return get_mode_size_bits(new_mode) >= get_mode_size_bits(old_mode);
} /* is_completely_overwritten */
+/**
+ * Check whether small is a part of large (starting at same address).
+ */
+static int is_partially_same(ir_node *small, ir_node *large)
+{
+ ir_mode *sm = get_irn_mode(small);
+ ir_mode *lm = get_irn_mode(large);
+
+ /* FIXME: Check endianness */
+ return is_Conv(small) && get_Conv_op(small) == large
+ && get_mode_size_bytes(sm) < get_mode_size_bytes(lm)
+ && get_mode_arithmetic(sm) == irma_twos_complement
+ && get_mode_arithmetic(lm) == irma_twos_complement
+ && get_;
+} /* is_partially_same */
+
/**
* follow the memory chain as long as there are only Loads and alias free Stores.
*
* if the pointers are identical, they refer to the same object.
* This is only true in strong typed languages, not is C were the following
* is possible *(ir_type1 *)p = a; *(ir_type2 *)p = b ...
- * However, if the mode that is written have a bigger or equal size the the old
- * one, the old value is completely overwritten and can be killed ...
+ * However, if the size of the mode that is written is bigger or equal the
+ * size of the old one, the old value is completely overwritten and can be
+ * killed ...
*/
if (is_Store(pred) && get_Store_ptr(pred) == ptr &&
- get_nodes_MacroBlock(pred) == mblk &&
- is_completely_overwritten(get_irn_mode(get_Store_value(pred)), mode)) {
+ get_nodes_MacroBlock(pred) == mblk) {
/*
* a Store after a Store in the same MacroBlock -- a write after write.
- * We may remove the first Store, if it does not have an exception handler.
+ */
+
+ /*
+ * We may remove the first Store, if the old value is completely
+ * overwritten or the old value is a part of the new value,
+ * and if it does not have an exception handler.
*
* TODO: What, if both have the same exception handler ???
*/
- if (get_Store_volatility(pred) != volatility_is_volatile && !pred_info->projs[pn_Store_X_except]) {
- DBG_OPT_WAW(pred, store);
- exchange(pred_info->projs[pn_Store_M], get_Store_mem(pred));
- kill_node(pred);
- reduce_adr_usage(ptr);
- return DF_CHANGED;
+ if (get_Store_volatility(pred) != volatility_is_volatile
+ && !pred_info->projs[pn_Store_X_except]) {
+ ir_node *predvalue = get_Store_value(pred);
+ ir_mode *predmode = get_irn_mode(predvalue);
+
+ if(is_completely_overwritten(predmode, mode)
+ || is_partially_same(predvalue, value)) {
+ DBG_OPT_WAW(pred, store);
+ exchange(pred_info->projs[pn_Store_M], get_Store_mem(pred));
+ kill_node(pred);
+ reduce_adr_usage(ptr);
+ return DF_CHANGED;
+ }
+ }
+
+ /*
+ * We may remove the Store, if the old value already contains
+ * the new value, and if it does not have an exception handler.
+ *
+ * TODO: What, if both have the same exception handler ???
+ */
+ if (get_Store_volatility(store) != volatility_is_volatile
+ && !info->projs[pn_Store_X_except]) {
+ ir_node *predvalue = get_Store_value(pred);
+
+ if(is_partially_same(value, predvalue)) {
+ DBG_OPT_WAW(pred, store);
+ exchange(info->projs[pn_Store_M], mem);
+ kill_node(store);
+ reduce_adr_usage(ptr);
+ return DF_CHANGED;
+ }
}
} else if (is_Load(pred) && get_Load_ptr(pred) == ptr &&
value == pred_info->projs[pn_Load_res]) {