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

[Eric Christopher via llvm-dev]

On Thu, Mar 2, 2017 at 6:22 AM Alex Bradbury <asb at asbradbury.org> wrote:

> 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?
>
>
Scheduling can interfere with this as you might schedule or move something
before saves on occasion.

-eric
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