Add invariant.load metadata to loads from selector references. Allows these loads to later be moved/combined in the optimizer. Fixes <rdar://problem/6027699>

llvm-svn: 144318

clang/lib/CodeGen/CGObjCMac.cpp

@@ -5887,7 +5887,12 @@ llvm::Value *CGObjCNonFragileABIMac::EmitSelector(CGBuilderTy &Builder,
 
   if (lval)
     return Entry;
-  return Builder.CreateLoad(Entry);
+  llvm::LoadInst* LI = Builder.CreateLoad(Entry);
+  
+  LI->setMetadata(CGM.getModule().getMDKindID("invariant.load"), 
+                  llvm::MDNode::get(VMContext,
+                                    ArrayRef<llvm::Value*>()));
+  return LI;
 }
 /// EmitObjCIvarAssign - Code gen for assigning to a __strong object.
 /// objc_assign_ivar (id src, id *dst, ptrdiff_t)

clang/test/CodeGenObjC/selector-ref-invariance.m

@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin11 -emit-llvm -fblocks -o - %s | FileCheck %s
+
+// rdar://6027699
+
+void test(id x) {
+// CHECK: load i8** @"\01L_OBJC_SELECTOR_REFERENCES_", !invariant.load
+// CHECK: @objc_msgSend
+  [x foo];
+}