   }
3104 
3105   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
3106     if (do_intrinsify_fill()) {
3107       C->set_major_progress();
3108     }
3109   }
3110 
3111   // Perform iteration-splitting on inner loops.  Split iterations to avoid
3112   // range checks or one-shot null checks.
3113 
3114   // If split-if's didn't hack the graph too bad (no CFG changes)
3115   // then do loop opts.
3116   if (C->has_loops() && !C->major_progress()) {
3117     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3118     _ltree_root->_child->iteration_split( this, worklist );
3119     // No verify after peeling!  GCM has hoisted code out of the loop.
3120     // After peeling, the hoisted code could sink inside the peeled area.
3121     // The peeling code does not try to recompute the best location for
3122     // all the code before the peeled area, so the verify pass will always
3123     // complain about it.
3124   }
3125   // Do verify graph edges in any case
3126   NOT_PRODUCT( C->verify_graph_edges(); );
3127 
3128   if (!do_split_ifs) {
3129     // We saw major progress in Split-If to get here.  We forced a
3130     // pass with unrolling and not split-if, however more split-if's
3131     // might make progress.  If the unrolling didn't make progress
3132     // then the major-progress flag got cleared and we won't try
3133     // another round of Split-If.  In particular the ever-common
3134     // instance-of/check-cast pattern requires at least 2 rounds of
3135     // Split-If to clear out.
3136     C->set_major_progress();
3137   }
3138 
3139   // Repeat loop optimizations if new loops were seen
3140   if (created_loop_node()) {
3141     C->set_major_progress();
3142   }
3143 
3144   // Keep loop predicates and perform optimizations with them
3145   // until no more loop optimizations could be done.
3146   // After that switch predicates off and do more loop optimizations.
3147   if (!C->major_progress() && (C->predicate_count() > 0)) {
3148      C->cleanup_loop_predicates(_igvn);
3149      if (TraceLoopOpts) {
3150        tty->print_cr("PredicatesOff");
3151      }
3152      C->set_major_progress();
3153   }
3154 
3155   // Convert scalar to superword operations at the end of all loop opts.
3156   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
3157     // SuperWord transform
3158     SuperWord sw(this);
3159     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3160       IdealLoopTree* lpt = iter.current();
3161       if (lpt->is_counted()) {
3162         CountedLoopNode *cl = lpt->_head->as_CountedLoop();
3163 
3164         if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
3165           // Check that the rce'd post loop is encountered first, multiversion after all
3166           // major main loop optimization are concluded
3167           if (!C->major_progress()) {
3168             IdealLoopTree *lpt_next = lpt->_next;
3169             if (lpt_next && lpt_next->is_counted()) {
3170               CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
3171               has_range_checks(lpt_next);
3172               if (cl->is_post_loop() && cl->range_checks_present()) {
3173                 if (!cl->is_multiversioned()) {
3174                   if (multi_version_post_loops(lpt, lpt_next) == false) {
3175                     // Cause the rce loop to be optimized away if we fail
3176                     cl->mark_is_multiversioned();
3177                     cl->set_slp_max_unroll(0);
3178                     poison_rce_post_loop(lpt);
3179                   }
3180                 }
3181               }
3182             }
3183             sw.transform_loop(lpt, true);
3184           }
3185         } else if (cl->is_main_loop()) {
3186           sw.transform_loop(lpt, true);
3187         }
3188       }
3189     }
3190   }
3191 
3192   // Cleanup any modified bits
3193   _igvn.optimize();
3194 
3195   // disable assert until issue with split_flow_path is resolved (6742111)
3196   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
3197   //        "shouldn't introduce irreducible loops");
3198 
3199   if (C->log() != NULL) {
3200     log_loop_tree(_ltree_root, _ltree_root, C->log());
3201   }
3202 }
3203 
3204 #ifndef PRODUCT
3205 //------------------------------print_statistics-------------------------------
3206 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
3207 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
3208 void PhaseIdealLoop::print_statistics() {
3209   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
3210 }
3211 
3212 //------------------------------verify-----------------------------------------
3213 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
3214 static int fail;                // debug only, so its multi-thread dont care
3215 void PhaseIdealLoop::verify() const {
3216   int old_progress = C->major_progress();
3217   ResourceMark rm;
3218   PhaseIdealLoop loop_verify( _igvn, this );
3219   VectorSet visited(Thread::current()->resource_area());
3220 
3221   fail = 0;
3222   verify_compare( C->root(), &loop_verify, visited );
3223   assert( fail == 0, "verify loops failed" );
3224   // Verify loop structure is the same
3225   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
3226   // Reset major-progress.  It was cleared by creating a verify version of
3227   // PhaseIdealLoop.
3228   C->restore_major_progress(old_progress);
3229 }
3230 
3231 //------------------------------verify_compare---------------------------------
3232 // Make sure me and the given PhaseIdealLoop agree on key data structures
3233 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
3234   if( !n ) return;
3235   if( visited.test_set( n->_idx ) ) return;
3236   if( !_nodes[n->_idx] ) {      // Unreachable
3237     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
3238     return;
3239   }
3240 
3241   uint i;
3242   for( i = 0; i < n->req(); i++ )
3243     verify_compare( n->in(i), loop_verify, visited );
3244 
3245   // Check the '_nodes' block/loop structure
3246   i = n->_idx;
3247   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
3248     if( _nodes[i] != loop_verify->_nodes[i] &&
3249         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
3250       tty->print("Mismatched control setting for: ");
3251       n->dump();
3252       if( fail++ > 10 ) return;
3253       Node *c = get_ctrl_no_update(n);
3254       tty->print("We have it as: ");
3255       if( c->in(0) ) c->dump();
3256         else tty->print_cr("N%d",c->_idx);
3257       tty->print("Verify thinks: ");
3258       if( loop_verify->has_ctrl(n) )
3259         loop_verify->get_ctrl_no_update(n)->dump();
3260       else
3261         loop_verify->get_loop_idx(n)->dump();
3262       tty->cr();
3263     }
3264   } else {                    // We have a loop
3265     IdealLoopTree *us = get_loop_idx(n);
3266     if( loop_verify->has_ctrl(n) ) {
3267       tty->print("Mismatched loop setting for: ");
3268       n->dump();
3269       if( fail++ > 10 ) return;
3270       tty->print("We have it as: ");
3271       us->dump();
3272       tty->print("Verify thinks: ");
3273       loop_verify->get_ctrl_no_update(n)->dump();
3274       tty->cr();
3275     } else if (!C->major_progress()) {
3276       // Loop selection can be messed up if we did a major progress
3277       // operation, like split-if.  Do not verify in that case.
