[all-commits] [llvm/llvm-project] 7f9365: [SelectionDAG] Deal with POISON for INSERT_VECTOR_...

[Björn Pettersson via All-commits]

  Branch: refs/heads/users/bjope/insertundef_4
  Home:   https://github.com/llvm/llvm-project
  Commit: 7f93651bdc0268aa76f005da5906a4fe380cfa67
      https://github.com/llvm/llvm-project/commit/7f93651bdc0268aa76f005da5906a4fe380cfa67
  Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
  Date:   2025-06-06 (Fri, 06 Jun 2025)

  Changed paths:
    M llvm/include/llvm/CodeGen/SelectionDAG.h
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll
    M llvm/test/CodeGen/AArch64/sve-fixed-length-fp-vselect.ll
    M llvm/test/CodeGen/AArch64/sve-fixed-length-frame-offests.ll
    M llvm/test/CodeGen/AArch64/sve-fixed-length-int-vselect.ll
    M llvm/test/CodeGen/AArch64/sve-fixed-length-masked-gather.ll
    M llvm/test/CodeGen/AArch64/sve-streaming-mode-fixed-length-fp-vselect.ll
    M llvm/test/CodeGen/AArch64/sve-streaming-mode-fixed-length-int-vselect.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vfw-web-simplification.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vw-web-simplification.ll

  Log Message:
  -----------
  [SelectionDAG] Deal with POISON for INSERT_VECTOR_ELT/INSERT_SUBVECTOR (part 3)

Target specific patches to avoid regressions seen after "part 1"
aiming at fixing github issue #141034.

One perhaps controversial change here is that convertToScalableVector
now uses POISON instead of UNDEF for any additional elements added
when converting to the scalable vector. This can avoid that we end
up with things like
  t31: nxv1f32 =
  t32: v2f32 = extract_subvector t31, Constant:i64<0>
  t38: nxv1f32 = insert_subvector undef:nxv1f32, t32, Constant:i64<0>
since if we instead try to insert into poison we can just use t31
instead of t38 without the risk that t31 would be more poisonous.



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