ddidderr/zstd-rs
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Use __assume(0) for unreachable code path in msvc

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msvc will optimize away the condition check.
This commit is contained in:
Ma Lin
2021-09-27 19:23:57 +08:00
parent e5ba858270
commit ae986fcdb8
6 changed files with 113 additions and 32 deletions
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lib/compress/zstd_compress_internal.h
+32 -8
View File
@@ -672,8 +672,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
# if STATIC_BMI2
return _tzcnt_u64(val) >> 3;
# else
unsigned long r;
return _BitScanForward64( &r, (U64)val ) ? (unsigned)(r >> 3) : 0;
if (val != 0) {
unsigned long r;
_BitScanForward64(&r, (U64)val);
return (unsigned)(r >> 3);
} else {
/* Should not reach this code path */
__assume(0);
}
# endif
# elif defined(__GNUC__) && (__GNUC__ >= 4)
return (__builtin_ctzll((U64)val) >> 3);
@@ -690,8 +696,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
# endif
} else { /* 32 bits */
# if defined(_MSC_VER)
unsigned long r;
return _BitScanForward( &r, (U32)val ) ? (unsigned)(r >> 3) : 0;
if (val != 0) {
unsigned long r;
_BitScanForward(&r, (U32)val);
return (unsigned)(r >> 3);
} else {
/* Should not reach this code path */
__assume(0);
}
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_ctz((U32)val) >> 3);
# else
@@ -708,8 +720,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
# if STATIC_BMI2
return _lzcnt_u64(val) >> 3;
# else
unsigned long r;
return _BitScanReverse64(&r, (U64)val) ? (unsigned)(r >> 3) : 0;
if (val != 0) {
unsigned long r;
_BitScanReverse64(&r, (U64)val);
return (unsigned)(r >> 3);
} else {
/* Should not reach this code path */
__assume(0);
}
# endif
# elif defined(__GNUC__) && (__GNUC__ >= 4)
return (__builtin_clzll(val) >> 3);
@@ -723,8 +741,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
# endif
} else { /* 32 bits */
# if defined(_MSC_VER)
unsigned long r;
return _BitScanReverse( &r, (unsigned long)val ) ? (unsigned)(r >> 3) : 0;
if (val != 0) {
unsigned long r;
_BitScanReverse(&r, (unsigned long)val);
return (unsigned)(r >> 3);
} else {
/* Should not reach this code path */
__assume(0);
}
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_clz((U32)val) >> 3);
# else
lib/compress/zstd_lazy.c
+8 -5
View File
@@ -881,11 +881,14 @@ typedef U64 ZSTD_VecMask; /* Clarifies when we are interacting with a U64 repr
static U32 ZSTD_VecMask_next(ZSTD_VecMask val) {
assert(val != 0);
# if defined(_MSC_VER) && defined(_WIN64)
{
unsigned long r;
/* _BitScanForward64 is not defined outside of x64 */
return _BitScanForward64(&r, val) ? (U32)r : 0;
}
if (val != 0) {
unsigned long r;
_BitScanForward64(&r, val);
return (U32)(r);
} else {
/* Should not reach this code path */
__assume(0);
}
# elif (defined(__GNUC__) && ((__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))
if (sizeof(size_t) == 4) {
U32 mostSignificantWord = (U32)(val >> 32);