[all-commits] [llvm/llvm-project] 06d245: [RISCV] Recursively split concat_vector into small...

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 06d245242e3e24cd4558f545fb5ceba0582c4f03
      https://github.com/llvm/llvm-project/commit/06d245242e3e24cd4558f545fb5ceba0582c4f03
  Author: Luke Lau <luke at igalia.com>
  Date:   2024-03-22 (Fri, 22 Mar 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/active_lane_mask.ll
    M llvm/test/CodeGen/RISCV/rvv/combine-store-extract-crash.ll
    M llvm/test/CodeGen/RISCV/rvv/extract-subvector.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-shuffle-concat.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-strided-load-combine.ll
    M llvm/test/CodeGen/RISCV/rvv/fpclamptosat_vec.ll
    M llvm/test/CodeGen/RISCV/rvv/mgather-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/pr63596.ll

  Log Message:
  -----------
  [RISCV] Recursively split concat_vector into smaller LMULs when lowering (#85825)

This is a reimplementation of the combine added in #83035 but as a
lowering instead of a combine, so we don't regress the test case added
in e59f120e3a14ccdc55fcb7be996efaa768daabe0 by interfering with the
strided load combine

Previously the combine had to concatenate the split vectors with
insert_subvector instead of concat_vectors to prevent an infinite
combine loop. And the reasoning behind keeping it as a combine was
because if we emitted the insert_subvector during lowering then we
didn't fold away inserts of undef subvectors.

However it turns out we can avoid this if we just do this in lowering
and select a concat_vector directly, since we get the undef folding for
free with `DAG.getNode(ISD::CONCAT_VECTOR, ...)` via foldCONCAT_VECTORS.



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