[PATCH] D137699: [RISCV] Don't use zero-stride vector load if there's no optimized u-arch

[Wang Pengcheng via Phabricator via llvm-commits]

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For vector strided instructions, as the RVV spec says:

> When rs2=x0, then an implementation is allowed, but not required, to
> perform fewer memory operations than the number of active elements, and
> may perform different numbers of memory operations across different
> dynamic executions of the same static instruction.

So compiler shouldn't assume that fewer memory operations will be
performed when rs2=x0.

We add a target feature to specify whether u-arch supports optimized
zero-stride vector load. And we do vector splat optimization iff this
feature is supported.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137699

Files:
  llvm/lib/Target/RISCV/RISCV.td
  llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
  llvm/lib/Target/RISCV/RISCVSubtarget.h
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-buildvec.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-shuffles.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-vrgather.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-insert.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-buildvec.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-vrgather.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-mask-buildvec.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-masked-gather.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-masked-scatter.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-reduction-fp.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vwadd.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vwaddu.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vwmulsu.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vwsub.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vwsubu.ll
  llvm/test/CodeGen/RISCV/rvv/vreductions-fp-sdnode.ll
  llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
  llvm/test/CodeGen/RISCV/rvv/vsplats-fp.ll

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