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avoid using popcnt intrinsics to support older processors such as the 

core 2 duo which are plenty fast enough to support
This commit is contained in:
Anthony Pesch 2017-10-18 17:37:10 -04:00
parent 1e412dac1d
commit 29c86bb03a
1 changed files with 11 additions and 8 deletions
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19
src/core/math.h
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@ -17,14 +17,21 @@ static inline uint32_t bswap24(uint32_t v) {
return ((v & 0xff) << 16) | (v & 0x00ff00) | ((v & 0xff0000) >> 16);
}
static inline int popcnt32(uint32_t v) {
/* avoid using popcnt intrinsics to support older processors such as the
core 2 duo which are plenty fast enough to support */
v = (v & 0x55555555) + ((v >> 1) & 0x55555555);
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
v = (v & 0x0f0f0f0f) + ((v >> 4) & 0x0f0f0f0f);
v = (v & 0x00ff00ff) + ((v >> 8) & 0x00ff00ff);
v = (v & 0x0000ffff) + ((v >> 16) & 0x0000ffff);
return (int)v;
}
#if COMPILER_MSVC
#include <intrin.h>
static inline int popcnt32(uint32_t v) {
return __popcnt(v);
}
static inline int clz32(uint32_t v) {
unsigned long r = 0;
_BitScanReverse(&r, v);
@ -55,10 +62,6 @@ static inline uint32_t bswap32(uint32_t v) {
#else
static inline int popcnt32(uint32_t v) {
return __builtin_popcount(v);
}
static inline int clz32(uint32_t v) {
return __builtin_clz(v);
}