On Fri, 14 Jun 2019, Jan Hubicka wrote:
> >
> > I think this is still error-prone since we look past
> > VIEW_CONVERT_EXPRs in the path so we happily disambiguate,
> > say,
> >
> > struct X { int e; int d; };
> > struct Y { int d; int e; };
> >
> > VIEW_CONVERT<X>(p->b).d
> > VIEW_CONVERT<Y>(q->b).e
> >
> > where in reality only the access paths from the base up to
> > the first view-conversion are relevant for path-based
> > analysis.
> >
> > So upon seeing a VIEW_CONVERT (or BIT_FIELD_REF which
> > has the same issue) simply truncate the vector.
> >
> > As said, it's a pre-existing issue but you are extending
> > things to possibly handle more stuff...
> >
> > Otherwise looks good.
> OK, i added the check and also managed to construct testcase that we do
> not optimize otherwise.
>
> I think same view convert bug ought to exist also in
> aliasing_component_refs_p and IMO ao_ref_alias set should also look
> for VCEs otherwise I can't make sense of
>
> /* First defer to TBAA if possible. */
> if (tbaa_p
> && flag_strict_aliasing
> && !alias_sets_conflict_p (ao_ref_alias_set (ref1),
> ao_ref_alias_set (ref2)))
> return false;
get_alias_set already handles VCEs properly. Btw I've said
BIT_FIELD_REF has the same issue but you didn't include that
case below.
Richard.
> Honza
>
> * gcc.dg/tree-ssa/alias-access-path-2.c: New testcase.
>
> * tree-ssa-alias.c (alias_stats): Add
> nonoverlapping_component_refs_p_may_alias,
> nonoverlapping_component_refs_p_no_alias,
> nonoverlapping_component_refs_of_decl_p_may_alias,
> nonoverlapping_component_refs_of_decl_p_no_alias.
> (dump_alias_stats): Dump them.
> (nonoverlapping_component_refs_of_decl_p): Add stats.
> (nonoverlapping_component_refs_p): Add stats; do not stop on first
> ARRAY_REF.
>
> Index: testsuite/gcc.dg/tree-ssa/alias-access-path-2.c
> ===================================================================
> --- testsuite/gcc.dg/tree-ssa/alias-access-path-2.c (nonexistent)
> +++ testsuite/gcc.dg/tree-ssa/alias-access-path-2.c (working copy)
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-fre3" } */
> +struct a {
> + int val;
> +};
> +struct b {
> + struct a a[10],a2[10];
> +};
> +struct c {
> + struct b b[10];
> +} *cptr;
> +
> +struct d {struct c c;} *dptr;
> +
> +int
> +test (int i, int j, int k, int l)
> +{
> + cptr->b[i].a[j].val=123;
> + dptr->c.b[k].a2[l].val=2;
> + return cptr->b[i].a[j].val;
> +}
> +/* { dg-final { scan-tree-dump-times "return 123" 1 "fre3"} } */
> Index: tree-ssa-alias.c
> ===================================================================
> --- tree-ssa-alias.c (revision 272283)
> +++ tree-ssa-alias.c (working copy)
> @@ -100,6 +100,10 @@ static struct {
> unsigned HOST_WIDE_INT call_may_clobber_ref_p_no_alias;
> unsigned HOST_WIDE_INT aliasing_component_refs_p_may_alias;
> unsigned HOST_WIDE_INT aliasing_component_refs_p_no_alias;
> + unsigned HOST_WIDE_INT nonoverlapping_component_refs_p_may_alias;
> + unsigned HOST_WIDE_INT nonoverlapping_component_refs_p_no_alias;
> + unsigned HOST_WIDE_INT nonoverlapping_component_refs_of_decl_p_may_alias;
