On Thu, 23 May 2019, Bernhard Reutner-Fischer wrote:
> On 20 May 2019 11:40:17 CEST, Richard Biener <rguent...@suse.de> wrote:
> >On Sun, 19 May 2019, Jan Hubicka wrote:
> >
> >> > On Fri, 17 May 2019, Jan Hubicka wrote:
> >> >
> >> > > Hi,
> >> > > this patch cuts walks in aliasing_component_refs_p if the type we
> >look for
> >> > > can not fit into a given type by comparing their sizes. Similar
> >logic
> >> > > already exists in indirect_ref_may_alias_decl_p.
> >> > >
> >> > > When we walk reference a.b.c.d.e looking for type x we only need
> >to do
> >> > > it if sizeof(a)>=sizeof(x) and continue woking from e until
> >> > > sizeof(e)<=sizeof(x). We do not need to compare types where sizes
> >are
> >> > > known to be different.
> >> > >
> >> > > This saves some work (by not walking refs and not comparing their
> >types
> >> > > if they can not match) but also increases number of
> >disambiguations
> >> > > quite noticably. This is because same_type_for_tbaa often returns
> >-1 and
> >> > > makes aliasing_compinent_refs_p to give up. Using the simple
> >size check
> >> > > prevents hitting such problematic type pairs in many common
> >cases.
> >> > >
> >> > > Stats on tramp3d lto build change From:
> >> > >
> >> > > Alias oracle query stats:
> >> > > refs_may_alias_p: 0 disambiguations, 0 queries
> >> > > ref_maybe_used_by_call_p: 6451 disambiguations, 25578 queries
> >> > > call_may_clobber_ref_p: 817 disambiguations, 817 queries
> >> > > aliasing_component_ref_p: 14 disambiguations, 12528 queries
> >> > > TBAA oracle: 1468347 disambiguations 3010562 queries
> >> > > 550690 are in alias set 0
> >> > > 614235 queries asked about the same object
> >> > > 0 queries asked about the same alias set
> >> > > 0 access volatile
> >> > > 260937 are dependent in the DAG
> >> > > 116353 are aritificially in conflict with void *
> >> > >
> >> > > to:
> >> > >
> >> > > Alias oracle query stats:
> >> > > refs_may_alias_p: 0 disambiguations, 0 queries
> >> > > ref_maybe_used_by_call_p: 6451 disambiguations, 25580 queries
> >> > > call_may_clobber_ref_p: 817 disambiguations, 817 queries
> >> > > aliasing_component_ref_p: 118 disambiguations, 12552 queries
> >> > > TBAA oracle: 1468413 disambiguations 3010714 queries
> >> > > 550719 are in alias set 0
> >> > > 614247 queries asked about the same object
> >> > > 0 queries asked about the same alias set
> >> > > 0 access volatile
> >> > > 260970 are dependent in the DAG
> >> > > 116365 are aritificially in conflict with void *
> >> > >
> >> > > So disambiguations are up from 14 to 118 which is still quite
> >low.
> >> > >
> >> > > A followup patch making types_same_for_tbaa to not give up for
> >> > > TYPE_STRUCTURAL_EQUALITY pointers and arrays improves hitrate to
> >2723.
> >> > >
> >> > > Bootstrapped/regtested x86_64-linux, OK?
> >> > >
> >> > > * tree-ssa-alias.c (type_big_enough_for_type_p): New function.
> >> > > (aliasing_component_refs_p): Use it.
> >> > > Index: tree-ssa-alias.c
> >> > >
> >===================================================================
> >> > > --- tree-ssa-alias.c (revision 271292)
> >> > > +++ tree-ssa-alias.c (working copy)
> >> > > @@ -735,6 +735,27 @@ ao_ref_init_from_ptr_and_size (ao_ref *r
> >> > > ref->volatile_p = false;
> >> > > }
> >> > >
> >> > > +/* Return true if TYPE1 may contain TYPE2 by its size. */
> >> > > +
> >> > > +static bool
> >> > > +type_big_enough_for_type_p (tree type1, tree type2)
> >> > > +{
> >> > > + if (!TYPE_SIZE (type1) || !TYPE_SIZE (type2))
> >> > > + return true;
> >> > > + /* Be conservative for arrays and vectors. We want to support
> >partial
> >> > > + overlap on int[3] and int[3] as tested in
> >gcc.dg/torture/alias-2.c. */
> >> > > + while (TREE_CODE (type2) == ARRAY_TYPE
> >> > > + || TREE_CODE (type2) == VECTOR_TYPE)
> >> > > + type2 = TREE_TYPE (type2);
> >> >
> >> > Eww ;) I guess this means same-type can never return true for
> >> > array or vectors?
