[all-commits] [llvm/llvm-project] be15fd: [InitUndef] handleSubReg should skip artificial su...

[Sander de Smalen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: be15fd5085680cc5ed9ec4f4f2258b504cdd55db
      https://github.com/llvm/llvm-project/commit/be15fd5085680cc5ed9ec4f4f2258b504cdd55db
  Author: Sander de Smalen <sander.desmalen at arm.com>
  Date:   2024-11-14 (Thu, 14 Nov 2024)

  Changed paths:
    M llvm/lib/CodeGen/InitUndef.cpp
    M llvm/test/CodeGen/AArch64/init-undef.mir

  Log Message:
  -----------
  [InitUndef] handleSubReg should skip artificial subregs. (#116248)

When enabling subreg liveness tracking for AArch64, this pass fails
because it tries to get the register class for the artificial subreg
`sub_32_hi` of a 64-bit GPR. It tries to create an INIT_UNDEF
instruction for the top 32-bits of the 64-bit GPR, which are not
directly addressable, so getSubRegisterClass() returns a nullptr,
crashing this pass.

It should instead just avoid trying to create the INIT_UNDEF
instruction.



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