diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/include/port/pg_bitutils.h | 32 | ||||
| -rw-r--r-- | src/port/pg_bitutils.c | 48 |
2 files changed, 53 insertions, 27 deletions
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h index 086bd08132f..7dd7fef4f74 100644 --- a/src/include/port/pg_bitutils.h +++ b/src/include/port/pg_bitutils.h @@ -253,10 +253,40 @@ pg_ceil_log2_64(uint64 num) return pg_leftmost_one_pos64(num - 1) + 1; } -/* Count the number of one-bits in a uint32 or uint64 */ +/* + * With MSVC on x86_64 builds, try using native popcnt instructions via the + * __popcnt and __popcnt64 intrinsics. These don't work the same as GCC's + * __builtin_popcount* intrinsic functions as they always emit popcnt + * instructions. + */ +#if defined(_MSC_VER) && defined(_M_AMD64) +#define HAVE_X86_64_POPCNTQ +#endif + +/* + * On x86_64, we can use the hardware popcount instruction, but only if + * we can verify that the CPU supports it via the cpuid instruction. + * + * Otherwise, we fall back to a hand-rolled implementation. + */ +#ifdef HAVE_X86_64_POPCNTQ +#if defined(HAVE__GET_CPUID) || defined(HAVE__CPUID) +#define TRY_POPCNT_FAST 1 +#endif +#endif + +#ifdef TRY_POPCNT_FAST +/* Attempt to use the POPCNT instruction, but perform a runtime check first */ extern int (*pg_popcount32) (uint32 word); extern int (*pg_popcount64) (uint64 word); +#else +/* Use a portable implementation -- no need for a function pointer. */ +extern int pg_popcount32(uint32 word); +extern int pg_popcount64(uint64 word); + +#endif /* TRY_POPCNT_FAST */ + /* Count the number of one-bits in a byte array */ extern uint64 pg_popcount(const char *buf, int bytes); diff --git a/src/port/pg_bitutils.c b/src/port/pg_bitutils.c index 10676b285ca..9d0e2016c31 100644 --- a/src/port/pg_bitutils.c +++ b/src/port/pg_bitutils.c @@ -103,29 +103,6 @@ const uint8 pg_number_of_ones[256] = { 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8 }; -/* - * With MSVC on x86_64 builds, try using native popcnt instructions via the - * __popcnt and __popcnt64 intrinsics. These don't work the same as GCC's - * __builtin_popcount* intrinsic functions as they always emit popcnt - * instructions. - */ -#if defined(_MSC_VER) && defined(_M_AMD64) -#define HAVE_X86_64_POPCNTQ -#endif - -/* - * On x86_64, we can use the hardware popcount instruction, but only if - * we can verify that the CPU supports it via the cpuid instruction. - * - * Otherwise, we fall back to __builtin_popcount if the compiler has that, - * or a hand-rolled implementation if not. - */ -#ifdef HAVE_X86_64_POPCNTQ -#if defined(HAVE__GET_CPUID) || defined(HAVE__CPUID) -#define TRY_POPCNT_FAST 1 -#endif -#endif - static int pg_popcount32_slow(uint32 word); static int pg_popcount64_slow(uint64 word); @@ -138,9 +115,6 @@ static int pg_popcount64_fast(uint64 word); int (*pg_popcount32) (uint32 word) = pg_popcount32_choose; int (*pg_popcount64) (uint64 word) = pg_popcount64_choose; -#else -int (*pg_popcount32) (uint32 word) = pg_popcount32_slow; -int (*pg_popcount64) (uint64 word) = pg_popcount64_slow; #endif /* TRY_POPCNT_FAST */ #ifdef TRY_POPCNT_FAST @@ -291,6 +265,28 @@ pg_popcount64_slow(uint64 word) #endif /* HAVE__BUILTIN_POPCOUNT */ } +#ifndef TRY_POPCNT_FAST + +/* + * When the POPCNT instruction is not available, there's no point in using + * function pointers to vary the implementation between the fast and slow + * method. We instead just make these actual external functions when + * TRY_POPCNT_FAST is not defined. The compiler should be able to inline + * the slow versions here. + */ +int +pg_popcount32(uint32 word) +{ + return pg_popcount32_slow(word); +} + +int +pg_popcount64(uint64 word) +{ + return pg_popcount64_slow(word); +} + +#endif /* !TRY_POPCNT_FAST */ /* * pg_popcount |