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 Partial condition evaluation
24 * @author Christoph Mallon, Matthias Braun
31 #include "iroptimize.h"
43 #include "iredges_t.h"
47 #include "opt_confirms.h"
51 DEBUG_ONLY(static firm_dbg_module_t *dbg);
54 * Add the new predecessor x to node node, which is either a Block or a Phi
56 static void add_pred(ir_node* node, ir_node* x)
62 assert(is_Block(node) || is_Phi(node));
64 n = get_irn_arity(node);
65 NEW_ARR_A(ir_node*, ins, n + 1);
66 for (i = 0; i < n; i++)
67 ins[i] = get_irn_n(node, i);
69 set_irn_in(node, n + 1, ins);
72 static ir_node *ssa_second_def;
73 static ir_node *ssa_second_def_block;
75 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode,
84 /* This is needed because we create bads sometimes */
88 /* already processed this block? */
89 if(irn_visited(block)) {
90 ir_node *value = (ir_node*) get_irn_link(block);
94 /* the other defs can't be marked for cases where a user of the original
95 * value is in the same block as the alternative definition.
96 * In this case we mustn't use the alternative definition.
97 * So we keep a flag that indicated wether we walked at least 1 block
98 * away and may use the alternative definition */
99 if (block == ssa_second_def_block && !first) {
100 return ssa_second_def;
103 irg = get_irn_irg(block);
104 assert(block != get_irg_start_block(irg));
106 /* a Block with only 1 predecessor needs no Phi */
107 n_cfgpreds = get_Block_n_cfgpreds(block);
108 if(n_cfgpreds == 1) {
109 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
110 ir_node *value = search_def_and_create_phis(pred_block, mode, 0);
112 set_irn_link(block, value);
113 mark_irn_visited(block);
117 /* create a new Phi */
118 NEW_ARR_A(ir_node*, in, n_cfgpreds);
119 for(i = 0; i < n_cfgpreds; ++i)
120 in[i] = new_Unknown(mode);
122 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
123 set_irn_link(block, phi);
124 mark_irn_visited(block);
126 /* set Phi predecessors */
127 for(i = 0; i < n_cfgpreds; ++i) {
128 ir_node *pred_block = get_Block_cfgpred_block(block, i);
129 ir_node *pred_val = search_def_and_create_phis(pred_block, mode, 0);
131 set_irn_n(phi, i, pred_val);
138 * Given a set of values this function constructs SSA-form for the users of the
139 * first value (the users are determined through the out-edges of the value).
140 * Uses the irn_visited flags. Works without using the dominance tree.
142 static void construct_ssa(ir_node *orig_block, ir_node *orig_val,
143 ir_node *second_block, ir_node *second_val)
147 const ir_edge_t *edge;
148 const ir_edge_t *next;
150 irg = get_irn_irg(orig_val);
151 inc_irg_visited(irg);
153 mode = get_irn_mode(orig_val);
154 set_irn_link(orig_block, orig_val);
155 mark_irn_visited(orig_block);
157 ssa_second_def_block = second_block;
158 ssa_second_def = second_val;
160 /* Only fix the users of the first, i.e. the original node */
161 foreach_out_edge_safe(orig_val, edge, next) {
162 ir_node *user = get_edge_src_irn(edge);
163 int j = get_edge_src_pos(edge);
164 ir_node *user_block = get_nodes_block(user);
171 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
174 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
175 newval = search_def_and_create_phis(pred_block, mode, 1);
177 newval = search_def_and_create_phis(user_block, mode, 1);
180 /* don't fix newly created Phis from the SSA construction */
181 if (newval != user) {
182 DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
183 set_irn_n(user, j, newval);
188 static void split_critical_edge(ir_node *block, int pos) {
189 ir_graph *irg = get_irn_irg(block);
194 in[0] = get_Block_cfgpred(block, pos);
195 new_block = new_r_Block(irg, 1, in);
