[llvm-commits] [llvm] r67103 - in /llvm/trunk: include/llvm/Support/Compiler.h lib/Support/raw_ostream.cpp

[Daniel Dunbar]

Author: ddunbar
Date: Tue Mar 17 16:15:18 2009
New Revision: 67103

URL: http://llvm.org/viewvc/llvm-project?rev=67103&view=rev
Log:
Add BUILTIN_EXPECT Support/Compiler macro.
 - Use for exceptional buffer conditions in raw_ostream:write to shave
   off a cycle or two.

 - Please rename if you have a better one.

Modified:
    llvm/trunk/include/llvm/Support/Compiler.h
    llvm/trunk/lib/Support/raw_ostream.cpp

Modified: llvm/trunk/include/llvm/Support/Compiler.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Compiler.h?rev=67103&r1=67102&r2=67103&view=diff

==============================================================================
--- llvm/trunk/include/llvm/Support/Compiler.h (original)
+++ llvm/trunk/include/llvm/Support/Compiler.h Tue Mar 17 16:15:18 2009
@@ -29,6 +29,12 @@
 #define ATTRIBUTE_USED
 #endif
 
+#if (__GNUC__ >= 4)
+#define BUILTIN_EXPECT(EXPR, VALUE) __builtin_expect((EXPR), (VALUE))
+#else
+#define BUILTIN_EXPECT(EXPR, VALUE) (EXPR)
+#endif
+
 // C++ doesn't support 'extern template' of template specializations.  GCC does,
 // but requires __extension__ before it.  In the header, use this:
 //   EXTERN_TEMPLATE_INSTANTIATION(class foo<bar>);

Modified: llvm/trunk/lib/Support/raw_ostream.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/raw_ostream.cpp?rev=67103&r1=67102&r2=67103&view=diff

==============================================================================
--- llvm/trunk/lib/Support/raw_ostream.cpp (original)
+++ llvm/trunk/lib/Support/raw_ostream.cpp Tue Mar 17 16:15:18 2009
@@ -16,6 +16,7 @@
 #include "llvm/System/Program.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Config/config.h"
+#include "llvm/Support/Compiler.h"
 #include <ostream>
 
 #if defined(HAVE_UNISTD_H)
@@ -142,7 +143,7 @@
 
 raw_ostream &raw_ostream::write(const char *Ptr, unsigned Size) {
   // Group exceptional cases into a single branch.
-  if (OutBufCur+Size > OutBufEnd) {
+  if (BUILTIN_EXPECT(OutBufCur+Size > OutBufEnd, false)) {
     if (Unbuffered) {
       write_impl(Ptr, Size);
       return *this;