[PATCH] D55590: [CostModel][X86] Don't count 2 shuffles on the last level of a pairwise arithmetic or min/max reduction
Craig Topper via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Dec 11 18:00:30 PST 2018
craig.topper created this revision.
craig.topper added reviewers: RKSimon, ABataev, spatel.
This is split from D55452 <https://reviews.llvm.org/D55452>
Pairwise reductions require two shuffles on every level but the last. On the last level the two shuffles are <1, u, u, u...> and <0, u, u, u...>, but <0, u, u, u...> will be dropped by InstCombine/DAGCombine as being an identity shuffle.
https://reviews.llvm.org/D55590
Files:
include/llvm/CodeGen/BasicTTIImpl.h
test/Analysis/CostModel/X86/reduction.ll
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