[PATCH] D49837: [SelectionDAG] Handle unary SelectPatternFlavor for ABS case in SelectionDAGBuilder::visitSelect.

Fri Mar 15 00:03:05 PDT 2019

ikulagin marked 3 inline comments as done.
ikulagin added inline comments.

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Comment at: llvm/test/CodeGen/AArch64/iabs.ll:46
+; CHECK-NEXT:  abs d0, d0
+; CHECK-NEXT:  fmov x0, d0
 ; CHECK-NEXT:  ret
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efriedma wrote:
> RKSimon wrote:
> > @efriedma IIRC we hit this before?
> Yes; we intentionally marked "abs" as Expand for i64 to avoid this sort of sequence, since it's much higher latency.  Not sure why this patch is reversing that decision.
it is, indeed, so. Latency 3 (abs) + 2*3(fmov) vs 1 (cneg) + 1(cmp). Fixed.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D49837/new/

https://reviews.llvm.org/D49837