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Commit 4aa83879 by Richard Biener Committed by Richard Biener
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re PR middle-end/71002 (-fstrict-aliasing breaks Boost's short string optimization implementation) 

2016-06-29  Richard Biener  <rguenther@suse.de>

	PR middle-end/71002
	* alias.c (component_uses_parent_alias_set_from): Handle
	type punning through union accesses by using the union alias set.
	* gimple.c (gimple_get_alias_set): Remove union type punning case.

	c-family/
	* c-common.c (c_common_get_alias_set): Remove union type punning case.
	
	fortran/
	* f95-lang.c (LANG_HOOKS_GET_ALIAS_SET): Remove (un-)define.
	(gfc_get_alias_set): Remove.

	* g++.dg/torture/pr71002.C: Adjust testcase.

From-SVN: r237839
parent 36088299
Showing with 34 additions and 59 deletions
gcc/ChangeLog
2016-06-29 Richard Biener <rguenther@suse.de>
PR middle-end/71002
* alias.c (component_uses_parent_alias_set_from): Handle
type punning through union accesses by using the union alias set.
* gimple.c (gimple_get_alias_set): Remove union type punning case.
2016-07-29 Richard Biener <rguenther@suse.de>
* match.pd ((T)(T2)x -> (T)x): Remove restriction on final
......
gcc/alias.c
......@@ -619,6 +619,14 @@ component_uses_parent_alias_set_from (const_tree t)
case COMPONENT_REF:
if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
found = t;
/* Permit type-punning when accessing a union, provided the access
is directly through the union. For example, this code does not
permit taking the address of a union member and then storing
through it. Even the type-punning allowed here is a GCC
extension, albeit a common and useful one; the C standard says
that such accesses have implementation-defined behavior. */
else if (TREE_CODE (TREE_TYPE (TREE_OPERAND (t, 0))) == UNION_TYPE)
found = t;
break;
case ARRAY_REF:
......
gcc/c-family/ChangeLog
2016-06-29 Richard Biener <rguenther@suse.de>
PR middle-end/71002
* c-common.c (c_common_get_alias_set): Remove union type punning case.
2016-06-24 Jason Merrill <jason@redhat.com>
P0145R2: Refining Expression Order for C++.
......
gcc/c-family/c-common.c
......@@ -4736,8 +4736,6 @@ static GTY(()) hash_table<c_type_hasher> *type_hash_table;
alias_set_type
c_common_get_alias_set (tree t)
{
tree u;
/* For VLAs, use the alias set of the element type rather than the
default of alias set 0 for types compared structurally. */
if (TYPE_P (t) && TYPE_STRUCTURAL_EQUALITY_P (t))
......@@ -4747,19 +4745,6 @@ c_common_get_alias_set (tree t)
return -1;
}
/* Permit type-punning when accessing a union, provided the access
is directly through the union. For example, this code does not
permit taking the address of a union member and then storing
through it. Even the type-punning allowed here is a GCC
extension, albeit a common and useful one; the C standard says
that such accesses have implementation-defined behavior. */
for (u = t;
TREE_CODE (u) == COMPONENT_REF || TREE_CODE (u) == ARRAY_REF;
u = TREE_OPERAND (u, 0))
if (TREE_CODE (u) == COMPONENT_REF
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
return 0;
/* That's all the expressions we handle specially. */
if (!TYPE_P (t))
return -1;
......
gcc/fortran/ChangeLog
2016-06-29 Richard Biener <rguenther@suse.de>
PR middle-end/71002
* f95-lang.c (LANG_HOOKS_GET_ALIAS_SET): Remove (un-)define.
(gfc_get_alias_set): Remove.
2016-06-25 Jerry DeLisle <jvdelisle@gcc.gnu.org>
PR fortran/71649
......
gcc/fortran/f95-lang.c
......@@ -74,7 +74,6 @@ static bool global_bindings_p (void);
static bool gfc_init (void);
static void gfc_finish (void);
static void gfc_be_parse_file (void);
static alias_set_type gfc_get_alias_set (tree);
static void gfc_init_ts (void);
static tree gfc_builtin_function (tree);
......@@ -110,7 +109,6 @@ static const struct attribute_spec gfc_attribute_table[] =
#undef LANG_HOOKS_MARK_ADDRESSABLE
#undef LANG_HOOKS_TYPE_FOR_MODE
#undef LANG_HOOKS_TYPE_FOR_SIZE
#undef LANG_HOOKS_GET_ALIAS_SET
#undef LANG_HOOKS_INIT_TS
#undef LANG_HOOKS_OMP_PRIVATIZE_BY_REFERENCE
#undef LANG_HOOKS_OMP_PREDETERMINED_SHARING
......@@ -142,7 +140,6 @@ static const struct attribute_spec gfc_attribute_table[] =
#define LANG_HOOKS_PARSE_FILE gfc_be_parse_file
#define LANG_HOOKS_TYPE_FOR_MODE gfc_type_for_mode
#define LANG_HOOKS_TYPE_FOR_SIZE gfc_type_for_size
#define LANG_HOOKS_GET_ALIAS_SET gfc_get_alias_set
#define LANG_HOOKS_INIT_TS gfc_init_ts
#define LANG_HOOKS_OMP_PRIVATIZE_BY_REFERENCE gfc_omp_privatize_by_reference
#define LANG_HOOKS_OMP_PREDETERMINED_SHARING gfc_omp_predetermined_sharing
......@@ -503,24 +500,6 @@ gfc_init_decl_processing (void)
}
/* Return the typed-based alias set for T, which may be an expression
or a type. Return -1 if we don't do anything special. */
static alias_set_type
gfc_get_alias_set (tree t)
{
tree u;
/* Permit type-punning when accessing an EQUIVALENCEd variable or
mixed type entry master's return value. */
for (u = t; handled_component_p (u); u = TREE_OPERAND (u, 0))
if (TREE_CODE (u) == COMPONENT_REF
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
return 0;
return -1;
}
/* Builtin function initialization. */
static tree
......
gcc/gimple.c
......@@ -2400,21 +2400,6 @@ gimple_signed_type (tree type)
alias_set_type
gimple_get_alias_set (tree t)
{
tree u;
/* Permit type-punning when accessing a union, provided the access
is directly through the union. For example, this code does not
permit taking the address of a union member and then storing
through it. Even the type-punning allowed here is a GCC
extension, albeit a common and useful one; the C standard says
that such accesses have implementation-defined behavior. */
for (u = t;
TREE_CODE (u) == COMPONENT_REF || TREE_CODE (u) == ARRAY_REF;
u = TREE_OPERAND (u, 0))
if (TREE_CODE (u) == COMPONENT_REF
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
return 0;
/* That's all the expressions we handle specially. */
if (!TYPE_P (t))
return -1;
......
gcc/testsuite/ChangeLog
2016-06-29 Richard Biener <rguenther@suse.de>
PR middle-end/71002
* g++.dg/torture/pr71002.C: Adjust testcase.
2016-06-29 Jakub Jelinek <jakub@redhat.com>
PR c/71685
......
gcc/testsuite/g++.dg/torture/pr71002.C
......@@ -16,11 +16,6 @@ struct long_t
char* pointer;
};
union long_raw_t {
unsigned char data[sizeof(long_t)];
struct __attribute__((aligned(alignof(long_t)))) { } align;
};
struct short_header
{
unsigned char is_short : 1;
......@@ -35,20 +30,20 @@ struct short_t
union repr_t
{
long_raw_t r;
long_t r;
short_t s;
const short_t& short_repr() const
{ return s; }
const long_t& long_repr() const
{ return *static_cast<const long_t*>(static_cast<const void*>(&r)); }
{ return r; }
short_t& short_repr()
{ return s; }
long_t& long_repr()
{ return *static_cast<long_t*>(static_cast<void*>(&r)); }
{ return r; }
};
class string
......
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