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Add hardware POPCNT support for gcc

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With new target 'make gcc-popcnt' it is now
possible to compile with enabled hardware POPCNT
support also with gcc. Until now was possible only
for Intel and MSVC compilers.

When this instruction is supported by CPU, for instance
on Intel i7 or i5 family, produced binary is a bit faster.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-01-30 19:18:27 +01:00
parent 17502a5659
commit d7d2c1b7e3
2 changed files with 32 additions and 0 deletions
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8
src/Makefile
View file

@ -80,6 +80,7 @@ help:
@echo "Makefile options:"
@echo ""
@echo "make > Default: Compiler = g++"
@echo "make gcc-popcnt > Compiler = g++ + popcnt-support"
@echo "make icc > Compiler = icpc"
@echo "make icc-profile > Compiler = icpc + automatic pgo-build"
@echo "make icc-profile-popcnt > Compiler = icpc + automatic pgo-build + popcnt-support"
@ -108,6 +109,13 @@ gcc:
CXXFLAGS="$(GCCFLAGS)" \
all
gcc-popcnt:
$(MAKE) \
CXX='g++' \
CXXFLAGS="$(GCCFLAGS) -DUSE_POPCNT" \
all
icc:
$(MAKE) \
CXX='icpc' \

24
src/bitcount.h
View file

@ -53,6 +53,30 @@ inline bool cpu_has_popcnt() {
#define POPCNT_INTRINSIC(x) __popcnt64(x)
#elif defined(__GNUC__) && defined(USE_POPCNT) // Gcc compiler
inline void __cpuid(unsigned int op,
unsigned int *eax, unsigned int *ebx,
unsigned int *ecx, unsigned int *edx)
{
*eax = op;
*ecx = 0;
__asm__("cpuid" : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
: "0" (*eax), "2" (*ecx));
}
inline bool cpu_has_popcnt() {
unsigned int eax, ebx, ecx, edx;
__cpuid(1, &eax, &ebx, &ecx, &edx);
return (ecx >> 23) & 1;
}
#define POPCNT_INTRINSIC(x) ({ \
unsigned long __ret; \
__asm__("popcnt %1, %0" : "=r" (__ret) : "r" (x)); \
__ret; })
#else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled
inline bool cpu_has_popcnt() { return false; }