fix PR4938 by recognizing % as a modifier on outputs,

previously we only recognized it on inputs.

llvm-svn: 83939

clang/lib/Basic/TargetInfo.cpp

@@ -188,6 +188,9 @@ bool TargetInfo::validateOutputConstraint(ConstraintInfo &Info) const {
       }
     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;

clang/test/CodeGen/asm.c

@@ -101,3 +101,12 @@ void t14(struct S *P) {
 }
 
 
+// PR4938
+int t16() {
+  int a,b;
+  asm ( "nop;"
+       :"=%c" (a)
+       : "r" (b)
+       );
+  return 0;
+}