2 * Copyright (C) 1995-2007 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 Partial condition evaluation
24 * @author Christoph Mallon, Matthias Braun
42 #include "iredges_t.h"
47 DEBUG_ONLY(static firm_dbg_module_t *dbg);
50 * Add the new predecessor x to node node, which is either a Block or a Phi
52 static void add_pred(ir_node* node, ir_node* x)
58 assert(is_Block(node) || is_Phi(node));
60 n = get_irn_arity(node);
61 NEW_ARR_A(ir_node*, ins, n + 1);
62 for (i = 0; i < n; i++)
63 ins[i] = get_irn_n(node, i);
65 set_irn_in(node, n + 1, ins);
69 * Remove predecessor j from node, which is either a Block or a Phi
70 * returns true if only one predecessor is left
72 static int remove_pred(ir_node* node, int j)
76 assert(is_Block(node) || is_Phi(node));
78 n = get_irn_arity(node);
80 ir_node* pred = get_irn_n(node, 1 - j);
83 pred = get_nodes_block(pred);
84 edges_reroute(node, pred, current_ir_graph);
93 NEW_ARR_A(ir_node*, ins, n - 1);
94 for (i = 0; i < j; i++)
95 ins[i] = get_irn_n(node, i);
97 ins[i - 1] = get_irn_n(node, i);
99 set_irn_in(node, n - 1, ins);
104 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
112 // This is needed because we create bads sometimes
116 // already processed this block?
117 if(irn_visited(block)) {
118 ir_node *value = (ir_node*) get_irn_link(block);
122 // blocks with only 1 pred need no phi
123 n_cfgpreds = get_Block_n_cfgpreds(block);
124 if(n_cfgpreds == 1) {
125 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
126 ir_node *value = search_def_and_create_phis(pred_block, mode);
128 set_irn_link(block, value);
129 mark_irn_visited(block);
134 NEW_ARR_A(ir_node*, in, n_cfgpreds);
135 for(i = 0; i < n_cfgpreds; ++i)
136 in[i] = new_Unknown(mode);
138 irg = get_irn_irg(block);
139 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
140 set_irn_link(block, phi);
141 mark_irn_visited(block);
144 for(i = 0; i < n_cfgpreds; ++i) {
145 ir_node *pred_block = get_Block_cfgpred_block(block, i);
146 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
148 set_irn_n(phi, i, pred_val);
155 * Given a set of values this function constructs SSA-form for the users of the
156 * first value (the users are determined through the out-edges of the value).
157 * Uses the irn_visited flags. Works without using the dominance tree.
159 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
164 const ir_edge_t *edge;
165 const ir_edge_t *next;
170 irg = get_irn_irg(vals[0]);
171 inc_irg_visited(irg);
173 mode = get_irn_mode(vals[0]);
174 for(i = 0; i < n_vals; ++i) {
175 ir_node *value = vals[i];
176 ir_node *value_block = blocks[i];
178 assert(get_irn_mode(value) == mode);
180 set_irn_link(value_block, value);
181 mark_irn_visited(value_block);
184 // Only fix the users of the first, i.e. the original node
187 // this can happen when fixing phi preds, we mustn't fix the users
188 if(get_nodes_block(value) != blocks[0]) return;
190 foreach_out_edge_safe(value, edge, next) {
191 ir_node *user = get_edge_src_irn(edge);
192 int j = get_edge_src_pos(edge);
193 ir_node *user_block = get_nodes_block(user);
197 if(get_irn_op(user) == op_End)
200 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
203 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
204 newval = search_def_and_create_phis(pred_block, mode);
206 newval = search_def_and_create_phis(user_block, mode);
209 // don't fix newly created phis from the SSA construction
210 if (newval != user) {
211 DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
212 set_irn_n(user, j, newval);
217 static void split_critical_edge(ir_node *block, int pos) {
218 ir_graph *irg = get_irn_irg(block);
223 in[0] = get_Block_cfgpred(block, pos);
224 new_block = new_r_Block(irg, 1, in);
225 new_jmp = new_r_Jmp(irg, new_block);
226 set_Block_cfgpred(block, pos, new_jmp);
229 typedef struct _condeval_env_t {
233 unsigned long visited_nr;
235 ir_node *cnst_pred; /**< the block before the constant */
236 int cnst_pos; /**< the pos to the constant block (needed to kill that edge later) */
239 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
240 const ir_edge_t *edge;
242 /* Look at all nodes in the cond_block and copy them into pred */
243 foreach_out_edge(block, edge) {
244 ir_node *node = get_edge_src_irn(edge);
246 ir_mode *mode = get_irn_mode(node);
248 /* ignore control flow */
251 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
252 be handled in all backends. Instead we duplicate the node and move it to it's users */
253 if (mode == mode_b) {
254 const ir_edge_t *edge, *next;
258 assert(is_Proj(node));
260 pred = get_Proj_pred(node);
261 pn = get_Proj_proj(node);
263 foreach_out_edge_safe(node, edge, next) {
265 ir_node *user = get_edge_src_irn(edge);
266 int pos = get_edge_src_pos(edge);
267 ir_node *user_block = get_nodes_block(user);
269 if(user_block == block)
272 cmp_copy = exact_copy(pred);
273 set_nodes_block(cmp_copy, user_block);
274 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
275 set_irn_n(user, pos, copy);
280 /* we can evaluate Phis right now, all other nodes get copied */
282 copy = get_Phi_pred(node, j);
284 copy = exact_copy(node);
285 set_nodes_block(copy, copy_block);
288 set_irn_link(node, copy);
289 set_irn_visited(node, env->visited_nr);
291 /* we might hit values in blocks that have already been processed by a
292 * recursive find_phi_with_const call */
293 assert(get_irn_visited(copy) <= env->visited_nr);
294 if(get_irn_visited(copy) >= env->visited_nr) {
295 ir_node *prev_copy = get_irn_link(copy);
296 if(prev_copy != NULL)
297 set_irn_link(node, prev_copy);
301 /* fix data-flow (and reconstruct SSA if needed) */
302 foreach_out_edge(block, edge) {
305 ir_node *node = get_edge_src_irn(edge);
306 ir_mode *mode = get_irn_mode(node);
313 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
317 blocks[1] = copy_block;
318 vals[1] = get_irn_link(node);
319 construct_ssa(blocks, vals, 2);
323 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
324 pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
326 // does the compare evaluate to true?
