[compiler-rt] r250359 - builtins: __builtin_clzll for x86 on MSVC

[Saleem Abdulrasool via llvm-commits]

Author: compnerd
Date: Wed Oct 14 21:46:37 2015
New Revision: 250359

URL: http://llvm.org/viewvc/llvm-project?rev=250359&view=rev
Log:
builtins: __builtin_clzll for x86 on MSVC

Add an implementation for __builtin_clzll on MSVC even when _BitScanForward4 is
unavailable.

Patch by Tee Hao Wei!

Modified:
    compiler-rt/trunk/lib/builtins/int_lib.h

Modified: compiler-rt/trunk/lib/builtins/int_lib.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/builtins/int_lib.h?rev=250359&r1=250358&r2=250359&view=diff
==============================================================================
--- compiler-rt/trunk/lib/builtins/int_lib.h (original)
+++ compiler-rt/trunk/lib/builtins/int_lib.h Wed Oct 14 21:46:37 2015
@@ -115,9 +115,19 @@ uint32_t __inline __builtin_clzll(uint64
     return 63 - leading_zero;
   return 64;
 }
+#else
+uint32_t __inline __builtin_clzll(uint64_t value) {
+  if (value == 0)
+    return 64;
+  uint32_t msh = (uint32_t)(value >> 32);
+  uint32_t lsh = (uint32_t)(value & 0xFFFFFFFF);
+  if (msh != 0)
+    return __builtin_clz(msh);
+  return 32 + __builtin_clz(lsh);
+}
+#endif
 
 #define __builtin_clzl __builtin_clzll
-#endif
-#endif
+#endif // defined(_MSC_VER) && !defined(__clang__)
 
 #endif /* INT_LIB_H */