RE: [PATCH] Fix PR79622

[Tamar Christina <Tamar dot Christina at arm dot com>]

> -----Original Message-----
> From: Richard Biener [mailto:richard.guenther@gmail.com]
> Sent: 20 September 2017 17:52
> To: Tamar Christina
> Cc: Richard Biener; gcc-patches@gcc.gnu.org; nd
> Subject: Re: [PATCH] Fix PR79622
> 
> On Tue, Sep 19, 2017 at 5:54 PM, Tamar Christina
> <Tamar.Christina@arm.com> wrote:
> > -- sorry for the duplicate, forgot to post to list as well first time
> > --
> >
> > Hi Richard,
> >
> > The testcase seems to fail on aarch64-none-elf when -O1 or -O2,
> >
> > -O0, -Os and -O3 seem to work fine.
> >
> > dc[0] ends up being 0 for the cases that fail.
> 
> What ISL version are you using?

Ah, it seems we had it set to 0.15.

Sorry for the noise,
Tamar

> 
> Richard.
> 
> > Kind regards,
> > Tamar
> > ________________________________________
> > From: gcc-patches-owner@gcc.gnu.org <gcc-patches-owner@gcc.gnu.org>
> on
> > behalf of Richard Biener <rguenther@suse.de>
> > Sent: Monday, September 18, 2017 8:31 AM
> > To: gcc-patches@gcc.gnu.org
> > Subject: [PATCH] Fix PR79622
> >
> > The following patch fixes the other known wrong-code bug in GRAPHITE
> > which shows we're mishandling PHIs in not properly considering the
> > edge copies they represent as living outside of the black-box we're
> > analyzing.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
> >
> > Note the testcase still fails with ISL 0.16.1 but passes with 0.18 for
> > me.  I'll update the version in download_prerequesites to 0.18.
> >
> > Richard.
> >
> > 2017-09-18  Richard Biener  <rguenther@suse.de>
> >
> >         PR tree-optimization/79622
> >         * graphite-scop-detection.c (build_cross_bb_scalars_def): Properly
> >         handle PHIs.
> >         (build_cross_bb_scalars_use): Likewise.
> >
> >         * gcc.dg/graphite/pr79622.c: New testcase.
> >
> > Index: gcc/graphite-scop-detection.c
> >
> ==========================================================
> =========
> > --- gcc/graphite-scop-detection.c       (revision 252806)
> > +++ gcc/graphite-scop-detection.c       (working copy)
> > @@ -1744,7 +1744,9 @@ build_cross_bb_scalars_def (scop_p scop,
> >    gimple *use_stmt;
> >    imm_use_iterator imm_iter;
> >    FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, def)
> > -    if (def_bb != gimple_bb (use_stmt) && !is_gimple_debug (use_stmt))
> > +    if ((def_bb != gimple_bb (use_stmt) && !is_gimple_debug (use_stmt))
> > +       /* PHIs have their effect at "BBs" on the edges.  See PR79622.  */
> > +       || gimple_code (SSA_NAME_DEF_STMT (def)) == GIMPLE_PHI)
> >        {
> >         writes->safe_push (def);
> >         DEBUG_PRINT (dp << "Adding scalar write: "; @@ -1758,7 +1760,8
> > @@ build_cross_bb_scalars_def (scop_p scop,
> >        }
> >  }
> >
> > -/* Record DEF if it is used in other bbs different than DEF_BB in the
> > SCOP.  */
> > +/* Record USE if it is defined in other bbs different than USE_STMT
> > +   in the SCOP.  */
> >
> >  static void
> >  build_cross_bb_scalars_use (scop_p scop, tree use, gimple *use_stmt,
> > @@ -1774,7 +1777,9 @@ build_cross_bb_scalars_use (scop_p scop,
> >      return;
> >
> >    gimple *def_stmt = SSA_NAME_DEF_STMT (use);
> > -  if (gimple_bb (def_stmt) != gimple_bb (use_stmt))
> > +  if (gimple_bb (def_stmt) != gimple_bb (use_stmt)
> > +      /* PHIs have their effect at "BBs" on the edges.  See PR79622.  */
> > +      || gimple_code (def_stmt) == GIMPLE_PHI)
> >      {
> >        DEBUG_PRINT (dp << "Adding scalar read: ";
> >                    print_generic_expr (dump_file, use);
> > Index: gcc/testsuite/gcc.dg/graphite/pr79622.c
> >
> ==========================================================
> =========
> > --- gcc/testsuite/gcc.dg/graphite/pr79622.c     (nonexistent)
> > +++ gcc/testsuite/gcc.dg/graphite/pr79622.c     (working copy)
> > @@ -0,0 +1,26 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -floop-nest-optimize" } */
> > +
> > +int bf;
> > +
> > +int
> > +main (void)
> > +{
> > +  int dc[5];
> > +
> > +  for (bf = 0; bf < 2; ++bf)
> > +    {
> > +      int l9, g5 = -1;
> > +
> > +      for (l9 = 0; l9 < 5; ++l9)
> > +       {
> > +         dc[l9] = g5;
> > +         g5 = (dc[l9] > 0);
> > +       }
> > +    }
> > +
> > +  if (dc[0] != -1)
> > +    __builtin_abort ();
> > +
> > +  return 0;
> > +}