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
29 #include "iroptimize.h"
41 #include "iredges_t.h"
45 #include "opt_confirms.h"
46 #include "iropt_dbg.h"
50 DEBUG_ONLY(static firm_dbg_module_t *dbg);
53 * Add the new predecessor x to node node, which is either a Block or a Phi
55 static void add_pred(ir_node* node, ir_node* x)
61 assert(is_Block(node) || is_Phi(node));
63 n = get_irn_arity(node);
64 NEW_ARR_A(ir_node*, ins, n + 1);
65 for (i = 0; i < n; i++)
66 ins[i] = get_irn_n(node, i);
68 set_irn_in(node, n + 1, ins);
71 static ir_node *ssa_second_def;
72 static ir_node *ssa_second_def_block;
74 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode,
83 /* This is needed because we create bads sometimes */
87 /* the other defs can't be marked for cases where a user of the original
88 * value is in the same block as the alternative definition.
89 * In this case we mustn't use the alternative definition.
90 * So we keep a flag that indicated wether we walked at least 1 block
91 * away and may use the alternative definition */
92 if (block == ssa_second_def_block && !first) {
93 return ssa_second_def;
96 /* already processed this block? */
97 if (irn_visited(block)) {
98 ir_node *value = (ir_node*) get_irn_link(block);
102 irg = get_irn_irg(block);
103 assert(block != get_irg_start_block(irg));
105 /* a Block with only 1 predecessor needs no Phi */
106 n_cfgpreds = get_Block_n_cfgpreds(block);
107 if (n_cfgpreds == 1) {
108 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
109 ir_node *value = search_def_and_create_phis(pred_block, mode, 0);
111 set_irn_link(block, value);
112 mark_irn_visited(block);
116 /* create a new Phi */
117 NEW_ARR_A(ir_node*, in, n_cfgpreds);
118 for(i = 0; i < n_cfgpreds; ++i)
119 in[i] = new_Unknown(mode);
121 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
122 set_irn_link(block, phi);
123 mark_irn_visited(block);
125 /* set Phi predecessors */
126 for(i = 0; i < n_cfgpreds; ++i) {
127 ir_node *pred_block = get_Block_cfgpred_block(block, i);
128 ir_node *pred_val = search_def_and_create_phis(pred_block, mode, 0);
130 set_irn_n(phi, i, pred_val);
137 * Given a set of values this function constructs SSA-form for the users of the
138 * first value (the users are determined through the out-edges of the value).
139 * Uses the irn_visited flags. Works without using the dominance tree.
141 static void construct_ssa(ir_node *orig_block, ir_node *orig_val,
142 ir_node *second_block, ir_node *second_val)
146 const ir_edge_t *edge;
147 const ir_edge_t *next;
149 /* no need to do anything */
150 if (orig_val == second_val)
153 irg = get_irn_irg(orig_val);
154 inc_irg_visited(irg);
156 mode = get_irn_mode(orig_val);
157 set_irn_link(orig_block, orig_val);
158 mark_irn_visited(orig_block);
160 ssa_second_def_block = second_block;
161 ssa_second_def = second_val;
163 /* Only fix the users of the first, i.e. the original node */
164 foreach_out_edge_safe(orig_val, edge, next) {
165 ir_node *user = get_edge_src_irn(edge);
166 int j = get_edge_src_pos(edge);
167 ir_node *user_block = get_nodes_block(user);
174 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
177 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
178 newval = search_def_and_create_phis(pred_block, mode, 1);
180 newval = search_def_and_create_phis(user_block, mode, 1);
183 /* don't fix newly created Phis from the SSA construction */
184 if (newval != user) {
185 DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
186 set_irn_n(user, j, newval);
191 static void split_critical_edge(ir_node *block, int pos) {
192 ir_graph *irg = get_irn_irg(block);
197 in[0] = get_Block_cfgpred(block, pos);
