[MemorySSA] Remove optimized value when reseting optimized.

If we don't reset the optimized value O for access A, even though A is no longer optimized to O, A will still show up in that O's users list.
This fails verification when hoisting a Def outside a loop, even though the updates are correct.
The reason is that the phi in the loop header still find as user the hoisted def, because the Def has a pointer to the Phi in its optimized operand.

Reviewers: george.burgess.iv

Subscribers: sanjoy, jlebar, Prazek, llvm-commits

Differential Revision: https://reviews.llvm.org/D56467

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350783 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed