[PATCH] D146930: [MCP] Do not try forward non-existent sub-register of a copy

[Xiang Zhang via Phabricator via llvm-commits]

xiangzhangllvm added inline comments.


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Comment at: llvm/lib/CodeGen/MachineCopyPropagation.cpp:653
+      ForwardedReg = TRI->getSubReg(CopySrcReg, SubRegIdx);
+      if (!ForwardedReg) {
+        LLVM_DEBUG(dbgs() << "MCP: Copy source does not have sub-register "
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I think there is unsafe to use the SubRegIdx when CopySrcReg and CopyDstReg reg are not same regclass or even different size.
I happen to meet this bug in our tests.
Pls refer to https://reviews.llvm.org/D147031 


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D146930/new/

https://reviews.llvm.org/D146930