198 new_block = new_r_Block(irg, 1, in);
199 new_jmp = new_r_Jmp(irg, new_block);
200 set_Block_cfgpred(block, pos, new_jmp);
203 typedef struct condeval_env_t {
205 ir_node *cmp; /**< The Compare node that might be partial evaluated */
206 pn_Cmp pnc; /**< The Compare mode of the Compare node. */
209 ir_visited_t visited_nr;
211 ir_node *cnst_pred; /**< the block before the constant */
212 int cnst_pos; /**< the pos to the constant block (needed to
213 kill that edge later) */
216 static ir_node *copy_and_fix_node(const condeval_env_t *env, ir_node *block,
217 ir_node *copy_block, int j, ir_node *node) {
221 /* we can evaluate Phis right now, all other nodes get copied */
223 copy = get_Phi_pred(node, j);
224 /* we might have to evaluate a Phi-cascade */
225 if (get_irn_visited(copy) >= env->visited_nr) {
226 copy = get_irn_link(copy);
229 copy = exact_copy(node);
230 set_nodes_block(copy, copy_block);
232 assert(get_irn_mode(copy) != mode_X);
234 arity = get_irn_arity(copy);
235 for(i = 0; i < arity; ++i) {
236 ir_node *pred = get_irn_n(copy, i);
239 if (get_nodes_block(pred) != block)
242 if (get_irn_visited(pred) >= env->visited_nr) {
243 new_pred = get_irn_link(pred);
245 new_pred = copy_and_fix_node(env, block, copy_block, j, pred);
247 DB((dbg, LEVEL_2, ">> Set Pred of %+F to %+F\n", copy, new_pred));
248 set_irn_n(copy, i, new_pred);
252 set_irn_link(node, copy);
253 set_irn_visited(node, env->visited_nr);
258 static void copy_and_fix(const condeval_env_t *env, ir_node *block,
259 ir_node *copy_block, int j) {
260 const ir_edge_t *edge;
262 /* Look at all nodes in the cond_block and copy them into pred */
263 foreach_out_edge(block, edge) {
264 ir_node *node = get_edge_src_irn(edge);
268 if (is_Block(node)) {
269 /* Block->Block edge, should be the MacroBlock edge */
270 assert(get_Block_MacroBlock(node) == block && "Block->Block edge found");
274 /* ignore control flow */
275 mode = get_irn_mode(node);
276 if (mode == mode_X || is_Cond(node))
279 /* we may not copy mode_b nodes, because this could produce Phi with
280 * mode_bs which can't be handled in all backends. Instead we duplicate
281 * the node and move it to its users */
282 if (mode == mode_b) {
283 const ir_edge_t *edge, *next;
287 assert(is_Proj(node));
289 pred = get_Proj_pred(node);
290 pn = get_Proj_proj(node);
292 foreach_out_edge_safe(node, edge, next) {
294 ir_node *user = get_edge_src_irn(edge);
295 int pos = get_edge_src_pos(edge);
296 ir_node *user_block = get_nodes_block(user);
298 if (user_block == block)
301 cmp_copy = exact_copy(pred);
302 set_nodes_block(cmp_copy, user_block);
303 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
304 set_irn_n(user, pos, copy);
310 copy = copy_and_fix_node(env, block, copy_block, j, node);
312 /* we might hit values in blocks that have already been processed by a
313 * recursive find_phi_with_const() call */
314 assert(get_irn_visited(copy) <= env->visited_nr);
315 if (get_irn_visited(copy) >= env->visited_nr) {
316 ir_node *prev_copy = get_irn_link(copy);
317 if (prev_copy != NULL)
318 set_irn_link(node, prev_copy);
322 /* fix data-flow (and reconstruct SSA if needed) */
323 foreach_out_edge(block, edge) {
324 ir_node *node = get_edge_src_irn(edge);
328 if (is_Block(node)) {
329 /* Block->Block edge, should be the MacroBlock edge */
330 assert(get_Block_MacroBlock(node) == block && "Block->Block edge found");
334 mode = get_irn_mode(node);
335 if (mode == mode_X || is_Cond(node))
342 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
344 copy_node = get_irn_link(node);
345 construct_ssa(block, node, copy_block, copy_node);
350 * returns whether the cmp evaluates to true or false, or can't be evaluated!
