history-museum/winamp
1
0
Fork 0
mirror of https://github.com/WinampDesktop/winamp.git synced 2025-06-18 00:05:45 -04:00
Code Issues Actions Packages Projects Releases Wiki Activity

BitUtils: Make Count{Leading,Trailing}Zeros UB for value==0

Browse Source
This commit is contained in:
Connor McLaughlin
2020-04-26 18:32:23 +10:00
parent 38b075c014
commit 5671fde1ae
3 changed files with 19 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
src/common/bitutils.h
View File

@ -5,6 +5,7 @@
#include <intrin.h>
#endif
/// Returns the number of zero bits before the first set bit, going MSB->LSB.
template<typename T>
ALWAYS_INLINE unsigned CountLeadingZeros(T value)
{
@ -12,27 +13,26 @@ ALWAYS_INLINE unsigned CountLeadingZeros(T value)
if constexpr (sizeof(value) >= sizeof(u64))
{
unsigned long index;
return _BitScanReverse64(&index, ZeroExtend64(value)) ? static_cast<unsigned>(index) : 0;
_BitScanReverse64(&index, ZeroExtend64(value));
return static_cast<unsigned>(index) ^ static_cast<unsigned>((sizeof(value) * 8u) - 1u);
}
else
{
unsigned long index;
return _BitScanReverse(&index, ZeroExtend32(value)) ? static_cast<unsigned>(index) : 0;
_BitScanReverse(&index, ZeroExtend32(value));
return static_cast<unsigned>(index) ^ static_cast<unsigned>((sizeof(value) * 8u) - 1u);
}
#else
if constexpr (sizeof(value) >= sizeof(u64))
{
const unsigned bits = static_cast<unsigned>(__builtin_clzl(ZeroExtend64(value)));
return (value != 0) ? static_cast<unsigned>(bits) : 0;
}
return static_cast<unsigned>(__builtin_clzl(ZeroExtend64(value)));
else if constexpr (sizeof(value) == sizeof(u32))
return static_cast<unsigned>(__builtin_clz(ZeroExtend32(value)));
else
{
const unsigned bits = static_cast<unsigned>(__builtin_clz(ZeroExtend32(value)));
return (value != 0) ? static_cast<unsigned>(bits) : 0;
}
return static_cast<unsigned>(__builtin_clz(ZeroExtend32(value))) & static_cast<unsigned>((sizeof(value) * 8u) - 1u);
#endif
}
/// Returns the number of zero bits before the first set bit, going LSB->MSB.
template<typename T>
ALWAYS_INLINE unsigned CountTrailingZeros(T value)
{
@ -40,23 +40,19 @@ ALWAYS_INLINE unsigned CountTrailingZeros(T value)
if constexpr (sizeof(value) >= sizeof(u64))
{
unsigned long index;
return _BitScanForward64(&index, ZeroExtend64(value)) ? static_cast<unsigned>(index) : 0;
_BitScanForward64(&index, ZeroExtend64(value));
return index;
}
else
{
unsigned long index;
return _BitScanForward(&index, ZeroExtend32(value)) ? static_cast<unsigned>(index) : 0;
_BitScanForward(&index, ZeroExtend32(value));
return index;
}
#else
if constexpr (sizeof(value) >= sizeof(u64))
{
const unsigned bits = static_cast<unsigned>(__builtin_ctzl(ZeroExtend64(value)));
return (value != 0) ? static_cast<unsigned>(bits) : 0;
}
return static_cast<unsigned>(__builtin_ctzl(ZeroExtend64(value)));
else
{
const unsigned bits = static_cast<unsigned>(__builtin_ctz(ZeroExtend32(value)));
return (value != 0) ? static_cast<unsigned>(bits) : 0;
}
return static_cast<unsigned>(__builtin_ctz(ZeroExtend32(value)));
#endif
}