Re: [patch] Fix PR tree-optimization/49471

[Zdenek Dvorak <rakdver at kam dot mff dot cuni dot cz>]

Hi,

> > This patch fixes the build failure of cactusADM and dealII spec2006
> > benchmarks when autopar is enabled.
> > (for powerpc they fail only when -m32 is additionally enabled)
> >
> > The problem originated in canonicalize_loop_ivs, where we iterate the
> > header's phis in order to base all
> > the induction variables on a single control variable.
> > We use the largest precision of the loop's ivs in order to determine the
> > type of the control variable.
> >
> > Since iterating the loop's phis takes into account not only the loop's
> > ivs, but also reduction variables,
> > we got precision values like 80 for x86, or 128 for ppc.
> > The compilers failed to create proper types for these sizes
> > (respectively).
> >
> > The proper behavior for determining the control variable's type is to take
> > into account only the loop's ivs,
> > which is what this patch does.
> >
> > Bootstrap and testsuite pass successfully (as autopar is not enabled by
> > default).
> > No new regressions when the testsuite is run with autopar enabled.
> > No new regressions for the run of spec2006 with autopar enabled,
> >
> > cactusADM and dealII benchmarks now pass successfully with autopar on
> > powerpc and x86.
> >
> > Thanks to Zdenek who helped me figure out the failure/fix.
> > OK for trunk?
> 
> It'll collide with Sebastians patch in that area.  I suggested a
> INTEGRAL_TYPE_P check instead of the simple_iv one, it
> should be cheaper.  Zdenek, do you think it will be "incorrect"
> in some cases?

well, it does not make much sense -- reductions of integral type would
be taken into consideration for determining the size of the canonical
variable.  However, it is not a big issue (the choice of the type is more
or less arbitrary, as long as the number of iterations fits into it; selecting
the type based on another existing iv is just to avoid unnecessary extensions),

Zdenek

> Thanks,
> Richard.
> 
> > Thanks,
> > Razya
> >
> > ChangeLog:
> >
> > ? PR tree-optimization/49471
> > ? * tree-vect-loop-manip.c (canonicalize_loop_ivs): Add condition to
> > ? ignore reduction variables when iterating the loop header's phis.
> >
> >
> >