> >> >
> >> > > + if (!poly_int_tree_p (TYPE_SIZE (type1))
> >> > > + || !poly_int_tree_p (TYPE_SIZE (type2)))
> >> > > + return true;
> >> >
> >> > Use
> >> >
> >> > poly_uint64 size1;
> >> > if (!poly_int_tree_p (TYPE_SIZE (type1), &size1)
> >> > ...
> >> >
> >> > > + if (known_lt (wi::to_poly_widest (TYPE_SIZE (type1)),
> >> > > + wi::to_poly_widest (TYPE_SIZE (type2))))
> >> >
> >> > and
> >> >
> >> > if (known_lt (size1, size2))
> >> >
> >> > I wonder if you can compute whether type1 fits in type2 and
> >> > the other way around at the same time, saving seemingly
> >> > redundant work since you test both ways most of the time below.
> >> > So sth like type_size_compare_for_fitting () returning
> >> > -1, 0, 1 and use zero for "don't know"?
> >>
> >> Hi,
> >> this patch implements the three way compare and also merges the code
> >> with same logic in indirect_ref_may_alias_decl_p.
> >> We end up doing more known_lt calls than necessary because sometimes
> >we
> >> do not care about the three way outcome, but I asusme that this
> >should
> >> be relatively cheap once we pass the earlier test and tree to
> >poly_int
> >> conversion.
> >>
> >> Bootstrapped/regtested x86_64-linux, OK?
> >>
> >> * tree-ssa-alias.c (compare_sizes): New function.
> >> (sompare_type_sizes): New function
> >> (aliasing_component_refs_p): Use it.
> >> (indirect_ref_may_alias_decl_p): Likewise.
> >> Index: tree-ssa-alias.c
> >> ===================================================================
> >> --- tree-ssa-alias.c (revision 271379)
> >> +++ tree-ssa-alias.c (working copy)
> >> @@ -735,6 +735,48 @@ ao_ref_init_from_ptr_and_size (ao_ref *r
> >> ref->volatile_p = false;
> >> }
> >>
> >> +/* S1 and S2 are TYPE_SIZE or DECL_SIZE. Compare them:
> >> + Return -1 if S1 < S2
> >> + Return 1 if S1 > S2
> >> + Return 0 if equal or incoparable. */
> >
> >incomparable.
> >
> >OK with that fix.
>
> Really? See below.
>
> >
> >Richard.
> >
> >> +
> >> +static int
> >> +compare_sizes (tree s1, tree s2)
> >> +{
> >> + if (!s1 || !s2)
> >> + return 0;
> >> +
> >> + poly_uint64 size1 = poly_int_tree_p (s1, &size1);
> >> + poly_uint64 size2 = poly_int_tree_p (s2, &size2);
>
> Doesn't poly_into_tree_p return a bool?
> I think we want to omit these two initializers.
> thanks,
Whoops, didn't notice that.
Indeed - Honza please fix.
Richard.
> >> +
> >> + if (!poly_int_tree_p (s1, &size1) || !poly_int_tree_p (s2,
> >&size2))
> >> + return 0;
> >> + if (known_lt (size1, size2))
> >> + return -1;
> >> + if (known_lt (size2, size1))
> >> + return 1;
> >> + return 0;
> >> +}
> >> +
> >> +/* Compare TYPE1 and TYPE2 by its size.
> >> + Return -1 if size of TYPE1 < size of TYPE2
> >> + Return 1 if size of TYPE1 > size of TYPE2
> >> + Return 0 if types are of equal sizes or we can not compare them.
