+
+/* Add VAR to the list of may-aliases of PTR's type tag. If PTR
+ doesn't already have a type tag, create one. */
+
+void
+add_type_alias (tree ptr, tree var)
+{
+ varray_type aliases;
+ tree tag;
+ var_ann_t ann = var_ann (ptr);
+ subvar_t svars;
+
+ if (ann->type_mem_tag == NULL_TREE)
+ {
+ size_t i;
+ tree q = NULL_TREE;
+ tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
+ HOST_WIDE_INT tag_set = get_alias_set (tag_type);
+
+ /* PTR doesn't have a type tag, create a new one and add VAR to
+ the new tag's alias set.
+
+ FIXME, This is slower than necessary. We need to determine
+ whether there is another pointer Q with the same alias set as
+ PTR. This could be sped up by having type tags associated
+ with types. */
+ for (i = 0; i < num_referenced_vars; i++)
+ {
+ q = referenced_var (i);
+
+ if (POINTER_TYPE_P (TREE_TYPE (q))
+ && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q))))
+ {
+ /* Found another pointer Q with the same alias set as
+ the PTR's pointed-to type. If Q has a type tag, use
+ it. Otherwise, create a new memory tag for PTR. */
+ var_ann_t ann1 = var_ann (q);
+ if (ann1->type_mem_tag)
+ ann->type_mem_tag = ann1->type_mem_tag;
+ else
+ ann->type_mem_tag = create_memory_tag (tag_type, true);
+ goto found_tag;
+ }
+ }
+
+ /* Couldn't find any other pointer with a type tag we could use.
+ Create a new memory tag for PTR. */
+ ann->type_mem_tag = create_memory_tag (tag_type, true);
+ }
+
+found_tag:
+ /* If VAR is not already PTR's type tag, add it to the may-alias set
+ for PTR's type tag. */
+ gcc_assert (var_ann (var)->type_mem_tag == NOT_A_TAG);
+ tag = ann->type_mem_tag;
+
+ /* If VAR has subvars, add the subvars to the tag instead of the
+ actual var. */
+ if (var_can_have_subvars (var)
+ && (svars = get_subvars_for_var (var)))
+ {
+ subvar_t sv;
+ for (sv = svars; sv; sv = sv->next)
+ add_may_alias (tag, sv->var);
+ }
+ else
+ add_may_alias (tag, var);
+
+ /* TAG and its set of aliases need to be marked for renaming. */
+ mark_sym_for_renaming (tag);
+ if ((aliases = var_ann (tag)->may_aliases) != NULL)
+ {
+ size_t i;
+ for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
+ mark_sym_for_renaming (VARRAY_TREE (aliases, i));
+ }
+
+ /* If we had grouped aliases, VAR may have aliases of its own. Mark
+ them for renaming as well. Other statements referencing the
+ aliases of VAR will need to be updated. */
+ if ((aliases = var_ann (var)->may_aliases) != NULL)
+ {
+ size_t i;
+ for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
+ mark_sym_for_renaming (VARRAY_TREE (aliases, i));
+ }
+}
+
+
+/* This structure is simply used during pushing fields onto the fieldstack
+ to track the offset of the field, since bitpos_of_field gives it relative
+ to its immediate containing type, and we want it relative to the ultimate
+ containing object. */
+
+typedef struct fieldoff
+{
+ tree field;
+ HOST_WIDE_INT offset;
+} fieldoff_s;
+
+DEF_VEC_O (fieldoff_s);
+DEF_VEC_ALLOC_O(fieldoff_s,heap);
+
+/* Return the position, in bits, of FIELD_DECL from the beginning of its
+ structure.
+ Return -1 if the position is conditional or otherwise non-constant
+ integer. */
+
+static HOST_WIDE_INT
+bitpos_of_field (const tree fdecl)
+{
+
+ if (TREE_CODE (DECL_FIELD_OFFSET (fdecl)) != INTEGER_CST
+ || TREE_CODE (DECL_FIELD_BIT_OFFSET (fdecl)) != INTEGER_CST)
+ return -1;
+
+ return (tree_low_cst (DECL_FIELD_OFFSET (fdecl), 1) * 8)
+ + tree_low_cst (DECL_FIELD_BIT_OFFSET (fdecl), 1);
+}
+
+/* Given a TYPE, and a vector of field offsets FIELDSTACK, push all the fields
+ of TYPE onto fieldstack, recording their offsets along the way.
