[PATCH] D147031: [MachineCopy] Enhance sub register machine copy propagation

[Sergei Barannikov via Phabricator via llvm-commits]

barannikov88 added inline comments.


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Comment at: llvm/lib/CodeGen/MachineCopyPropagation.cpp:555
+  // renamable $rcx = COPY killed renamable $k0
+  // renamable $k1 = COPY renamable $ecx
+  Register CopyDstReg = CopyOperands->Destination->getReg();
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This method is not called for this example (look for "MCP: Copy source does not have sub-register" below).
`$ecx` is a sub-register of `$rcx`, and its sub-register index is `sub_32bit`. `$k0` does not have sub-registers with index `sub_32bit`.
You can check my assertion by removing this code and making sure that the added test still passes.



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https://reviews.llvm.org/D147031