Add MS __nop intrinsic to intrin.h

Summary: There was no definition for __nop function - added inline
assembly.

Patch by Albert Gutowski!

Reviewers: rnk, thakis

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D24286

llvm-svn: 280826
diff --git a/clang/lib/Headers/intrin.h b/clang/lib/Headers/intrin.h
index 268ac4a..d68fdfc 100644
--- a/clang/lib/Headers/intrin.h
+++ b/clang/lib/Headers/intrin.h
@@ -97,6 +97,7 @@
 void __movsd(unsigned long *, unsigned long const *, size_t);
 static __inline__
 void __movsw(unsigned short *, unsigned short const *, size_t);
+static __inline__
 void __nop(void);
 void __nvreg_restore_fence(void);
 void __nvreg_save_fence(void);
@@ -918,6 +919,10 @@
 __halt(void) {
   __asm__ volatile ("hlt");
 }
+static __inline__ void __DEFAULT_FN_ATTRS
+__nop(void) {
+  __asm__ volatile ("nop");
+}
 #endif
 
 /*----------------------------------------------------------------------------*\