1 /*
2 * Copyright (c) 2019, 2020, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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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 *
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23 */
24
25 #ifndef SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP
26 #define SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP
27
28 #include "classfile/classFileParser.hpp"
29 #include "classfile/classLoaderData.hpp"
30 #include "memory/allocation.hpp"
31 #include "oops/fieldStreams.hpp"
32 #include "utilities/growableArray.hpp"
33
34 // Classes below are used to compute the field layout of classes.
35
36 // A LayoutRawBlock describes an element of a layout.
37 // Each field is represented by a LayoutRawBlock.
38 // LayoutRawBlocks can also represent elements injected by the JVM:
39 // padding, empty blocks, inherited fields, etc.
40 // All LayoutRawBlocks must have a size and an alignment. The size is the
41 // exact size of the field expressed in bytes. The alignment is
42 // the alignment constraint of the field (1 for byte, 2 for short,
43 // 4 for int, 8 for long, etc.)
44 //
45 // LayoutRawBlock are designed to be used in two data structures:
46 // - a linked list in a layout (using _next_block, _prev_block)
47 // - a GrowableArray in field group (the growable array contains pointers to LayoutRawBlocks)
48 //
49 // next/prev pointers are included in the LayoutRawBlock class to narrow
50 // the number of allocation required during the computation of a layout.
51 //
52 class LayoutRawBlock : public ResourceObj {
53 public:
54 // Some code relies on the order of values below.
55 enum Kind {
56 EMPTY, // empty slot, space is taken from this to allocate fields
57 RESERVED, // reserved for JVM usage (for instance object header)
58 PADDING, // padding (because of alignment constraints or @Contended)
59 REGULAR, // primitive or oop field (including non-flattened inline fields)
60 FLATTENED, // flattened field
61 INHERITED // field(s) inherited from super classes
62 };
63
64 private:
65 LayoutRawBlock* _next_block;
66 LayoutRawBlock* _prev_block;
67 ValueKlass* _value_klass;
68 Kind _kind;
69 int _offset;
70 int _alignment;
71 int _size;
72 int _field_index;
73 bool _is_reference;
74
75 public:
76 LayoutRawBlock(Kind kind, int size);
77 LayoutRawBlock(int index, Kind kind, int size, int alignment, bool is_reference = false);
78 LayoutRawBlock* next_block() const { return _next_block; }
79 void set_next_block(LayoutRawBlock* next) { _next_block = next; }
80 LayoutRawBlock* prev_block() const { return _prev_block; }
81 void set_prev_block(LayoutRawBlock* prev) { _prev_block = prev; }
82 Kind kind() const { return _kind; }
83 int offset() const {
84 assert(_offset >= 0, "Must be initialized");
85 return _offset;
86 }
87 void set_offset(int offset) { _offset = offset; }
88 int alignment() const { return _alignment; }
89 int size() const { return _size; }
90 void set_size(int size) { _size = size; }
91 int field_index() const {
92 assert(_field_index != -1, "Must be initialized");
93 return _field_index;
94 }
95 bool is_reference() const { return _is_reference; }
96 ValueKlass* value_klass() const {
97 assert(_value_klass != NULL, "Must be initialized");
98 return _value_klass;
99 }
100 void set_value_klass(ValueKlass* value_klass) { _value_klass = value_klass; }
101
102 bool fit(int size, int alignment);
103
104 static int compare_offset(LayoutRawBlock** x, LayoutRawBlock** y) { return (*x)->offset() - (*y)->offset(); }
105 // compare_size_inverted() returns the opposite of a regular compare method in order to
106 // sort fields in decreasing order.
