[PATCH] D100376: [ARM] Prevent phi-node-elimination from generating copy above t2WhileLoopStartLR

[Malhar via Phabricator via llvm-commits]

malharJ created this revision.
malharJ added reviewers: dmgreen, SjoerdMeijer.
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This patch prevents phi-node-elimination from generating a COPY operation for the register
defined by t2WhileLoopStartLR, as it is a terminator that defines a value.

This happens because of the presence of phi-nodes in the loop body (the Preheader
of which is the block containing the t2WhileLoopStartLR). If this is not done,
the COPY is generated above/before the terminator (t2WhileLoopStartLR here),
and since it uses the value defined by t2WhileLoopStartLR, MachineVerifier throws
a 'use before define' error.

This essentially adds on to the change in differential D91887 <https://reviews.llvm.org/D91887>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100376

Files:
  llvm/lib/Target/ARM/ARMBaseInstrInfo.h
  llvm/test/CodeGen/Thumb2/phi_prevent_copy.mir

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