351 * 1: true, 0: false, -1: can't evaluate
353 * @param pnc the compare mode of the Compare
354 * @param tv_left the left tarval
355 * @param tv_right the right tarval
357 static int eval_cmp_tv(pn_Cmp pnc, tarval *tv_left, tarval *tv_right) {
358 pn_Cmp cmp_result = tarval_cmp(tv_left, tv_right);
360 /* does the compare evaluate to true? */
361 if (cmp_result == pn_Cmp_False)
363 if ((cmp_result & pnc) != cmp_result)
370 * returns whether the cmp evaluates to true or false, or can't be evaluated!
371 * 1: true, 0: false, -1: can't evaluate
373 * @param env the environment
374 * @param cand the candidate node, either a Const or a Confirm
376 static int eval_cmp(condeval_env_t *env, ir_node *cand) {
377 if (is_Const(cand)) {
378 tarval *tv_cand = get_Const_tarval(cand);
379 tarval *tv_cmp = get_Const_tarval(env->cnst);
381 return eval_cmp_tv(env->pnc, tv_cand, tv_cmp);
382 } else { /* a Confirm */
383 tarval *res = computed_value_Cmp_Confirm(env->cmp, cand, env->cnst, env->pnc);
385 if (res == tarval_bad)
387 return res == tarval_b_true;
392 * Check for Const or Confirm with Const.
394 static int is_Const_or_Confirm(const ir_node *node) {
395 if (is_Confirm(node))
396 node = get_Confirm_bound(node);
397 return is_Const(node);
401 * get the tarval of a Const or Confirm with
403 static tarval *get_Const_or_Confirm_tarval(const ir_node *node) {
404 if (is_Confirm(node)) {
405 if (get_Confirm_bound(node))
406 node = get_Confirm_bound(node);
408 return get_Const_tarval(node);
411 static ir_node *find_const_or_confirm(condeval_env_t *env, ir_node *jump, ir_node *value)
413 ir_node *block = get_nodes_block(jump);
415 if (irn_visited_else_mark(value))
418 if (is_Const_or_Confirm(value)) {
419 if (eval_cmp(env, value) <= 0) {
425 "> Found condition evaluation candidate %+F->%+F\n",
426 env->true_block, block
429 /* adjust true_block to point directly towards our jump */
430 add_pred(env->true_block, jump);
432 split_critical_edge(env->true_block, 0);
434 /* we need a bigger visited nr when going back */
443 /* the Phi has to be in the same Block as the Jmp */
444 if (get_nodes_block(value) != block) {
448 arity = get_irn_arity(value);
449 for(i = 0; i < arity; ++i) {
451 ir_node *phi_pred = get_Phi_pred(value, i);
452 ir_node *cfgpred = get_Block_cfgpred(block, i);
454 copy_block = find_const_or_confirm(env, cfgpred, phi_pred);
455 if (copy_block == NULL)
458 /* copy duplicated nodes in copy_block and fix SSA */
459 copy_and_fix(env, block, copy_block, i);
461 if (copy_block == get_nodes_block(cfgpred)) {
462 env->cnst_pred = block;
466 /* return now as we can't process more possibilities in 1 run */
474 static ir_node *find_candidate(condeval_env_t *env, ir_node *jump,
477 ir_node *block = get_nodes_block(jump);
479 if (irn_visited_else_mark(value)) {
483 if (is_Const_or_Confirm(value)) {
484 tarval *tv = get_Const_or_Confirm_tarval(value);
491 "> Found condition evaluation candidate %+F->%+F\n",
492 env->true_block, block
495 /* adjust true_block to point directly towards our jump */
496 add_pred(env->true_block, jump);
498 split_critical_edge(env->true_block, 0);
500 /* we need a bigger visited nr when going back */
508 /* the Phi has to be in the same Block as the Jmp */
509 if (get_nodes_block(value) != block)
512 arity = get_irn_arity(value);
513 for(i = 0; i < arity; ++i) {
515 ir_node *phi_pred = get_Phi_pred(value, i);
516 ir_node *cfgpred = get_Block_cfgpred(block, i);
518 copy_block = find_candidate(env, cfgpred, phi_pred);
519 if (copy_block == NULL)
522 /* copy duplicated nodes in copy_block and fix SSA */
523 copy_and_fix(env, block, copy_block, i);
525 if (copy_block == get_nodes_block(cfgpred)) {
526 env->cnst_pred = block;
530 /* return now as we can't process more possibilities in 1 run */
534 if (is_Proj(value)) {
