[all-commits] [llvm/llvm-project] 6117bd: [DAGCombiner] Fix subvector extraction index for b...

[陈子昂 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6117bdd90324af22a920d56d673acff21342a1cb
      https://github.com/llvm/llvm-project/commit/6117bdd90324af22a920d56d673acff21342a1cb
  Author: 陈子昂 <2802328816 at qq.com>
  Date:   2026-02-12 (Thu, 12 Feb 2026)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    A llvm/test/CodeGen/ARM/stlf-vector-extract.ll
    M llvm/test/CodeGen/X86/avx512-shuffles/shuffle-chained-bf16.ll

  Log Message:
  -----------
  [DAGCombiner] Fix subvector extraction index for big-endian STLF (#180795)

This PR fixes a big-endian regression in `ForwardStoreValueToDirectLoad`
where the wrong subvector was being extracted. In big-endian, memory
offset 0 corresponds to the high bits, so the extraction index needs to
be adjusted.

As suggested by @KennethHilmersson, calculate the extraction index as
the difference between the number of elements in the intermediate vector
and the load vector when in big-endian mode.

Special thanks to Kenneth Hilmersson for providing the fix logic and the
ARM regression test.
https://github.com/llvm/llvm-project/pull/172523#issuecomment-3878065191
https://github.com/llvm/llvm-project/pull/172523#issuecomment-3879575092



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