[PATCH] Bugfix for Codegen of atomic load/store ops.

[John McCall]

Thanks for splitting the patch.  Generally looks good.  One comment:

================
Comment at: lib/CodeGen/CGAtomic.cpp:985
@@ +984,3 @@
+  // Okay, turn that back into the original value type.
+  if (auto *Result = atomics.tryConvertIntToValue(load))
+    return RValue::get(Result);
----------------
Is there a good reason that this has to be conditional rather than just being a single convertIntToRValue method?  It's okay to pass a ReturnValueSlot in.

http://reviews.llvm.org/D6499