+ OFFSET is used to keep track of the offset in this entire structure, rather
+ than just the immediately containing structure. Returns the number
+ of fields pushed. */
+
+static int
+push_fields_onto_fieldstack (tree type, VEC(fieldoff_s,heap) **fieldstack,
+ HOST_WIDE_INT offset)
+{
+ tree field;
+ int count = 0;
+
+ for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
+ if (TREE_CODE (field) == FIELD_DECL)
+ {
+ bool push = false;
+
+ if (!var_can_have_subvars (field))
+ push = true;
+ else if (!(push_fields_onto_fieldstack
+ (TREE_TYPE (field), fieldstack,
+ offset + bitpos_of_field (field)))
+ && DECL_SIZE (field)
+ && !integer_zerop (DECL_SIZE (field)))
+ /* Empty structures may have actual size, like in C++. So
+ see if we didn't push any subfields and the size is
+ nonzero, push the field onto the stack */
+ push = true;
+
+ if (push)
+ {
+ fieldoff_s *pair;
+
+ pair = VEC_safe_push (fieldoff_s, heap, *fieldstack, NULL);
+ pair->field = field;
+ pair->offset = offset + bitpos_of_field (field);
+ count++;
+ }
+ }
+ return count;
+}
+
+
+/* This represents the used range of a variable. */
+
+typedef struct used_part
+{
+ HOST_WIDE_INT minused;
+ HOST_WIDE_INT maxused;
+ /* True if we have an explicit use/def of some portion of this variable,
+ even if it is all of it. i.e. a.b = 5 or temp = a.b. */
+ bool explicit_uses;
+ /* True if we have an implicit use/def of some portion of this
+ variable. Implicit uses occur when we can't tell what part we
+ are referencing, and have to make conservative assumptions. */
+ bool implicit_uses;
+} *used_part_t;
+
+/* An array of used_part structures, indexed by variable uid. */
+
+static used_part_t *used_portions;
+
+/* Given a variable uid, UID, get or create the entry in the used portions
+ table for the variable. */
+
+static used_part_t
+get_or_create_used_part_for (size_t uid)
+{
+ used_part_t up;
+ if (used_portions[uid] == NULL)
+ {
+ up = xcalloc (1, sizeof (struct used_part));
+ up->minused = INT_MAX;
+ up->maxused = 0;
+ up->explicit_uses = false;
+ up->implicit_uses = false;
+ }
+ else
+ up = used_portions[uid];
+ return up;
+}
+
+/* qsort comparison function for two fieldoff's PA and PB */
+
+static int
+fieldoff_compare (const void *pa, const void *pb)
+{
+ const fieldoff_s *foa = (const fieldoff_s *)pa;
+ const fieldoff_s *fob = (const fieldoff_s *)pb;
+ HOST_WIDE_INT foasize, fobsize;
+
+ if (foa->offset != fob->offset)
+ return foa->offset - fob->offset;
+
+ foasize = TREE_INT_CST_LOW (DECL_SIZE (foa->field));
+ fobsize = TREE_INT_CST_LOW (DECL_SIZE (fob->field));
+ return foasize - fobsize;
+}
+
+/* Given an aggregate VAR, create the subvariables that represent its
+ fields. */
+
+static void
+create_overlap_variables_for (tree var)
+{
+ VEC(fieldoff_s,heap) *fieldstack = NULL;
+ used_part_t up;
+ size_t uid = var_ann (var)->uid;
+
+ if (used_portions[uid] == NULL)
+ return;
+
+ up = used_portions[uid];
+ push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0);
+ if (VEC_length (fieldoff_s, fieldstack) != 0)
+ {
+ subvar_t *subvars;
+ fieldoff_s *fo;
+ bool notokay = false;
+ int fieldcount = 0;
+ int i;
+ HOST_WIDE_INT lastfooffset = -1;
+ HOST_WIDE_INT lastfosize = -1;
+ tree lastfotype = NULL_TREE;
+
+ /* Not all fields have DECL_SIZE set, and those that don't, we don't
+ know their size, and thus, can't handle.
