On 04/05/17 19:22, Bernd Edlinger wrote:
> On 04/05/17 18:08, Jakub Jelinek wrote:
>
> Yes, exactly. I really want to reach the deadline for gcc-7.
> Fixing the name is certainly the most important first step,
> and if everybody agrees on "typeless_storage", for the name
> I can start with adjusting the name, and look into how
> to use a spare type-flag that should be a mechanical change.
>
Jakub, I just renamed the attribute and reworked the patch
as you suggested, reg-testing is not yet completed, but
it looks good so far. I also added a few more tests.
I have changed the documentation as Richi suggested, but
I am not too sure what to say here.
Thanks
Bernd.
gcc
2017-04-05 Bernd Edlinger <bernd.edlin...@hotmail.de>
* doc/extend.texi: Document the typeless_storage type attribute.
* alias.c (get_alias_set): Honor the typeless_storage attribute.
(record_component_aliases): Don't ignore the typeless_storage
attribute.
* tree.c (build_pointer_type_for_mode,
build_reference_type_for_mode): Handle the typeless_storage
attribute.
* print-tree.c (print_node): Likewise.
* tree-streamer-in.c (unpack_ts_type_common_value_fields): Likewise.
* tree-streamer-out.c (pack_ts_type_common_value_fields): Likewise.
* tre.h (TYPE_TYPELESS_STORAGE): New access macro.
* tree-core.h (tree_type_common::typeless_storage_flag): New flag.
gcc/c-family
2017-04-05 Bernd Edlinger <bernd.edlin...@hotmail.de>
* c-attribs.c (c_common_attribute_tab): Add the typeless_storage
attribute.
(handle_typeless_storage_attribute): New function.
gcc/cp
2017-04-05 Bernd Edlinger <bernd.edlin...@hotmail.de>
* class.c (fixup_attribute_variants): Handle the typeless_storage
attribute.
(finish_struct_1): Set the typeless_storage attribute if required
by C++17.
* decl.c (start_enum): Likewise.
* pt.c (lookup_template_class_1): Handle the typeless_storage
attribute.
* typeck2.c (cxx_type_contains_byte_buffer): New function.
* cp-tree.h (cxx_type_contains_byte_buffer): Declare.
gcc/lto
2017-04-05 Bernd Edlinger <bernd.edlin...@hotmail.de>
* lto.c (compare_tree_sccs_1, hash_tree): Handle the typeless_storage
attribute.
gcc/testsuite
2017-04-05 Bernd Edlinger <bernd.edlin...@hotmail.de>
* c-c++-common/attr-typeless-storage-1.c: New test.
* c-c++-common/attr-typeless-storage-2.c: New test.
* gcc.c-torture/execute/typeless-storage-1.c: New test.
Index: gcc/alias.c
===================================================================
--- gcc/alias.c (revision 246678)
+++ gcc/alias.c (working copy)
@@ -879,6 +879,10 @@ get_alias_set (tree t)
t = TREE_TYPE (t);
}
+ /* Honor the typeless_storage type attribute. */
+ if (TYPE_TYPELESS_STORAGE (t))
+ return 0;
+
/* Variant qualifiers don't affect the alias set, so get the main
variant. */
t = TYPE_MAIN_VARIANT (t);
@@ -1234,7 +1238,8 @@ record_component_aliases (tree type)
/* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
element type and that type has to be normalized to void *,
too, in the case it is a pointer. */
