Run the combine part of combine_and_move_insns even if -fsched-pressure

[Segher Boessenkool]

On Wed, Aug 07, 2019 at 11:21:48PM +0100, Richard Sandiford wrote:
> Segher Boessenkool <segher@kernel.crashing.org> writes:
> > On Wed, Aug 07, 2019 at 07:16:03PM +0100, Richard Sandiford wrote:
> >> The main IRA routine includes the code:
> >> 
> >>   /* Don't move insns if live range shrinkage or register
> >>      pressure-sensitive scheduling were done because it will not
> >>      improve allocation but likely worsen insn scheduling.  */
> >>   if (optimize
> >>       && !flag_live_range_shrinkage
> >>       && !(flag_sched_pressure && flag_schedule_insns))
> >>     combine_and_move_insns ();
> >> 
> >> The comment about not moving insns for pressure-sensitive scheduling
> >> makes sense, but I think the combine part of combine_and_move_insns is
> >> still useful, since it's folding a set of an equivalent value into its
> >> single user and so eliminates the need for one register altogether.
> >
> > During which pass are the newly combined instructions created?  If not
> > late, why does combine refuse to do this combination?
> 
> During if_after_combine.

So immediately after combine.

Why did combine refuse to do this itself?  What am I missing?


Segher