[PATCH] D125895: [AArch64] implement isReassocProfitable, disable for (u|s)mlal.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: dmgreen, t.p.northover, ab.
Herald added subscribers: steven.zhang, hiraditya, kristof.beyls.
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fhahn requested review of this revision.
Herald added a project: LLVM.

Currently reassociating add expressions can lead to failing to select
(u|s)mlal. Implement isReassocProfitable to skip reassociating
expressions that can be lowered to (u|s)mlal.

The same issue exists for the *mlsl variants as well, but the DAG
combiner doesn't use the isReassocProfitable hook before reassociating.
To be fixed in a follow-up commit as this requires DAGCombiner changes
as well.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125895

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.h
  llvm/test/CodeGen/AArch64/arm64-vmul.ll

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