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[util] Add tzcnt function

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This commit is contained in:
Philip Rebohle 2018-05-09 00:01:00 +02:00
parent 33e511485c
commit 5465ee8a85
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1 changed files with 27 additions and 0 deletions
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27
src/util/util_math.h
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@ -1,5 +1,7 @@
#pragma once
#include <x86intrin.h>
namespace dxvk {
constexpr size_t CACHE_LINE_SIZE = 64;
@ -16,4 +18,29 @@ namespace dxvk {
return (what + to - 1) & ~(to - 1);
}
inline uint32_t tzcnt(uint32_t n) {
#if defined(__BMI__)
return __tzcnt_u32(n);
#elif defined(__GNUC__)
uint32_t res;
uint32_t tmp;
asm (
"xor %1, %1;"
"bsf %2, %0;"
"cmovz %1, %0;"
: "=&r" (res), "=&r" (tmp)
: "r" (n));
return res;
#else
uint32_t r = 31;
n &= -n;
r -= (n & 0x0000FFFF) ? 16 : 0;
r -= (n & 0x00FF00FF) ? 8 : 0;
r -= (n & 0x0F0F0F0F) ? 4 : 0;
r -= (n & 0x33333333) ? 2 : 0;
r -= (n & 0x55555555) ? 1 : 0;
return n != 0 ? r : 32;
#endif
}
}