Revert "[PeepholeOptimizer] Look through PHIs to find additional register sources"

Reported to Broke some internal tests: PR24303

This reverts commit r243486.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243540 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed