[PATCH] D83605: [SelectionDAG][WebAssembly] Recognize splat value ABS operations

[Thomas Lively via Phabricator via llvm-commits]

tlively created this revision.
tlively added reviewers: aheejin, dschuff, RKSimon, david-arm.
Herald added subscribers: llvm-commits, sunfish, hiraditya, jgravelle-google, sbc100.
Herald added a project: LLVM.

This patch gives SelectionDAG::isSplatValue the ability to look
through ABS nodes, which allows the combine introduced in D83602 <https://reviews.llvm.org/D83602> to
scalarize ABS operations when only a single lane is needed.

WebAssembly does not support ABS natively as a scalar operation, but
we still want it to be scalarized and expanded, so this patch also
adds a custom combine in the WebAssembly backend that scalarizes ABS
specifically when it is a splat and only one lane is needed. This is
useful when scalarizing WebAssembly shift values, which often contain
ABS operations in Halide output.

Depends on D83602 <https://reviews.llvm.org/D83602>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83605

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
  llvm/test/CodeGen/WebAssembly/simd-shift-complex-splats.ll

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