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alias.c (alias_set_entry_d): Add is_pointer and has_pointer.

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* alias.c (alias_set_entry_d): Add is_pointer and has_pointer.
	(alias_stats): Add num_universal.
	(alias_set_subset_of): Special case pointers; be ready for NULL
	children.
	(alias_sets_conflict_p): Special case pointers; be ready for NULL
	children.
	(init_alias_set_entry): Break out from ...
	(record_alias_subset): ... here; propagate new fields;
	allocate children only when really needed.
	(get_alias_set): Do less generous pointer globbing.
	(dump_alias_stats_in_alias_c): Update statistics.
	* gcc.dg/alias-8.c: Do not xfail.
	* gcc.dg/pr62167.c: Prevent FRE.
	* gcc.dg/alias-14.c: New testcase.

From-SVN: r223883
This commit is contained in:
Jan Hubicka 2015-05-30 02:32:04 +02:00 • committed by Jan Hubicka
parent 530141b637
commit 6e042ef4e2
6 changed files with 310 additions and 58 deletions
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14
gcc/ChangeLog
View file

@ -1,3 +1,17 @@
2015-05-30 Jan Hubicka <hubicka@ucw.cz>
* alias.c (alias_set_entry_d): Add is_pointer and has_pointer.
(alias_stats): Add num_universal.
(alias_set_subset_of): Special case pointers; be ready for NULL
children.
(alias_sets_conflict_p): Special case pointers; be ready for NULL
children.
(init_alias_set_entry): Break out from ...
(record_alias_subset): ... here; propagate new fields;
allocate children only when really needed.
(get_alias_set): Do less generous pointer globbing.
(dump_alias_stats_in_alias_c): Update statistics.
2015-05-30 Alan Modra <amodra@gmail.com>
* config/rs6000/rs6000.c (split_stack_arg_pointer_used_p): Scan

