[all-commits] [llvm/llvm-project] 263f1b: [PowerPC] Fix combine step for shufflevector.

[stefanp-ibm via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 263f1b2f5df71c71397f5bb05c353f3d9d27522e
      https://github.com/llvm/llvm-project/commit/263f1b2f5df71c71397f5bb05c353f3d9d27522e
  Author: Stefan Pintilie <stefanp at ca.ibm.com>
  Date:   2022-06-14 (Tue, 14 Jun 2022)

  Changed paths:
    M llvm/lib/Target/PowerPC/PPCISelLowering.cpp
    A llvm/test/CodeGen/PowerPC/ppc-shufflevector-combine.ll

  Log Message:
  -----------
  [PowerPC] Fix combine step for shufflevector.

The combine step for shufflevector will sometimes replace undef in the mask
with a defined value. This can cause an infinite loop in some cases as another
combine will then put the undef back in the mask.

This patch fixes the issue so that undefs are not replaced when doing a combine.

Reviewed By: ZarkoCA, amyk, quinnp, saghir

Differential Revision: https://reviews.llvm.org/D127439