- ldst_info_t *info = get_irn_link(load);
- ir_mode *load_mode = get_Load_mode(load);
- ir_node *pred, *mem, *ptr, *new_node;
- entity *ent;
- int res = 0;
-
- /* do NOT touch volatile loads for now */
- if (get_Load_volatility(load) == volatility_is_volatile)
- return 0;
-
- /* the address of the load to be optimized */
- ptr = get_Load_ptr(load);
-
- /*
- * Check if we can remove the exception from a Load:
- * This can be done, if the address is from an Sel(Alloc) and
- * the Sel type is a subtype of the allocated type.
- *
- * This optimizes some often used OO constructs,
- * like x = new O; x->t;
- */
- if (info->projs[pn_Load_X_except]) {
- if (get_irn_op(ptr) == op_Sel) {
- ir_node *mem = get_Sel_mem(ptr);
-
- if (get_irn_op(skip_Proj(mem)) == op_Alloc) {
- /* ok, check the types */
- entity *ent = get_Sel_entity(ptr);
- type *s_type = get_entity_type(ent);
- type *a_type = get_Alloc_type(mem);
-
- if (is_subclass_of(s_type, a_type)) {
- /* ok, condition met: there can't be an exception because
- * Alloc guarantees that enough memory was allocated */
-
- exchange(info->projs[pn_Load_X_except], new_Bad());
- info->projs[pn_Load_X_except] = NULL;
- res = 1;
- }
- }
- }
- else if ((get_irn_op(skip_Proj(ptr)) == op_Alloc) ||
- ((get_irn_op(ptr) == op_Cast) && (get_irn_op(skip_Proj(get_Cast_op(ptr))) == op_Alloc))) {
- /* simple case: a direct load after an Alloc. Firm Alloc throw
- * an exception in case of out-of-memory. So, there is no way for an
- * exception in this load.
- * This code is constructed by the "exception lowering" in the Jack compiler.
- */
- exchange(info->projs[pn_Load_X_except], new_Bad());
- info->projs[pn_Load_X_except] = NULL;
- res = 1;
- }
- }
-
- /* the mem of the Load. Must still be returned after optimization */
- mem = get_Load_mem(load);
-
- if (! info->projs[pn_Load_res] && ! info->projs[pn_Load_X_except]) {
- /* a Load which value is neither used nor exception checked, remove it */
- exchange(info->projs[pn_Load_M], mem);
-
- return 1;
- }
-
- /* Load from a constant polymorphic field, where we can resolve
- polymorphy. */
- new_node = transform_node_Load(load);
- if (new_node != load) {
- if (info->projs[pn_Load_M]) {
- exchange(info->projs[pn_Load_M], mem);
- info->projs[pn_Load_M] = NULL;
- }
- if (info->projs[pn_Load_X_except]) {
- exchange(info->projs[pn_Load_X_except], new_Bad());
- info->projs[pn_Load_X_except] = NULL;
- }
- if (info->projs[pn_Load_res])
- exchange(info->projs[pn_Load_res], new_node);
- return 1;
- }
-
- /* check if we can determine the entity that will be loaded */
- ent = find_constant_entity(ptr);
- if (ent) {
- if ((allocation_static == get_entity_allocation(ent)) &&
- (visibility_external_allocated != get_entity_visibility(ent))) {
- /* a static allocation that is not external: there should be NO exception
- * when loading. */
-
- /* no exception, clear the info field as it might be checked later again */
- if (info->projs[pn_Load_X_except]) {
- exchange(info->projs[pn_Load_X_except], new_Bad());
- info->projs[pn_Load_X_except] = NULL;
- res = 1;
- }
-
- if (variability_constant == get_entity_variability(ent)
- && is_atomic_entity(ent)) {
- /* Might not be atomic after
- lowering of Sels. In this
- case we could also load, but
- it's more complicated. */
- /* more simpler case: we load the content of a constant value:
- * replace it by the constant itself
- */
-
- /* no memory */
- if (info->projs[pn_Load_M]) {
- exchange(info->projs[pn_Load_M], mem);
- res = 1;
- }
-
- /* no result :-) */
- if (info->projs[pn_Load_res]) {
- if (is_atomic_entity(ent)) {
- ir_node *c = copy_const_value(get_atomic_ent_value(ent));
-
- DBG_OPT_RC(load, c);
- exchange(info->projs[pn_Load_res], c);
- return 1;
- }
- }
- }
- else if (variability_constant == get_entity_variability(ent)) {
- compound_graph_path *path = get_accessed_path(ptr);
-
- if (path) {
- ir_node *c;
-
- assert(is_proper_compound_graph_path(path, get_compound_graph_path_length(path)-1));
- /*
- {
- int j;
- for (j = 0; j < get_compound_graph_path_length(path); ++j) {
- entity *node = get_compound_graph_path_node(path, j);
- fprintf(stdout, ".%s", get_entity_name(node));
- if (is_Array_type(get_entity_owner(node)))
- fprintf(stdout, "[%d]", get_compound_graph_path_array_index(path, j));
- }
- printf("\n");
- }
- */
-
- c = get_compound_ent_value_by_path(ent, path);
- free_compound_graph_path(path);
-
- /* printf(" cons: "); DDMN(c); */
-
- if (info->projs[pn_Load_M]) {
- exchange(info->projs[pn_Load_M], mem);
- res = 1;
- }
- if (info->projs[pn_Load_res]) {
- exchange(info->projs[pn_Load_res], copy_const_value(c));
- return 1;
- }
- }
- else {
- /* We can not determine a correct access path. E.g., in jack, we load
- a byte from an object to generate an exception. Happens in test program
- Reflectiontest.
