[all-commits] [llvm/llvm-project] d6fe8d: [DAG] Fold concat_vectors(concat_vectors(x, y), conc...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d6fe8d37c68d9fc7a23a3fb15cdda7102d16ce69
      https://github.com/llvm/llvm-project/commit/d6fe8d37c68d9fc7a23a3fb15cdda7102d16ce69
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-08-16 (Mon, 16 Aug 2021)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Target/ARM/ARMISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-extload-truncstore.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-conv.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp2i.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-i2fp.ll
    M llvm/test/CodeGen/RISCV/rvv/mgather-sdnode.ll
    M llvm/test/CodeGen/X86/merge-consecutive-loads-512.ll
    M llvm/test/CodeGen/X86/vector-shuffle-512-v16.ll
    M llvm/test/CodeGen/X86/x86-interleaved-access.ll

  Log Message:
  -----------
  [DAG] Fold concat_vectors(concat_vectors(x,y),concat_vectors(a,b)) -> concat_vectors(x,y,a,b)

Follow-up to D107068, attempt to fold nested concat_vectors/undefs, as long as both the vector and inner subvector types are legal.

This exposed the same issue in ARM's MVE LowerCONCAT_VECTORS_i1 (raised as PR51365) and AArch64's performConcatVectorsCombine which both assumed concat_vectors only took 2 subvector operands.

Differential Revision: https://reviews.llvm.org/D107597