[all-commits] [llvm/llvm-project] c22364: [AArch64] Eliminate Common SUBS by Reassociating N...

[Marius Kamp via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c22364a4324218e29512740466a2b2cb1a406d8b
      https://github.com/llvm/llvm-project/commit/c22364a4324218e29512740466a2b2cb1a406d8b
  Author: Marius Kamp <msk at posteo.org>
  Date:   2025-01-21 (Tue, 21 Jan 2025)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/test/CodeGen/AArch64/csel-cmp-cse.ll

  Log Message:
  -----------
  [AArch64] Eliminate Common SUBS by Reassociating Non-Constants (#123344)

Commit 1eed46960c217f9480865702f06fb730c7521e61 added logic to
reassociate a (add (add x y) -c) operand to a CSEL instruction with a
comparison involving x and c (or a similar constant) in order to obtain
a common (SUBS x c) instruction.
    
This commit extends this logic to non-constants. In this way, we also
reassociate a (sub (add x y) z) operand of a CSEL instruction to
(add (sub x z) y) if the CSEL compares x and z, for example.
    
Alive proof: https://alive2.llvm.org/ce/z/SEVpR



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