[PATCH] D107790: [RISCV] Add a pass to recognize VLS strided loads/store from gather/scatter.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
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For strided accesses the loop vectorizer seems to prefer creating a
vector induction variable with a start value of the form
<i32 0, i32 1, i32 2, ...>. This value will be incremented each
loop iteration by a splat constant equal to the length of the vector.
Within the loop, arithmetic using splat values will be done on this
vector induction variable to produce indices for a vector GEP.

This pass attempts to dig through the arithmetic back to the phi
to create a new scalar induction variable and a stride. We push
all of the arithmetic out of the loop by folding it into the start,
step, and stride values. Then we create a scalar GEP to use as the
base pointer for a strided load or store using the computed stride.
Loop strength reduce will run after this pass and can do some
cleanups to the scalar GEP and induction variable.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107790

Files:
  llvm/include/llvm/IR/IntrinsicsRISCV.td
  llvm/lib/Target/RISCV/CMakeLists.txt
  llvm/lib/Target/RISCV/RISCV.h
  llvm/lib/Target/RISCV/RISCVGatherScatterLowering.cpp
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/lib/Target/RISCV/RISCVISelLowering.h
  llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
  llvm/test/CodeGen/RISCV/rvv/fixed-vector-strided-load-store-negative.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vector-strided-load-store.ll
  llvm/tools/opt/opt.cpp

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