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#ifndef FALLBACK_BUILTINS_H
#define FALLBACK_BUILTINS_H
#if defined(_MSC_VER) && !defined(__clang__)
#if defined(_M_IX86) || defined(_M_AMD64) || defined(_M_IA64) || defined(_M_ARM) || defined(_M_ARM64) || defined(_M_ARM64EC)
#include <intrin.h>
/* This is not a general purpose replacement for __builtin_ctz. The function expects that value is != 0.
* Because of that assumption trailing_zero is not initialized and the return value is not checked.
* Tzcnt and bsf give identical results except when input value is 0, therefore this can not be allowed.
* If tzcnt instruction is not supported, the cpu will itself execute bsf instead.
* Performance tzcnt/bsf is identical on Intel cpu, tzcnt is faster than bsf on AMD cpu.
*/
static __forceinline int __builtin_ctz(unsigned int value) {
Assert(value != 0, "Invalid input value: 0");
# if defined(X86_FEATURES) && !(_MSC_VER < 1700)
return (int)_tzcnt_u32(value);
# else
unsigned long trailing_zero;
_BitScanForward(&trailing_zero, value);
return (int)trailing_zero;
# endif
}
#define HAVE_BUILTIN_CTZ
#ifdef _M_AMD64
/* This is not a general purpose replacement for __builtin_ctzll. The function expects that value is != 0.
* Because of that assumption trailing_zero is not initialized and the return value is not checked.
*/
static __forceinline int __builtin_ctzll(unsigned long long value) {
Assert(value != 0, "Invalid input value: 0");
# if defined(X86_FEATURES) && !(_MSC_VER < 1700)
return (int)_tzcnt_u64(value);
# else
unsigned long trailing_zero;
_BitScanForward64(&trailing_zero, value);
return (int)trailing_zero;
# endif
}
#define HAVE_BUILTIN_CTZLL
#endif // Microsoft AMD64
#endif // Microsoft AMD64/IA64/x86/ARM/ARM64 test
#endif // _MSC_VER & !clang
#endif // include guard FALLBACK_BUILTINS_H
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