[ThinLTO] Attempt to recommit r365040 after caching fix

[ThinLTO] Attempt to recommit r365040 after caching fix

It's possible that some function can load and store the same
variable using the same constant expression:

store %Derived* @foo, %Derived** bitcast (%Base** @bar to %Derived**)
%42 = load %Derived*, %Derived** bitcast (%Base** @bar to %Derived**)

The bitcast expression was mistakenly cached while processing loads,
and never examined later when processing store. This caused @bar to
be mistakenly treated as read-only variable. See load-store-caching.ll.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365188 91177308-0d34-0410-b5e6-96231b3b80d8