[CodeGen] Avoid handling DBG_VALUE in the LivePhysRegs (addUses,removeDefs,stepForward)
Summary:
This patch prevents DBG_VALUE instructions from influencing
LivePhysRegs::stepBackwards and stepForwards. In at least one case,
specifically branch folding, the stepBackwards logic was having an
influence on code generation. The result was that certain code
compiled with '-g -O2' would differ from that compiled with '-O2'
alone. It seems that the original logic, accounting for DBG_VALUE,
was influencing the placement of an IMPLICIT_DEF which had a later
impact on how blocks were processed in branch folding.
Reviewers: kparzysz, MatzeB
Reviewed By: kparzysz
Subscribers: bjope, llvm-commits
Tags: #debug-info
Differential Revision: https://reviews.llvm.org/D43850
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327862
91177308-0d34-0410-b5e6-
96231b3b80d8