107 // Note: with line types, the comparison should include alignment constraint if sizes are equals
108 static int compare_size_inverted(LayoutRawBlock** x, LayoutRawBlock** y) {
109 #ifdef _WINDOWS
110 // qsort() on Windows reverse the order of fields with the same size
111 // the extension of the comparison function below preserves this order
112 int diff = (*y)->size() - (*x)->size();
113 if (diff == 0) {
114 diff = (*x)->field_index() - (*y)->field_index();
115 }
116 return diff;
117 #else
118 return (*y)->size() - (*x)->size();
119 #endif // _WINDOWS
120 }
121 };
122
123 // A Field group represents a set of fields that have to be allocated together,
124 // this is the way the @Contended annotation is supported.
125 // Inside a FieldGroup, fields are sorted based on their kind: primitive,
126 // oop, or flattened.
127 //
128 class FieldGroup : public ResourceObj {
129
130 private:
131 FieldGroup* _next;
132
133 GrowableArray<LayoutRawBlock*>* _primitive_fields;
134 GrowableArray<LayoutRawBlock*>* _oop_fields;
135 GrowableArray<LayoutRawBlock*>* _flattened_fields;
136 int _contended_group;
137 int _oop_count;
138 static const int INITIAL_LIST_SIZE = 16;
139
140 public:
141 FieldGroup(int contended_group = -1);
142
143 FieldGroup* next() const { return _next; }
144 void set_next(FieldGroup* next) { _next = next; }
145 GrowableArray<LayoutRawBlock*>* primitive_fields() const { return _primitive_fields; }
146 GrowableArray<LayoutRawBlock*>* oop_fields() const { return _oop_fields; }
147 GrowableArray<LayoutRawBlock*>* flattened_fields() const { return _flattened_fields; }
148 int contended_group() const { return _contended_group; }
149 int oop_count() const { return _oop_count; }
150
151 void add_primitive_field(AllFieldStream fs, BasicType type);
152 void add_oop_field(AllFieldStream fs);
153 void add_flattened_field(AllFieldStream fs, ValueKlass* vk);
154 void add_block(LayoutRawBlock** list, LayoutRawBlock* block);
155 void sort_by_size();
156 };
157
158 // The FieldLayout class represents a set of fields organized
159 // in a layout.
160 // An instance of FieldLayout can either represent the layout
161 // of non-static fields (used in an instance object) or the
162 // layout of static fields (to be included in the class mirror).
163 //
164 // _block is a pointer to a list of LayoutRawBlock ordered by increasing
165 // offsets.
166 // _start points to the LayoutRawBlock with the first offset that can
167 // be used to allocate fields of the current class
168 // _last points to the last LayoutRawBlock of the list. In order to
169 // simplify the code, the LayoutRawBlock list always ends with an
170 // EMPTY block (the kind of LayoutRawBlock from which space is taken
171 // to allocate fields) with a size big enough to satisfy all
172 // field allocations.
173 //
174 class FieldLayout : public ResourceObj {
175 private:
176 Array<u2>* _fields;
177 ConstantPool* _cp;
178 LayoutRawBlock* _blocks; // the layout being computed
179 LayoutRawBlock* _start; // points to the first block where a field can be inserted
180 LayoutRawBlock* _last; // points to the last block of the layout (big empty block)
181
182 public:
183 FieldLayout(Array<u2>* fields, ConstantPool* cp);
184 void initialize_static_layout();
185 void initialize_instance_layout(const InstanceKlass* ik);
186
187 LayoutRawBlock* first_empty_block() {
188 LayoutRawBlock* block = _start;
189 while (block->kind() != LayoutRawBlock::EMPTY) {
190 block = block->next_block();
191 }
192 return block;
193 }
194
195 LayoutRawBlock* blocks() { return _blocks; }
196
197 LayoutRawBlock* start() { return _start; }
198 void set_start(LayoutRawBlock* start) { _start = start; }
199 LayoutRawBlock* last_block() { return _last; }
200
201 LayoutRawBlock* first_field_block();
202 void add(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = NULL);
203 void add_field_at_offset(LayoutRawBlock* blocks, int offset, LayoutRawBlock* start = NULL);
204 void add_contiguously(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start = NULL);
205 LayoutRawBlock* insert_field_block(LayoutRawBlock* slot, LayoutRawBlock* block);
206 bool reconstruct_layout(const InstanceKlass* ik);
207 void fill_holes(const InstanceKlass* ik);
208 LayoutRawBlock* insert(LayoutRawBlock* slot, LayoutRawBlock* block);
209 void remove(LayoutRawBlock* block);
210 void print(outputStream* output, bool is_static, const InstanceKlass* super);
211 };
212
213
214 // FieldLayoutBuilder is the main entry point for layout computation.