274
gcc/alias.c
View file

@ -183,10 +183,6 @@ struct GTY(()) alias_set_entry_d {
/* The alias set number, as stored in MEM_ALIAS_SET. */
alias_set_type alias_set;
/* Nonzero if would have a child of zero: this effectively makes this
alias set the same as alias set zero. */
int has_zero_child;
/* The children of the alias set. These are not just the immediate
children, but, in fact, all descendants. So, if we have:
@ -195,6 +191,17 @@ struct GTY(()) alias_set_entry_d {
continuing our example above, the children here will be all of
`int', `double', `float', and `struct S'. */
hash_map<int, int, alias_set_traits> *children;
/* Nonzero if would have a child of zero: this effectively makes this
alias set the same as alias set zero. */
bool has_zero_child;
/* Nonzero if alias set corresponds to pointer type itself (i.e. not to
aggregate contaiing pointer.
This is used for a special case where we need an universal pointer type
compatible with all other pointer types. */
bool is_pointer;
/* Nonzero if is_pointer or if one of childs have has_pointer set. */
bool has_pointer;
};
typedef struct alias_set_entry_d *alias_set_entry;
@ -222,6 +229,7 @@ static struct {
unsigned long long num_same_objects;
unsigned long long num_volatile;
unsigned long long num_dag;
unsigned long long num_universal;
unsigned long long num_disambiguated;
} alias_stats;
@ -454,18 +462,58 @@ mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2)
bool
alias_set_subset_of (alias_set_type set1, alias_set_type set2)
{
alias_set_entry ase;
alias_set_entry ase2;
/* Everything is a subset of the "aliases everything" set. */
if (set2 == 0)
return true;
/* Otherwise, check if set1 is a subset of set2. */
ase = get_alias_set_entry (set2);
if (ase != 0
&& (ase->has_zero_child
|| ase->children->get (set1)))
/* Check if set1 is a subset of set2. */
ase2 = get_alias_set_entry (set2);
if (ase2 != 0
&& (ase2->has_zero_child
|| (ase2->children && ase2->children->get (set1))))
return true;
/* As a special case we consider alias set of "void *" to be both subset
and superset of every alias set of a pointer. This extra symmetry does
not matter for alias_sets_conflict_p but it makes aliasing_component_refs_p
to return true on the following testcase:
void *ptr;
char **ptr2=(char **)&ptr;
*ptr2 = ...
Additionally if a set contains universal pointer, we consider every pointer
to be a subset of it, but we do not represent this explicitely - doing so
would require us to update transitive closure each time we introduce new
pointer type. This makes aliasing_component_refs_p to return true
on the following testcase:
struct a {void *ptr;}
char **ptr = (char **)&a.ptr;
ptr = ...
This makes void * truly universal pointer type. See pointer handling in
get_alias_set for more details. */
if (ase2 && ase2->has_pointer)
{
alias_set_entry ase1 = get_alias_set_entry (set1);
if (ase1 && ase1->is_pointer)
{
alias_set_type voidptr_set = TYPE_ALIAS_SET (ptr_type_node);
/* If one is ptr_type_node and other is pointer, then we consider
them subset of each other. */
if (set1 == voidptr_set || set2 == voidptr_set)
return true;
/* If SET2 contains universal pointer's alias set, then we consdier
every (non-universal) pointer. */
if (ase2->children && set1 != voidptr_set
&& ase2->children->get (voidptr_set))
return true;
}
}
return false;
}
@ -474,29 +522,68 @@ alias_set_subset_of (alias_set_type set1, alias_set_type set2)
int
alias_sets_conflict_p (alias_set_type set1, alias_set_type set2)
{
alias_set_entry ase;
alias_set_entry ase1;
alias_set_entry ase2;
/* The easy case. */
if (alias_sets_must_conflict_p (set1, set2))
return 1;
/* See if the first alias set is a subset of the second. */
ase = get_alias_set_entry (set1);
if (ase != 0
&& ase->children->get (set2))
ase1 = get_alias_set_entry (set1);
if (ase1 != 0
&& ase1->children && ase1->children->get (set2))
{
++alias_stats.num_dag;
return 1;
}
/* Now do the same, but with the alias sets reversed. */
ase = get_alias_set_entry (set2);
if (ase != 0
&& ase->children->get (set1))
ase2 = get_alias_set_entry (set2);
if (ase2 != 0
&& ase2->children && ase2->children->get (set1))
{
++alias_stats.num_dag;
return 1;
}
/* We want void * to be compatible with any other pointer without
really dropping it to alias set 0. Doing so would make it
compatible with all non-pointer types too.
This is not strictly necessary by the C/C++ language
standards, but avoids common type punning mistakes. In
addition to that, we need the existence of such universal
pointer to implement Fortran's C_PTR type (which is defined as
type compatible with all C pointers). */
if (ase1 && ase2 && ase1->has_pointer && ase2->has_pointer)
{
alias_set_type voidptr_set = TYPE_ALIAS_SET (ptr_type_node);
/* If one of the sets corresponds to universal pointer,
we consider it to conflict with anything that is
or contains pointer. */
if (set1 == voidptr_set || set2 == voidptr_set)
{
++alias_stats.num_universal;
return true;
}
/* If one of sets is (non-universal) pointer and the other
contains universal pointer, we also get conflict. */
if (ase1->is_pointer && set2 != voidptr_set
&& ase2->children && ase2->children->get (voidptr_set))
{
++alias_stats.num_universal;
return true;
}
if (ase2->is_pointer && set1 != voidptr_set
&& ase1->children && ase1->children->get (voidptr_set))
{
++alias_stats.num_universal;
return true;
}
}
++alias_stats.num_disambiguated;
/* The two alias sets are distinct and neither one is the
@ -764,6 +851,22 @@ alias_ptr_types_compatible_p (tree t1, tree t2)
== TYPE_MAIN_VARIANT (TREE_TYPE (t2)));
}
/* Create emptry alias set entry. */
alias_set_entry
init_alias_set_entry (alias_set_type set)
{
alias_set_entry ase = ggc_alloc<alias_set_entry_d> ();
ase->alias_set = set;
ase->children = NULL;
ase->has_zero_child = false;
ase->is_pointer = false;
ase->has_pointer = false;
gcc_checking_assert (!get_alias_set_entry (set));
(*alias_sets)[set] = ase;
return ase;
}
/* Return the alias set for T, which may be either a type or an
expression. Call language-specific routine for help, if needed. */
@ -903,35 +1006,77 @@ get_alias_set (tree t)
the pointed-to types. This issue has been reported to the
C++ committee.
In addition to the above canonicalization issue, with LTO
we should also canonicalize `T (*)[]' to `T *' avoiding
alias issues with pointer-to element types and pointer-to
array types.
