[all-commits] [llvm/llvm-project] cdb692: [X86] Add X86ISD::SUBV_BROADCAST_LOAD and begin re...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: cdb692ee0c6745ea008ee6cc00fe1e65021516bb
      https://github.com/llvm/llvm-project/commit/cdb692ee0c6745ea008ee6cc00fe1e65021516bb
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2020-12-17 (Thu, 17 Dec 2020)

  Changed paths:
    M llvm/include/llvm/CodeGen/SelectionDAG.h
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/lib/Target/X86/X86ISelLowering.h
    M llvm/lib/Target/X86/X86InstrAVX512.td
    M llvm/lib/Target/X86/X86InstrFragmentsSIMD.td
    M llvm/lib/Target/X86/X86InstrSSE.td
    M llvm/test/CodeGen/X86/broadcast-elm-cross-splat-vec.ll
    M llvm/test/CodeGen/X86/subvector-broadcast.ll

  Log Message:
  -----------
  [X86] Add X86ISD::SUBV_BROADCAST_LOAD and begin removing X86ISD::SUBV_BROADCAST (PR38969)

Subvector broadcasts are only load instructions, yet X86ISD::SUBV_BROADCAST treats them more generally, requiring a lot of fallback tablegen patterns.

This initial patch replaces constant vector lowering inside lowerBuildVectorAsBroadcast with direct X86ISD::SUBV_BROADCAST_LOAD loads which helps us merge a number of equivalent loads/broadcasts.

As well as general plumbing/analysis additions for SUBV_BROADCAST_LOAD, I needed to wrap SelectionDAG::makeEquivalentMemoryOrdering so it can handle result chains from non generic LoadSDNode nodes.

Later patches will continue to replace X86ISD::SUBV_BROADCAST usage.

Differential Revision: https://reviews.llvm.org/D92645