Re: CAN_ELIMINATE question

[Denis Chertykov <denisc@overta.ru>]

Denis Chertykov <denisc@overta.ru> writes:

> Ian Lance Taylor <ian@airs.com> writes:
> 
> > Denis Chertykov <denisc@overta.ru> writes:
> > 
> > > > > I think that better to call update_eliminables() somewhere after
> > > > > setup_save_areas()
> > > > 
> > > > Exactly.  We do that.  About 15 lines after the lines you quoted
> > > > above.
> > > > 
> > > > What am I missing?
> > > 
> > > I'm (exactly AVR port) need in call to update_eliminables() somewhere
> > > between setup_save_areas() and calculate_needs_all_insns()
> > > (Not "about 15 lines after" ;) because all bad things happened inside
> > > calculate_needs_all_insns(). 
> > > 
> > > calculate_needs_all_insns() collect wrong reloads because
> > > reg_eliminate structure for FP->SP have wrong can_eliminate field.
> > 
> > But then we go around the loop again, so everything should get
> > recalculated based on the new assumptions.  Doesn't that happen for
> > you?
> 
> If you mean the "continue" here:
>       if (caller_save_needed)
> 	setup_save_areas ();
> 
>       /* If we allocated another stack slot, redo elimination bookkeeping.  */
>       if (starting_frame_size != get_frame_size ())
> 	continue;
> -------^^^^^^^^^
> then answer no because only set_initial_elim_offsets() will be called.
> set_initial_elim_offsets() doesn't change reg_eliminate[].can_eliminate
> flag.
> 
> If you mean a call update_eliminables() after
> calculate_needs_all_insns() then answer no (again :) because all wrong
> things already happened inside calculate_needs_all_insns() and
> compiler will call
> select_reload_regs() -> find_reload_regs() -> spill_failure()

Can somebody comment the problem, please ?

Denis.