[PATCH] D61426: [X86][SSE] lowerAddSubToHorizontalOp - enable ymm extraction+fold

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, andreadb, craig.topper.
Herald added a project: LLVM.

Limiting scalar hadd/hsub generation to the lowest xmm looks to be unnecessary - we will be extracting one upper xmm whatever, and we can remove a shuffle by using the hop which is inline with what shouldUseHorizontalOp expects to happen anyway.

Testing on btver2 (the main target for fast-hops) shows this is beneficial even for float ops where we have a 'shuffle' to extract the float result:
https://godbolt.org/z/0R-U-K


Repository:
  rL LLVM

https://reviews.llvm.org/D61426

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/haddsub.ll
  test/CodeGen/X86/phaddsub-extract.ll

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