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improve generic ctz/clz

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This commit is contained in:
daanx 2024-12-09 20:25:22 -08:00
parent e44815ed6f
commit 3a92c35270
1 changed files with 23 additions and 15 deletions
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38
src/libc.c
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@ -289,7 +289,7 @@ static size_t mi_ctz_generic32(uint32_t x) {
31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
};
if (x==0) return 32;
return debruijn[((x & -(int32_t)x) * (uint32_t)(0x077CB531U)) >> 27];
return debruijn[(uint32_t)((x & -(int32_t)x) * (uint32_t)(0x077CB531U)) >> 27];
}
static size_t mi_clz_generic32(uint32_t x) {
@ -307,25 +307,33 @@ static size_t mi_clz_generic32(uint32_t x) {
return debruijn[(uint32_t)(x * (uint32_t)(0x07C4ACDDU)) >> 27];
}
size_t _mi_clz_generic(size_t x) {
if (x==0) return MI_SIZE_BITS;
#if (MI_SIZE_BITS <= 32)
return mi_clz_generic32((uint32_t)x);
#else
const size_t count = mi_clz_generic32((uint32_t)(x >> 32));
if (count < 32) return count;
return (32 + mi_clz_generic32((uint32_t)x));
#endif
}
size_t _mi_ctz_generic(size_t x) {
if (x==0) return MI_SIZE_BITS;
#if (MI_SIZE_BITS <= 32)
return mi_ctz_generic32((uint32_t)x);
#else
const size_t count = mi_ctz_generic32((uint32_t)x);
if (count < 32) return count;
return (32 + mi_ctz_generic32((uint32_t)(x>>32)));
const uint32_t lo = (uint32_t)x;
if (lo != 0) {
return mi_ctz_generic32(lo);
}
else {
return (32 + mi_ctz_generic32((uint32_t)(x>>32)));
}
#endif
}
size_t _mi_clz_generic(size_t x) {
if (x==0) return MI_SIZE_BITS;
#if (MI_SIZE_BITS <= 32)
return mi_clz_generic32((uint32_t)x);
#else
const uint32_t hi = (uint32_t)(x>>32);
if (hi != 0) {
return mi_clz_generic32(hi);
}
else {
return 32 + mi_clz_generic32((uint32_t)x);
}
#endif
}