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48 lines
1.8 KiB
48 lines
1.8 KiB
11 months ago
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#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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