3278       IdealLoopTree *them = loop_verify->get_loop_idx(n);
3279       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
3280         tty->print("Unequals loops for: ");
3281         n->dump();
3282         if( fail++ > 10 ) return;
3283         tty->print("We have it as: ");
3284         us->dump();
3285         tty->print("Verify thinks: ");
3286         them->dump();
3287         tty->cr();
3288       }
3289     }
3290   }
3291 
3292   // Check for immediate dominators being equal
3293   if( i >= _idom_size ) {
3294     if( !n->is_CFG() ) return;
3295     tty->print("CFG Node with no idom: ");
3296     n->dump();
3297     return;
3298   }
3299   if( !n->is_CFG() ) return;
3300   if( n == C->root() ) return; // No IDOM here
3301 
3302   assert(n->_idx == i, "sanity");
3303   Node *id = idom_no_update(n);
3304   if( id != loop_verify->idom_no_update(n) ) {
3305     tty->print("Unequals idoms for: ");
3306     n->dump();
3307     if( fail++ > 10 ) return;
3308     tty->print("We have it as: ");
3309     id->dump();
3310     tty->print("Verify thinks: ");
3311     loop_verify->idom_no_update(n)->dump();
3312     tty->cr();
3313   }
3314 
3315 }
3316 
3317 //------------------------------verify_tree------------------------------------
3318 // Verify that tree structures match.  Because the CFG can change, siblings
3319 // within the loop tree can be reordered.  We attempt to deal with that by
3320 // reordering the verify's loop tree if possible.
3321 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
3322   assert( _parent == parent, "Badly formed loop tree" );
3323 
3324   // Siblings not in same order?  Attempt to re-order.
3325   if( _head != loop->_head ) {
3326     // Find _next pointer to update
3327     IdealLoopTree **pp = &loop->_parent->_child;
3328     while( *pp != loop )
3329       pp = &((*pp)->_next);
3330     // Find proper sibling to be next
3331     IdealLoopTree **nn = &loop->_next;
3332     while( (*nn) && (*nn)->_head != _head )
3333       nn = &((*nn)->_next);
3334 
3335     // Check for no match.
3336     if( !(*nn) ) {
3337       // Annoyingly, irreducible loops can pick different headers
3338       // after a major_progress operation, so the rest of the loop
3339       // tree cannot be matched.
3340       if (_irreducible && Compile::current()->major_progress())  return;
3341       assert( 0, "failed to match loop tree" );
3342     }
3343 
3344     // Move (*nn) to (*pp)
3345     IdealLoopTree *hit = *nn;
3346     *nn = hit->_next;
3347     hit->_next = loop;
3348     *pp = loop;
3349     loop = hit;
3350     // Now try again to verify
3351   }
3352 
3353   assert( _head  == loop->_head , "mismatched loop head" );
3354   Node *tail = _tail;           // Inline a non-updating version of
3355   while( !tail->in(0) )         // the 'tail()' call.
3356     tail = tail->in(1);
3357   assert( tail == loop->_tail, "mismatched loop tail" );
3358 
3359   // Counted loops that are guarded should be able to find their guards
3360   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
3361     CountedLoopNode *cl = _head->as_CountedLoop();
3362     Node *init = cl->init_trip();
3363     Node *ctrl = cl->in(LoopNode::EntryControl);
3364     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
3365     Node *iff  = ctrl->in(0);
3366     assert( iff->Opcode() == Op_If, "" );
3367     Node *bol  = iff->in(1);
3368     assert( bol->Opcode() == Op_Bool, "" );
3369     Node *cmp  = bol->in(1);
3370     assert( cmp->Opcode() == Op_CmpI, "" );
3371     Node *add  = cmp->in(1);
3372     Node *opaq;
3373     if( add->Opcode() == Op_Opaque1 ) {
3374       opaq = add;
3375     } else {
3376       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
3377       assert( add == init, "" );
3378       opaq = cmp->in(2);
3379     }
3380     assert( opaq->Opcode() == Op_Opaque1, "" );
3381 
3382   }
3383 
3384   if (_child != NULL)  _child->verify_tree(loop->_child, this);
3385   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
3386   // Innermost loops need to verify loop bodies,
3387   // but only if no 'major_progress'
3388   int fail = 0;
3389   if (!Compile::current()->major_progress() && _child == NULL) {
3390     for( uint i = 0; i < _body.size(); i++ ) {
3391       Node *n = _body.at(i);
3392       if (n->outcnt() == 0)  continue; // Ignore dead
3393       uint j;
3394       for( j = 0; j < loop->_body.size(); j++ )
3395         if( loop->_body.at(j) == n )
3396           break;
3397       if( j == loop->_body.size() ) { // Not found in loop body
3398         // Last ditch effort to avoid assertion: Its possible that we
3399         // have some users (so outcnt not zero) but are still dead.
3400         // Try to find from root.
3401         if (Compile::current()->root()->find(n->_idx)) {
3402           fail++;
3403           tty->print("We have that verify does not: ");
3404           n->dump();
3405         }
3406       }
3407     }
3408     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
3409       Node *n = loop->_body.at(i2);
3410       if (n->outcnt() == 0)  continue; // Ignore dead
3411       uint j;
3412       for( j = 0; j < _body.size(); j++ )
3413         if( _body.at(j) == n )
3414           break;
3415       if( j == _body.size() ) { // Not found in loop body
3416         // Last ditch effort to avoid assertion: Its possible that we
3417         // have some users (so outcnt not zero) but are still dead.
3418         // Try to find from root.
3419         if (Compile::current()->root()->find(n->_idx)) {
3420           fail++;
3421           tty->print("Verify has that we do not: ");
3422           n->dump();
3423         }
3424       }
3425     }
3426     assert( !fail, "loop body mismatch" );
3427   }
3428 }
3429 
3430 #endif
3431 
3432 //------------------------------set_idom---------------------------------------
3433 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
3434   uint idx = d->_idx;
3435   if (idx >= _idom_size) {
3436     uint newsize = next_power_of_2(idx);
3437     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
3438     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
3439     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
3440     _idom_size = newsize;
3441   }
3442   _idom[idx] = n;
3443   _dom_depth[idx] = dom_depth;
3444 }
3445 
3446 //------------------------------recompute_dom_depth---------------------------------------
3447 // The dominator tree is constructed with only parent pointers.
3448 // This recomputes the depth in the tree by first tagging all
3449 // nodes as "no depth yet" marker.  The next pass then runs up
3450 // the dom tree from each node marked "no depth yet", and computes
3451 // the depth on the way back down.
3452 void PhaseIdealLoop::recompute_dom_depth() {
3453   uint no_depth_marker = C->unique();
3454   uint i;
3455   // Initialize depth to "no depth yet" and realize all lazy updates
3456   for (i = 0; i < _idom_size; i++) {
3457     // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized).
3458     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
3459       _dom_depth[i] = no_depth_marker;
3460 
3461       // heal _idom if it has a fwd mapping in _nodes
3462       if (_idom[i]->in(0) == NULL) {
3463         idom(i);
3464       }
3465     }
3466   }
3467   if (_dom_stk == NULL) {
3468     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
3469     if (init_size < 10) init_size = 10;
3470     _dom_stk = new GrowableArray<uint>(init_size);
3471   }
3472   // Compute new depth for each node.
3473   for (i = 0; i < _idom_size; i++) {
3474     uint j = i;
3475     // Run up the dom tree to find a node with a depth
3476     while (_dom_depth[j] == no_depth_marker) {
3477       _dom_stk->push(j);
3478       j = _idom[j]->_idx;
3479     }
3480     // Compute the depth on the way back down this tree branch
3481     uint dd = _dom_depth[j] + 1;
3482     while (_dom_stk->length() > 0) {
3483       uint j = _dom_stk->pop();
3484       _dom_depth[j] = dd;
3485       dd++;
3486     }
3487   }
3488 }
3489 
3490 //------------------------------sort-------------------------------------------
3491 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
3492 // loop tree, not the root.
3493 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
3494   if( !innermost ) return loop; // New innermost loop
3495 
3496   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
3497   assert( loop_preorder, "not yet post-walked loop" );
3498   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
3499   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
3500 
3501   // Insert at start of list
3502   while( l ) {                  // Insertion sort based on pre-order
3503     if( l == loop ) return innermost; // Already on list!
3504     int l_preorder = get_preorder(l->_head); // Cache pre-order number
3505     assert( l_preorder, "not yet post-walked l" );
3506     // Check header pre-order number to figure proper nesting
3507     if( loop_preorder > l_preorder )
3508       break;                    // End of insertion
3509     // If headers tie (e.g., shared headers) check tail pre-order numbers.
3510     // Since I split shared headers, you'd think this could not happen.
3511     // BUT: I must first do the preorder numbering before I can discover I
3512     // have shared headers, so the split headers all get the same preorder
3513     // number as the RegionNode they split from.
3514     if( loop_preorder == l_preorder &&
3515         get_preorder(loop->_tail) < get_preorder(l->_tail) )
3516       break;                    // Also check for shared headers (same pre#)
3517     pp = &l->_parent;           // Chain up list
3518     l = *pp;
3519   }
3520   // Link into list
3521   // Point predecessor to me
3522   *pp = loop;
3523   // Point me to successor
3524   IdealLoopTree *p = loop->_parent;
3525   loop->_parent = l;            // Point me to successor
3526   if( p ) sort( p, innermost ); // Insert my parents into list as well
3527   return innermost;
3528 }
3529 
3530 //------------------------------build_loop_tree--------------------------------
3531 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
3532 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
3533 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
3534 // tightest enclosing IdealLoopTree for post-walked.
3535 //
3536 // During my forward walk I do a short 1-layer lookahead to see if I can find
3537 // a loop backedge with that doesn't have any work on the backedge.  This
3538 // helps me construct nested loops with shared headers better.
3539 //
3540 // Once I've done the forward recursion, I do the post-work.  For each child
3541 // I check to see if there is a backedge.  Backedges define a loop!  I
3542 // insert an IdealLoopTree at the target of the backedge.
3543 //
3544 // During the post-work I also check to see if I have several children
3545 // belonging to different loops.  If so, then this Node is a decision point
3546 // where control flow can choose to change loop nests.  It is at this
3547 // decision point where I can figure out how loops are nested.  At this
3548 // time I can properly order the different loop nests from my children.
3549 // Note that there may not be any backedges at the decision point!
3550 //
3551 // Since the decision point can be far removed from the backedges, I can't
3552 // order my loops at the time I discover them.  Thus at the decision point
3553 // I need to inspect loop header pre-order numbers to properly nest my
3554 // loops.  This means I need to sort my childrens' loops by pre-order.
3555 // The sort is of size number-of-control-children, which generally limits
3556 // it to size 2 (i.e., I just choose between my 2 target loops).
3557 void PhaseIdealLoop::build_loop_tree() {
3558   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
3559   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
3560   Node *n = C->root();
3561   bltstack.push(n);
3562   int pre_order = 1;
3563   int stack_size;
3564 
3565   while ( ( stack_size = bltstack.length() ) != 0 ) {
3566     n = bltstack.top(); // Leave node on stack
3567     if ( !is_visited(n) ) {
3568       // ---- Pre-pass Work ----
3569       // Pre-walked but not post-walked nodes need a pre_order number.
3570 
3571       set_preorder_visited( n, pre_order ); // set as visited
3572 
3573       // ---- Scan over children ----
3574       // Scan first over control projections that lead to loop headers.
3575       // This helps us find inner-to-outer loops with shared headers better.
3576 
3577       // Scan children's children for loop headers.
3578       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
3579         Node* m = n->raw_out(i);       // Child
3580         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
3581           // Scan over children's children to find loop
3582           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3583             Node* l = m->fast_out(j);
3584             if( is_visited(l) &&       // Been visited?
3585                 !is_postvisited(l) &&  // But not post-visited
3586                 get_preorder(l) < pre_order ) { // And smaller pre-order
3587               // Found!  Scan the DFS down this path before doing other paths
3588               bltstack.push(m);
3589               break;
3590             }
3591           }
3592         }
3593       }
3594       pre_order++;
3595     }
3596     else if ( !is_postvisited(n) ) {
3597       // Note: build_loop_tree_impl() adds out edges on rare occasions,
3598       // such as com.sun.rsasign.am::a.
3599       // For non-recursive version, first, process current children.
3600       // On next iteration, check if additional children were added.
3601       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
3602         Node* u = n->raw_out(k);
3603         if ( u->is_CFG() && !is_visited(u) ) {
3604           bltstack.push(u);
3605         }
3606       }
3607       if ( bltstack.length() == stack_size ) {
3608         // There were no additional children, post visit node now
3609         (void)bltstack.pop(); // Remove node from stack
3610         pre_order = build_loop_tree_impl( n, pre_order );
3611         // Check for bailout
3612         if (C->failing()) {
3613           return;
3614         }
3615         // Check to grow _preorders[] array for the case when
3616         // build_loop_tree_impl() adds new nodes.
3617         check_grow_preorders();
3618       }
3619     }
3620     else {
3621       (void)bltstack.pop(); // Remove post-visited node from stack
3622     }
3623   }
3624 }
3625 
3626 //------------------------------build_loop_tree_impl---------------------------
3627 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
3628   // ---- Post-pass Work ----
3629   // Pre-walked but not post-walked nodes need a pre_order number.
3630 
3631   // Tightest enclosing loop for this Node
3632   IdealLoopTree *innermost = NULL;
3633 
3634   // For all children, see if any edge is a backedge.  If so, make a loop
3635   // for it.  Then find the tightest enclosing loop for the self Node.
3636   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3637     Node* m = n->fast_out(i);   // Child
3638     if( n == m ) continue;      // Ignore control self-cycles
3639     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
3640 
3641     IdealLoopTree *l;           // Child's loop
3642     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
3643       // Found a backedge
3644       assert( get_preorder(m) < pre_order, "should be backedge" );
3645       // Check for the RootNode, which is already a LoopNode and is allowed
3646       // to have multiple "backedges".
3647       if( m == C->root()) {     // Found the root?
3648         l = _ltree_root;        // Root is the outermost LoopNode
3649       } else {                  // Else found a nested loop
3650         // Insert a LoopNode to mark this loop.
3651         l = new IdealLoopTree(this, m, n);
3652       } // End of Else found a nested loop
3653       if( !has_loop(m) )        // If 'm' does not already have a loop set
3654         set_loop(m, l);         // Set loop header to loop now
3655 
3656     } else {                    // Else not a nested loop
3657       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
3658       l = get_loop(m);          // Get previously determined loop
3659       // If successor is header of a loop (nest), move up-loop till it
3660       // is a member of some outer enclosing loop.  Since there are no
3661       // shared headers (I've split them already) I only need to go up
3662       // at most 1 level.
3663       while( l && l->_head == m ) // Successor heads loop?
3664         l = l->_parent;         // Move up 1 for me
3665       // If this loop is not properly parented, then this loop
3666       // has no exit path out, i.e. its an infinite loop.
3667       if( !l ) {
3668         // Make loop "reachable" from root so the CFG is reachable.  Basically
3669         // insert a bogus loop exit that is never taken.  'm', the loop head,
3670         // points to 'n', one (of possibly many) fall-in paths.  There may be
3671         // many backedges as well.