- printf(">>>>>>>>>>>>> Found access to constant entity %s in function %s\n", get_entity_name(ent),
- get_entity_name(get_irg_entity(current_ir_graph)));
- printf(" load: "); DDMN(load);
- printf(" ptr: "); DDMN(ptr);
- */
- }
- }
- }
- }
-
- /* Check, if the address of this load is used more than once.
- * If not, this load cannot be removed in any case. */
- if (get_irn_out_n(ptr) <= 1)
- return res;
-
- /* follow the memory chain as long as there are only Loads
- * and try to replace current Load or Store by a previous one
- */
- for (pred = skip_Proj(mem); ; pred = skip_Proj(get_Load_mem(pred))) {
- /*
- * BEWARE: one might think that checking the modes is useless, because
- * if the pointers are identical, they refer to the same object.
- * This is only true in strong typed languages, not in C were the following
- * is possible a = *(type1 *)p; b = *(type2 *)p ...
- */
-
- if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
- get_irn_mode(get_Store_value(pred)) == load_mode) {
- ldst_info_t *pred_info = get_irn_link(pred);
-
- /*
- * a Load immediately after a Store -- a read after write.
- * We may remove the Load, if both Load & Store does not have an exception handler
- * OR they are in the same block. In the latter case the Load cannot
- * throw an exception when the previous Store was quiet.
- *
- * Why we need to check for Store Exception? If the Store cannot
- * be executed (ROM) the exception handler might simply jump into
- * the load block :-(
- * We could make it a little bit better if we would know that the exception
- * handler of the Store jumps directly to the end...
- */
- if ((!pred_info->projs[pn_Store_X_except] && !info->projs[pn_Load_X_except]) ||
- get_nodes_block(load) == get_nodes_block(pred)) {
- ir_node *value = get_Store_value(pred);
-
- DBG_OPT_RAW(load, value);
- if (info->projs[pn_Load_M])
- exchange(info->projs[pn_Load_M], mem);
-
- /* no exception */
- if (info->projs[pn_Load_X_except])
- exchange( info->projs[pn_Load_X_except], new_Bad());
-
- if (info->projs[pn_Load_res])
- exchange(info->projs[pn_Load_res], value);
-
- return 1;
- }
- }
- else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
- get_Load_mode(pred) == load_mode) {
- /*
- * a Load after a Load -- a read after read.
- * We may remove the second Load, if it does not have an exception handler
- * OR they are in the same block. In the later case the Load cannot
- * throw an exception when the previous Load was quiet.
- *
- * Here, there is no need to check if the previous Load has an exception
- * hander because they would have exact the same exception...
- */
- if (! info->projs[pn_Load_X_except] || get_nodes_block(load) == get_nodes_block(pred)) {
- ldst_info_t *pred_info = get_irn_link(pred);
-
- DBG_OPT_RAR(load, pred);
-
- if (pred_info->projs[pn_Load_res]) {
- /* we need a data proj from the previous load for this optimization */
- if (info->projs[pn_Load_res])
- exchange(info->projs[pn_Load_res], pred_info->projs[pn_Load_res]);
-
- if (info->projs[pn_Load_M])
- exchange(info->projs[pn_Load_M], mem);
- }
- else {
- if (info->projs[pn_Load_res]) {
- set_Proj_pred(info->projs[pn_Load_res], pred);
- set_nodes_block(info->projs[pn_Load_res], get_nodes_block(pred));
- pred_info->projs[pn_Load_res] = info->projs[pn_Load_res];
- }
- if (info->projs[pn_Load_M]) {
- /* Actually, this if should not be necessary. Construct the Loads
- properly!!! */
- exchange(info->projs[pn_Load_M], mem);
- }
- }
-
- /* no exception */
- if (info->projs[pn_Load_X_except])
- exchange(info->projs[pn_Load_X_except], new_Bad());
-
- return 1;
- }
- }
-
- /* follow only Load chains */
- if (get_irn_op(pred) != op_Load)
- break;
- }
- return res;
-}