[all-commits] [llvm/llvm-project] fdaccc: [AMDGPU] Handle direct loads to LDS in memory model

[Austin Kerbow via All-commits]

  Branch: refs/heads/users/kerbowa/direct-lds-load-memory-legalizer
  Home:   https://github.com/llvm/llvm-project
  Commit: fdaccc9069203d753367ad1ec50da7ac7a601a7a
      https://github.com/llvm/llvm-project/commit/fdaccc9069203d753367ad1ec50da7ac7a601a7a
  Author: Austin Kerbow <Austin.Kerbow at amd.com>
  Date:   2025-05-29 (Thu, 29 May 2025)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIMemoryLegalizer.cpp
    M llvm/test/CodeGen/AMDGPU/GlobalISel/memory-legalizer-atomic-fence.ll
    M llvm/test/CodeGen/AMDGPU/branch-condition-and.ll
    M llvm/test/CodeGen/AMDGPU/cf-loop-on-constant.ll
    M llvm/test/CodeGen/AMDGPU/indirect-addressing-si.ll
    M llvm/test/CodeGen/AMDGPU/kernel-vgpr-spill-mubuf-with-voffset.ll
    M llvm/test/CodeGen/AMDGPU/llvm.amdgcn.update.dpp.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-fence-mmra-local.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-fence.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-flat-singlethread.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-flat-volatile.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-flat-wavefront.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-flat-workgroup.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-global-singlethread.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-global-volatile.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-global-wavefront.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-global-workgroup.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-agent.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-nontemporal.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-singlethread.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-system.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-volatile.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-wavefront.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local-workgroup.ll
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-local.mir
    M llvm/test/CodeGen/AMDGPU/memory-legalizer-region.mir

  Log Message:
  -----------
  [AMDGPU] Handle direct loads to LDS in memory model

Add additional waitcnt insertion to ensure proper ordering between LDS
operations and direct loads from global memory to LDS on pre-GFX10
hardware.

Direct LDS loads perform both a global memory load and an LDS store,
which can be reordered with respect to other LDS operations without
explicit synchronization. This can cause ordering violations even within
a single thread.

The change conservatively inserts vmcnt(0) waits for all sync scopes
when the LDS address space is involved. Future optimizations in
SIInsertWaitcnts can relax this to only wait for outstanding direct LDS
loads rather than all vmcnt events.

This change only affects LDS address space synchronization and preserves
existing cross-address space ordering behavior.



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