196 new_jmp = new_r_Jmp(irg, new_block);
197 set_Block_cfgpred(block, pos, new_jmp);
200 typedef struct condeval_env_t {
202 ir_node *cmp; /**< The Compare node that might be partial evaluated */
203 pn_Cmp pnc; /**< The Compare mode of the Compare node. */
206 ir_visited_t visited_nr;
208 ir_node *cnst_pred; /**< the block before the constant */
209 int cnst_pos; /**< the pos to the constant block (needed to
210 kill that edge later) */
213 static ir_node *copy_and_fix_node(const condeval_env_t *env, ir_node *block,
214 ir_node *copy_block, int j, ir_node *node) {
218 /* we can evaluate Phis right now, all other nodes get copied */
220 copy = get_Phi_pred(node, j);
221 /* we might have to evaluate a Phi-cascade */
222 if(get_irn_visited(copy) >= env->visited_nr) {
223 copy = get_irn_link(copy);
226 copy = exact_copy(node);
227 set_nodes_block(copy, copy_block);
229 assert(get_irn_mode(copy) != mode_X);
231 arity = get_irn_arity(copy);
232 for(i = 0; i < arity; ++i) {
233 ir_node *pred = get_irn_n(copy, i);
236 if(get_nodes_block(pred) != block)
239 if(get_irn_visited(pred) >= env->visited_nr) {
240 new_pred = get_irn_link(pred);
242 new_pred = copy_and_fix_node(env, block, copy_block, j, pred);
244 DB((dbg, LEVEL_2, ">> Set Pred of %+F to %+F\n", copy, new_pred));
245 set_irn_n(copy, i, new_pred);
249 set_irn_link(node, copy);
250 set_irn_visited(node, env->visited_nr);
255 static void copy_and_fix(const condeval_env_t *env, ir_node *block,
256 ir_node *copy_block, int j) {
257 const ir_edge_t *edge;
259 /* Look at all nodes in the cond_block and copy them into pred */
260 foreach_out_edge(block, edge) {
261 ir_node *node = get_edge_src_irn(edge);
265 if (is_Block(node)) {
266 /* Block->Block edge, should be the MacroBlock edge */
267 assert(get_Block_MacroBlock(node) == block && "Block->Block edge found");
271 /* ignore control flow */
272 mode = get_irn_mode(node);
273 if (mode == mode_X || is_Cond(node))
276 /* we may not copy mode_b nodes, because this could produce Phi with
277 * mode_bs which can't be handled in all backends. Instead we duplicate
278 * the node and move it to its users */
279 if (mode == mode_b) {
280 const ir_edge_t *edge, *next;
284 assert(is_Proj(node));
286 pred = get_Proj_pred(node);
287 pn = get_Proj_proj(node);
289 foreach_out_edge_safe(node, edge, next) {
291 ir_node *user = get_edge_src_irn(edge);
292 int pos = get_edge_src_pos(edge);
293 ir_node *user_block = get_nodes_block(user);
295 if(user_block == block)
298 cmp_copy = exact_copy(pred);
299 set_nodes_block(cmp_copy, user_block);
300 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
301 set_irn_n(user, pos, copy);
307 copy = copy_and_fix_node(env, block, copy_block, j, node);
309 /* we might hit values in blocks that have already been processed by a
310 * recursive find_phi_with_const() call */
311 assert(get_irn_visited(copy) <= env->visited_nr);
312 if(get_irn_visited(copy) >= env->visited_nr) {
313 ir_node *prev_copy = get_irn_link(copy);
314 if(prev_copy != NULL)
315 set_irn_link(node, prev_copy);
319 /* fix data-flow (and reconstruct SSA if needed) */
320 foreach_out_edge(block, edge) {
321 ir_node *node = get_edge_src_irn(edge);
325 if (is_Block(node)) {
326 /* Block->Block edge, should be the MacroBlock edge */
327 assert(get_Block_MacroBlock(node) == block && "Block->Block edge found");
331 mode = get_irn_mode(node);
332 if (mode == mode_X || is_Cond(node))
339 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
341 copy_node = get_irn_link(node);
342 construct_ssa(block, node, copy_block, copy_node);
347 * returns whether the cmp evaluates to true or false, or can't be evaluated!
