[all-commits] [llvm/llvm-project] 3b48d8: [RISCV] Optimize more redundant VSETVLIs

[Fraser Cormack via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3b48d849d44367ff351f58ce7a4949d104a30dea
      https://github.com/llvm/llvm-project/commit/3b48d849d44367ff351f58ce7a4949d104a30dea
  Author: Fraser Cormack <fraser at codeplay.com>
  Date:   2021-04-02 (Fri, 02 Apr 2021)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVCleanupVSETVLI.cpp
    M llvm/test/CodeGen/RISCV/rvv/cleanup-vsetvli.mir
    M llvm/test/CodeGen/RISCV/rvv/rv32-vsetvli-intrinsics.ll
    M llvm/test/CodeGen/RISCV/rvv/rv64-vsetvli-intrinsics.ll

  Log Message:
  -----------
  [RISCV] Optimize more redundant VSETVLIs

D99717 introduced some test cases which showed that the output of one
vsetvli into another would not be picked up by the RISCVCleanupVSETVLI
pass. This patch teaches the optimization about such a pattern. The
pattern is quite common when using the RVV vsetvli intrinsic to pass the
VL onto other intrinsics.

The second test case introduced by D99717 is left unoptimized by this
patch. It is a rarer case and will require us to rewire any uses of the
redundant vset[i]vli's output to the previous one's.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D99730