> >*/
> >> +
> >> +static int
> >> +compare_type_sizes (tree type1, tree type2)
> >> +{
> >> + /* Be conservative for arrays and vectors. We want to support
> >partial
> >> + overlap on int[3] and int[3] as tested in
> >gcc.dg/torture/alias-2.c. */
> >> + while (TREE_CODE (type1) == ARRAY_TYPE
> >> + || TREE_CODE (type1) == VECTOR_TYPE)
> >> + type1 = TREE_TYPE (type1);
> >> + while (TREE_CODE (type2) == ARRAY_TYPE
> >> + || TREE_CODE (type2) == VECTOR_TYPE)
> >> + type2 = TREE_TYPE (type2);
> >> + return compare_sizes (TYPE_SIZE (type1), TYPE_SIZE (type2));
> >> +}
> >> +
> >> /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for
> >the
> >> purpose of TBAA. Return 0 if they are distinct and -1 if we
> >cannot
> >> decide. */
> >> @@ -803,7 +845,7 @@ aliasing_component_refs_p (tree ref1,
> >> tree base1, base2;
> >> tree type1, type2;
> >> tree *refp;
> >> - int same_p, same_p2;
> >> + int same_p1 = 0, same_p2 = 0;
> >>
> >> /* Choose bases and base types to search for. */
> >> base1 = ref1;
> >> @@ -816,65 +858,93 @@ aliasing_component_refs_p (tree ref1,
> >> type2 = TREE_TYPE (base2);
> >>
> >> /* Now search for the type1 in the access path of ref2. This
> >> - would be a common base for doing offset based disambiguation
> >on. */
> >> - refp = &ref2;
> >> - while (handled_component_p (*refp)
> >> - && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
> >> - refp = &TREE_OPERAND (*refp, 0);
> >> - same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
> >> - if (same_p == 1)
> >> - {
> >> - poly_int64 offadj, sztmp, msztmp;
> >> - bool reverse;
> >> - get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> - offset2 -= offadj;
> >> - get_ref_base_and_extent (base1, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> - offset1 -= offadj;
> >> - if (ranges_maybe_overlap_p (offset1, max_size1, offset2,
> >max_size2))
> >> + would be a common base for doing offset based disambiguation
> >on.
> >> + This however only makes sense if type2 is big enough to hold
> >type1. */
> >> + int cmp_outer = compare_type_sizes (type2, type1);
> >> + if (cmp_outer >= 0)
> >> + {
> >> + refp = &ref2;
> >> + while (true)
> >> {
> >> - ++alias_stats.aliasing_component_refs_p_may_alias;
> >> - return true;
> >> + /* We walk from inner type to the outer types. If type we see is
> >> + already too large to be part of type1, terminate the search.
> >*/
> >> + int cmp = compare_type_sizes (type1, TREE_TYPE (*refp));
> >> + if (cmp < 0)
> >> + break;
> >> + /* If types may be of same size, see if we can decide about their
> >> + equality. */
> >> + if (cmp >= 0)
> >> + {
> >> + same_p2 = same_type_for_tbaa (TREE_TYPE (*refp), type1);
> >> + if (same_p2 != 0)
> >> + break;
> >> + }
> >> + if (!handled_component_p (*refp))
> >> + break;
> >> + refp = &TREE_OPERAND (*refp, 0);
> >> }
> >> - else
> >> + if (same_p2 == 1)
> >> {
> >> - ++alias_stats.aliasing_component_refs_p_no_alias;
> >> - return false;
> >> + poly_int64 offadj, sztmp, msztmp;
> >> + bool reverse;
> >> + get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> + offset2 -= offadj;
> >> + get_ref_base_and_extent (base1, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> + offset1 -= offadj;
> >> + if (ranges_maybe_overlap_p (offset1, max_size1, offset2,
> >max_size2))
> >> + {
> >> + ++alias_stats.aliasing_component_refs_p_may_alias;
> >> + return true;
> >> + }
> >> + else
> >> + {
> >> + ++alias_stats.aliasing_component_refs_p_no_alias;
> >> + return false;
> >> + }
> >> }
> >> }
> >>
> >> /* If we didn't find a common base, try the other way around. */
> >> - refp = &ref1;
> >> - while (handled_component_p (*refp)
> >> - && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
> >> - refp = &TREE_OPERAND (*refp, 0);
> >> - same_p2 = same_type_for_tbaa (TREE_TYPE (*refp), type2);
> >> - if (same_p2 == 1)
> >> - {
> >> - poly_int64 offadj, sztmp, msztmp;
> >> - bool reverse;
> >> -
> >> - get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> - offset1 -= offadj;
