[PATCH] D17834: [AArch64] fold 'isPositive' vector integer operations (PR26819)

[Sanjay Patel via llvm-commits]

spatel created this revision.
spatel added reviewers: t.p.northover, rengolin, jmolloy.
spatel added a subscriber: llvm-commits.
Herald added subscribers: mcrosier, rengolin, aemerson.

This is one of the cases shown in:
https://llvm.org/bugs/show_bug.cgi?id=26819

Shift and negate is what InstCombine prefers to produce (and I tried to make it do more of that in http://reviews.llvm.org/rL262424 ), so we should recognize that pattern as something that might come from autovectorization even if it's unlikely to be produced from C NEON intrinsics.

The patch is largely a copy/paste of the x86 equivalent:
http://reviews.llvm.org/rL262036

...so it might be worth noting as something that could be refactored into DAGCombiner so all backends can share it.

http://reviews.llvm.org/D17834

Files:
  lib/Target/AArch64/AArch64ISelLowering.cpp
  test/CodeGen/AArch64/neon-compare-instructions.ll

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