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tuklib_integer: Use __builtin_clz() with Clang.
Clang has support for __builtin_clz(), but previously Clang would fallback to either the MSVC intrinsic or the regular C code. This was discovered due to a bug where a new version of Clang required the <intrin.h> header file in order to use the MSVC intrinsics. Thanks to Anton Kochkov for notifying us about the bug.
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1 changed files with 3 additions and 3 deletions
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@ -630,7 +630,7 @@ bsr32(uint32_t n)
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#if defined(__INTEL_COMPILER)
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return _bit_scan_reverse(n);
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#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
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#elif (TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) && UINT_MAX == UINT32_MAX
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// GCC >= 3.4 has __builtin_clz(), which gives good results on
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// multiple architectures. On x86, __builtin_clz() ^ 31U becomes
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// either plain BSR (so the XOR gets optimized away) or LZCNT and
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@ -684,7 +684,7 @@ clz32(uint32_t n)
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#if defined(__INTEL_COMPILER)
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return _bit_scan_reverse(n) ^ 31U;
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#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
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#elif (TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) && UINT_MAX == UINT32_MAX
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return (uint32_t)__builtin_clz(n);
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#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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@ -739,7 +739,7 @@ ctz32(uint32_t n)
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#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX >= UINT32_MAX
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return (uint32_t)__builtin_ctz(n);
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#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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#elif (TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) && UINT_MAX == UINT32_MAX
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uint32_t i;
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__asm__("bsfl %1, %0" : "=r" (i) : "rm" (n));
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return i;
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