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 #120622Fixes#120553
a0b049055d