327 if(cmp_result == pn_Cmp_False)
329 if((cmp_result & pnc) != cmp_result)
335 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
336 ir_node *block = get_nodes_block(jump);
338 if(irn_visited(value))
340 mark_irn_visited(value);
342 if(is_Const(value)) {
343 tarval *tv_const = get_Const_tarval(env->cnst);
344 tarval *tv = get_Const_tarval(value);
346 if(!eval_cmp(env->pnc, tv, tv_const))
351 "> Found condition evaluation candidate %+F->%+F\n",
352 env->true_block, block
355 // adjust true_block to point directly towards our jump
356 add_pred(env->true_block, jump);
358 split_critical_edge(env->true_block, 0);
360 // we need a bigger visited nr when going back
369 // the phi has to be in the same block as the jump
370 if(get_nodes_block(value) != block)
373 arity = get_irn_arity(value);
374 for(i = 0; i < arity; ++i) {
376 ir_node *phi_pred = get_Phi_pred(value, i);
377 ir_node *cfgpred = get_Block_cfgpred(block, i);
379 copy_block = find_phi_with_const(cfgpred, phi_pred, env);
380 if(copy_block == NULL)
383 /* copy duplicated nodes in copy_block and fix SSA */
384 copy_and_fix(block, copy_block, i, env);
386 if(copy_block == get_nodes_block(cfgpred)) {
387 env->cnst_pred = block;
391 // return now as we can't process more possibilities in 1 run
401 * Block-walker: searches for the following construct
403 * Const or Phi with constants
413 static void cond_eval(ir_node* block, void* data)
417 ir_graph *irg = current_ir_graph;
428 if(get_Block_n_cfgpreds(block) != 1)
431 projx = get_Block_cfgpred(block, 0);
434 assert(get_irn_mode(projx) == mode_X);
436 cond = get_Proj_pred(projx);
440 pred = get_Cond_selector(cond);
441 // TODO handle switches
442 if (get_irn_mode(pred) != mode_b)
446 pnc = get_Proj_proj(pred);
448 cmp = get_Proj_pred(pred);
451 left = get_Cmp_left(cmp);
452 right = get_Cmp_right(cmp);
453 assert(get_irn_mode(left) == get_irn_mode(right));
455 /* we assume that the cond_block is the true case */
456 if (get_Proj_proj(projx) == pn_Cond_false) {
457 pnc = get_negated_pnc(pnc, get_irn_mode(left));
460 /* we assume that the constant is on the right side, swap left/right
467 pnc = get_inversed_pnc(pnc);
473 cond_block = get_nodes_block(cond);
475 // special case: comparing a constant with a constant
477 tarval *tv1 = get_Const_tarval(left);
478 tarval *tv2 = get_Const_tarval(right);
480 if(eval_cmp(pnc, tv1, tv2)) {
481 pred = new_r_Jmp(irg, cond_block);
485 set_Block_cfgpred(block, 0, pred);
487 set_irg_doms_inconsistent(irg);
488 set_irg_extblk_inconsistent(irg);
489 set_irg_loopinfo_inconsistent(irg);
491 if(get_nodes_block(left) != cond_block)
494 // (recursively) look if a pred of a phi is a constant
495 env.true_block = block;
498 inc_irg_visited(current_ir_graph);
499 env.visited_nr = get_irg_visited(irg);
501 copy_block = find_phi_with_const(projx, left, &env);
503 if(copy_block != NULL) {
504 /* we have to remove the edge towards the pred as the pred now
505 * jumps into the true_block. We also have to shorten phis
506 * in our block because of this */
507 const ir_edge_t *edge, *next;
510 foreach_out_edge_safe(env.cnst_pred, edge, next) {
511 ir_node *node = get_edge_src_irn(edge);
514 remove_pred(node, env.cnst_pos);
517 remove_pred(env.cnst_pred, env.cnst_pos);
519 /* the graph is changed now */
525 void opt_cond_eval(ir_graph* irg)
529 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
531 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
533 remove_critical_cf_edges(irg);
534 normalize_proj_nodes(irg);
537 set_using_irn_link(irg);
538 set_using_visited(irg);
543 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
548 /* control flow changed, some blocks may become dead */
549 set_irg_doms_inconsistent(irg);
550 set_irg_extblk_inconsistent(irg);
551 set_irg_loopinfo_inconsistent(irg);
554 clear_using_visited(irg);
555 clear_using_irn_link(irg);