Switch assert(0/false) llvm_unreachable.

llvm-svn: 140367
diff --git a/clang/lib/CodeGen/CGObjCRuntime.h b/clang/lib/CodeGen/CGObjCRuntime.h
index 7accc70..4fa47a7 100644
--- a/clang/lib/CodeGen/CGObjCRuntime.h
+++ b/clang/lib/CodeGen/CGObjCRuntime.h
@@ -208,8 +208,7 @@
   
   
   virtual llvm::Value *EmitNSAutoreleasePoolClassRef(CGBuilderTy &Builder) {
-    assert(false &&"autoreleasepool unsupported in this ABI");
-    return 0;
+    llvm_unreachable("autoreleasepool unsupported in this ABI");
   }
   
   /// EnumerationMutationFunction - Return the function that's called by the