- while (!canonical_type_used_p (t) && !POINTER_TYPE_P (t))
+ while (!canonical_type_used_p (t) && !POINTER_TYPE_P (t)
+ && !TYPE_TYPELESS_STORAGE (t))
{
gcc_checking_assert (TYPE_STRUCTURAL_EQUALITY_P (t));
t = TREE_TYPE (t);
Index: gcc/c-family/c-attribs.c
===================================================================
--- gcc/c-family/c-attribs.c (revision 246678)
+++ gcc/c-family/c-attribs.c (working copy)
@@ -113,6 +113,7 @@ static tree handle_vector_size_attribute (tree *,
bool *);
static tree handle_nonnull_attribute (tree *, tree, tree, int, bool *);
static tree handle_nothrow_attribute (tree *, tree, tree, int, bool *);
+static tree handle_typeless_storage_attribute (tree *, tree, tree, int, bool *);
static tree handle_cleanup_attribute (tree *, tree, tree, int, bool *);
static tree handle_warn_unused_result_attribute (tree *, tree, tree, int,
bool *);
@@ -265,6 +266,8 @@ const struct attribute_spec c_common_attribute_tab
{ "nothrow", 0, 0, true, false, false,
handle_nothrow_attribute, false },
{ "may_alias", 0, 0, false, true, false, NULL, false },
+ { "typeless_storage", 0, 0, false, true, false,
+ handle_typeless_storage_attribute, false },
{ "cleanup", 1, 1, true, false, false,
handle_cleanup_attribute, false },
{ "warn_unused_result", 0, 0, false, true, true,
@@ -2879,6 +2882,24 @@ handle_nothrow_attribute (tree *node, tree name, t
return NULL_TREE;
}
+/* Handle a "typeless_storage" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_typeless_storage_attribute (tree *node, tree name, tree ARG_UNUSED (args),
+ int ARG_UNUSED (flags), bool *no_add_attrs)
+{
+ if (TYPE_P (*node))
+ TYPE_TYPELESS_STORAGE (*node) = 1;
+ else
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+ *no_add_attrs = true;
+ }
+
+ return NULL_TREE;
+}
+
/* Handle a "cleanup" attribute; arguments as in
struct attribute_spec.handler. */
Index: gcc/cp/class.c
===================================================================
--- gcc/cp/class.c (revision 246678)
+++ gcc/cp/class.c (working copy)
@@ -2083,7 +2083,8 @@ fixup_attribute_variants (tree t)
tree attrs = TYPE_ATTRIBUTES (t);
unsigned align = TYPE_ALIGN (t);
bool user_align = TYPE_USER_ALIGN (t);
- bool may_alias = lookup_attribute ("may_alias", attrs);
+ bool may_alias = TYPE_TYPELESS_STORAGE (t)
+ || lookup_attribute ("may_alias", attrs);
if (may_alias)
fixup_may_alias (t);
@@ -7345,6 +7348,12 @@ finish_struct_1 (tree t)
the class or perform any other required target modifications. */
targetm.cxx.adjust_class_at_definition (t);
+ if (cxx_dialect >= cxx1z && cxx_type_contains_byte_buffer (t))
+ {
+ TYPE_TYPELESS_STORAGE (t) = 1;
+ fixup_attribute_variants (t);
+ }
+
maybe_suppress_debug_info (t);
if (flag_vtable_verify)
Index: gcc/cp/cp-tree.h
===================================================================
--- gcc/cp/cp-tree.h (revision 246678)
+++ gcc/cp/cp-tree.h (working copy)
@@ -6858,6 +6858,7 @@ extern tree finish_binary_fold_expr (tree
