[all-commits] [llvm/llvm-project] 273a0c: PrologEpilogInserter: Use explicit control for sca...

[Matt Arsenault via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 273a0c8bc9c774aa0d5982c23dc3d62b68ef4338
      https://github.com/llvm/llvm-project/commit/273a0c8bc9c774aa0d5982c23dc3d62b68ef4338
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2021-11-23 (Tue, 23 Nov 2021)

  Changed paths:
    M llvm/include/llvm/CodeGen/TargetFrameLowering.h
    M llvm/lib/CodeGen/PrologEpilogInserter.cpp
    M llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp
    M llvm/lib/Target/AMDGPU/SIFrameLowering.cpp
    M llvm/lib/Target/AMDGPU/SIFrameLowering.h
    M llvm/lib/Target/Mips/MipsFrameLowering.h
    M llvm/lib/Target/SystemZ/SystemZFrameLowering.h
    M llvm/test/CodeGen/AMDGPU/GlobalISel/flat-scratch.ll
    M llvm/test/CodeGen/AMDGPU/callee-frame-setup.ll
    M llvm/test/CodeGen/AMDGPU/flat-scratch.ll
    M llvm/test/CodeGen/AMDGPU/load-hi16.ll
    M llvm/test/CodeGen/AMDGPU/load-lo16.ll
    M llvm/test/CodeGen/AMDGPU/local-stack-alloc-block-sp-reference.ll
    M llvm/test/CodeGen/AMDGPU/need-fp-from-vgpr-spills.ll
    M llvm/test/CodeGen/AMDGPU/pei-scavenge-sgpr-carry-out.mir
    M llvm/test/CodeGen/AMDGPU/pei-scavenge-sgpr-gfx9.mir
    M llvm/test/CodeGen/AMDGPU/pei-scavenge-sgpr.mir
    M llvm/test/CodeGen/AMDGPU/pei-scavenge-vgpr-spill.mir
    M llvm/test/CodeGen/AMDGPU/spill-offset-calculation.ll
    M llvm/test/CodeGen/AMDGPU/store-hi16.ll

  Log Message:
  -----------
  PrologEpilogInserter: Use explicit control for scavenge slot placement

AMDGPU is unusual in that the both stack is indexed in the same
direction as stack growth (up). We therefore always need the emergency
stack slots placed as low as possible to ensure they are in range of
load/store instruction immediate offsets. The existing logic is mostly
OK, but failed if we required stack realignment.

I don't understand what the existing control isFPCloseToIncomingSP is
supposed to mean, but can only be used to stop placing the scavenge
slots earlier. Make this explicit so that targets can opt-in rather
than opt-out only.