215 // This class has two methods to generate layout: one for identity classes
216 // and one for inline classes. The rational for having two methods
217 // is that each kind of classes has a different set goals regarding
218 // its layout, so instead of mixing two layout strategies into a
219 // single method, each kind has its own method (see comments below
220 // for more details about the allocation strategies).
221 //
222 // Computing the layout of a class always goes through 4 steps:
223 // 1 - Prologue: preparation of data structure and gathering of
224 // layout information inherited from super classes
225 // 2 - Field sorting: fields are sorted according to their
226 // kind (oop, primitive, inline class) and their contention
227 // annotation (if any)
228 // 3 - Layout is computed from the set of lists generated during
229 // step 2
230 // 4 - Epilogue: oopmaps are generated, layout information is
231 // prepared so other VM components can use it (instance size,
232 // static field size, non-static field size, etc.)
233 //
234 // Steps 1 and 4 are common to all layout computations. Step 2 and 3
235 // differ for inline classes and identity classes.
236 //
237 class FieldLayoutBuilder : public ResourceObj {
238 private:
239 const Symbol* _classname;
240 const InstanceKlass* _super_klass;
241 ConstantPool* _constant_pool;
242 Array<u2>* _fields;
243 FieldLayoutInfo* _info;
244 FieldGroup* _root_group;
245 GrowableArray<FieldGroup*> _contended_groups;
246 FieldGroup* _static_fields;
247 FieldLayout* _layout;
248 FieldLayout* _static_layout;
249 ClassLoaderData* _class_loader_data;
250 Handle _protection_domain;
251 int _nonstatic_oopmap_count;
252 int _alignment;
253 int _first_field_offset;
254 int _exact_size_in_bytes;
255 bool _has_nonstatic_fields;
256 bool _is_contended;
257 bool _is_value_type;
258 bool _has_flattening_information;
259
260 FieldGroup* get_or_create_contended_group(int g);
261
262 public:
263 FieldLayoutBuilder(const Symbol* classname, const InstanceKlass* super_klass, ConstantPool* constant_pool,
264 Array<u2>* fields, bool is_contended, bool is_value_type, ClassLoaderData* class_loader_data,
265 Handle protection_domain, FieldLayoutInfo* info);
266
267 int get_alignment() {
268 assert(_alignment != -1, "Uninitialized");
269 return _alignment;
270 }
271
272 int get_first_field_offset() {
273 assert(_first_field_offset != -1, "Uninitialized");
274 return _first_field_offset;
275 }
276
277 int get_exact_size_in_byte() {
278 assert(_exact_size_in_bytes != -1, "Uninitialized");
279 return _exact_size_in_bytes;
280 }
281
282 void build_layout(TRAPS);
283 void compute_regular_layout();
284 void compute_java_lang_ref_Reference_layout();
285 void compute_boxing_class_layout();
286 void compute_inline_class_layout(TRAPS);
287 void insert_contended_padding(LayoutRawBlock* slot);
288
289 protected:
290 void prologue();
291 void epilogue();
292 void regular_field_sorting();
293 void inline_class_field_sorting(TRAPS);
294 void add_flattened_field_oopmap(OopMapBlocksBuilder* nonstatic_oop_map, ValueKlass* vk, int offset);
295 };
296
297 #endif // SHARE_CLASSFILE_FIELDLAYOUTBUILDER_HPP