[PATCH] D66805: [MIPS] For vectors, select `add %x, -1` as `sub %x, 1`

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: atanasyan, Petar.Avramovic, RKSimon.
lebedev.ri added a project: LLVM.
Herald added subscribers: jrtc27, hiraditya, arichardson, sdardis.
lebedev.ri added a parent revision: D62341: [DAGCombine][X86][AArch64][AMDGPU][MIPS][PPC] (sub x, c) -> (add x, -c)  vector edition..

As discussed in https://reviews.llvm.org/D62341#1515637, 
for MIPS `add %x, -1` isn't optimal. Unlike X86 there
are no fastpaths to matearialize such `-1`/`1` vector constants,
and `sub %x, 1` results in better codegen,
so undo canonicalization


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D66805

Files:
  llvm/include/llvm/CodeGen/SelectionDAGNodes.h
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
  llvm/lib/Target/Mips/MipsISelDAGToDAG.h
  llvm/test/CodeGen/Mips/msa/arithmetic.ll

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