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Optimize 32-bit VecMask_next()

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Sen Huang
2021-08-04 17:14:58 -04:00
committed by senhuang42
parent e411040ea1
commit 539b3aab9b
2 changed files with 110 additions and 294 deletions
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lib/compress/zstd_lazy.c
+12 -2
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@@ -882,9 +882,19 @@ static U32 ZSTD_VecMask_next(ZSTD_VecMask val) {
assert(val != 0);
# if defined(_MSC_VER) && defined(_WIN64)
unsigned long r=0;
return _BitScanForward64(&r, val) ? (U64)r : 0; /* _BitScanForward64 not defined outside of x86/64 */
return _BitScanForward64(&r, val) ? (U32)r : 0; /* _BitScanForward64 not defined outside of x86/64 */
# elif (defined(__GNUC__) && ((__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))
return (U32)__builtin_ctzll(val);
if (sizeof(size_t) == 4) {
U32 mostSignificantWord = (U32)(val >> 32);
U32 leastSignificantWord = (U32)val;
if (leastSignificantWord == 0) {
return 32 + (U32)__builtin_ctz(mostSignificantWord);
} else {
return (U32)__builtin_ctz(leastSignificantWord);
}
} else {
return (U32)__builtin_ctzll(val);
}
# else
/* Software ctz version: http://aggregate.org/MAGIC/#Trailing%20Zero%20Count
* and: https://stackoverflow.com/questions/2709430/count-number-of-bits-in-a-64-bit-long-big-integer