3672 
3673         // Here I set the loop to be the root loop.  I could have, after
3674         // inserting a bogus loop exit, restarted the recursion and found my
3675         // new loop exit.  This would make the infinite loop a first-class
3676         // loop and it would then get properly optimized.  What's the use of
3677         // optimizing an infinite loop?
3678         l = _ltree_root;        // Oops, found infinite loop
3679 
3680         if (!_verify_only) {
3681           // Insert the NeverBranch between 'm' and it's control user.
3682           NeverBranchNode *iff = new NeverBranchNode( m );
3683           _igvn.register_new_node_with_optimizer(iff);
3684           set_loop(iff, l);
3685           Node *if_t = new CProjNode( iff, 0 );
3686           _igvn.register_new_node_with_optimizer(if_t);
3687           set_loop(if_t, l);
3688 
3689           Node* cfg = NULL;       // Find the One True Control User of m
3690           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3691             Node* x = m->fast_out(j);
3692             if (x->is_CFG() && x != m && x != iff)
3693               { cfg = x; break; }
3694           }
3695           assert(cfg != NULL, "must find the control user of m");
3696           uint k = 0;             // Probably cfg->in(0)
3697           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
3698           cfg->set_req( k, if_t ); // Now point to NeverBranch
3699           _igvn._worklist.push(cfg);
3700 
3701           // Now create the never-taken loop exit
3702           Node *if_f = new CProjNode( iff, 1 );
3703           _igvn.register_new_node_with_optimizer(if_f);
3704           set_loop(if_f, l);
3705           // Find frame ptr for Halt.  Relies on the optimizer
3706           // V-N'ing.  Easier and quicker than searching through
3707           // the program structure.
3708           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
3709           _igvn.register_new_node_with_optimizer(frame);
3710           // Halt & Catch Fire
3711           Node* halt = new HaltNode(if_f, frame, "never-taken loop exit reached");
3712           _igvn.register_new_node_with_optimizer(halt);
3713           set_loop(halt, l);
3714           C->root()->add_req(halt);
3715         }
3716         set_loop(C->root(), _ltree_root);
3717       }
3718     }
3719     // Weeny check for irreducible.  This child was already visited (this
3720     // IS the post-work phase).  Is this child's loop header post-visited
3721     // as well?  If so, then I found another entry into the loop.
3722     if (!_verify_only) {
3723       while( is_postvisited(l->_head) ) {
3724         // found irreducible
3725         l->_irreducible = 1; // = true
3726         l = l->_parent;
3727         _has_irreducible_loops = true;
3728         // Check for bad CFG here to prevent crash, and bailout of compile
3729         if (l == NULL) {
3730           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
3731           return pre_order;
3732         }
3733       }
3734       C->set_has_irreducible_loop(_has_irreducible_loops);
3735     }
3736 
3737     // This Node might be a decision point for loops.  It is only if
3738     // it's children belong to several different loops.  The sort call
3739     // does a trivial amount of work if there is only 1 child or all
3740     // children belong to the same loop.  If however, the children
3741     // belong to different loops, the sort call will properly set the
3742     // _parent pointers to show how the loops nest.
3743     //
3744     // In any case, it returns the tightest enclosing loop.
3745     innermost = sort( l, innermost );
3746   }
3747 
3748   // Def-use info will have some dead stuff; dead stuff will have no
3749   // loop decided on.
3750 
3751   // Am I a loop header?  If so fix up my parent's child and next ptrs.
3752   if( innermost && innermost->_head == n ) {
3753     assert( get_loop(n) == innermost, "" );
3754     IdealLoopTree *p = innermost->_parent;
3755     IdealLoopTree *l = innermost;
3756     while( p && l->_head == n ) {
3757       l->_next = p->_child;     // Put self on parents 'next child'
3758       p->_child = l;            // Make self as first child of parent
3759       l = p;                    // Now walk up the parent chain
3760       p = l->_parent;
3761     }
3762   } else {
3763     // Note that it is possible for a LoopNode to reach here, if the
3764     // backedge has been made unreachable (hence the LoopNode no longer
3765     // denotes a Loop, and will eventually be removed).
3766 
3767     // Record tightest enclosing loop for self.  Mark as post-visited.
3768     set_loop(n, innermost);
3769     // Also record has_call flag early on
3770     if( innermost ) {
3771       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3772         // Do not count uncommon calls
3773         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3774           Node *iff = n->in(0)->in(0);
3775           // No any calls for vectorized loops.
3776           if( UseSuperWord || !iff->is_If() ||
3777               (n->in(0)->Opcode() == Op_IfFalse &&
3778                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3779               (iff->as_If()->_prob >= 0.01) )
3780             innermost->_has_call = 1;
3781         }
3782       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3783         // Disable loop optimizations if the loop has a scalar replaceable
3784         // allocation. This disabling may cause a potential performance lost
3785         // if the allocation is not eliminated for some reason.
3786         innermost->_allow_optimizations = false;
3787         innermost->_has_call = 1; // = true
3788       } else if (n->Opcode() == Op_SafePoint) {
3789         // Record all safepoints in this loop.
3790         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3791         innermost->_safepts->push(n);
3792       }
3793     }
3794   }
3795 
3796   // Flag as post-visited now
3797   set_postvisited(n);
3798   return pre_order;
3799 }
3800 
3801 
3802 //------------------------------build_loop_early-------------------------------
3803 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3804 // First pass computes the earliest controlling node possible.  This is the
3805 // controlling input with the deepest dominating depth.
3806 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3807   while (worklist.size() != 0) {
3808     // Use local variables nstack_top_n & nstack_top_i to cache values
3809     // on nstack's top.
3810     Node *nstack_top_n = worklist.pop();
3811     uint  nstack_top_i = 0;
3812 //while_nstack_nonempty:
3813     while (true) {
3814       // Get parent node and next input's index from stack's top.
3815       Node  *n = nstack_top_n;
3816       uint   i = nstack_top_i;
3817       uint cnt = n->req(); // Count of inputs
3818       if (i == 0) {        // Pre-process the node.
3819         if( has_node(n) &&            // Have either loop or control already?
3820             !has_ctrl(n) ) {          // Have loop picked out already?
3821           // During "merge_many_backedges" we fold up several nested loops
3822           // into a single loop.  This makes the members of the original
3823           // loop bodies pointing to dead loops; they need to move up
3824           // to the new UNION'd larger loop.  I set the _head field of these
3825           // dead loops to NULL and the _parent field points to the owning
3826           // loop.  Shades of UNION-FIND algorithm.
3827           IdealLoopTree *ilt;
3828           while( !(ilt = get_loop(n))->_head ) {
3829             // Normally I would use a set_loop here.  But in this one special
3830             // case, it is legal (and expected) to change what loop a Node
3831             // belongs to.
3832             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3833           }
3834           // Remove safepoints ONLY if I've already seen I don't need one.
3835           // (the old code here would yank a 2nd safepoint after seeing a
3836           // first one, even though the 1st did not dominate in the loop body
3837           // and thus could be avoided indefinitely)
3838           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3839               is_deleteable_safept(n)) {
3840             Node *in = n->in(TypeFunc::Control);
3841             lazy_replace(n,in);       // Pull safepoint now
3842             if (ilt->_safepts != NULL) {
3843               ilt->_safepts->yank(n);
3844             }
3845             // Carry on with the recursion "as if" we are walking
3846             // only the control input
3847             if( !visited.test_set( in->_idx ) ) {
3848               worklist.push(in);      // Visit this guy later, using worklist
3849             }
3850             // Get next node from nstack:
3851             // - skip n's inputs processing by setting i > cnt;
3852             // - we also will not call set_early_ctrl(n) since
3853             //   has_node(n) == true (see the condition above).
