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To: Ian Lance Taylor <ian@airs.com>
Cc: Denis Chertykov <denisc@overta.ru>,  Eric Christopher <echristo@apple.com>, 	  gcc@gcc.gnu.org
Subject: Re: CAN_ELIMINATE question
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From: Denis Chertykov <denisc@overta.ru>
Date: Fri, 17 Feb 2006 17:49:00 -0000
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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()

Denis.