[all-commits] [llvm/llvm-project] 021def: [AMDGPU] Use alias info to relax waitcounts for LD...

[Stanislav Mekhanoshin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 021def6c2278fd932d18b4d891c2e75c1d8e6f1d
      https://github.com/llvm/llvm-project/commit/021def6c2278fd932d18b4d891c2e75c1d8e6f1d
  Author: Stanislav Mekhanoshin <rampitec at users.noreply.github.com>
  Date:   2024-01-17 (Wed, 17 Jan 2024)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
    M llvm/test/CodeGen/AMDGPU/lds-dma-waits.ll

  Log Message:
  -----------
  [AMDGPU] Use alias info to relax waitcounts for LDS DMA (#74537)

LDA DMA loads increase VMCNT and a load from the LDS stored must wait on
this counter to only read memory after it is written. Wait count
insertion pass does not track memory dependencies, it tracks register
dependencies. To model the LDS dependency a pseudo register is used in
the scoreboard, acting like if LDS DMA writes it and LDS load reads it.

This patch adds 8 more pseudo registers to use for independent LDS
locations if we can prove they are disjoint using alias analysis.

Fixes: SWDEV-433427