2 * Copyright (C) 1995-2008 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Normalize returns.
23 * @author Michael Beck
29 #include "iroptimize.h"
30 #include "irgraph_t.h"
36 #include "raw_bitset.h"
39 * Normalize the Returns of a graph by creating a new End block
40 * with One Return(Phi).
41 * This is the preferred input for the if-conversion.
43 * In pseudocode, it means:
58 void normalize_one_return(ir_graph *irg)
60 ir_node *endbl = get_irg_end_block(irg);
61 ir_entity *entity = get_irg_entity(irg);
62 ir_type *type = get_entity_type(entity);
63 int n_ret_vals = get_method_n_ress(type) + 1;
65 bool filter_dbgi = false;
66 dbg_info *combined_dbgi = NULL;
67 int i, j, k, n, last_idx;
68 ir_node **in, **retvals, **endbl_in;
71 /* look, if we have more than one return */
72 n = get_Block_n_cfgpreds(endbl);
74 /* The end block has no predecessors, we have an endless
75 loop. In that case, no returns exists. */
76 confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_ALL);
77 add_irg_properties(irg, IR_GRAPH_PROPERTY_ONE_RETURN);
81 unsigned *const returns = rbitset_alloca(n);
82 for (i = 0; i < n; ++i) {
83 ir_node *node = get_Block_cfgpred(endbl, i);
85 if (is_Return(node)) {
86 dbg_info *dbgi = get_irn_dbg_info(node);
88 if (dbgi != NULL && dbgi != combined_dbgi) {
98 rbitset_set(returns, i);
103 confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_ALL);
104 add_irg_properties(irg, IR_GRAPH_PROPERTY_ONE_RETURN);
108 in = ALLOCAN(ir_node*, MAX(n_rets, n_ret_vals));
109 retvals = ALLOCAN(ir_node*, n_rets * n_ret_vals);
110 endbl_in = ALLOCAN(ir_node*, n);
113 for (j = i = 0; i < n; ++i) {
114 ir_node *ret = get_Block_cfgpred(endbl, i);
116 if (rbitset_is_set(returns, i)) {
117 ir_node *block = get_nodes_block(ret);
119 /* create a new Jmp for every Ret and place the in in */
120 in[j] = new_r_Jmp(block);
122 /* save the return values and shuffle them */
123 for (k = 0; k < n_ret_vals; ++k)
124 retvals[j + k*n_rets] = get_irn_n(ret, k);
128 endbl_in[last_idx++] = ret;
132 /* ok, create a new block with all created in's */
133 block = new_r_Block(irg, n_rets, in);
135 /* now create the Phi nodes */
136 for (j = i = 0; i < n_ret_vals; ++i, j += n_rets) {
137 ir_mode *mode = get_irn_mode(retvals[j]);
138 in[i] = new_r_Phi(block, n_rets, &retvals[j], mode);
141 endbl_in[last_idx++] = new_rd_Return(combined_dbgi, block, in[0], n_ret_vals-1, &in[1]);
143 set_irn_in(endbl, last_idx, endbl_in);
145 /* invalidate analysis information:
146 * a new Block was added, so dominator, outs and loop are inconsistent,
147 * trouts and callee-state should be still valid */
148 confirm_irg_properties(irg,
149 IR_GRAPH_PROPERTY_NO_BADS
150 | IR_GRAPH_PROPERTY_NO_TUPLES
151 | IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES
152 | IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE
153 | IR_GRAPH_PROPERTY_CONSISTENT_ENTITY_USAGE);
154 add_irg_properties(irg, IR_GRAPH_PROPERTY_ONE_RETURN);
157 /* Create a graph pass. */
158 ir_graph_pass_t *normalize_one_return_pass(const char *name)
160 return def_graph_pass(name ? name : "one_ret", normalize_one_return);
164 * Check, whether a Return can be moved on block upwards.
166 * In a block with a Return, all live nodes must be linked
167 * with the Return, otherwise they are dead (because the Return leaves
168 * the graph, so no more users of the other nodes can exists.
170 * We can move a Return, if its predecessors are Phi nodes or
171 * comes from another block. In the later case, it is always possible
172 * to move the Return one block up, because the predecessor block must
173 * dominate the Return block (SSA) and then it dominates the predecessor
174 * block of the Return block as well.
176 * All predecessors of the Return block must be Jmp's of course, or we
177 * cannot move it up, so we add blocks if needed.
