[all-commits] [llvm/llvm-project] 02c2bf: [RISCV] Change heuristic used for load clustering ...

[Alex Bradbury via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 02c2bf8c054c8a425f7347a4a276e2dbf4b10e5a
      https://github.com/llvm/llvm-project/commit/02c2bf8c054c8a425f7347a4a276e2dbf4b10e5a
  Author: Alex Bradbury <asb at igalia.com>
  Date:   2024-01-02 (Tue, 02 Jan 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

  Log Message:
  -----------
  [RISCV] Change heuristic used for load clustering (#75341)

Split out from #73789, so as to leave that PR just for flipping load
clustering to on by default. Clusters if the operations are within a
cache line of each other (as AMDGPU does in shouldScheduleLoadsNear).
X86 does something similar, but does `((Offset2 - Offset1) / 8 > 64)`.
I'm not sure if that's intentionally set to 512 bytes or if the division
is in error.

Adopts the suggestion from @wangpc-pp to query the cache line size and
use it if available.

We also cap the maximum cluster size to cap the potential register
pressure impact (which may lead to additional spills).