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