[PATCH] D147031: [MachineCopy] Bug fix sub register machine copy propagation

[Xiang Zhang via Phabricator via llvm-commits]

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The machine copy propagation logic has some problem:
When do machine copy propagation for subreg we need to consider the CopyDstReg and CopySrcReg's regclass and size.
(because we want to get SubReg from CopySrcReg by using SubregIdx which we got from CopyDstReg)
Take follow case for example:

  MCP: Replacing $ecx
       with $k0
       in renamable $k1 = COPY renamable $ecx
       from renamable $rcx = COPY renamable $k0, implicit-def $ecx

We can not use SubregIdx (ecx of rcx) to get anything from k0 register.


https://reviews.llvm.org/D147031

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

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