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/dictBuilder/zdict.c
+32 -8
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@@ -135,8 +135,14 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
if (MEM_isLittleEndian()) {
if (MEM_64bits()) {
# if defined(_MSC_VER) && defined(_WIN64)
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);
}
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (unsigned)(__builtin_ctzll((U64)val) >> 3);
# else
@@ -145,8 +151,14 @@ static unsigned ZDICT_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 (unsigned)(__builtin_ctz((U32)val) >> 3);
# else
@@ -157,8 +169,14 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
} else { /* Big Endian CPU */
if (MEM_64bits()) {
# if defined(_MSC_VER) && defined(_WIN64)
unsigned long r;
return _BitScanReverse64(&r, val) ? (unsigned)(r >> 3) : 0;
if (val != 0) {
unsigned long r;
_BitScanReverse64(&r, val);
return (unsigned)(r >> 3);
} else {
/* Should not reach this code path */
__assume(0);
}
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (unsigned)(__builtin_clzll(val) >> 3);
# else
@@ -171,8 +189,14 @@ static unsigned ZDICT_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 (unsigned)(__builtin_clz((U32)val) >> 3);
# else