179 static bool can_move_ret(ir_node *ret)
181 ir_node *retbl = get_nodes_block(ret);
182 int i, n = get_irn_arity(ret);
184 for (i = 0; i < n; ++i) {
185 ir_node *pred = get_irn_n(ret, i);
187 if (! is_Phi(pred) && retbl == get_nodes_block(pred)) {
188 /* first condition failed, found a non-Phi predecessor
189 * then is in the Return block */
194 /* check, that predecessors are Jmps */
195 n = get_Block_n_cfgpreds(retbl);
196 /* we cannot move above a labeled block, as this might kill the block */
197 if (n <= 1 || get_Block_entity(retbl) != NULL)
199 for (i = 0; i < n; ++i) {
200 ir_node *pred = get_Block_cfgpred(retbl, i);
202 pred = skip_Tuple(pred);
203 if (! is_Jmp(pred) && !is_Bad(pred)) {
204 /* simply place a new block here */
205 ir_graph *irg = get_irn_irg(retbl);
206 ir_node *block = new_r_Block(irg, 1, &pred);
207 ir_node *jmp = new_r_Jmp(block);
208 set_Block_cfgpred(retbl, i, jmp);
215 * Normalize the Returns of a graph by moving
216 * the Returns upwards as much as possible.
217 * This might be preferred for code generation.
219 * In pseudocode, it means:
227 * is transformed into
234 void normalize_n_returns(ir_graph *irg)
237 ir_node *list = NULL;
238 ir_node *final = NULL;
240 unsigned n_finals = 0;
241 ir_node *endbl = get_irg_end_block(irg);
247 * First, link all returns:
248 * These must be predecessors of the endblock.
249 * Place Returns that can be moved on list, all others
252 n = get_Block_n_cfgpreds(endbl);
253 for (i = 0; i < n; ++i) {
254 ir_node *ret = get_Block_cfgpred(endbl, i);
258 } else if (is_Return(ret) && can_move_ret(ret)) {
260 * Ok, all conditions met, we can move this Return, put it
263 set_irn_link(ret, list);
267 /* Put all nodes that are not changed on the final list. */
268 set_irn_link(ret, final);
275 confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_ALL);
276 add_irg_properties(irg, IR_GRAPH_PROPERTY_MANY_RETURNS);
281 * Now move the Returns upwards. We move always one block up (and create n
282 * new Returns), than we check if a newly created Return can be moved even
283 * further. If yes, we simply add it to our work list, else to the final
286 end = get_irg_end(irg);
287 n_ret_vals = get_irn_arity(list);
288 in = ALLOCAN(ir_node*, n_ret_vals);
289 while (list != NULL) {
291 ir_node *block = get_nodes_block(ret);
292 dbg_info *dbgi = get_irn_dbg_info(ret);
295 list = (ir_node*)get_irn_link(ret);
298 n = get_Block_n_cfgpreds(block);
299 for (i = 0; i < n; ++i) {
300 ir_node *jmp = get_Block_cfgpred(block, i);
301 ir_node *new_bl, *new_ret;
307 new_bl = get_nodes_block(jmp);
309 /* create the in-array for the new Return */
310 for (j = 0; j < n_ret_vals; ++j) {
311 ir_node *pred = get_irn_n(ret, j);
313 in[j] = (is_Phi(pred) && get_nodes_block(pred) == block) ? get_Phi_pred(pred, i) : pred;
316 new_ret = new_rd_Return(dbgi, new_bl, in[0], n_ret_vals-1, &in[1]);
318 if (! is_Bad(new_ret)) {
320 * The newly created node might be bad, if we
321 * create it in a block with only Bad predecessors.
322 * In that case ignore this block.
324 * We could even kill the jmp then ...
326 if (can_move_ret(new_ret)) {
327 set_irn_link(new_ret, list);
331 set_irn_link(new_ret, final);
337 /* remove the Jmp, we have placed a Return here */
338 exchange(jmp, new_r_Bad(irg, mode_X));
342 * if the memory of the old Return is a PhiM, remove it
343 * from the keep-alives, or it will keep the block which
344 * will crash the dominator algorithm.
346 phiM = get_Return_mem(ret);
348 n = get_End_n_keepalives(end);
349 for (i = 0; i < n; ++i) {
350 if (get_End_keepalive(end, i) == phiM) {
351 set_End_keepalive(end, i, new_r_Bad(irg, mode_M));
359 * Last step: Create a new endblock, with all nodes on the final list as
362 in = ALLOCAN(ir_node*, n_finals);
364 for (i = 0; final != NULL; ++i, final = (ir_node*)get_irn_link(final)) {
368 exchange(endbl, new_r_Block(irg, n_finals, in));
370 /* Invalidate analysis information:
371 * Blocks become dead and new Returns were deleted, so dominator, outs and
372 * loop are inconsistent, trouts and callee-state should be still valid */
373 confirm_irg_properties(irg,
374 IR_GRAPH_PROPERTY_NO_TUPLES
375 | IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES
376 | IR_GRAPH_PROPERTY_CONSISTENT_ENTITY_USAGE);
377 add_irg_properties(irg, IR_GRAPH_PROPERTY_MANY_RETURNS);
380 /* Create a graph pass. */
381 ir_graph_pass_t *normalize_n_returns_pass(const char *name)
383 return def_graph_pass(name ? name : "n_rets", normalize_n_returns);