Hi,
I have noticed that record_component_aliases is called during LTO time and it
examines contents of BINFO:
0x5cd7a5 record_component_aliases(tree_node*)
../../gcc/alias.c:1005
0x5cd4a9 get_alias_set(tree_node*)
../../gcc/alias.c:895
0x5cc67a component_uses_parent_alias_set_from(tree_node const*)
../../gcc/alias.c:548
0x5ccc42 reference_alias_ptr_type_1
../../gcc/alias.c:660
0x5ccf93 get_alias_set(tree_node*)
../../gcc/alias.c:740
0xb823d8 indirect_refs_may_alias_p
../../gcc/tree-ssa-alias.c:1125
0xb82d8d refs_may_alias_p_1(ao_ref*, ao_ref*, bool)
../../gcc/tree-ssa-alias.c:1279
0xb848df stmt_may_clobber_ref_p_1(gimple_statement_base*, ao_ref*)
../../gcc/tree-ssa-alias.c:2013
0xb85d27 walk_non_aliased_vuses(ao_ref*, tree_node*, void* (*)(ao_ref*,
tree_node*, unsigned int, void*), void* (*)(ao_ref*, tree_node*, void*), void*)
../../gcc/tree-ssa-alias.c:2411
0xc509f3 vn_reference_lookup(tree_node*, tree_node*, vn_lookup_kind,
vn_reference_s**)
../../gcc/tree-ssa-sccvn.c:2063
0xc52ea4 visit_reference_op_store
../../gcc/tree-ssa-sccvn.c:2970
0xc55404 extract_and_process_scc_for_name
../../gcc/tree-ssa-sccvn.c:3825
This smells bad, since it is given a canonical type that is after the
structural equivalency merging that ignores BINFOs, so it may be completely
different class with completely different bases than the original. Bases are
structuraly merged, too and may be exchanged for normal fields because
DECL_ARTIFICIAL (that separate bases and fields) does not seem to be part of
the canonical type definition in LTO.
I wonder if that code is needed after all:
case QUAL_UNION_TYPE:
/* Recursively record aliases for the base classes, if there are any. */
if (TYPE_BINFO (type))
{
int i;
tree binfo, base_binfo;
for (binfo = TYPE_BINFO (type), i = 0;
BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
record_alias_subset (superset,
get_alias_set (BINFO_TYPE (base_binfo)));
}
for (field = TYPE_FIELDS (type); field != 0; field = DECL_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
break;
all bases are also fields of within the type, so the second loop should notice
all the types seen by first loop if I am correct?
So perhaps the loop can be dropped at first place.
Honza