3854             i = cnt + 1;
3855           }
3856         }
3857       } // if (i == 0)
3858 
3859       // Visit all inputs
3860       bool done = true;       // Assume all n's inputs will be processed
3861       while (i < cnt) {
3862         Node *in = n->in(i);
3863         ++i;
3864         if (in == NULL) continue;
3865         if (in->pinned() && !in->is_CFG())
3866           set_ctrl(in, in->in(0));
3867         int is_visited = visited.test_set( in->_idx );
3868         if (!has_node(in)) {  // No controlling input yet?
3869           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3870           assert( !is_visited, "visit only once" );
3871           nstack.push(n, i);  // Save parent node and next input's index.
3872           nstack_top_n = in;  // Process current input now.
3873           nstack_top_i = 0;
3874           done = false;       // Not all n's inputs processed.
3875           break; // continue while_nstack_nonempty;
3876         } else if (!is_visited) {
3877           // This guy has a location picked out for him, but has not yet
3878           // been visited.  Happens to all CFG nodes, for instance.
3879           // Visit him using the worklist instead of recursion, to break
3880           // cycles.  Since he has a location already we do not need to
3881           // find his location before proceeding with the current Node.
3882           worklist.push(in);  // Visit this guy later, using worklist
3883         }
3884       }
3885       if (done) {
3886         // All of n's inputs have been processed, complete post-processing.
3887 
3888         // Compute earliest point this Node can go.
3889         // CFG, Phi, pinned nodes already know their controlling input.
3890         if (!has_node(n)) {
3891           // Record earliest legal location
3892           set_early_ctrl( n );
3893         }
3894         if (nstack.is_empty()) {
3895           // Finished all nodes on stack.
3896           // Process next node on the worklist.
3897           break;
3898         }
3899         // Get saved parent node and next input's index.
3900         nstack_top_n = nstack.node();
3901         nstack_top_i = nstack.index();
3902         nstack.pop();
3903       }
3904     } // while (true)
3905   }
3906 }
3907 
3908 //------------------------------dom_lca_internal--------------------------------
3909 // Pair-wise LCA
3910 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3911   if( !n1 ) return n2;          // Handle NULL original LCA
3912   assert( n1->is_CFG(), "" );
3913   assert( n2->is_CFG(), "" );
3914   // find LCA of all uses
3915   uint d1 = dom_depth(n1);
3916   uint d2 = dom_depth(n2);
3917   while (n1 != n2) {
3918     if (d1 > d2) {
3919       n1 =      idom(n1);
3920       d1 = dom_depth(n1);
3921     } else if (d1 < d2) {
3922       n2 =      idom(n2);
3923       d2 = dom_depth(n2);
3924     } else {
3925       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3926       // of the tree might have the same depth.  These sections have
3927       // to be searched more carefully.
3928 
3929       // Scan up all the n1's with equal depth, looking for n2.
3930       Node *t1 = idom(n1);
3931       while (dom_depth(t1) == d1) {
3932         if (t1 == n2)  return n2;
3933         t1 = idom(t1);
3934       }
3935       // Scan up all the n2's with equal depth, looking for n1.
3936       Node *t2 = idom(n2);
3937       while (dom_depth(t2) == d2) {
3938         if (t2 == n1)  return n1;
3939         t2 = idom(t2);
3940       }
3941       // Move up to a new dominator-depth value as well as up the dom-tree.
3942       n1 = t1;
3943       n2 = t2;
3944       d1 = dom_depth(n1);
3945       d2 = dom_depth(n2);
3946     }
3947   }
3948   return n1;
3949 }
3950 
3951 //------------------------------compute_idom-----------------------------------
3952 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3953 // IDOMs are correct.
3954 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3955   assert( region->is_Region(), "" );
3956   Node *LCA = NULL;
3957   for( uint i = 1; i < region->req(); i++ ) {
3958     if( region->in(i) != C->top() )
3959       LCA = dom_lca( LCA, region->in(i) );
3960   }
3961   return LCA;
3962 }
3963 
3964 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3965   bool had_error = false;
3966 #ifdef ASSERT
3967   if (early != C->root()) {
3968     // Make sure that there's a dominance path from LCA to early
3969     Node* d = LCA;
3970     while (d != early) {
3971       if (d == C->root()) {
3972         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3973         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3974         had_error = true;
3975         break;
3976       }
3977       d = idom(d);
3978     }
3979   }
3980 #endif
3981   return had_error;
3982 }
3983 
3984 
3985 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3986   // Compute LCA over list of uses
3987   bool had_error = false;
3988   Node *LCA = NULL;
3989   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3990     Node* c = n->fast_out(i);
3991     if (_nodes[c->_idx] == NULL)
3992       continue;                 // Skip the occasional dead node
3993     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3994       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3995         if( c->in(j) == n ) {   // Found matching input?
3996           Node *use = c->in(0)->in(j);
3997           if (_verify_only && use->is_top()) continue;
3998           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3999           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
4000         }
4001       }
4002     } else {
4003       // For CFG data-users, use is in the block just prior
4004       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
4005       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
4006       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
4007     }
4008   }
4009   assert(!had_error, "bad dominance");
4010   return LCA;
4011 }
4012 
4013 // Check the shape of the graph at the loop entry. In some cases,
4014 // the shape of the graph does not match the shape outlined below.
4015 // That is caused by the Opaque1 node "protecting" the shape of
4016 // the graph being removed by, for example, the IGVN performed
4017 // in PhaseIdealLoop::build_and_optimize().
4018 //
4019 // After the Opaque1 node has been removed, optimizations (e.g., split-if,
4020 // loop unswitching, and IGVN, or a combination of them) can freely change
4021 // the graph's shape. As a result, the graph shape outlined below cannot
4022 // be guaranteed anymore.
4023 bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) {
4024   if (!cl->is_main_loop() && !cl->is_post_loop()) {
4025     return false;
4026   }
4027   Node* ctrl = cl->skip_predicates();
4028 
4029   if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
4030     return false;
4031   }
4032   Node* iffm = ctrl->in(0);
4033   if (iffm == NULL || !iffm->is_If()) {
4034     return false;
4035   }
4036   Node* bolzm = iffm->in(1);
4037   if (bolzm == NULL || !bolzm->is_Bool()) {
4038     return false;
4039   }
4040   Node* cmpzm = bolzm->in(1);
4041   if (cmpzm == NULL || !cmpzm->is_Cmp()) {
4042     return false;
4043   }
4044   // compares can get conditionally flipped
4045   bool found_opaque = false;
4046   for (uint i = 1; i < cmpzm->req(); i++) {
4047     Node* opnd = cmpzm->in(i);
4048     if (opnd && opnd->Opcode() == Op_Opaque1) {
4049       found_opaque = true;
4050       break;
4051     }
4052   }
4053   if (!found_opaque) {
4054     return false;
4055   }
4056   return true;
4057 }
4058 
4059 //------------------------------get_late_ctrl----------------------------------
4060 // Compute latest legal control.
