[llvm-dev] RFC: Setting MachineInstr flags through storeRegToStackSlot

[Alex Bradbury via llvm-dev]

On 21 February 2017 at 18:23, Robinson, Paul <paul.robinson at sony.com> wrote:

> In DWARF, the idea is that if the debugger is doing a "step in" operation
> for a call to the function, where is the most reasonable place to stop
> execution, that is still "before" the first statement?  Debug info for
> parameters and local variables commonly points to stack frame slots, so
> generally it's not helpful (for the user) to stop before the stack/frame
> pointer is set up the way the debug info expects.
>
> Stashing callee-saved registers is not necessarily part of this, although
> if you're using the stack pointer as a frame pointer and doing pushes to
> save registers, you need to be done fiddling with SP before you can say
> the prologue is ended.
> --paulr

Thanks. I'm starting to think the better fix might be to add an
iterator argument to emitPrologue and emitEpilogue to indicate
after/before the callee-saves. Does anyone have particular views on
this one way or another?

Best,

Alex