[all-commits] [llvm/llvm-project] a0b049: [RISC-V] Fix incorrect epilogue_begin setting in d...

[Venkata Ramanaiah Nalamothu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a0b049055df592759e4ac1d8032139f385581c63
      https://github.com/llvm/llvm-project/commit/a0b049055df592759e4ac1d8032139f385581c63
  Author: Venkata Ramanaiah Nalamothu <quic_vnalamot at quicinc.com>
  Date:   2025-01-28 (Tue, 28 Jan 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
    M llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
    A llvm/test/CodeGen/RISCV/debug-line.ll
    M llvm/test/CodeGen/RISCV/kcfi-mir.ll
    M llvm/test/CodeGen/RISCV/live-sp.mir
    M llvm/test/CodeGen/RISCV/rvv/addi-scalable-offset.mir
    M llvm/test/CodeGen/RISCV/rvv/emergency-slot.mir
    M llvm/test/CodeGen/RISCV/stack-inst-compress.mir
    M llvm/test/CodeGen/RISCV/zcmp-cm-popretz.mir
    M llvm/test/CodeGen/RISCV/zcmp-cm-push-pop.mir
    M llvm/test/DebugInfo/RISCV/dwarf-riscv-relocs.ll

  Log Message:
  -----------
  [RISC-V] Fix incorrect epilogue_begin setting in debug line table (#120623)

The DwarfDebug.cpp implementation expects the epilogue instructions to
have source location of last non-debug instruction after which the epilogue
instructions are inserted. The epilogue_begin is set on location of the first
FrameDestroy instruction with source line information that has been seen in
the epilogue basic block.

In the trunk, the risc-v backend sets the epilogue_begin after the epilogue has
actually begun i.e. after callee saved register reloads and the source line
information is not set on those reload instructions. This is leading to #120553
where, while debugging, breaking on or single stepping to the epilogue_begin
location will make accessing the variables from wrong place as the FP has been
restored to the parent frame's FP.

To fix that, this patch sets FrameSetup/FrameDestroy flags on the callee saved
register spill/reload instructions which is actually correct. Then the
RISCVInstrInfo::loadRegFromStackSlot uses FrameDestroy flag to identify a
reload of the callee saved register in the epilogue and copies the source
line information from insert position instruction to that reload instruction.

Requires PR #120622

Fixes #120553



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