[all-commits] [llvm/llvm-project] 05b16a: [DAGCombiner] Add combine for vector interleave of...

[David Sherwood via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 05b16aff0f4d5132799d7d4470ca13db3afe13ae
      https://github.com/llvm/llvm-project/commit/05b16aff0f4d5132799d7d4470ca13db3afe13ae
  Author: David Sherwood <david.sherwood at arm.com>
  Date:   2025-08-01 (Fri, 01 Aug 2025)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AArch64/complex-deinterleaving-reductions-predicated-scalable.ll
    M llvm/test/CodeGen/AArch64/complex-deinterleaving-reductions-scalable.ll
    M llvm/test/CodeGen/AArch64/fixed-vector-interleave.ll
    M llvm/test/CodeGen/AArch64/sve-vector-interleave.ll
    M llvm/test/CodeGen/RISCV/rvv/vector-interleave-fixed.ll
    M llvm/test/CodeGen/RISCV/rvv/vector-interleave.ll

  Log Message:
  -----------
  [DAGCombiner] Add combine for vector interleave of splats (#151110)

This patch adds two DAG combines:

1. vector_interleave(splat, splat, ...) -> {splat,splat,...}
2. concat_vectors(splat, splat, ...) -> wide_splat

where all the input splats are identical. Both of these
together enable us to fold
  concat_vectors(vector_interleave(splat, splat, ...))
into a wide splat. Post-legalisation we must only do the
concat_vector combine if the wider type and splat operation
is legal.

For fixed-width vectors the DAG combine only occurs for
interleave factors of 3 or more, however it's not currently
safe to test this for AArch64 since there isn't any lowering
support for fixed-width interleaves. I've only added
fixed-width tests for RISCV.



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