> >> - get_ref_base_and_extent (base2, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> - offset2 -= offadj;
> >> - if (ranges_maybe_overlap_p (offset1, max_size1, offset2,
> >max_size2))
> >> + if (cmp_outer <= 0)
> >> + {
> >> + refp = &ref1;
> >> + while (true)
> >> {
> >> - ++alias_stats.aliasing_component_refs_p_may_alias;
> >> - return true;
> >> + int cmp = compare_type_sizes (type2, TREE_TYPE (*refp));
> >> + if (cmp < 0)
> >> + break;
> >> + /* If types may be of same size, see if we can decide about their
> >> + equality. */
> >> + if (cmp >= 0)
> >> + {
> >> + same_p1 = same_type_for_tbaa (TREE_TYPE (*refp), type2);
> >> + if (same_p1 != 0)
> >> + break;
> >> + }
> >> + if (!handled_component_p (*refp))
> >> + break;
> >> + refp = &TREE_OPERAND (*refp, 0);
> >> }
> >> - else
> >> + if (same_p1 == 1)
> >> {
> >> - ++alias_stats.aliasing_component_refs_p_no_alias;
> >> - return false;
> >> - }
> >> - }
> >> + poly_int64 offadj, sztmp, msztmp;
> >> + bool reverse;
> >>
> >> - /* In the remaining test we assume that there is no overlapping
> >type
> >> - at all. So if we are unsure, we need to give up. */
> >> - if (same_p == -1 || same_p2 == -1)
> >> - {
> >> - ++alias_stats.aliasing_component_refs_p_may_alias;
> >> - return true;
> >> + get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> + offset1 -= offadj;
> >> + get_ref_base_and_extent (base2, &offadj, &sztmp, &msztmp,
> >&reverse);
> >> + offset2 -= offadj;
> >> + if (ranges_maybe_overlap_p (offset1, max_size1, offset2,
> >max_size2))
> >> + {
> >> + ++alias_stats.aliasing_component_refs_p_may_alias;
> >> + return true;
> >> + }
> >> + else
> >> + {
> >> + ++alias_stats.aliasing_component_refs_p_no_alias;
> >> + return false;
> >> + }
> >> + }
> >> }
> >>
> >> /* If we have two type access paths B1.path1 and B2.path2 they may
> >> @@ -883,15 +953,19 @@ aliasing_component_refs_p (tree ref1,
> >> a part that we do not see. So we can only disambiguate now
> >> if there is no B2 in the tail of path1 and no B1 on the
> >> tail of path2. */
> >> - if (base1_alias_set == ref2_alias_set
> >> - || alias_set_subset_of (base1_alias_set, ref2_alias_set))
> >> + if (compare_type_sizes (TREE_TYPE (ref2), type1) >= 0
> >> + && (same_p2 == -1
> >> + || base1_alias_set == ref2_alias_set
> >> + || alias_set_subset_of (base1_alias_set, ref2_alias_set)))
> >> {
> >> ++alias_stats.aliasing_component_refs_p_may_alias;
> >> return true;
> >> }
> >> /* If this is ptr vs. decl then we know there is no ptr ... decl
> >path. */
> >> if (!ref2_is_decl
> >> - && (base2_alias_set == ref1_alias_set
> >> + && compare_type_sizes (TREE_TYPE (ref1), type2) >= 0
> >> + && (same_p1 == -1
> >> + || base2_alias_set == ref1_alias_set
> >> || alias_set_subset_of (base2_alias_set, ref1_alias_set)))
> >> {
> >> ++alias_stats.aliasing_component_refs_p_may_alias;
> >> @@ -1221,16 +1295,13 @@ indirect_ref_may_alias_decl_p (tree ref1
> >> /* If the size of the access relevant for TBAA through the pointer
> >> is bigger than the size of the decl we can't possibly access
> >the
> >> decl via that pointer. */
> >> - if (DECL_SIZE (base2) && COMPLETE_TYPE_P (TREE_TYPE (ptrtype1))
> >> - && poly_int_tree_p (DECL_SIZE (base2))
> >> - && poly_int_tree_p (TYPE_SIZE (TREE_TYPE (ptrtype1)))
> >> - /* ??? This in turn may run afoul when a decl of type T which
> >is
> >> + if (/* ??? This in turn may run afoul when a decl of type T which
> >is
> >> a member of union type U is accessed through a pointer to
> >> type U and sizeof T is smaller than sizeof U. */
> >> - && TREE_CODE (TREE_TYPE (ptrtype1)) != UNION_TYPE
> >> + TREE_CODE (TREE_TYPE (ptrtype1)) != UNION_TYPE
> >> && TREE_CODE (TREE_TYPE (ptrtype1)) != QUAL_UNION_TYPE
> >> - && known_lt (wi::to_poly_widest (DECL_SIZE (base2)),
> >> - wi::to_poly_widest (TYPE_SIZE (TREE_TYPE (ptrtype1)))))
> >> + && compare_sizes (DECL_SIZE (base2),
> >> + TYPE_SIZE (TREE_TYPE (ptrtype1))) < 0)
> >> return false;
> >>
> >> if (!ref2)
> >>
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
