Re: [PATCH][GRAPHITE] Fix PR82449

[Sebastian Pop <sebpop at gmail dot com>]

On Oct 9, 2017 8:48 AM, "Richard Biener" <rguenther@suse.de> wrote:

On Mon, 9 Oct 2017, Richard Biener wrote:

> On Fri, 6 Oct 2017, Sebastian Pop wrote:
>
> > On Fri, Oct 6, 2017 at 8:33 AM, Richard Biener <rguenther@suse.de>
wrote:
> >
> > > On Fri, 6 Oct 2017, Sebastian Pop wrote:
> > >
> > > > On Fri, Oct 6, 2017 at 6:56 AM, Richard Biener <rguenther@suse.de>
> > > wrote:
> > > >
> > > > >
> > > > > The following fences off a few more SCEVs through
scev_analyzable_p
> > > given
> > > > > at the end we need those pass chrec_apply when getting a rename
through
> > > > > SCEV.
> > > > >
> > > > > The SCEV in question is
> > > > >
> > > > >   {(integer(kind=4)) {0, +, {1, +, 1}_1}_1, + 1}_2
> > > > >
> > > > > which fails to chrec_apply in the CHREC_LEFT part because that
part
> > > > > is not affine (and we're usually not replacing a IV with a
constant
> > > > > where chrec_apply might handle one or the other case).
> > > > >
> > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > > > >
> > > > > This fixes three out of the remaining 8 codegen errors in SPEC CPU
> > > 2006.
> > > > >
> > > > > Ok?
> > > > >
> > > > > Thanks,
> > > > > Richard.
> > > > >
> > > > > 2017-10-06  Richard Biener  <rguenther@suse.de>
> > > > >
> > > > >         PR tree-optimization/82449
> > > > >         * sese.c (can_chrec_apply): New function.
> > > > >         (scev_analyzable_p): Check we can call chrec_apply on the
SCEV.
> > > > >
> > > > >         * gfortran.dg/graphite/pr82449.f: New testcase.
> > >
> > > >
> > > > > Index: gcc/sese.c
> > > > > ============================================================
=======
> > > > > --- gcc/sese.c  (revision 253477)
> > > > > +++ gcc/sese.c  (working copy)
> > > > > @@ -421,6 +421,27 @@ invariant_in_sese_p_rec (tree t, const s
> > > > >    return true;
> > > > >  }
> > > > >
> > > > > +/* Check whether we can call chrec_apply on CHREC with arbitrary
X and
> > > > > VAR.  */
> > >
> > > > +
> > > > > +static bool
> > > > > +can_chrec_apply (tree chrec)
> > >
> >
> > Could we use scev_is_linear_expression ?
> > It seems like can_chrec_apply has the same semantics.
>
> Looks like that works.
>
> >
> > > > > +{
> > > > > +  if (automatically_generated_chrec_p (chrec))
> > > > > +    return false;
> > > > > +  switch (TREE_CODE (chrec))
> > > > > +    {
> > > > > +    case POLYNOMIAL_CHREC:
> > > > > +      if (evolution_function_is_affine_p (chrec))
> > > > > +       return (can_chrec_apply (CHREC_LEFT (chrec))
> > > > > +               && can_chrec_apply (CHREC_RIGHT (chrec)));
> > > > > +      return false;
> > > > > +    CASE_CONVERT:
> > > > > +      return can_chrec_apply (TREE_OPERAND (chrec, 0));
> > > > > +    default:;
> > > > > +      return tree_does_not_contain_chrecs (chrec);
> > > > > +    }
> > > > > +}
> > > > > +
> > > > >  /* Return true when DEF can be analyzed in REGION by the scalar
> > > > >     evolution analyzer.  */
> > > > >
> > > > > @@ -449,6 +470,7 @@ scev_analyzable_p (tree def, sese_l &reg
> > > > >         || !defined_in_sese_p (scev, region))
> > > > >      && (tree_does_not_contain_chrecs (scev)
> > > > >         || evolution_function_is_affine_p (scev))
> > > > >
> > > >
> > > > Why isn't evolution_function_is_affine_p returning false on {0, +,
{1, +,
> > > > 1}_1}_1?
> > > > This is quadratic.
> > >
> > > It returns false on that but the CHREC we ask it on is
> > >
> > > {(integer(kind=4)) {0, +, {1, +, 1}_1}_1, + 1}_2
> > >
> > > only the initial value is "quadratic".
> > >
> >
> > Right.
> > If I understand correctly, the scop is the body of loop_1,
> > and we do not need to represent the quadratic evolution
> > of the initial value.
>
> Giving the following full testing now.