extern void require_complete_eh_spec_types (tree, tree);
extern void cxx_incomplete_type_diagnostic (location_t, const_tree,
const_tree, diagnostic_t);
+extern bool cxx_type_contains_byte_buffer (tree);
inline void
cxx_incomplete_type_diagnostic (const_tree value, const_tree type,
diagnostic_t diag_kind)
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c (revision 246678)
+++ gcc/cp/decl.c (working copy)
@@ -14081,10 +14081,11 @@ start_enum (tree name, tree enumtype, tree underly
enumtype = pushtag (name, enumtype, /*tag_scope=*/ts_current);
/* std::byte aliases anything. */
- if (enumtype != error_mark_node
+ if (cxx_dialect >= cxx1z
+ && enumtype != error_mark_node
&& TYPE_CONTEXT (enumtype) == std_node
&& !strcmp ("byte", TYPE_NAME_STRING (enumtype)))
- TYPE_ALIAS_SET (enumtype) = 0;
+ TYPE_TYPELESS_STORAGE (enumtype) = 1;
}
else
enumtype = xref_tag (enum_type, name, /*tag_scope=*/ts_current,
Index: gcc/cp/pt.c
===================================================================
--- gcc/cp/pt.c (revision 246678)
+++ gcc/cp/pt.c (working copy)
@@ -8853,7 +8853,8 @@ lookup_template_class_1 (tree d1, tree arglist, tr
{
static const char *tags[] = {"abi_tag", "may_alias"};
- for (unsigned ix = 0; ix != 2; ix++)
+ TYPE_TYPELESS_STORAGE (t) |= TYPE_TYPELESS_STORAGE (template_type);
+ for (unsigned ix = 0; ix < sizeof (tags) / sizeof (tags[0]); ix++)
{
tree attributes
= lookup_attribute (tags[ix], TYPE_ATTRIBUTES (template_type));
Index: gcc/cp/typeck2.c
===================================================================
--- gcc/cp/typeck2.c (revision 246678)
+++ gcc/cp/typeck2.c (working copy)
@@ -2234,5 +2234,29 @@ require_complete_eh_spec_types (tree fntype, tree
}
}
+/* True iff type either is or contains a byte buffer (which can be used for
+ storing any trivially copyable type). */
+
+bool
+cxx_type_contains_byte_buffer (tree type)
+{
+ if (TREE_CODE (type) == ARRAY_TYPE
+ && (cxx_type_contains_byte_buffer (TREE_TYPE (type))
+ || TREE_TYPE (type) == unsigned_char_type_node
+ || (TREE_CODE (TREE_TYPE (type)) == ENUMERAL_TYPE
+ && TYPE_CONTEXT (TREE_TYPE (type)) == std_node
+ && !strcmp ("byte", TYPE_NAME_STRING (TREE_TYPE (type))))))
+ return true;
+
+ if (CLASS_TYPE_P (type))
+ for (tree field = next_initializable_field (TYPE_FIELDS (type));
+ field;
+ field = next_initializable_field (DECL_CHAIN (field)))
+ if (cxx_type_contains_byte_buffer (TREE_TYPE (field)))
+ return true;
+
+ return false;
+}
+
#include "gt-cp-typeck2.h"
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi (revision 246678)
+++ gcc/doc/extend.texi (working copy)
@@ -6656,6 +6656,11 @@ declaration, the above program would abort when co
@option{-fstrict-aliasing}, which is on by default at @option{-O2} or
above.
+@item typeless_storage
+@cindex @code{typeless_storage} type attribute
+An object declared with a type with this attribute behaves like a
+character type with respect to aliasing semantics.
