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[util] Implement lzcnt

This commit is contained in:
Joshua Ashton 2019-07-27 18:47:32 +01:00 committed by Philip Rebohle
parent aef12f7ee3
commit 57b2c02528
1 changed files with 20 additions and 0 deletions
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20
src/util/util_bit.h
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@ -75,6 +75,26 @@ namespace dxvk::bit {
#endif
}
inline uint32_t lzcnt(uint32_t n) {
#if (defined(_MSC_VER) && !defined(__clang__)) || defined(__LZCNT__)
return _lzcnt_u32(n);
#elif defined(__GNUC__) || defined(__clang__)
return n != 0 ? __builtin_clz(n) : 32;
#else
uint32_t r = 0;
if (n == 0) return 32;
if (n <= 0x0000FFFF) { r += 16; n <<= 16; }
if (n <= 0x00FFFFFF) { r += 8; n <<= 8; }
if (n <= 0x0FFFFFFF) { r += 4; n <<= 4; }
if (n <= 0x3FFFFFFF) { r += 2; n <<= 2; }
if (n <= 0x7FFFFFFF) { r += 1; n <<= 1; }
return r;
#endif
}
template<typename T>
uint32_t pack(T& dst, uint32_t& shift, T src, uint32_t count) {
constexpr uint32_t Bits = 8 * sizeof(T);