And the following is what I have applied after bootstrap / testing
on x86_64-unknown-linux-gnu.

As you can see I needed some adjustments to not reject otherwise
valid SCEVs with address constants.

Richard.

2017-10-09  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/82449
        * sese.c (scev_analyzable_p): Check whether the SCEV is linear.
        * tree-chrec.h (evolution_function_is_constant_p): Adjust to
        allow constant addresses.
        * tree-chrec.c (scev_is_linear_expression): Constant evolutions
        are linear.

        * gfortran.dg/graphite/pr82449.f: New testcase.


Looks good to me.

Thanks.


Index: gcc/sese.c
===================================================================
--- gcc/sese.c  (revision 253486)
+++ gcc/sese.c  (working copy)
@@ -444,14 +444,13 @@ scev_analyzable_p (tree def, sese_l &reg
   loop = loop_containing_stmt (SSA_NAME_DEF_STMT (def));
   scev = scalar_evolution_in_region (region, loop, def);

-  return !chrec_contains_undetermined (scev)
-    && (TREE_CODE (scev) != SSA_NAME
-       || !defined_in_sese_p (scev, region))
-    && (tree_does_not_contain_chrecs (scev)
-       || evolution_function_is_affine_p (scev))
-    && (! loop
-       || ! loop_in_sese_p (loop, region)
-       || ! chrec_contains_symbols_defined_in_loop (scev, loop->num));
+  return (!chrec_contains_undetermined (scev)
+         && (TREE_CODE (scev) != SSA_NAME
+             || !defined_in_sese_p (scev, region))
+         && scev_is_linear_expression (scev)
+         && (! loop
+             || ! loop_in_sese_p (loop, region)
+             || ! chrec_contains_symbols_defined_in_loop (scev,
loop->num)));
 }

 /* Returns the scalar evolution of T in REGION.  Every variable that
Index: gcc/testsuite/gfortran.dg/graphite/pr82449.f
===================================================================
--- gcc/testsuite/gfortran.dg/graphite/pr82449.f        (nonexistent)
+++ gcc/testsuite/gfortran.dg/graphite/pr82449.f        (working copy)
@@ -0,0 +1,11 @@
+! { dg-do compile }
+! { dg-options "-O2 -floop-nest-optimize" }
+
+      SUBROUTINE JDFIDX(MKL,KGSH)
+      DIMENSION MKL(6,6)
+      NKL=0
+  400 DO 40 KG = 1,KGSH
+      DO 40 LG = 1,KG
+      NKL = NKL + 1
+   40 MKL(LG,KG) = NKL
+      END
Index: gcc/tree-chrec.c
===================================================================
--- gcc/tree-chrec.c    (revision 253486)
+++ gcc/tree-chrec.c    (working copy)
@@ -1610,6 +1610,9 @@ operator_is_linear (tree scev)
 bool
 scev_is_linear_expression (tree scev)
 {
+  if (evolution_function_is_constant_p (scev))
+    return true;
+
   if (scev == NULL
       || !operator_is_linear (scev))
     return false;
Index: gcc/tree-chrec.h
===================================================================
--- gcc/tree-chrec.h    (revision 253486)
+++ gcc/tree-chrec.h    (working copy)
@@ -169,15 +169,9 @@ evolution_function_is_constant_p (const_
   if (chrec == NULL_TREE)
     return false;

-  switch (TREE_CODE (chrec))
-    {
-    case INTEGER_CST:
-    case REAL_CST:
-      return true;
-
-    default:
-      return false;
-    }
+  if (CONSTANT_CLASS_P (chrec))
+    return true;
+  return is_gimple_min_invariant (chrec);
 }

 /* Determine whether CHREC is an affine evolution function in LOOPNUM.  */