4061 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
4062   assert(early != NULL, "early control should not be NULL");
4063 
4064   Node* LCA = compute_lca_of_uses(n, early);
4065 #ifdef ASSERT
4066   if (LCA == C->root() && LCA != early) {
4067     // def doesn't dominate uses so print some useful debugging output
4068     compute_lca_of_uses(n, early, true);
4069   }
4070 #endif
4071 
4072   // if this is a load, check for anti-dependent stores
4073   // We use a conservative algorithm to identify potential interfering
4074   // instructions and for rescheduling the load.  The users of the memory
4075   // input of this load are examined.  Any use which is not a load and is
4076   // dominated by early is considered a potentially interfering store.
4077   // This can produce false positives.
4078   if (n->is_Load() && LCA != early) {
4079     int load_alias_idx = C->get_alias_index(n->adr_type());
4080     if (C->alias_type(load_alias_idx)->is_rewritable()) {
4081 
4082       Node_List worklist;
4083 
4084       Node *mem = n->in(MemNode::Memory);
4085       for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
4086         Node* s = mem->fast_out(i);
4087         worklist.push(s);
4088       }
4089       while(worklist.size() != 0 && LCA != early) {
4090         Node* s = worklist.pop();
4091         if (s->is_Load() || s->Opcode() == Op_SafePoint ||
4092             (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
4093           continue;
4094         } else if (s->is_MergeMem()) {
4095           for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
4096             Node* s1 = s->fast_out(i);
4097             worklist.push(s1);
4098           }
4099         } else {
4100           Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
4101           const TypePtr* adr_type = s->adr_type();
4102           if (s->is_ArrayCopy()) {
4103             // Copy to known instance needs destination type to test for aliasing
4104             const TypePtr* dest_type = s->as_ArrayCopy()->_dest_type;
4105             if (dest_type != TypeOopPtr::BOTTOM) {
4106               adr_type = dest_type;
4107             }
4108           }
4109           assert(sctrl != NULL || !s->is_reachable_from_root(), "must have control");
4110           if (sctrl != NULL && !sctrl->is_top() && C->can_alias(adr_type, load_alias_idx) && is_dominator(early, sctrl)) {
4111             LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
4112           }
4113         }
4114       }
4115     }
4116   }
4117 
4118   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
4119   return LCA;
4120 }
4121 
4122 // true if CFG node d dominates CFG node n
4123 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
4124   if (d == n)
4125     return true;
4126   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
4127   uint dd = dom_depth(d);
4128   while (dom_depth(n) >= dd) {
4129     if (n == d)
4130       return true;
4131     n = idom(n);
4132   }
4133   return false;
4134 }
4135 
4136 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
4137 // Pair-wise LCA with tags.
4138 // Tag each index with the node 'tag' currently being processed
4139 // before advancing up the dominator chain using idom().
4140 // Later calls that find a match to 'tag' know that this path has already
4141 // been considered in the current LCA (which is input 'n1' by convention).
4142 // Since get_late_ctrl() is only called once for each node, the tag array
4143 // does not need to be cleared between calls to get_late_ctrl().
4144 // Algorithm trades a larger constant factor for better asymptotic behavior
4145 //
4146 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
4147   uint d1 = dom_depth(n1);
4148   uint d2 = dom_depth(n2);
4149 
4150   do {
4151     if (d1 > d2) {
4152       // current lca is deeper than n2
4153       _dom_lca_tags.map(n1->_idx, tag);
4154       n1 =      idom(n1);
4155       d1 = dom_depth(n1);
4156     } else if (d1 < d2) {
4157       // n2 is deeper than current lca
4158       Node *memo = _dom_lca_tags[n2->_idx];
4159       if( memo == tag ) {
4160         return n1;    // Return the current LCA
4161       }
4162       _dom_lca_tags.map(n2->_idx, tag);
4163       n2 =      idom(n2);
4164       d2 = dom_depth(n2);
4165     } else {
4166       // Here d1 == d2.  Due to edits of the dominator-tree, sections
4167       // of the tree might have the same depth.  These sections have
4168       // to be searched more carefully.
4169 
4170       // Scan up all the n1's with equal depth, looking for n2.
4171       _dom_lca_tags.map(n1->_idx, tag);
4172       Node *t1 = idom(n1);
4173       while (dom_depth(t1) == d1) {
4174         if (t1 == n2)  return n2;
4175         _dom_lca_tags.map(t1->_idx, tag);
4176         t1 = idom(t1);
4177       }
4178       // Scan up all the n2's with equal depth, looking for n1.
4179       _dom_lca_tags.map(n2->_idx, tag);
4180       Node *t2 = idom(n2);
4181       while (dom_depth(t2) == d2) {
4182         if (t2 == n1)  return n1;
4183         _dom_lca_tags.map(t2->_idx, tag);
4184         t2 = idom(t2);
4185       }
4186       // Move up to a new dominator-depth value as well as up the dom-tree.
4187       n1 = t1;
4188       n2 = t2;
4189       d1 = dom_depth(n1);
4190       d2 = dom_depth(n2);
4191     }
4192   } while (n1 != n2);
4193   return n1;
4194 }
4195 
4196 //------------------------------init_dom_lca_tags------------------------------
4197 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4198 // Intended use does not involve any growth for the array, so it could
4199 // be of fixed size.
4200 void PhaseIdealLoop::init_dom_lca_tags() {
4201   uint limit = C->unique() + 1;
4202   _dom_lca_tags.map( limit, NULL );
4203 #ifdef ASSERT
4204   for( uint i = 0; i < limit; ++i ) {
4205     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4206   }
4207 #endif // ASSERT
4208 }
4209 
4210 //------------------------------clear_dom_lca_tags------------------------------
4211 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4212 // Intended use does not involve any growth for the array, so it could
4213 // be of fixed size.
4214 void PhaseIdealLoop::clear_dom_lca_tags() {
4215   uint limit = C->unique() + 1;
4216   _dom_lca_tags.map( limit, NULL );
4217   _dom_lca_tags.clear();
4218 #ifdef ASSERT
4219   for( uint i = 0; i < limit; ++i ) {
4220     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4221   }
4222 #endif // ASSERT
4223 }
4224 
4225 //------------------------------build_loop_late--------------------------------
4226 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4227 // Second pass finds latest legal placement, and ideal loop placement.
4228 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
4229   while (worklist.size() != 0) {
4230     Node *n = worklist.pop();
4231     // Only visit once
4232     if (visited.test_set(n->_idx)) continue;
4233     uint cnt = n->outcnt();
4234     uint   i = 0;
4235     while (true) {
4236       assert( _nodes[n->_idx], "no dead nodes" );
4237       // Visit all children
4238       if (i < cnt) {
4239         Node* use = n->raw_out(i);
4240         ++i;
4241         // Check for dead uses.  Aggressively prune such junk.  It might be
4242         // dead in the global sense, but still have local uses so I cannot
4243         // easily call 'remove_dead_node'.
4244         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
4245           // Due to cycles, we might not hit the same fixed point in the verify
4246           // pass as we do in the regular pass.  Instead, visit such phis as
4247           // simple uses of the loop head.
4248           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
4249             if( !visited.test(use->_idx) )
4250               worklist.push(use);
4251           } else if( !visited.test_set(use->_idx) ) {
4252             nstack.push(n, i); // Save parent and next use's index.
4253             n   = use;         // Process all children of current use.
