[PATCH] D111006: [PHIElimination] Enable machine verification after this pass

[Mikael Holmén via Phabricator via llvm-commits]

uabelho added a comment.

Hi,

I ran into a verifier error after PHIElimination with this patch.

I saw this for my out-of-tree target, but I think the following mir-testcase exposes the same thing on X86:

  llc -verify-machineinstrs -o /dev/null bbi-61405_x86.mir -run-pass=livevars,phi-node-elimination,twoaddressinstruction

Result:

  *** Bad machine code: LiveVariables: Block should not be in AliveBlocks ***
  - function:    f245
  - basic block: %bb.1  (0x7353b68)
  Virtual register %6 is not needed live through the block.
  LLVM ERROR: Found 1 machine code errors.

It seems to be the undef use of %6 in

  dead %2:gr16 = PHI undef %6, %bb.1, undef %3, %bb.5

that trips PHI Elimination over.
Without it, the inserted COPY for the other PHI gets a kill marking on its source (%6), and all is fine.
But with the "undef %6" operand in the second PHI, the kill marking is skipped and then we get the verifier error.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D111006/new/

https://reviews.llvm.org/D111006