348 * 1: true, 0: false, -1: can't evaluate
350 * @param pnc the compare mode of the Compare
351 * @param tv_left the left tarval
352 * @param tv_right the right tarval
354 static int eval_cmp_tv(pn_Cmp pnc, tarval *tv_left, tarval *tv_right) {
355 pn_Cmp cmp_result = tarval_cmp(tv_left, tv_right);
357 /* does the compare evaluate to true? */
358 if (cmp_result == pn_Cmp_False)
360 if ((cmp_result & pnc) != cmp_result)
367 * returns whether the cmp evaluates to true or false, or can't be evaluated!
368 * 1: true, 0: false, -1: can't evaluate
370 * @param env the environment
371 * @param cand the candidate node, either a Const or a Confirm
373 static int eval_cmp(condeval_env_t *env, ir_node *cand) {
374 if (is_Const(cand)) {
375 tarval *tv_cand = get_Const_tarval(cand);
376 tarval *tv_cmp = get_Const_tarval(env->cnst);
378 return eval_cmp_tv(env->pnc, tv_cand, tv_cmp);
379 } else { /* a Confirm */
380 tarval *res = computed_value_Cmp_Confirm(env->cmp, cand, env->cnst, env->pnc);
382 if (res == tarval_bad)
384 return res == tarval_b_true;
389 * Check for Const or Confirm with Const.
391 static int is_Const_or_Confirm(const ir_node *node) {
392 if (is_Confirm(node))
393 node = get_Confirm_bound(node);
394 return is_Const(node);
398 * get the tarval of a Const or Confirm with
400 static tarval *get_Const_or_Confirm_tarval(const ir_node *node) {
401 if (is_Confirm(node)) {
402 if (get_Confirm_bound(node))
403 node = get_Confirm_bound(node);
405 return get_Const_tarval(node);
408 static ir_node *find_const_or_confirm(condeval_env_t *env, ir_node *jump, ir_node *value)
410 ir_node *block = get_nodes_block(jump);
412 if (irn_visited(value))
414 mark_irn_visited(value);
416 if (is_Const_or_Confirm(value)) {
417 if (eval_cmp(env, value) <= 0) {
423 "> Found condition evaluation candidate %+F->%+F\n",
424 env->true_block, block
427 /* adjust true_block to point directly towards our jump */
428 add_pred(env->true_block, jump);
430 split_critical_edge(env->true_block, 0);
432 /* we need a bigger visited nr when going back */
441 /* the Phi has to be in the same Block as the Jmp */
442 if(get_nodes_block(value) != block) {
446 arity = get_irn_arity(value);
447 for(i = 0; i < arity; ++i) {
449 ir_node *phi_pred = get_Phi_pred(value, i);
450 ir_node *cfgpred = get_Block_cfgpred(block, i);
452 copy_block = find_const_or_confirm(env, cfgpred, phi_pred);
453 if(copy_block == NULL)
456 /* copy duplicated nodes in copy_block and fix SSA */
457 copy_and_fix(env, block, copy_block, i);
459 if(copy_block == get_nodes_block(cfgpred)) {
460 env->cnst_pred = block;
464 /* return now as we can't process more possibilities in 1 run */
472 static ir_node *find_candidate(condeval_env_t *env, ir_node *jump,
475 ir_node *block = get_nodes_block(jump);
477 if(irn_visited(value)) {
480 mark_irn_visited(value);
482 if (is_Const_or_Confirm(value)) {
483 tarval *tv = get_Const_or_Confirm_tarval(value);
490 "> Found condition evaluation candidate %+F->%+F\n",
491 env->true_block, block
494 /* adjust true_block to point directly towards our jump */
495 add_pred(env->true_block, jump);
497 split_critical_edge(env->true_block, 0);
499 /* we need a bigger visited nr when going back */
507 /* the Phi has to be in the same Block as the Jmp */
508 if(get_nodes_block(value) != block)
511 arity = get_irn_arity(value);
512 for(i = 0; i < arity; ++i) {
514 ir_node *phi_pred = get_Phi_pred(value, i);
515 ir_node *cfgpred = get_Block_cfgpred(block, i);
517 copy_block = find_candidate(env, cfgpred, phi_pred);
518 if(copy_block == NULL)
521 /* copy duplicated nodes in copy_block and fix SSA */
522 copy_and_fix(env, block, copy_block, i);
524 if(copy_block == get_nodes_block(cfgpred)) {
525 env->cnst_pred = block;
