Use IgnoreParenCasts. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59371 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index 1e22457..e187d89 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -619,16 +619,7 @@
 
     // Handle __builtin___CFStringMakeConstantString.
     if (E->isBuiltinCall() ==Builtin::BI__builtin___CFStringMakeConstantString){
-      const Expr *Arg = E->getArg(0);
-      
-      while (1) {
-        if (const ParenExpr *PE = dyn_cast<ParenExpr>(Arg))
-          Arg = PE->getSubExpr();
-        else if (const ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(Arg))
-          Arg = CE->getSubExpr();
-        else
-          break;
-      }
+      const Expr *Arg = E->getArg(0)->IgnoreParenCasts();
       
       const StringLiteral *Literal = cast<StringLiteral>(Arg);
       std::string S(Literal->getStrData(), Literal->getByteLength());