> + unsigned HOST_WIDE_INT nonoverlapping_component_refs_of_decl_p_no_alias;
> } alias_stats;
>
> void
> @@ -124,7 +128,19 @@ dump_alias_stats (FILE *s)
> alias_stats.call_may_clobber_ref_p_no_alias,
> alias_stats.call_may_clobber_ref_p_no_alias
> + alias_stats.call_may_clobber_ref_p_may_alias);
> - fprintf (s, " aliasing_component_ref_p: "
> + fprintf (s, " nonoverlapping_component_refs_p: "
> + HOST_WIDE_INT_PRINT_DEC" disambiguations, "
> + HOST_WIDE_INT_PRINT_DEC" queries\n",
> + alias_stats.nonoverlapping_component_refs_p_no_alias,
> + alias_stats.nonoverlapping_component_refs_p_no_alias
> + + alias_stats.nonoverlapping_component_refs_p_may_alias);
> + fprintf (s, " nonoverlapping_component_refs_of_decl_p: "
> + HOST_WIDE_INT_PRINT_DEC" disambiguations, "
> + HOST_WIDE_INT_PRINT_DEC" queries\n",
> + alias_stats.nonoverlapping_component_refs_of_decl_p_no_alias,
> + alias_stats.nonoverlapping_component_refs_of_decl_p_no_alias
> + + alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias);
> + fprintf (s, " aliasing_component_refs_p: "
> HOST_WIDE_INT_PRINT_DEC" disambiguations, "
> HOST_WIDE_INT_PRINT_DEC" queries\n",
> alias_stats.aliasing_component_refs_p_no_alias,
> @@ -1047,7 +1063,10 @@ nonoverlapping_component_refs_of_decl_p
> if (TREE_CODE (ref1) == MEM_REF)
> {
> if (!integer_zerop (TREE_OPERAND (ref1, 1)))
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
> ref1 = TREE_OPERAND (TREE_OPERAND (ref1, 0), 0);
> }
>
> @@ -1060,7 +1079,10 @@ nonoverlapping_component_refs_of_decl_p
> if (TREE_CODE (ref2) == MEM_REF)
> {
> if (!integer_zerop (TREE_OPERAND (ref2, 1)))
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
> ref2 = TREE_OPERAND (TREE_OPERAND (ref2, 0), 0);
> }
>
> @@ -1080,7 +1102,10 @@ nonoverlapping_component_refs_of_decl_p
> do
> {
> if (component_refs1.is_empty ())
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
> ref1 = component_refs1.pop ();
> }
> while (!RECORD_OR_UNION_TYPE_P (TREE_TYPE (TREE_OPERAND (ref1, 0))));
> @@ -1088,7 +1113,10 @@ nonoverlapping_component_refs_of_decl_p
> do
> {
> if (component_refs2.is_empty ())
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
> ref2 = component_refs2.pop ();
> }
> while (!RECORD_OR_UNION_TYPE_P (TREE_TYPE (TREE_OPERAND (ref2, 0))));
> @@ -1096,7 +1124,10 @@ nonoverlapping_component_refs_of_decl_p
> /* Beware of BIT_FIELD_REF. */
> if (TREE_CODE (ref1) != COMPONENT_REF
> || TREE_CODE (ref2) != COMPONENT_REF)
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
>
> tree field1 = TREE_OPERAND (ref1, 1);
> tree field2 = TREE_OPERAND (ref2, 1);
> @@ -1109,7 +1140,10 @@ nonoverlapping_component_refs_of_decl_p
>
> /* We cannot disambiguate fields in a union or qualified union. */
> if (type1 != type2 || TREE_CODE (type1) != RECORD_TYPE)
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
>
> if (field1 != field2)
> {
> @@ -1117,15 +1151,23 @@ nonoverlapping_component_refs_of_decl_p
> same. */
> if (DECL_BIT_FIELD_REPRESENTATIVE (field1) == field2
> || DECL_BIT_FIELD_REPRESENTATIVE (field2) == field1)
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
> /* Different fields of the same record type cannot overlap.