529 /* return now as we can't process more possibilities in 1 run */
537 ir_node *cmp = get_Proj_pred(value);
541 left = get_Cmp_left(cmp);
542 right = get_Cmp_right(cmp);
543 pnc = get_Proj_proj(value);
545 /* we assume that the constant is on the right side, swap left/right
552 pnc = get_inversed_pnc(pnc);
558 if(get_nodes_block(left) != block) {
562 /* negate condition when we're looking for the false block */
563 if(env->tv == tarval_b_false) {
564 pnc = get_negated_pnc(pnc, get_irn_mode(right));
567 /* (recursively) look if a pred of a Phi is a constant or a Confirm */
572 return find_const_or_confirm(env, jump, left);
579 * Block-walker: searches for the following construct
581 * Const or Phi with constants
591 static void cond_eval(ir_node* block, void* data)
599 int selector_evaluated;
600 const ir_edge_t *edge, *next;
604 if(get_Block_n_cfgpreds(block) != 1)
607 projx = get_Block_cfgpred(block, 0);
610 assert(get_irn_mode(projx) == mode_X);
612 cond = get_Proj_pred(projx);
616 selector = get_Cond_selector(cond);
617 /* TODO handle switch Conds */
618 if (get_irn_mode(selector) != mode_b)
621 /* handle cases that can be immediately evaluated */
622 selector_evaluated = -1;
623 if(is_Proj(selector)) {
624 ir_node *cmp = get_Proj_pred(selector);
626 ir_node *left = get_Cmp_left(cmp);
627 ir_node *right = get_Cmp_right(cmp);
628 if(is_Const(left) && is_Const(right)) {
629 int pnc = get_Proj_proj(selector);
630 tarval *tv_left = get_Const_tarval(left);
631 tarval *tv_right = get_Const_tarval(right);
633 selector_evaluated = eval_cmp_tv(pnc, tv_left, tv_right);
634 if(selector_evaluated < 0)
638 } else if (is_Const_or_Confirm(selector)) {
639 tarval *tv = get_Const_or_Confirm_tarval(selector);
640 if(tv == tarval_b_true) {
641 selector_evaluated = 1;
643 assert(tv == tarval_b_false);
644 selector_evaluated = 0;
648 env.cnst_pred = NULL;
649 if (get_Proj_proj(projx) == pn_Cond_false) {
650 env.tv = tarval_b_false;
651 if(selector_evaluated >= 0)
652 selector_evaluated = !selector_evaluated;
654 env.tv = tarval_b_true;
657 if(selector_evaluated == 0) {
659 exchange(projx, bad);
662 } else if(selector_evaluated == 1) {
663 dbg_info *dbgi = get_irn_dbg_info(selector);
664 ir_node *jmp = new_rd_Jmp(dbgi, current_ir_graph, get_nodes_block(projx));
665 exchange(projx, jmp);
670 /* (recursively) look if a pred of a Phi is a constant or a Confirm */
671 env.true_block = block;
672 inc_irg_visited(current_ir_graph);
673 env.visited_nr = get_irg_visited(current_ir_graph);
675 copy_block = find_candidate(&env, projx, selector);
676 if (copy_block == NULL)
679 /* we have to remove the edge towards the pred as the pred now
680 * jumps into the true_block. We also have to shorten Phis
681 * in our block because of this */
683 cnst_pos = env.cnst_pos;
686 foreach_out_edge_safe(env.cnst_pred, edge, next) {
687 ir_node *node = get_edge_src_irn(edge);
690 set_Phi_pred(node, cnst_pos, bad);
693 set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
695 /* the graph is changed now */
699 void opt_cond_eval(ir_graph* irg)
703 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
705 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
707 remove_critical_cf_edges(irg);
708 normalize_proj_nodes(irg);
711 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
716 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
720 ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
723 /* control flow changed, some blocks may become dead */
724 set_irg_outs_inconsistent(irg);
725 set_irg_doms_inconsistent(irg);
726 set_irg_extblk_inconsistent(irg);
727 set_irg_loopinfo_inconsistent(irg);
729 /* Dead code might be created. Optimize it away as it is dangerous
730 * to call optimize_df() an dead code. */