Return "[NFC] Add severe validation of InstructionPrecedenceTracking"

This validation patch has been reverted as rL341147 because of conserns raised by
@reames. This revision returns it as is to raise a discussion and address the concerns.

Differential Revision: https://reviews.llvm.org/D51523
Reviewed By: reames


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341526 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed