[all-commits] [llvm/llvm-project] 910098: [RISCV] Match strided vector bases in RISCVGatherS...

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 910098e40572f9fe6bfde161eafd1b390a356043
      https://github.com/llvm/llvm-project/commit/910098e40572f9fe6bfde161eafd1b390a356043
  Author: Luke Lau <luke at igalia.com>
  Date:   2024-06-03 (Mon, 03 Jun 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVGatherScatterLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/strided-load-store.ll

  Log Message:
  -----------
  [RISCV] Match strided vector bases in RISCVGatherScatterLowering (#93972)

Currently we only match GEPs with a scalar base pointer, but a common
pattern that's emitted from the loop vectorizer is a strided vector base
plus some sort of scalar offset:

    %base = getelementptr i64, ptr %p, <vscale x 1 x i64> %step
    %gep = getelementptr i64, <vscale x 1 x ptr> %base, i64 %offset

This is common for accesses into a struct e.g. f[i].b below:

    struct F { int a; char b; };

    void foo(struct F *f) {
      for (int i = 0; i < 1024; i += 2) {
        f[i].a++;
        f[i].b++;
      }
    }

This patch handles this case in RISCVGatherScatterLowering by recursing
on the base pointer if it's a vector.

With this we can convert roughly 80% of the indexed loads and stores
emitted to strided loads and stores on SPEC CPU 2017, -O3
-march=rva22u64_v



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