[LICM] Fix PR35342

Summary: This change fix PR35342 by replacing only the current use with undef in unreachable blocks.

Reviewers: efriedma, mcrosier, igor-laevsky

Reviewed By: efriedma

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D40184

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318551 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed