[PATCH] D74231: [X86] combineFneg - generalize FMA negations with isNegatibleForFree/getNegatedExpression

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, craig.topper, lebedev.ri.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

This has a really interesting side effect in that it improves some UMAX/UMIN reduction code which had redundant XOR(SHUFFLE(XOR(X,SIGNMASK)),SIGNMASK) patterns - the isNegatible recognises it as FNEG(SHUFFLE(FNEG(X))).... We have a lot of FNEG patterns bitcasted to the integer domain for XOR signbit twiddling which is similar to what we do to allow UMAX/UMIN to be lowered using SMAX/SMIN.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74231

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/horizontal-reduce-umax.ll
  llvm/test/CodeGen/X86/horizontal-reduce-umin.ll
  llvm/test/CodeGen/X86/vector-reduce-umax.ll
  llvm/test/CodeGen/X86/vector-reduce-umin.ll

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