[all-commits] [llvm/llvm-project] e26ec3: [DAG][AArch64][ARM] Combine abd(sub(x, y)) to abd ...

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e26ec330c4ff26c4f51e1bac4669b57c0edb5d3e
      https://github.com/llvm/llvm-project/commit/e26ec330c4ff26c4f51e1bac4669b57c0edb5d3e
  Author: David Green <david.green at arm.com>
  Date:   2023-01-18 (Wed, 18 Jan 2023)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AArch64/neon-abd.ll

  Log Message:
  -----------
  [DAG][AArch64][ARM] Combine abd(sub(x, y)) to abd if the sub is nsw

This implements the fold (abs (sub nsw x, y)) -> abds(x, y). Providing
the sub is nsw this appears to be valid without the extensions that are
usually used for abds. https://alive2.llvm.org/ce/z/XHVaB3. The
equivalent abdu combine seems to not be valid.

Differential Revision: https://reviews.llvm.org/D141665