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BitUtils: Add CountLeadingZeros

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This commit is contained in:
MerryMage 2020-12-27 22:37:37 +00:00
commit d695fcb126
4 changed files with 52 additions and 45 deletions
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44
Source/Core/Common/BitUtils.h
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@ -11,6 +11,10 @@
#include <initializer_list>
#include <type_traits>
#ifdef _MSC_VER
#include <intrin.h>
#endif
namespace Common
{
///
@ -357,4 +361,44 @@ T ExpandValue(T value, size_t left_shift_amount)
(T(-ExtractBit<0>(value)) >> (BitSize<T>() - left_shift_amount));
}
constexpr int CountLeadingZeros(uint64_t value)
{
#if defined(__GNUC__)
return __builtin_clzll(value);
#elif defined(_MSC_VER) && defined(_M_ARM_64)
return _CountLeadingZeros64(value);
#elif defined(_MSC_VER) && defined(_M_X86_64)
unsigned long index;
return _BitScanReverse64(&index, value) ? 63 - index : 64;
#else
int result = 64;
while (value)
{
result--;
value >>= 1;
}
return result;
#endif
}
constexpr int CountLeadingZeros(uint32_t value)
{
#if defined(__GNUC__)
return __builtin_clz(value);
#elif defined(_MSC_VER) && defined(_M_ARM_64)
return _CountLeadingZeros(value);
#elif defined(_MSC_VER) && defined(_M_X86_64)
unsigned long index;
return _BitScanReverse(&index, value) ? 31 - index : 32;
#else
int result = 32;
while (value)
{
result--;
value >>= 1;
}
return result;
#endif
}
} // namespace Common