For this reason go to canonical type of the unqalified pointer type.
Until GCC 6 this code set all pointers sets to have alias set of
ptr_type_node but that is a bad idea, because it prevents disabiguations
in between pointers. For Firefox this accounts about 20% of all
disambiguations in the program. */
else if (POINTER_TYPE_P (t) && t != ptr_type_node && !in_lto_p)
{
tree p;
auto_vec <bool, 8> reference;
Likewise we need to deal with the situation of incomplete
pointed-to types and make `*(struct X **)&a' and
`*(struct X {} **)&a' alias. Otherwise we will have to
guarantee that all pointer-to incomplete type variants
will be replaced by pointer-to complete type variants if
they are available.
/* Unnest all pointers and references.
We also want to make pointer to array equivalent to pointer to its
element. So skip all array types, too. */
for (p = t; POINTER_TYPE_P (p)
|| (TREE_CODE (p) == ARRAY_TYPE && !TYPE_NONALIASED_COMPONENT (p));
p = TREE_TYPE (p))
{
if (TREE_CODE (p) == REFERENCE_TYPE)
reference.safe_push (true);
if (TREE_CODE (p) == POINTER_TYPE)
reference.safe_push (false);
}
p = TYPE_MAIN_VARIANT (p);
With LTO the convenient situation of using `void *' to
access and store any pointer type will also become
more apparent (and `void *' is just another pointer-to
incomplete type). Assigning alias-set zero to `void *'
and all pointer-to incomplete types is a not appealing
solution. Assigning an effective alias-set zero only
affecting pointers might be - by recording proper subset
relationships of all pointer alias-sets.
/* Make void * compatible with char * and also void **.
Programs are commonly violating TBAA by this.
Pointer-to function types are another grey area which
needs caution. Globbing them all into one alias-set
or the above effective zero set would work.
We also make void * to conflict with every pointer
(see record_component_aliases) and thus it is safe it to use it for
pointers to types with TYPE_STRUCTURAL_EQUALITY_P. */
if (TREE_CODE (p) == VOID_TYPE || TYPE_STRUCTURAL_EQUALITY_P (p))
set = get_alias_set (ptr_type_node);
else
{
/* Rebuild pointer type from starting from canonical types using
unqualified pointers and references only. This way all such
pointers will have the same alias set and will conflict with
each other.
For now just assign the same alias-set to all pointers.
That's simple and avoids all the above problems. */
else if (POINTER_TYPE_P (t)
&& t != ptr_type_node)
Most of time we already have pointers or references of a given type.
If not we build new one just to be sure that if someone later
(probably only middle-end can, as we should assign all alias
classes only after finishing translation unit) builds the pointer
type, the canonical type will match. */
p = TYPE_CANONICAL (p);
while (!reference.is_empty ())
{
if (reference.pop ())
p = build_reference_type (p);
else
p = build_pointer_type (p);
p = TYPE_CANONICAL (TYPE_MAIN_VARIANT (p));
}
gcc_checking_assert (TYPE_CANONICAL (p) == p);
/* Assign the alias set to both p and t.
We can not call get_alias_set (p) here as that would trigger
infinite recursion when p == t. In other cases it would just
trigger unnecesary legwork of rebuilding the pointer again. */
if (TYPE_ALIAS_SET_KNOWN_P (p))
set = TYPE_ALIAS_SET (p);
else
{
set = new_alias_set ();
TYPE_ALIAS_SET (p) = set;
}
}
}
/* In LTO the rules above needs to be part of canonical type machinery.
For now just punt. */
else if (POINTER_TYPE_P (t) && t != ptr_type_node && in_lto_p)
set = get_alias_set (ptr_type_node);
/* Otherwise make a new alias set for this type. */
@ -953,6 +1098,16 @@ get_alias_set (tree t)
if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
record_component_aliases (t);
/* We treat pointer types specially in alias_set_subset_of. */
if (POINTER_TYPE_P (t) && set)
{
alias_set_entry ase = get_alias_set_entry (set);
if (!ase)
ase = init_alias_set_entry (set);
ase->is_pointer = true;
ase->has_pointer = true;
}
return set;
}
@ -1003,12 +1158,7 @@ record_alias_subset (alias_set_type superset, alias_set_type subset)
{
/* Create an entry for the SUPERSET, so that we have a place to
attach the SUBSET. */
superset_entry = ggc_cleared_alloc<alias_set_entry_d> ();
superset_entry->alias_set = superset;
superset_entry->children
= hash_map<int, int, alias_set_traits>::create_ggc (64);
superset_entry->has_zero_child = 0;
(*alias_sets)[superset] = superset_entry;
superset_entry = init_alias_set_entry (superset);
}
if (subset == 0)
@ -1016,17 +1166,25 @@ record_alias_subset (alias_set_type superset, alias_set_type subset)
else
{
subset_entry = get_alias_set_entry (subset);
if (!superset_entry->children)
superset_entry->children
= hash_map<int, int, alias_set_traits>::create_ggc (64);
/* If there is an entry for the subset, enter all of its children
(if they are not already present) as children of the SUPERSET. */
if (subset_entry)
{
if (subset_entry->has_zero_child)
superset_entry->has_zero_child = 1;
superset_entry->has_zero_child = true;
if (subset_entry->has_pointer)
superset_entry->has_pointer = true;
hash_map<int, int, alias_set_traits>::iterator iter
= subset_entry->children->begin ();
for (; iter != subset_entry->children->end (); ++iter)
superset_entry->children->put ((*iter).first, (*iter).second);
if (subset_entry->children)
{
hash_map<int, int, alias_set_traits>::iterator iter
= subset_entry->children->begin ();
for (; iter != subset_entry->children->end (); ++iter)
superset_entry->children->put ((*iter).first, (*iter).second);
}
}
/* Enter the SUBSET itself as a child of the SUPERSET. */
@ -3086,13 +3244,15 @@ dump_alias_stats_in_alias_c (FILE *s)
" %llu queries asked about the same object\n"
" %llu queries asked about the same alias set\n"
" %llu access volatile\n"
" %llu are dependent in the DAG\n",
" %llu are dependent in the DAG\n"
" %llu are aritificially in conflict with void *\n",
alias_stats.num_disambiguated,
alias_stats.num_alias_zero + alias_stats.num_same_alias_set
+ alias_stats.num_same_objects + alias_stats.num_volatile
+ alias_stats.num_dag,
+ alias_stats.num_dag + alias_stats.num_disambiguated
+ alias_stats.num_universal,
alias_stats.num_alias_zero, alias_stats.num_same_alias_set,
+ alias_stats.num_same_objects, alias_stats.num_volatile,
+ alias_stats.num_dag);
alias_stats.num_same_objects, alias_stats.num_volatile,
alias_stats.num_dag, alias_stats.num_universal);
}
#include "gt-alias.h"

