[all-commits] [llvm/llvm-project] 6ec889: [DAG] Add support for neg(abd(x, y)) patterns.

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6ec889e53f1ae048cc9aee79c91118fc8bbc6974
      https://github.com/llvm/llvm-project/commit/6ec889e53f1ae048cc9aee79c91118fc8bbc6974
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-09-06 (Fri, 06 Sep 2024)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/PowerPC/ppc64-P9-vabsd.ll
    M llvm/test/CodeGen/X86/abds-neg.ll
    M llvm/test/CodeGen/X86/abdu-neg.ll

  Log Message:
  -----------
  [DAG] Add support for neg(abd(x,y)) patterns.

Currently limited to cases which have legal/custom ABDS/ABDU handling - I'll extend this for all targets in future (similar to how we support neg(abs(x))) once I've addressed some outstanding regressions on aarch64/riscv.

Helps avoid a lot of extra cmov instructions on x86 in particular, and allows us to more easily improve the codegen in future commits.



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