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make/autoconf/flags-cflags.m4
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@ rev 51624 : 8210416: [linux] Poor StrictMath performance due to non-optimized compilation
| Summary: Compile fdlibm with -O2 -ffp-contract=off on gcc/clang arches.
~ Reviewed-by: aph, erikj, dholmes, darcy
@@ -371,10 +371,24 @@
FLAGS_CPU_LEGACY=$OPENJDK_BUILD_CPU_LEGACY
FLAGS_CPU_LEGACY_LIB=$OPENJDK_BUILD_CPU_LEGACY_LIB
FLAGS_SETUP_CFLAGS_CPU_DEP([BUILD], [OPENJDK_BUILD_])
+ COMPILER_FP_CONTRACT_OFF_FLAG="-ffp-contract=off"
+ # Check that the compiler supports -ffp-contract=off flag
+ # Set FDLIBM_CFLAGS to -ffp-contract=off if it does. Empty
+ # otherwise.
+ # These flags are required for GCC-based builds of
+ # fdlibm with optimization without losing precision.
+ # Notably, -ffp-contract=off needs to be added for GCC >= 4.6.
+ if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
+ FLAGS_COMPILER_CHECK_ARGUMENTS(ARGUMENT: [${COMPILER_FP_CONTRACT_OFF_FLAG}],
+ IF_TRUE: [FDLIBM_CFLAGS=${COMPILER_FP_CONTRACT_OFF_FLAG}],
+ IF_FALSE: [FDLIBM_CFLAGS=""])
+ fi
+ AC_SUBST(FDLIBM_CFLAGS)
+
# Tests are only ever compiled for TARGET
CFLAGS_TESTLIB="$CFLAGS_JDKLIB"
CXXFLAGS_TESTLIB="$CXXFLAGS_JDKLIB"
CFLAGS_TESTEXE="$CFLAGS_JDKEXE"
CXXFLAGS_TESTEXE="$CXXFLAGS_JDKEXE"
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