[PATCH] D50064: [MachineCopyPropagation] Improve redundant copy elimination

[Alexander Ivchenko via Phabricator via llvm-commits]

aivchenk created this revision.
aivchenk added reviewers: gberry, efriedma.

  We can go a little further and delete the first copy here as well:
     %R1 = COPY %R0         << Redundant
     ... // No clobber of %R1 and no uses of %R1 defined by the first copy.
     %R0 = COPY killed %R1  << Redundant
  In other words, The first copy is only used for defining a reg
  that is used only in the second copy.
  
  Previously, we deleted only the second copy as redundant.


https://reviews.llvm.org/D50064

Files:
  lib/CodeGen/MachineCopyPropagation.cpp
  test/CodeGen/X86/machine-copy-prop.mir

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