fix PR4938 by recognizing % as a modifier on outputs,
previously we only recognized it on inputs.

llvm-svn: 83939
diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 35d9ccd..9cd1249 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -188,6 +188,9 @@
       }
     case '&': // early clobber.
       break;
+    case '%': // commutative.
+      // FIXME: Check that there is a another register after this one.
+      break;
     case 'r': // general register.
       Info.setAllowsRegister();
       break;