6
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,9 @@
2015-05-30 Jan Hubicka <hubicka@ucw.cz>
* gcc.dg/alias-8.c: Do not xfail.
* gcc.dg/pr62167.c: Prevent FRE.
* gcc.dg/alias-14.c: New testcase.
2015-05-29 Christophe Lyon <christophe.lyon@linaro.org>
* gcc.target/arm/simd/vextp64_1.c: Close comment on final line.

70
gcc/testsuite/gcc.dg/alias-14.c Normal file
View file

@ -0,0 +1,70 @@
/* { dg-do compile } */
/* { dg-options "-O2" } */
#include <stddef.h>
void *a;
int *b;
struct c {void * a;} c;
struct d {short * a;} d;
int *ip= (int *)(size_t)2;
int **ipp = &ip;
int
main()
{
float **ptr;
void **uptr;
int* const* cipp = (int* const*)ipp;
/* as an extension we consider void * universal. Writes to it should alias. */
asm ("":"=r"(ptr):"0"(&a));
a=NULL;
*ptr=(float*)(size_t)1;
if (!a)
__builtin_abort ();
a=NULL;
if (*ptr)
__builtin_abort ();
asm ("":"=r"(uptr):"0"(&b));
b=NULL;
*uptr=(void*)(size_t)1;
if (!b)
__builtin_abort ();
b=NULL;
if (*uptr)
__builtin_abort ();
/* Check that we disambiguate int * and char *. */
asm ("":"=r"(ptr):"0"(&b));
b=NULL;
*ptr=(float*)(size_t)1;
if (b)
__builtin_abort ();
/* Again we should make void * in the structure conflict with any pointer. */
asm ("":"=r"(ptr):"0"(&c));
c.a=NULL;
*ptr=(float*)(size_t)1;
if (!c.a)
__builtin_abort ();
c.a=NULL;
if (*ptr)
__builtin_abort ();
asm ("":"=r"(uptr):"0"(&d));
d.a=NULL;
*uptr=(void*)(size_t)1;
if (!d.a)
__builtin_abort ();
d.a=NULL;
if (*uptr)
__builtin_abort ();
if ((void *)*cipp != (void*)(size_t)2)
__builtin_abort ();
*ipp = NULL;
if (*cipp)
__builtin_abort ();
return 0;
}

2
gcc/testsuite/gcc.dg/alias-8.c
View file

@ -8,5 +8,5 @@ struct s {
void
func(struct s *ptr)
{
*(void **)&ptr->p = 0; /* { dg-warning "type-punned pointer" "" { xfail *-*-* } } */
*(void **)&ptr->p = 0; /* { dg-warning "type-punned pointer" "" { } } */
}

2
gcc/testsuite/gcc.dg/pr62167.c
View file

@ -29,6 +29,8 @@ main ()
node.prev = (void *)head;
asm("":"=m"(node.prev));
head->first = &node;
struct node *n = head->first;