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authorJia Tan <jiat0218@gmail.com>2023-04-19 21:59:03 +0800
committerLasse Collin <lasse.collin@tukaani.org>2023-05-03 22:33:10 +0300
commit8efb6ea63ba4353104add3cbf9fb76203142ea4c (patch)
tree3f7dccac3fa23af499e6cadf244049d1eee5f46d
parentliblzma: Update project maintainers in lzma.h. (diff)
downloadxz-8efb6ea63ba4353104add3cbf9fb76203142ea4c.tar.xz
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.
-rw-r--r--src/common/tuklib_integer.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/src/common/tuklib_integer.h b/src/common/tuklib_integer.h
index 6f44a7a0..bfb8683b 100644
--- a/src/common/tuklib_integer.h
+++ b/src/common/tuklib_integer.h
@@ -588,7 +588,7 @@ bsr32(uint32_t n)
#if defined(__INTEL_COMPILER)
return _bit_scan_reverse(n);
-#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
+#elif (TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) && UINT_MAX == UINT32_MAX
// GCC >= 3.4 has __builtin_clz(), which gives good results on
// multiple architectures. On x86, __builtin_clz() ^ 31U becomes
// either plain BSR (so the XOR gets optimized away) or LZCNT and
@@ -642,7 +642,7 @@ clz32(uint32_t n)
#if defined(__INTEL_COMPILER)
return _bit_scan_reverse(n) ^ 31U;
-#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX == UINT32_MAX
+#elif (TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) && UINT_MAX == UINT32_MAX
return (uint32_t)__builtin_clz(n);
#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
@@ -697,7 +697,7 @@ ctz32(uint32_t n)
#elif TUKLIB_GNUC_REQ(3, 4) && UINT_MAX >= UINT32_MAX
return (uint32_t)__builtin_ctz(n);
-#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+#elif (TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) && UINT_MAX == UINT32_MAX
uint32_t i;
__asm__("bsfl %1, %0" : "=r" (i) : "rm" (n));
return i;