[PATCH] D22083: Revert "[X86]: Improve Liveness checking for X86FixupBWInsts.cpp"

Kevin B. Smith via llvm-commits llvm-commits at lists.llvm.org
Wed Jul 6 21:38:41 PDT 2016

kbsmith1 added a comment.

What have you done to prove to yourself that this code is no longer necessary?
If unnecessary, then both before and after the change, the code for 401.bzip2 from spec20006 ought to
be identical.

One way of showing that this code is no longer necessary would be to use the new code and simply
add an assertion after line 389 that NewMI was always nullptr.  Once that code had been in for a while,
you could make the extra forward pass be a debug-only code in an attempt to catch other regressions
that might occur in live-reg tracking.

Also, I kind of liked the better abstraction of tryReplaceInstr. I thought that was an improvement, and is another
reason I don't think just a simple revert is the ideal fix.



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