4254             cnt = use->outcnt();
4255             i   = 0;
4256           }
4257         } else {
4258           // Do not visit around the backedge of loops via data edges.
4259           // push dead code onto a worklist
4260           _deadlist.push(use);
4261         }
4262       } else {
4263         // All of n's children have been processed, complete post-processing.
4264         build_loop_late_post(n);
4265         if (nstack.is_empty()) {
4266           // Finished all nodes on stack.
4267           // Process next node on the worklist.
4268           break;
4269         }
4270         // Get saved parent node and next use's index. Visit the rest of uses.
4271         n   = nstack.node();
4272         cnt = n->outcnt();
4273         i   = nstack.index();
4274         nstack.pop();
4275       }
4276     }
4277   }
4278 }
4279 
4280 // Verify that no data node is scheduled in the outer loop of a strip
4281 // mined loop.
4282 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
4283 #ifdef ASSERT
4284   if (get_loop(least)->_nest == 0) {
4285     return;
4286   }
4287   IdealLoopTree* loop = get_loop(least);
4288   Node* head = loop->_head;
4289   if (head->is_OuterStripMinedLoop() &&
4290       // Verification can't be applied to fully built strip mined loops
4291       head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
4292     Node* sfpt = head->as_Loop()->outer_safepoint();
4293     ResourceMark rm;
4294     Unique_Node_List wq;
4295     wq.push(sfpt);
4296     for (uint i = 0; i < wq.size(); i++) {
4297       Node *m = wq.at(i);
4298       for (uint i = 1; i < m->req(); i++) {
4299         Node* nn = m->in(i);
4300         if (nn == n) {
4301           return;
4302         }
4303         if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
4304           wq.push(nn);
4305         }
4306       }
4307     }
4308     ShouldNotReachHere();
4309   }
4310 #endif
4311 }
4312 
4313 
4314 //------------------------------build_loop_late_post---------------------------
4315 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4316 // Second pass finds latest legal placement, and ideal loop placement.
4317 void PhaseIdealLoop::build_loop_late_post(Node *n) {
4318   build_loop_late_post_work(n, true);
4319 }
4320 
4321 void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
4322 
4323   if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
4324     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
4325   }
4326 
4327 #ifdef ASSERT
4328   if (_verify_only && !n->is_CFG()) {
4329     // Check def-use domination.
4330     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
4331   }
4332 #endif
4333 
4334   // CFG and pinned nodes already handled
4335   if( n->in(0) ) {
4336     if( n->in(0)->is_top() ) return; // Dead?
4337 
4338     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
4339     // _must_ be pinned (they have to observe their control edge of course).
4340     // Unlike Stores (which modify an unallocable resource, the memory
4341     // state), Mods/Loads can float around.  So free them up.
4342     switch( n->Opcode() ) {
4343     case Op_DivI:
4344     case Op_DivF:
4345     case Op_DivD:
4346     case Op_ModI:
4347     case Op_ModF:
4348     case Op_ModD:
4349     case Op_LoadB:              // Same with Loads; they can sink
4350     case Op_LoadUB:             // during loop optimizations.
4351     case Op_LoadUS:
4352     case Op_LoadD:
4353     case Op_LoadF:
4354     case Op_LoadI:
4355     case Op_LoadKlass:
4356     case Op_LoadNKlass:
4357     case Op_LoadL:
4358     case Op_LoadS:
4359     case Op_LoadP:
4360     case Op_LoadN:
4361     case Op_LoadRange:
4362     case Op_LoadD_unaligned:
4363     case Op_LoadL_unaligned:
4364     case Op_StrComp:            // Does a bunch of load-like effects
4365     case Op_StrEquals:
4366     case Op_StrIndexOf:
4367     case Op_StrIndexOfChar:
4368     case Op_AryEq:
4369     case Op_HasNegatives:
4370       pinned = false;
4371     }
4372     if (n->is_CMove()) {
4373       pinned = false;
4374     }
4375     if( pinned ) {
4376       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
4377       if( !chosen_loop->_child )       // Inner loop?
4378         chosen_loop->_body.push(n); // Collect inner loops
4379       return;
4380     }
4381   } else {                      // No slot zero
4382     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
4383       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
4384       return;
4385     }
4386     assert(!n->is_CFG() || n->outcnt() == 0, "");
4387   }
4388 
4389   // Do I have a "safe range" I can select over?
4390   Node *early = get_ctrl(n);// Early location already computed
4391 
4392   // Compute latest point this Node can go
4393   Node *LCA = get_late_ctrl( n, early );
4394   // LCA is NULL due to uses being dead
4395   if( LCA == NULL ) {
4396 #ifdef ASSERT
4397     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
4398       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
4399     }
4400 #endif
4401     _nodes.map(n->_idx, 0);     // This node is useless
4402     _deadlist.push(n);
4403     return;
4404   }
4405   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
4406 
4407   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
4408   Node *least = legal;          // Best legal position so far
4409   while( early != legal ) {     // While not at earliest legal
4410 #ifdef ASSERT
4411     if (legal->is_Start() && !early->is_Root()) {
4412       // Bad graph. Print idom path and fail.
4413       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
4414       assert(false, "Bad graph detected in build_loop_late");
4415     }
4416 #endif
4417     // Find least loop nesting depth
4418     legal = idom(legal);        // Bump up the IDOM tree
4419     // Check for lower nesting depth
4420     if( get_loop(legal)->_nest < get_loop(least)->_nest )
4421       least = legal;
4422   }
4423   assert(early == legal || legal != C->root(), "bad dominance of inputs");
4424 
4425   // Try not to place code on a loop entry projection
4426   // which can inhibit range check elimination.
4427   if (least != early) {
4428     Node* ctrl_out = least->unique_ctrl_out();
4429     if (ctrl_out && ctrl_out->is_Loop() &&
4430         least == ctrl_out->in(LoopNode::EntryControl)) {
4431       // Move the node above predicates as far up as possible so a
4432       // following pass of loop predication doesn't hoist a predicate
4433       // that depends on it above that node.
4434       Node* new_ctrl = least;
4435       for (;;) {
4436         if (!new_ctrl->is_Proj()) {
4437           break;
4438         }
4439         CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
4440         if (call == NULL) {
4441           break;
4442         }
4443         int req = call->uncommon_trap_request();
4444         Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
4445         if (trap_reason != Deoptimization::Reason_loop_limit_check &&
4446             trap_reason != Deoptimization::Reason_predicate &&
4447             trap_reason != Deoptimization::Reason_profile_predicate) {
4448           break;
4449         }
4450         Node* c = new_ctrl->in(0)->in(0);
4451         if (is_dominator(c, early) && c != early) {
4452           break;
4453         }
4454         new_ctrl = c;
4455       }
4456       least = new_ctrl;
4457     }
4458   }
4459 
4460 #ifdef ASSERT
4461   // If verifying, verify that 'verify_me' has a legal location
4462   // and choose it as our location.
4463   if( _verify_me ) {
4464     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
4465     Node *legal = LCA;
4466     while( early != legal ) {   // While not at earliest legal
4467       if( legal == v_ctrl ) break;  // Check for prior good location
4468       legal = idom(legal)      ;// Bump up the IDOM tree
4469     }
4470     // Check for prior good location
4471     if( legal == v_ctrl ) least = legal; // Keep prior if found
4472   }
4473 #endif
4474 
4475   // Assign discovered "here or above" point
4476   least = find_non_split_ctrl(least);
4477   verify_strip_mined_scheduling(n, least);
4478   set_ctrl(n, least);
4479 
4480   // Collect inner loop bodies
4481   IdealLoopTree *chosen_loop = get_loop(least);
4482   if( !chosen_loop->_child )   // Inner loop?
4483     chosen_loop->_body.push(n);// Collect inner loops
4484 }
4485 
4486 #ifdef ASSERT
4487 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
4488   tty->print_cr("%s", msg);
4489   tty->print("n: "); n->dump();
4490   tty->print("early(n): "); early->dump();
4491   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
4492       n->in(0) != early && !n->in(0)->is_Root()) {
4493     tty->print("n->in(0): "); n->in(0)->dump();
4494   }
4495   for (uint i = 1; i < n->req(); i++) {
4496     Node* in1 = n->in(i);
4497     if (in1 != NULL && in1 != n && !in1->is_top()) {
4498       tty->print("n->in(%d): ", i); in1->dump();
4499       Node* in1_early = get_ctrl(in1);
4500       tty->print("early(n->in(%d)): ", i); in1_early->dump();
4501       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
4502           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
4503         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
4504       }
4505       for (uint j = 1; j < in1->req(); j++) {
4506         Node* in2 = in1->in(j);
4507         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
4508           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
4509           Node* in2_early = get_ctrl(in2);
4510           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
4511           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
4512               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
4513             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
4514           }
4515         }
4516       }
4517     }
4518   }
4519   tty->cr();
4520   tty->print("LCA(n): "); LCA->dump();
4521   for (uint i = 0; i < n->outcnt(); i++) {
4522     Node* u1 = n->raw_out(i);
4523     if (u1 == n)
4524       continue;
4525     tty->print("n->out(%d): ", i); u1->dump();
4526     if (u1->is_CFG()) {
4527       for (uint j = 0; j < u1->outcnt(); j++) {
4528         Node* u2 = u1->raw_out(j);
4529         if (u2 != u1 && u2 != n && u2->is_CFG()) {
4530           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4531         }
4532       }
4533     } else {
4534       Node* u1_later = get_ctrl(u1);
4535       tty->print("later(n->out(%d)): ", i); u1_later->dump();
4536       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
4537           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
4538         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
4539       }
4540       for (uint j = 0; j < u1->outcnt(); j++) {
4541         Node* u2 = u1->raw_out(j);
4542         if (u2 == n || u2 == u1)
4543           continue;
4544         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4545         if (!u2->is_CFG()) {
4546           Node* u2_later = get_ctrl(u2);
4547           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
4548           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
4549               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
4550             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
4551           }
4552         }
4553       }
4554     }
4555   }
4556   tty->cr();
4557   int ct = 0;
4558   Node *dbg_legal = LCA;
4559   while(!dbg_legal->is_Start() && ct < 100) {
4560     tty->print("idom[%d] ",ct); dbg_legal->dump();
4561     ct++;
4562     dbg_legal = idom(dbg_legal);
4563   }
4564   tty->cr();
4565 }
4566 #endif
4567 
4568 #ifndef PRODUCT
4569 //------------------------------dump-------------------------------------------
4570 void PhaseIdealLoop::dump() const {
4571   ResourceMark rm;
4572   Arena* arena = Thread::current()->resource_area();
4573   Node_Stack stack(arena, C->live_nodes() >> 2);
4574   Node_List rpo_list;
4575   VectorSet visited(arena);
4576   visited.set(C->top()->_idx);
4577   rpo(C->root(), stack, visited, rpo_list);
4578   // Dump root loop indexed by last element in PO order
4579   dump(_ltree_root, rpo_list.size(), rpo_list);
4580 }
4581 
4582 void PhaseIdealLoop::dump(IdealLoopTree* loop, uint idx, Node_List &rpo_list) const {
4583   loop->dump_head();
4584 
4585   // Now scan for CFG nodes in the same loop
4586   for (uint j = idx; j > 0; j--) {
4587     Node* n = rpo_list[j-1];
4588     if (!_nodes[n->_idx])      // Skip dead nodes
4589       continue;
4590 
4591     if (get_loop(n) != loop) { // Wrong loop nest
4592       if (get_loop(n)->_head == n &&    // Found nested loop?
4593           get_loop(n)->_parent == loop)
4594         dump(get_loop(n), rpo_list.size(), rpo_list);     // Print it nested-ly
4595       continue;
4596     }
4597 
4598     // Dump controlling node
4599     tty->sp(2 * loop->_nest);
4600     tty->print("C");
4601     if (n == C->root()) {
4602       n->dump();
4603     } else {
4604       Node* cached_idom   = idom_no_update(n);
4605       Node* computed_idom = n->in(0);
4606       if (n->is_Region()) {
4607         computed_idom = compute_idom(n);
4608         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
4609         // any MultiBranch ctrl node), so apply a similar transform to
4610         // the cached idom returned from idom_no_update.
4611         cached_idom = find_non_split_ctrl(cached_idom);
4612       }
4613       tty->print(" ID:%d", computed_idom->_idx);
4614       n->dump();
4615       if (cached_idom != computed_idom) {
4616         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
4617                       computed_idom->_idx, cached_idom->_idx);
4618       }
4619     }
4620     // Dump nodes it controls
4621     for (uint k = 0; k < _nodes.Size(); k++) {
4622       // (k < C->unique() && get_ctrl(find(k)) == n)
4623       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
4624         Node* m = C->root()->find(k);
4625         if (m && m->outcnt() > 0) {
4626           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
4627             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
4628                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
4629           }
4630           tty->sp(2 * loop->_nest + 1);
4631           m->dump();
4632         }
4633       }
4634     }
4635   }
4636 }
4637 #endif
4638 
4639 // Collect a R-P-O for the whole CFG.
4640 // Result list is in post-order (scan backwards for RPO)
4641 void PhaseIdealLoop::rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const {
4642   stk.push(start, 0);
4643   visited.set(start->_idx);
4644 
4645   while (stk.is_nonempty()) {
4646     Node* m   = stk.node();
4647     uint  idx = stk.index();
4648     if (idx < m->outcnt()) {
4649       stk.set_index(idx + 1);
4650       Node* n = m->raw_out(idx);
4651       if (n->is_CFG() && !visited.test_set(n->_idx)) {
4652         stk.push(n, 0);
4653       }
4654     } else {
4655       rpo_list.push(m);
4656       stk.pop();
4657     }
4658   }
4659 }
4660 
4661 
4662 //=============================================================================
4663 //------------------------------LoopTreeIterator-------------------------------
4664 
4665 // Advance to next loop tree using a preorder, left-to-right traversal.
4666 void LoopTreeIterator::next() {
4667   assert(!done(), "must not be done.");
4668   if (_curnt->_child != NULL) {
4669     _curnt = _curnt->_child;
4670   } else if (_curnt->_next != NULL) {
4671     _curnt = _curnt->_next;
4672   } else {
4673     while (_curnt != _root && _curnt->_next == NULL) {
4674       _curnt = _curnt->_parent;
4675     }
4676     if (_curnt == _root) {
4677       _curnt = NULL;
4678       assert(done(), "must be done.");
4679     } else {
4680       assert(_curnt->_next != NULL, "must be more to do");
4681       _curnt = _curnt->_next;
4682     }
4683   }
4684 }