[PATCH] D47986: [CostModel] Treat Identity shuffle masks as zero cost

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: efriedma, ABataev, delena, craig.topper, dtemirbulatov, mkuper, spatel, javed.absar.

As discussed on https://reviews.llvm.org/D47985, identity shuffle masks should probably be free.

I've limited this to the case where the input and output types all match - but we could probably accept all cases.


Repository:
  rL LLVM

https://reviews.llvm.org/D47986

Files:
  lib/Analysis/TargetTransformInfo.cpp
  test/Analysis/CostModel/X86/reduction.ll

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