+
@item packed
@cindex @code{packed} type attribute
This attribute, attached to @code{struct} or @code{union} type
Index: gcc/lto/lto.c
===================================================================
--- gcc/lto/lto.c (revision 246678)
+++ gcc/lto/lto.c (working copy)
@@ -1164,6 +1164,7 @@ compare_tree_sccs_1 (tree t1, tree t2, tree **map)
compare_values (TYPE_NONALIASED_COMPONENT);
compare_values (TYPE_PACKED);
compare_values (TYPE_RESTRICT);
+ compare_values (TYPE_TYPELESS_STORAGE);
compare_values (TYPE_USER_ALIGN);
compare_values (TYPE_READONLY);
compare_values (TYPE_PRECISION);
Index: gcc/lto-streamer-out.c
===================================================================
--- gcc/lto-streamer-out.c (revision 246678)
+++ gcc/lto-streamer-out.c (working copy)
@@ -1134,6 +1134,7 @@ hash_tree (struct streamer_tree_cache_d *cache, ha
hstate.add_flag (TYPE_NEEDS_CONSTRUCTING (t));
hstate.add_flag (TYPE_PACKED (t));
hstate.add_flag (TYPE_RESTRICT (t));
+ hstate.add_flag (TYPE_TYPELESS_STORAGE (t));
hstate.add_flag (TYPE_USER_ALIGN (t));
hstate.add_flag (TYPE_READONLY (t));
if (RECORD_OR_UNION_TYPE_P (t))
Index: gcc/print-tree.c
===================================================================
--- gcc/print-tree.c (revision 246678)
+++ gcc/print-tree.c (working copy)
@@ -574,6 +574,9 @@ print_node (FILE *file, const char *prefix, tree n
if (TYPE_RESTRICT (node))
fputs (" restrict", file);
+ if (TYPE_TYPELESS_STORAGE (node))
+ fputs (" typeless-storage", file);
+
if (TYPE_LANG_FLAG_0 (node))
fputs (" type_0", file);
if (TYPE_LANG_FLAG_1 (node))
Index: gcc/testsuite/c-c++-common/attr-typeless-storage-1.c
===================================================================
--- gcc/testsuite/c-c++-common/attr-typeless-storage-1.c (revision 0)
+++ gcc/testsuite/c-c++-common/attr-typeless-storage-1.c (working copy)
@@ -0,0 +1,29 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wall" } */
+
+typedef int T __attribute__((typeless_storage));
+
+extern T t, v;
+extern T *p;
+extern int *p;
+
+extern int *p2;
+extern T *p2;
+
+void fn1 (T);
+void fn1 (int);
+
+void fn2 (int);
+void fn2 (T);
+
+/* Ensure that the composite types have typeless_storage. */
+void
+f (long *i)
+{
+ *i = *(__typeof (*p) *) &p;
+ asm ("" : : "r" (*p));
+ *i = *(__typeof (*p2) *) &p2;
+ asm ("" : : "r" (*p2));
+ t = v;
+ asm ("" : : "r" (t));
+}
Index: gcc/testsuite/c-c++-common/attr-typeless-storage-2.c
===================================================================
--- gcc/testsuite/c-c++-common/attr-typeless-storage-2.c (revision 0)
+++ gcc/testsuite/c-c++-common/attr-typeless-storage-2.c (working copy)
@@ -0,0 +1,17 @@
+/* We used to reject this because types differentiating only in
+ TYPE_REF_CAN_ALIAS_ALL were deemed incompatible. */
+/* { dg-do compile } */
+
+struct sockaddr;
+struct sockaddr *f (void);
+
+struct __attribute__((typeless_storage)) sockaddr { int j; };
+struct sockaddr *
+f (void)
+{
+ return
+#ifndef __cplusplus
+ (void *)
+#endif
+ 0;
+}
Index: gcc/testsuite/gcc.c-torture/execute/typeless-storage-1.c
===================================================================
--- gcc/testsuite/gcc.c-torture/execute/typeless-storage-1.c (revision 0)
+++ gcc/testsuite/gcc.c-torture/execute/typeless-storage-1.c (working copy)
@@ -0,0 +1,20 @@
+/* Tests that the typeless_storage attribute works as expected. */
+
+extern void abort(void);
+extern void exit(int);
+
+typedef int __attribute__((__typeless_storage__)) int_a;
+
+int
+main (void)
+{
+ int_a a = 0x12345678;
+ short *b = (short*) &a;
+
+ b[1] = 0;
+
+ if (a == 0x12345678)
+ abort();
+
+ exit(0);
+}
Index: gcc/tree-core.h
