[Builltins][X86] Provide implementations of __lzcnt16, __lzcnt, __lzcnt64 for MS compatibility. Remove declarations from intrin.h and implementations from lzcntintrin.h

intrin.h had forward declarations for these and lzcntintrin.h had implementations that were only available with -mlzcnt or a -march that supported the lzcnt feature.

For MS compatibility we should always have these builtins available regardless of X86 being the target or the CPU support the lzcnt instruction. The backends should be able to gracefully fallback to something support even if its just shifts and bit ops.

Unfortunately, gcc also implements 2 of the 3 function names here on X86 when lzcnt feature is enabled.

This patch adds builtins for these for MSVC compatibility and drops the forward declarations from intrin.h. To keep the gcc compatibility the two intrinsics that collided have been turned into macros that use the X86 specific builtins with the lzcnt feature check. These macros are only defined when _MSC_VER is not defined. Without them being macros we can get a redefinition error because -ms-extensions doesn't seem to set _MSC_VER but does make the MS builtins available.

Should fix PR40014

Differential Revision: https://reviews.llvm.org/D55677

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@349098 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 10 deletions

diff --git a/lib/Headers/lzcntintrin.h b/lib/Headers/lzcntintrin.h
index f2674d2a5a..35c1651cc4 100644
--- a/lib/Headers/lzcntintrin.h
+++ b/lib/Headers/lzcntintrin.h
@@ -31,6 +31,7 @@
 /* Define the default attributes for the functions in this file. */
 #define __DEFAULT_FN_ATTRS __attribute__((__always_inline__, __nodebug__, __target__("lzcnt")))
 
+#ifndef _MSC_VER
 /// Counts the number of leading zero bits in the operand.
 ///
 /// \headerfile <x86intrin.h>
@@ -41,11 +42,8 @@
 ///    An unsigned 16-bit integer whose leading zeros are to be counted.
 /// \returns An unsigned 16-bit integer containing the number of leading zero
 ///    bits in the operand.
-static __inline__ unsigned short __DEFAULT_FN_ATTRS
-__lzcnt16(unsigned short __X)
-{
-  return __builtin_ia32_lzcnt_u16(__X);
-}
+#define __lzcnt16(X) __builtin_ia32_lzcnt_u16((unsigned short)(X))
+#endif // _MSC_VER
 
 /// Counts the number of leading zero bits in the operand.
 ///
@@ -82,6 +80,7 @@ _lzcnt_u32(unsigned int __X)
 }
 
 #ifdef __x86_64__
+#ifndef _MSC_VER
 /// Counts the number of leading zero bits in the operand.
 ///
 /// \headerfile <x86intrin.h>
@@ -93,11 +92,8 @@ _lzcnt_u32(unsigned int __X)
 /// \returns An unsigned 64-bit integer containing the number of leading zero
 ///    bits in the operand.
 /// \see _lzcnt_u64
-static __inline__ unsigned long long __DEFAULT_FN_ATTRS
-__lzcnt64(unsigned long long __X)
-{
-  return __builtin_ia32_lzcnt_u64(__X);
-}
+#define __lzcnt64(X) __builtin_ia32_lzcnt_u64((unsigned long long)(X))
+#endif // _MSC_VER
 
 /// Counts the number of leading zero bits in the operand.
 ///