1 --- gcc-4_1-branch/gcc/cfgexpand.c (revision 110109)
2 +++ gcc-4_1-branch/gcc/cfgexpand.c (revision 110110)
4 gcc_assert (index < stack_vars_conflict_alloc);
5 return stack_vars_conflict[index];
9 +/* Returns true if TYPE is or contains a union type. */
12 +aggregate_contains_union_type (tree type)
16 + if (TREE_CODE (type) == UNION_TYPE
17 + || TREE_CODE (type) == QUAL_UNION_TYPE)
19 + if (TREE_CODE (type) == ARRAY_TYPE)
20 + return aggregate_contains_union_type (TREE_TYPE (type));
21 + if (TREE_CODE (type) != RECORD_TYPE)
24 + for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
25 + if (TREE_CODE (field) == FIELD_DECL)
26 + if (aggregate_contains_union_type (TREE_TYPE (field)))
32 /* A subroutine of expand_used_vars. If two variables X and Y have alias
33 sets that do not conflict, then do add a conflict for these variables
34 - in the interference graph. We also have to mind MEM_IN_STRUCT_P and
36 + in the interference graph. We also need to make sure to add conflicts
37 + for union containing structures. Else RTL alias analysis comes along
38 + and due to type based aliasing rules decides that for two overlapping
39 + union temporaries { short s; int i; } accesses to the same mem through
40 + different types may not alias and happily reorders stores across
41 + life-time boundaries of the temporaries (See PR25654).
42 + We also have to mind MEM_IN_STRUCT_P and MEM_SCALAR_P. */
45 add_alias_set_conflicts (void)
48 tree type_i = TREE_TYPE (stack_vars[i].decl);
49 bool aggr_i = AGGREGATE_TYPE_P (type_i);
50 + bool contains_union;
52 + contains_union = aggregate_contains_union_type (type_i);
53 for (j = 0; j < i; ++j)
55 tree type_j = TREE_TYPE (stack_vars[j].decl);
56 bool aggr_j = AGGREGATE_TYPE_P (type_j);
57 - if (aggr_i != aggr_j || !objects_must_conflict_p (type_i, type_j))
58 + if (aggr_i != aggr_j
59 + /* Either the objects conflict by means of type based
60 + aliasing rules, or we need to add a conflict. */
61 + || !objects_must_conflict_p (type_i, type_j)
62 + /* In case the types do not conflict ensure that access
63 + to elements will conflict. In case of unions we have
64 + to be careful as type based aliasing rules may say
65 + access to the same memory does not conflict. So play
66 + safe and add a conflict in this case. */
68 add_stack_var_conflict (i, j);