===================================================================
--- gcc/tree-core.h (revision 246678)
+++ gcc/tree-core.h (working copy)
@@ -1491,6 +1491,7 @@ struct GTY(()) tree_type_common {
unsigned needs_constructing_flag : 1;
unsigned transparent_aggr_flag : 1;
unsigned restrict_flag : 1;
+ unsigned typeless_storage_flag : 1;
unsigned contains_placeholder_bits : 2;
ENUM_BITFIELD(machine_mode) mode : 8;
@@ -1511,7 +1512,7 @@ struct GTY(()) tree_type_common {
so we need to store the value 32 (not 31, as we need the zero
as well), hence six bits. */
unsigned align : 6;
- unsigned spare : 25;
+ unsigned spare : 24;
alias_set_type alias_set;
tree pointer_to;
tree reference_to;
Index: gcc/tree-streamer-in.c
===================================================================
--- gcc/tree-streamer-in.c (revision 246678)
+++ gcc/tree-streamer-in.c (working copy)
@@ -367,6 +367,7 @@ unpack_ts_type_common_value_fields (struct bitpack
TYPE_NEEDS_CONSTRUCTING (expr) = (unsigned) bp_unpack_value (bp, 1);
TYPE_PACKED (expr) = (unsigned) bp_unpack_value (bp, 1);
TYPE_RESTRICT (expr) = (unsigned) bp_unpack_value (bp, 1);
+ TYPE_TYPELESS_STORAGE (expr) = (unsigned) bp_unpack_value (bp, 1);
TYPE_USER_ALIGN (expr) = (unsigned) bp_unpack_value (bp, 1);
TYPE_READONLY (expr) = (unsigned) bp_unpack_value (bp, 1);
if (RECORD_OR_UNION_TYPE_P (expr))
Index: gcc/tree-streamer-out.c
===================================================================
--- gcc/tree-streamer-out.c (revision 246678)
+++ gcc/tree-streamer-out.c (working copy)
@@ -316,6 +316,7 @@ pack_ts_type_common_value_fields (struct bitpack_d
bp_pack_value (bp, TYPE_NEEDS_CONSTRUCTING (expr), 1);
bp_pack_value (bp, TYPE_PACKED (expr), 1);
bp_pack_value (bp, TYPE_RESTRICT (expr), 1);
+ bp_pack_value (bp, TYPE_TYPELESS_STORAGE (expr), 1);
bp_pack_value (bp, TYPE_USER_ALIGN (expr), 1);
bp_pack_value (bp, TYPE_READONLY (expr), 1);
/* We used to stream TYPE_ALIAS_SET == 0 information to let frontends mark
Index: gcc/tree.c
===================================================================
--- gcc/tree.c (revision 246678)
+++ gcc/tree.c (working copy)
@@ -8041,7 +8041,8 @@ build_pointer_type_for_mode (tree to_type, machine
/* If the pointed-to type has the may_alias attribute set, force
a TYPE_REF_CAN_ALIAS_ALL pointer to be generated. */
- if (lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type)))
+ if (TYPE_TYPELESS_STORAGE (to_type)
+ || lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type)))
can_alias_all = true;
/* In some cases, languages will have things that aren't a POINTER_TYPE
@@ -8110,7 +8111,8 @@ build_reference_type_for_mode (tree to_type, machi
/* If the pointed-to type has the may_alias attribute set, force
a TYPE_REF_CAN_ALIAS_ALL pointer to be generated. */
- if (lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type)))
+ if (TYPE_TYPELESS_STORAGE (to_type)
+ || lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type)))
can_alias_all = true;
/* In some cases, languages will have things that aren't a REFERENCE_TYPE
Index: gcc/tree.h
===================================================================
--- gcc/tree.h (revision 246678)
+++ gcc/tree.h (working copy)
@@ -1944,6 +1944,11 @@ extern machine_mode element_mode (const_tree t);
the term. */
#define TYPE_RESTRICT(NODE) (TYPE_CHECK (NODE)->type_common.restrict_flag)
+/* Nonzero if the type should behave like a character type
+ with respect to aliasing sementics. */
+#define TYPE_TYPELESS_STORAGE(NODE) \
+ (TYPE_CHECK (NODE)->type_common.typeless_storage_flag)
+
/* If nonzero, type's name shouldn't be emitted into debug info. */
#define TYPE_NAMELESS(NODE) (TYPE_CHECK (NODE)->base.u.bits.nameless_flag)