538 ir_node *cmp = get_Proj_pred(value);
542 left = get_Cmp_left(cmp);
543 right = get_Cmp_right(cmp);
544 pnc = get_Proj_proj(value);
546 /* we assume that the constant is on the right side, swap left/right
548 if (is_Const(left)) {
553 pnc = get_inversed_pnc(pnc);
556 if (!is_Const(right))
559 if (get_nodes_block(left) != block) {
563 /* negate condition when we're looking for the false block */
564 if (env->tv == tarval_b_false) {
565 pnc = get_negated_pnc(pnc, get_irn_mode(right));
568 /* (recursively) look if a pred of a Phi is a constant or a Confirm */
573 return find_const_or_confirm(env, jump, left);
580 * Block-walker: searches for the following construct
582 * Const or Phi with constants
592 static void cond_eval(ir_node* block, void* data)
600 int selector_evaluated;
601 const ir_edge_t *edge, *next;
605 if (get_Block_n_cfgpreds(block) != 1)
608 projx = get_Block_cfgpred(block, 0);
611 assert(get_irn_mode(projx) == mode_X);
613 cond = get_Proj_pred(projx);
617 selector = get_Cond_selector(cond);
618 /* TODO handle switch Conds */
619 if (get_irn_mode(selector) != mode_b)
622 /* handle cases that can be immediately evaluated */
623 selector_evaluated = -1;
624 if (is_Proj(selector)) {
625 ir_node *cmp = get_Proj_pred(selector);
627 ir_node *left = get_Cmp_left(cmp);
628 ir_node *right = get_Cmp_right(cmp);
629 if (is_Const(left) && is_Const(right)) {
630 int pnc = get_Proj_proj(selector);
631 tarval *tv_left = get_Const_tarval(left);
632 tarval *tv_right = get_Const_tarval(right);
634 selector_evaluated = eval_cmp_tv(pnc, tv_left, tv_right);
635 if (selector_evaluated < 0)
639 } else if (is_Const_or_Confirm(selector)) {
640 tarval *tv = get_Const_or_Confirm_tarval(selector);
641 if (tv == tarval_b_true) {
642 selector_evaluated = 1;
644 assert(tv == tarval_b_false);
645 selector_evaluated = 0;
649 env.cnst_pred = NULL;
650 if (get_Proj_proj(projx) == pn_Cond_false) {
651 env.tv = tarval_b_false;
652 if (selector_evaluated >= 0)
653 selector_evaluated = !selector_evaluated;
655 env.tv = tarval_b_true;
658 if (selector_evaluated == 0) {
660 exchange(projx, bad);
663 } else if (selector_evaluated == 1) {
664 dbg_info *dbgi = get_irn_dbg_info(selector);
665 ir_node *jmp = new_rd_Jmp(dbgi, current_ir_graph, get_nodes_block(projx));
666 DBG_OPT_COND_EVAL(projx, jmp);
667 exchange(projx, jmp);
672 /* (recursively) look if a pred of a Phi is a constant or a Confirm */
673 env.true_block = block;
674 inc_irg_visited(current_ir_graph);
675 env.visited_nr = get_irg_visited(current_ir_graph);
677 copy_block = find_candidate(&env, projx, selector);
678 if (copy_block == NULL)
681 /* we have to remove the edge towards the pred as the pred now
682 * jumps into the true_block. We also have to shorten Phis
683 * in our block because of this */
685 cnst_pos = env.cnst_pos;
688 foreach_out_edge_safe(env.cnst_pred, edge, next) {
689 ir_node *node = get_edge_src_irn(edge);
692 set_Phi_pred(node, cnst_pos, bad);
695 set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
697 /* the graph is changed now */
701 void opt_cond_eval(ir_graph* irg)
705 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
707 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
709 remove_critical_cf_edges(irg);
710 normalize_proj_nodes(irg);
713 ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
718 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
722 ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
725 /* control flow changed, some blocks may become dead */
726 set_irg_outs_inconsistent(irg);
727 set_irg_doms_inconsistent(irg);
728 set_irg_extblk_inconsistent(irg);
729 set_irg_loopinfo_inconsistent(irg);
731 /* Dead code might be created. Optimize it away as it is dangerous
732 * to call optimize_df() an dead code. */