> ??? Bitfields can overlap at RTL level so punt on them. */
> if (DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2))
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> + return false;
> + }
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_no_alias;
> return true;
> }
> }
>
> + ++alias_stats.nonoverlapping_component_refs_of_decl_p_may_alias;
> return false;
> }
>
> @@ -1154,40 +1196,67 @@ nonoverlapping_component_refs_p (const_t
> {
> if (!flag_strict_aliasing
> || !x || !y
> - || TREE_CODE (x) != COMPONENT_REF
> - || TREE_CODE (y) != COMPONENT_REF)
> - return false;
> + || !handled_component_p (x)
> + || !handled_component_p (y))
> + {
> + ++alias_stats.nonoverlapping_component_refs_p_may_alias;
> + return false;
> + }
>
> auto_vec<const_tree, 16> fieldsx;
> - while (TREE_CODE (x) == COMPONENT_REF)
> + while (handled_component_p (x))
> {
> - tree field = TREE_OPERAND (x, 1);
> - tree type = DECL_FIELD_CONTEXT (field);
> - if (TREE_CODE (type) == RECORD_TYPE)
> - fieldsx.safe_push (field);
> + if (TREE_CODE (x) == COMPONENT_REF)
> + {
> + tree field = TREE_OPERAND (x, 1);
> + tree type = DECL_FIELD_CONTEXT (field);
> + if (TREE_CODE (type) == RECORD_TYPE)
> + fieldsx.safe_push (field);
> + }
> + else if (TREE_CODE (x) == VIEW_CONVERT_EXPR)
> + fieldsx.truncate (0);
> x = TREE_OPERAND (x, 0);
> }
> if (fieldsx.length () == 0)
> return false;
> auto_vec<const_tree, 16> fieldsy;
> - while (TREE_CODE (y) == COMPONENT_REF)
> + while (handled_component_p (y))
> {
> - tree field = TREE_OPERAND (y, 1);
> - tree type = DECL_FIELD_CONTEXT (field);
> - if (TREE_CODE (type) == RECORD_TYPE)
> - fieldsy.safe_push (TREE_OPERAND (y, 1));
> + if (TREE_CODE (y) == COMPONENT_REF)
> + {
> + tree field = TREE_OPERAND (y, 1);
> + tree type = DECL_FIELD_CONTEXT (field);
> + if (TREE_CODE (type) == RECORD_TYPE)
> + fieldsy.safe_push (TREE_OPERAND (y, 1));
> + }
> + else if (TREE_CODE (y) == VIEW_CONVERT_EXPR)
> + fieldsx.truncate (0);
> y = TREE_OPERAND (y, 0);
> }
> if (fieldsy.length () == 0)
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_p_may_alias;
> + return false;
> + }
>
> /* Most common case first. */
> if (fieldsx.length () == 1
> && fieldsy.length () == 1)
> - return ((DECL_FIELD_CONTEXT (fieldsx[0])
> - == DECL_FIELD_CONTEXT (fieldsy[0]))
> - && fieldsx[0] != fieldsy[0]
> - && !(DECL_BIT_FIELD (fieldsx[0]) && DECL_BIT_FIELD (fieldsy[0])));
> + {
> + if ((DECL_FIELD_CONTEXT (fieldsx[0])
> + == DECL_FIELD_CONTEXT (fieldsy[0]))
> + && fieldsx[0] != fieldsy[0]
> + && !(DECL_BIT_FIELD (fieldsx[0]) && DECL_BIT_FIELD (fieldsy[0])))
> + {
> + ++alias_stats.nonoverlapping_component_refs_p_no_alias;
> + return true;
> + }
> + else
> + {
> + ++alias_stats.nonoverlapping_component_refs_p_may_alias;
> + return false;
> + }
> + }
>
> if (fieldsx.length () == 2)
> {
> @@ -1222,11 +1291,18 @@ nonoverlapping_component_refs_p (const_t
> same. */
> if (DECL_BIT_FIELD_REPRESENTATIVE (fieldx) == fieldy
> || DECL_BIT_FIELD_REPRESENTATIVE (fieldy) == fieldx)
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_p_may_alias;
> + return false;
> + }
> /* Different fields of the same record type cannot overlap.
> ??? Bitfields can overlap at RTL level so punt on them. */
> if (DECL_BIT_FIELD (fieldx) && DECL_BIT_FIELD (fieldy))
> - return false;
> + {
> + ++alias_stats.nonoverlapping_component_refs_p_may_alias;
> + return false;
> + }
> + ++alias_stats.nonoverlapping_component_refs_p_no_alias;
> return true;
> }
> }
> @@ -1245,6 +1321,7 @@ nonoverlapping_component_refs_p (const_t
> }
> while (1);
>
> + ++alias_stats.nonoverlapping_component_refs_p_may_alias;
> return false;
> }
>
>
--
Richard Biener <[email protected]>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
