Re: [avr-gcc-list] [AVR] RTL prologue/epilogue ver.3

[Weddington, Eric]

> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On
> Behalf Of Georg-Johann Lay
> Sent: Thursday, October 13, 2011 10:44 AM
> To: Boyapati, Anitha
> Cc: address@hidden
> Subject: Re: [avr-gcc-list] [AVR] RTL prologue/epilogue ver.3
> 
> > I think this patch severely affects the step in/step out feature of
> > debugger like AVR Studio (here after referred to as AS). AS depends
on
> > 'rcall'/'ret' instruction sequences to recognize a function call and
> > step into. If a matching 'ret' is not found, the debugger gets
confused.
> > Currently, the problem is worked around but has much lower
performance.
> 
> The debugger has to cope with that. There are two ways of doing that:
> 
> 1) Analysing the prologue and knowing what sequences the compiler
might
>    generate.
> 

On further thought about that, it's actually pretty simple to determine
when an rcall is used in the context of a function prologue; It shows up
as "rcall 0", which is extremely unlikely that that form will ever be
used for a real subroutine call. (In fact, I can't think of any
situation where "rcall 0" could be used as a real subroutine call, but
maybe somebody has a real counter-example that could be generated by the
compiler.)