+ The same is true of fields with DECL_SIZE that is not an integer
+ constant (such as variable sized fields).
+ Fields with offsets which are not constant will have an offset < 0
+ We *could* handle fields that are constant sized arrays, but
+ currently don't. Doing so would require some extra changes to
+ tree-ssa-operands.c. */
+
+ for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
+ {
+ if (!DECL_SIZE (fo->field)
+ || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
+ || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
+ || fo->offset < 0)
+ {
+ notokay = true;
+ break;
+ }
+ fieldcount++;
+ }
+
+ /* The current heuristic we use is as follows:
+ If the variable has no used portions in this function, no
+ structure vars are created for it.
+ Otherwise,
+ If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
+ we always create structure vars for them.
+ If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
+ some explicit uses, we create structure vars for them.
+ If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
+ no explicit uses, we do not create structure vars for them.
+ */
+
+ if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
+ && !up->explicit_uses)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Variable ");
+ print_generic_expr (dump_file, var, 0);
+ fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
+ }
+ notokay = true;
+ }
+
+ /* Bail out, if we can't create overlap variables. */
+ if (notokay)
+ {
+ VEC_free (fieldoff_s, heap, fieldstack);
+ return;
+ }
+
+ /* Otherwise, create the variables. */
+ subvars = lookup_subvars_for_var (var);
+
+ qsort (VEC_address (fieldoff_s, fieldstack),
+ VEC_length (fieldoff_s, fieldstack),
+ sizeof (fieldoff_s),
+ fieldoff_compare);
+
+ for (i = VEC_length (fieldoff_s, fieldstack);
+ VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
+ {
+ subvar_t sv;
+ HOST_WIDE_INT fosize;
+ var_ann_t ann;
+ tree currfotype;
+
+ fosize = TREE_INT_CST_LOW (DECL_SIZE (fo->field));
+ currfotype = TREE_TYPE (fo->field);
+
+ /* If this field isn't in the used portion,
+ or it has the exact same offset and size as the last
+ field, skip it. */
+
+ if (((fo->offset <= up->minused
+ && fo->offset + fosize <= up->minused)
+ || fo->offset >= up->maxused)
+ || (fo->offset == lastfooffset
+ && fosize == lastfosize
+ && currfotype == lastfotype))
+ continue;
+ sv = ggc_alloc (sizeof (struct subvar));
+ sv->offset = fo->offset;
+ sv->size = fosize;
+ sv->next = *subvars;
+ sv->var = create_tmp_var_raw (TREE_TYPE (fo->field), "SFT");
+ if (dump_file)
+ {
+ fprintf (dump_file, "structure field tag %s created for var %s",
+ get_name (sv->var), get_name (var));
+ fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
+ sv->offset);
+ fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
+ sv->size);
+ fprintf (dump_file, "\n");
+ }
+
+ /* We need to copy the various flags from var to sv->var, so that
+ they are is_global_var iff the original variable was. */
+
+ DECL_EXTERNAL (sv->var) = DECL_EXTERNAL (var);
+ TREE_PUBLIC (sv->var) = TREE_PUBLIC (var);
+ TREE_STATIC (sv->var) = TREE_STATIC (var);
+ TREE_READONLY (sv->var) = TREE_READONLY (var);
+
+ /* Like other memory tags, these need to be marked addressable to
+ keep is_gimple_reg from thinking they are real. */
+ TREE_ADDRESSABLE (sv->var) = 1;
+
+ DECL_CONTEXT (sv->var) = DECL_CONTEXT (var);
+
+ ann = get_var_ann (sv->var);
+ ann->mem_tag_kind = STRUCT_FIELD;
+ ann->type_mem_tag = NULL;
+ add_referenced_tmp_var (sv->var);
+
+ lastfotype = currfotype;
+ lastfooffset = fo->offset;
+ lastfosize = fosize;
+ *subvars = sv;
+ }
+
+ /* Once we have created subvars, the original is no longer call
+ clobbered on its own. Its call clobbered status depends
+ completely on the call clobbered status of the subvars.
