[all-commits] [llvm/llvm-project] 4621e1: [DAGCombiner] Relax condition for extract_vector_e...

[ZhaoQi via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4621e17dee138381bd11c1b8dfe656ab8238cc1a
      https://github.com/llvm/llvm-project/commit/4621e17dee138381bd11c1b8dfe656ab8238cc1a
  Author: ZhaoQi <zhaoqi01 at loongson.cn>
  Date:   2025-09-10 (Wed, 10 Sep 2025)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AArch64/shufflevector.ll
    M llvm/test/CodeGen/Thumb2/active_lane_mask.ll
    M llvm/test/CodeGen/Thumb2/mve-complex-deinterleaving-i16-add.ll
    M llvm/test/CodeGen/Thumb2/mve-complex-deinterleaving-i8-add.ll
    M llvm/test/CodeGen/Thumb2/mve-fptosi-sat-vector.ll
    M llvm/test/CodeGen/Thumb2/mve-fptoui-sat-vector.ll
    M llvm/test/CodeGen/Thumb2/mve-laneinterleaving-cost.ll
    M llvm/test/CodeGen/Thumb2/mve-laneinterleaving.ll
    M llvm/test/CodeGen/Thumb2/mve-satmul-loops.ll
    M llvm/test/CodeGen/Thumb2/mve-sext-masked-load.ll
    M llvm/test/CodeGen/Thumb2/mve-vabdus.ll
    M llvm/test/CodeGen/Thumb2/mve-vld2.ll
    M llvm/test/CodeGen/Thumb2/mve-vld3.ll
    M llvm/test/CodeGen/Thumb2/mve-vld4-post.ll
    M llvm/test/CodeGen/Thumb2/mve-vld4.ll
    M llvm/test/CodeGen/Thumb2/mve-vmull-splat.ll
    M llvm/test/CodeGen/Thumb2/mve-vst3.ll
    M llvm/test/CodeGen/WebAssembly/vector-reduce.ll
    M llvm/test/CodeGen/X86/avx512fp16-mov.ll
    M llvm/test/CodeGen/X86/test-shrink-bug.ll
    M llvm/test/CodeGen/X86/vec_smulo.ll
    M llvm/test/CodeGen/X86/vec_umulo.ll

  Log Message:
  -----------
  [DAGCombiner] Relax condition for extract_vector_elt combine (#157658)

Checking `isOperationLegalOrCustom` instead of `isOperationLegal` allows
more optimization opportunities. In particular, if a target wants to
mark `extract_vector_elt` as `Custom` rather than `Legal` in order to
optimize some certain cases, this combiner would otherwise miss some
improvements.

Previously, using `isOperationLegalOrCustom` was avoided due to the risk
of getting stuck in infinite loops (as noted in
https://github.com/llvm/llvm-project/commit/61ec738b60a4fb47ec9b7195de55f1ecb5cbdb45).
After testing, the issue no longer reproduces, but the coverage is
limited to the regression/unit tests and the test-suite.



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