clang uses the llvm backend, so define __llvm__ like llvm-gcc.

Additionally, define __clang__ so clients can predicate based on
clang features.

llvm-svn: 52788

clang/lib/Lex/Preprocessor.cpp

@@ -415,6 +415,9 @@ static void InitializePredefinedMacros(Preprocessor &PP,
   // Get the target #defines.
   PP.getTargetInfo().getTargetDefines(Buf);
 
+  DefineBuiltinMacro(Buf, "__llvm__=1");   // LLVM Backend
+  DefineBuiltinMacro(Buf, "__clang__=1");  // Clang Frontend
+  
   // Compiler set macros.
   DefineBuiltinMacro(Buf, "__APPLE_CC__=5250");
   DefineBuiltinMacro(Buf, "__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__=1050");