On Wed, 5 Apr 2017, Bernd Edlinger wrote:
> 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.
The alias.c changes are not sufficient. I think what you want is
sth like
Index: gcc/alias.c
===================================================================
--- gcc/alias.c (revision 246678)
+++ gcc/alias.c (working copy)
@@ -136,6 +136,9 @@ struct GTY(()) alias_set_entry {
bool is_pointer;
/* Nonzero if is_pointer or if one of childs have has_pointer set. */
bool has_pointer;
+ /* Nonzero if we have a child serving as typeless storage (or are
+ such storage ourselves). */
+ bool has_typeless_storage;
/* The children of the alias set. These are not just the immediate
children, but, in fact, all descendants. So, if we have:
@@ -419,7 +422,8 @@ alias_set_subset_of (alias_set_type set1
/* Check if set1 is a subset of set2. */
ase2 = get_alias_set_entry (set2);
if (ase2 != 0
- && (ase2->has_zero_child
+ && (ase2->has_typeless_storage
+ || ase2->has_zero_child
|| (ase2->children && ase2->children->get (set1))))
return true;
@@ -825,6 +829,7 @@ init_alias_set_entry (alias_set_type set
ase->has_zero_child = false;
ase->is_pointer = false;
ase->has_pointer = false;
+ ase->has_typeless_storage = false;
gcc_checking_assert (!get_alias_set_entry (set));
(*alias_sets)[set] = ase;
return ase;
@@ -955,6 +960,7 @@ get_alias_set (tree t)
Just be pragmatic here and make sure the array and its element
type get the same alias set assigned. */
else if (TREE_CODE (t) == ARRAY_TYPE
+ && ! TYPE_TYPELESS_STORAGE (t)
&& (!TYPE_NONALIASED_COMPONENT (t)
|| TYPE_STRUCTURAL_EQUALITY_P (t)))
set = get_alias_set (TREE_TYPE (t));
@@ -1094,6 +1100,15 @@ get_alias_set (tree t)
TYPE_ALIAS_SET (t) = set;
+ if (TREE_CODE (t) == ARRAY_TYPE
+ && TYPE_TYPELESS_STORAGE (t))
+ {
+ alias_set_entry *ase = get_alias_set_entry (set);
+ if (!ase)
+ ase = init_alias_set_entry (set);
+ ase->has_typeless_storage = true;
+ }
+
/* If this is an aggregate type or a complex type, we must record any
component aliasing information. */
if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
@@ -1173,6 +1188,8 @@ record_alias_subset (alias_set_type supe
superset_entry->has_zero_child = true;
if (subset_entry->has_pointer)
superset_entry->has_pointer = true;
+ if (subset_entry->has_typeless_storage)
+ superset_entry->has_typeless_storage = true;
if (subset_entry->children)
{
please also restrict TYPE_TYPELESS_STORAGE to ARRAY_TYPEs (otherwise
more complications will arise).
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);
...
I don't think you need all this given alias.c only looks at
TYPE_MAIN_VARIANTs.
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
not needed (but also not sufficient - you need to handle arrays of
byte somewhere).
@@ -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;
bits are grouped in groups of 8 bits, this breaks it.
@@ -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
not needed.
+/* 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)
ARRAY_TYPE_CHECK (NODE)->
Richard.
