* Project: libFIRM
* File name: ir/opt/ldstopt.c
* Purpose: load store optimizations
- * Author:
+ * Author: Michael Beck
* Created:
* CVS-ID: $Id$
* Copyright: (c) 1998-2004 Universit\81ät Karlsruhe
return rec_get_accessed_path(ptr, 0);
}
+/**
+ * Follow the memory chain as long as there are only Loads
+ * and try to replace current Load or Store by a previous one.
+ * Note that in unreachable loops it might happen that we reach
+ * load again, as well as we can fall into a cycle.
+ * We break such cycles using a special visited flag.
+ *
+ * INC_MASTER() must be called before dive into
+ */
+static unsigned follow_Load_chain(ir_node *load, ir_node *curr) {
+ unsigned res = 0;
+ ldst_info_t *info = get_irn_link(load);
+ ir_node *pred;
+ ir_node *ptr = get_Load_ptr(load);
+ ir_node *mem = get_Load_mem(load);
+ ir_mode *load_mode = get_Load_mode(load);
+
+ for (pred = curr; load != pred; pred = skip_Proj(get_Load_mem(pred))) {
+ ldst_info_t *pred_info = get_irn_link(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 = *(ir_type1 *)p; b = *(ir_type2 *)p ...
+ */
+
+ if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
+ get_irn_mode(get_Store_value(pred)) == load_mode) {
+ /*
+ * 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());
+ res |= CF_CHANGED;
+ }
+
+ if (info->projs[pn_Load_res])
+ exchange(info->projs[pn_Load_res], value);
+
+ return res | DF_CHANGED;
+ }
+ }
+ 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)) {
+ 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());
+ res |= CF_CHANGED;
+ }
+
+ return res |= DF_CHANGED;
+ }
+ }
+
+ /* follow only Load chains */
+ if (get_irn_op(pred) != op_Load)
+ break;
+
+ /* check for cycles */
+ if (NODE_VISITED(pred_info))
+ break;
+ MARK_NODE(pred_info);
+ }
+
+ if (get_irn_op(pred) == op_Sync) {
+ int i;
+
+ /* handle all Sync predecessors */
+ for (i = get_Sync_n_preds(pred) - 1; i >= 0; --i) {
+ res |= follow_Load_chain(load, skip_Proj(get_Sync_pred(pred, i)));
+ if (res)
+ break;
+ }
+ }
+
+ return res;
+}
+
/**
* optimize a Load
*/
{
ldst_info_t *info = get_irn_link(load);
ir_mode *load_mode = get_Load_mode(load);
- ir_node *pred, *mem, *ptr, *new_node;
+ ir_node *mem, *ptr, *new_node;
entity *ent;
unsigned res = 0;
* We break such cycles using a special visited flag.
*/
INC_MASTER();
- for (pred = skip_Proj(mem); load != pred; pred = skip_Proj(get_Load_mem(pred))) {
+ res = follow_Load_chain(load, skip_Proj(mem));
+ return res;
+}
+
+/**
+ * follow the memory chain as long as there are only Loads.
+ *
+ * INC_MASTER() must be called before dive into
+ */
+static unsigned follow_Load_chain_for_Store(ir_node *store, ir_node *curr) {
+ unsigned res = 0;
+ ldst_info_t *info = get_irn_link(store);
+ ir_node *pred;
+ ir_node *ptr = get_Store_ptr(store);
+ ir_node *mem = get_Store_mem(store);
+ ir_node *value = get_Store_value(store);
+ ir_mode *mode = get_irn_mode(value);
+ ir_node *block = get_nodes_block(store);
+
+ for (pred = curr; pred != store; pred = skip_Proj(get_Load_mem(pred))) {
ldst_info_t *pred_info = get_irn_link(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 = *(ir_type1 *)p; b = *(ir_type2 *)p ...
+ * This is only true in strong typed languages, not is C were the following
+ * is possible *(ir_type1 *)p = a; *(ir_type2 *)p = b ...
*/
-
if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
- get_irn_mode(get_Store_value(pred)) == load_mode) {
+ get_nodes_block(pred) == block && get_irn_mode(get_Store_value(pred)) == mode) {
/*
- * 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.
+ * a Store after a Store in the same block -- a write after write.
+ * We may remove the first Store, if it does not have an exception handler.
*
- * 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...
+ * TODO: What, if both have the same exception handler ???
*/
- 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());
- res |= CF_CHANGED;
- }
-
- if (info->projs[pn_Load_res])
- exchange(info->projs[pn_Load_res], value);
-
- return res | DF_CHANGED;
+ 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) );
+ return DF_CHANGED;
}
}
else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
- get_Load_mode(pred) == load_mode) {
+ value == pred_info->projs[pn_Load_res]) {
/*
- * 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...
+ * a Store of a value after a Load -- a write after read.
+ * We may remove the second Store, if it does not have an exception handler.
*/
- if (! info->projs[pn_Load_X_except] || get_nodes_block(load) == get_nodes_block(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());
- res |= CF_CHANGED;
- }
-
- return res |= DF_CHANGED;
+ if (! info->projs[pn_Store_X_except]) {
+ DBG_OPT_WAR(store, pred);
+ exchange( info->projs[pn_Store_M], mem );
+ return DF_CHANGED;
}
}
break;
MARK_NODE(pred_info);
}
+
+ if (get_irn_op(pred) == op_Sync) {
+ int i;
+
+ /* handle all Sync predecessors */
+ for (i = get_Sync_n_preds(pred) - 1; i >= 0; --i) {
+ res |= follow_Load_chain_for_Store(store, skip_Proj(get_Sync_pred(pred, i)));
+ if (res)
+ break;
+ }
+ }
return res;
}
static unsigned optimize_store(ir_node *store)
{
ldst_info_t *info = get_irn_link(store);
- ir_node *pred, *mem, *ptr, *value, *block;
- ir_mode *mode;
- unsigned res = 0;
+ ir_node *ptr, *mem;
if (get_Store_volatility(store) == volatility_is_volatile)
return 0;
- /*
- * 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 is C were the following
- * is possible *(ir_type1 *)p = a; *(ir_type2 *)p = b ...
- */
-
- ptr = get_Store_ptr(store);
+ ptr = get_Store_ptr(store);
/* 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 0;
- block = get_nodes_block(store);
- mem = get_Store_mem(store);
- value = get_Store_value(store);
- mode = get_irn_mode(value);
+ mem = get_Store_mem(store);
/* follow the memory chain as long as there are only Loads */
INC_MASTER();
- for (pred = skip_Proj(mem); pred != store; pred = skip_Proj(get_Load_mem(pred))) {
- ldst_info_t *pred_info = get_irn_link(pred);
-
- if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
- get_nodes_block(pred) == block && get_irn_mode(get_Store_value(pred)) == mode) {
- /*
- * a Store after a Store in the same block -- a write after write.
- * We may remove the first Store, 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) );
- return DF_CHANGED;
- }
- }
- else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
- value == pred_info->projs[pn_Load_res]) {
- /*
- * a Store of a value after a Load -- a write after read.
- * We may remove the second Store, if it does not have an exception handler.
- */
- if (! info->projs[pn_Store_X_except]) {
- DBG_OPT_WAR(store, pred);
- exchange( info->projs[pn_Store_M], mem );
- return DF_CHANGED;
- }
- }
-
- /* follow only Load chains */
- if (get_irn_op(pred) != op_Load)
- break;
-
- /* check for cycles */
- if (NODE_VISITED(pred_info))
- break;
- MARK_NODE(pred_info);
- }
- return res;
+ return follow_Load_chain_for_Store(store, skip_Proj(mem));
}
/**
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