[all-commits] [llvm/llvm-project] 5f3c0b: [AArch64][NEON] Extend faminmax patterns with fmin...

[SpencerAbson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5f3c0b23759faa80b0be59531f7e6643f9c95d32
      https://github.com/llvm/llvm-project/commit/5f3c0b23759faa80b0be59531f7e6643f9c95d32
  Author: SpencerAbson <Spencer.Abson at arm.com>
  Date:   2024-08-20 (Tue, 20 Aug 2024)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64InstrInfo.td
    M llvm/test/CodeGen/AArch64/aarch64-neon-faminmax.ll

  Log Message:
  -----------
  [AArch64][NEON] Extend faminmax patterns with fminnm/fmaxnm (#104766)

Patterns were previously added to allow the following reductions
- fminimum(abs(a), abs(b)) -> famin(a, b)
- fmaximum(abs(a), abs(b)) -> famax(a, b)
- https://github.com/llvm/llvm-project/pull/103027
 
It was suggested by @davemgreen that the following reductions are also
possible
- fminnum[nnan](abs(a), abs(b)) -> famin(a, b)
- fmaxnum[nnan](abs(a), abs(b)) -> famax(a, b)

('nnan' documenatation:
https://llvm.org/docs/LangRef.html#fast-math-flags)

The 'no NaNs' flag allows optimisations to assume that neither argument
is a NaN, and so the differing NaN propagation semantics of
llvm.maxnum/llvm.minnum and FAMAX/FAMIN can be ignored in this
reduction.
(llvm.maxnum/llvm.minnum:
https://llvm.org/docs/LangRef.html#llvm-minnum-intrinsic)

- Changes to LLVM
	- lib/target/AArch64/AArch64InstrInfo.td
- add 'fminnm_nnan' and 'fmaxnm_nnan'; patfrags on fminnm/fmaxnm that
are predicated on the instrinsic call having the 'nnan' flag.
- add AArch64famin and AArch64famax patfrags, containing the new and
existing reductions.
	- test/CodeGen/AArch64/aarch64-neon-faminmax.ll
- add positive and negative tests for the new reduction, based on the
presence of 'nnan' in the IR intrinsic call.



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