[PATCH] D113584: [ARM] Fold (fadd x, (vselect c, y, -1.0)) into (vselect c, (fadd x, y), x)

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: SjoerdMeijer, samtebbs, ostannard, simon_tatham.
Herald added subscribers: hiraditya, kristof.beyls.
dmgreen requested review of this revision.
Herald added a project: LLVM.

This is similar to D113574 <https://reviews.llvm.org/D113574>, but as a DAG combine, not tablegen patterns. Doing the fold as a DAG combine allows the fadd to be folded with a fmul, finally producing a predicated vfma. It performs the same fold of `fadd(x, vselect(p, y, -0.0))` to `vselect p, (fadd x, y), x)` using -0.0 as the identity value of a fadd.


https://reviews.llvm.org/D113584

Files:
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/test/CodeGen/Thumb2/mve-pred-selectop3.ll

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