Re: [PATCH 2/7] Duplicate the range information of the phi onto the new ssa_name

[Andrew Pinski <pinskia@gmail.com>]

On Sun, Jun 20, 2021 at 11:50 PM Richard Biener via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Sat, Jun 19, 2021 at 9:49 PM apinski--- via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > From: Andrew Pinski <apinski@marvell.com>
> >
> > Since match_simplify_replacement uses gimple_simplify, there is a new
> > ssa name created sometimes and then we go and replace the phi edge with
> > this new ssa name, the range information on the phi is lost.
> > I don't have a testcase right now where we lose the range information
> > though but it does show up when enhancing match.pd to handle
> > some min/max patterns and g++.dg/warn/Wstringop-overflow-1.C starts
> > to fail.
> >
> > OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
> >
> > gcc/ChangeLog:
> >
> >         * tree-ssa-phiopt.c (match_simplify_replacement): Duplicate range
> >         info if we're the only things setting the target PHI.
> > ---
> >  gcc/tree-ssa-phiopt.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
> > index 24cbce9955a..feb8ca8d0d1 100644
> > --- a/gcc/tree-ssa-phiopt.c
> > +++ b/gcc/tree-ssa-phiopt.c
> > @@ -894,6 +894,14 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
> >        gsi_move_before (&gsi1, &gsi);
> >        reset_flow_sensitive_info (gimple_assign_lhs (stmt_to_move));
> >      }
> > +  /* Duplicate range info if we're the only things setting the target PHI.  */
> > +  tree phi_result = PHI_RESULT (phi);
> > +  if (!gimple_seq_empty_p (seq)
> > +      && EDGE_COUNT (gimple_bb (phi)->preds) == 2
> > +      && !POINTER_TYPE_P (TREE_TYPE (phi_result))
>
> Please use INTEGRAL_TYPE_P (...)

Yes, using INTEGRAL_TYPE_P makes more sense here.
Note I copied exactly what was already done in minmax_replacement.

>
> > +      && SSA_NAME_RANGE_INFO (phi_result)
>
> && !SSA_NAME_RANGE_INFO (result)
>
> ?  Why conditional on !gimple_seq_empty_p (seq)?

The way I understand it is if !gimple_seq_empty_p (seq) is true then
the result will be a new SSA name and therefore !SSA_NAME_RANGE_INFO
(result) will also be true

> It looks like we could do this trick (actually in both directions,
> wherever the range
> info is missing?) in replace_phi_edge_with_variable instead?

Let me look into doing that.

Thanks,
Andrew

>
> Thanks,
> Richard.
>
> )
> > +    duplicate_ssa_name_range_info (result, SSA_NAME_RANGE_TYPE (phi_result),
> > +                                  SSA_NAME_RANGE_INFO (phi_result));
> >    if (seq)
> >      gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
> >
> > --
> > 2.27.0
> >