+
+ add_referenced_var in the above loop will take care of
+ marking subvars of global variables as call clobbered for us
+ to start, since they are global as well. */
+ clear_call_clobbered (var);
+ }
+
+ VEC_free (fieldoff_s, heap, fieldstack);
+}
+
+
+/* Find the conservative answer to the question of what portions of what
+ structures are used by this statement. We assume that if we have a
+ component ref with a known size + offset, that we only need that part
+ of the structure. For unknown cases, or cases where we do something
+ to the whole structure, we assume we need to create fields for the
+ entire structure. */
+
+static tree
+find_used_portions (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
+{
+ switch (TREE_CODE (*tp))
+ {
+ case COMPONENT_REF:
+ {
+ HOST_WIDE_INT bitsize;
+ HOST_WIDE_INT bitpos;
+ tree offset;
+ enum machine_mode mode;
+ int unsignedp;
+ int volatilep;
+ tree ref;
+ ref = get_inner_reference (*tp, &bitsize, &bitpos, &offset, &mode,
+ &unsignedp, &volatilep, false);
+ if (DECL_P (ref) && offset == NULL && bitsize != -1)
+ {
+ size_t uid = var_ann (ref)->uid;
+ used_part_t up;
+
+ up = get_or_create_used_part_for (uid);
+
+ if (bitpos <= up->minused)
+ up->minused = bitpos;
+ if ((bitpos + bitsize >= up->maxused))
+ up->maxused = bitpos + bitsize;
+
+ up->explicit_uses = true;
+ used_portions[uid] = up;
+
+ *walk_subtrees = 0;
+ return NULL_TREE;
+ }
+ else if (DECL_P (ref))
+ {
+ if (DECL_SIZE (ref)
+ && var_can_have_subvars (ref)
+ && TREE_CODE (DECL_SIZE (ref)) == INTEGER_CST)
+ {
+ used_part_t up;
+ size_t uid = var_ann (ref)->uid;
+
+ up = get_or_create_used_part_for (uid);
+
+ up->minused = 0;
+ up->maxused = TREE_INT_CST_LOW (DECL_SIZE (ref));
+
+ up->implicit_uses = true;
+
+ used_portions[uid] = up;
+
+ *walk_subtrees = 0;
+ return NULL_TREE;
+ }
+ }
+ }
+ break;
+ case VAR_DECL:
+ case PARM_DECL:
+ {
+ tree var = *tp;
+ if (DECL_SIZE (var)
+ && var_can_have_subvars (var)
+ && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
+ {
+ used_part_t up;
+ size_t uid = var_ann (var)->uid;
+
+ up = get_or_create_used_part_for (uid);
+
+ up->minused = 0;
+ up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
+ up->implicit_uses = true;
+
+ used_portions[uid] = up;
+ *walk_subtrees = 0;
+ return NULL_TREE;
+ }
+ }
+ break;
+
+ default:
+ break;
+
+ }
+ return NULL_TREE;
+}
+
+/* We are about to create some new referenced variables, and we need the
+ before size. */
+
+static size_t old_referenced_vars;
+
+
+/* Create structure field variables for structures used in this function. */
+
+static void
+create_structure_vars (void)
+{
+ basic_block bb;
+ size_t i;
+
+ old_referenced_vars = num_referenced_vars;
+ used_portions = xcalloc (num_referenced_vars, sizeof (used_part_t));
+
+ FOR_EACH_BB (bb)
+ {
+ block_stmt_iterator bsi;
+ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ {
+ walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
+ find_used_portions,
+ NULL);
+ }
+ }
+ for (i = 0; i < old_referenced_vars; i++)
+ {
+ tree var = referenced_var (i);
+ /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
+ if (var
+ && DECL_SIZE (var)
+ && var_can_have_subvars (var)
+ && var_ann (var)->mem_tag_kind == NOT_A_TAG
+ && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
+ create_overlap_variables_for (var);
+ }
+ for (i = 0; i < old_referenced_vars; i++)
+ free (used_portions[i]);
+
+ free (used_portions);
+}
+
+static bool
+gate_structure_vars (void)
+{
+ return flag_tree_salias != 0;
+}
+
+struct tree_opt_pass pass_create_structure_vars =
+{
+ "salias", /* name */
+ gate_structure_vars, /* gate */
+ create_structure_vars, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ 0, /* tv_id */
+ PROP_cfg, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func, /* todo_flags_finish */
+ 0 /* letter */
+};
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