[all-commits] [llvm/llvm-project] 2f005d: [DAG][X86] Fold mgather/mscatter/etc with splat in...

[Philip Reames via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2f005df066e07d93e3d6aa04748c158f883197b7
      https://github.com/llvm/llvm-project/commit/2f005df066e07d93e3d6aa04748c158f883197b7
  Author: Philip Reames <preames at rivosinc.com>
  Date:   2023-09-13 (Wed, 13 Sep 2023)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/X86/masked_gather.ll

  Log Message:
  -----------
  [DAG][X86] Fold mgather/mscatter/etc with splat index (#65980)

A splat index means the operation is reading from (writing to) the same
memory location. Generally, zero is the cheapest value to splat. As
such, we'd prefer to add the splatted value to the base, and use a
constant zero as the index operand.