[all-commits] [llvm/llvm-project] 02f851: [DAG] Prevent infinite loop combining bitcast shuffle

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 02f8519502447de6ef69a85fa8de5732dd59d853
      https://github.com/llvm/llvm-project/commit/02f8519502447de6ef69a85fa8de5732dd59d853
  Author: David Green <david.green at arm.com>
  Date:   2022-05-09 (Mon, 09 May 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/ARM/vector-DAGCombine.ll
    A llvm/test/CodeGen/X86/shuffle-combine-crash-4.ll

  Log Message:
  -----------
  [DAG] Prevent infinite loop combining bitcast shuffle

This prevents an infinite loop from D123801, where code trying to reduce
the total number of bitcasts, but also handling constants, could create
the opposite transform. Prevent the transform in these case to let the
bitcast of a constant transform naturally.

Fixes #55345