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 *search_def_and_create_phis(ir_node *block, ir_mode *mode)
80 /* This is needed because we create bads sometimes */
84 /* already processed this block? */
85 if(irn_visited(block)) {
86 ir_node *value = (ir_node*) get_irn_link(block);
90 irg = get_irn_irg(block);
91 assert(block != get_irg_start_block(irg));
93 /* a Block with only 1 predecessor needs no Phi */
94 n_cfgpreds = get_Block_n_cfgpreds(block);
96 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
97 ir_node *value = search_def_and_create_phis(pred_block, mode);
99 set_irn_link(block, value);
100 mark_irn_visited(block);
104 /* create a new Phi */
105 NEW_ARR_A(ir_node*, in, n_cfgpreds);
106 for(i = 0; i < n_cfgpreds; ++i)
107 in[i] = new_Unknown(mode);
109 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
110 set_irn_link(block, phi);
111 mark_irn_visited(block);
113 /* set Phi predecessors */
114 for(i = 0; i < n_cfgpreds; ++i) {
115 ir_node *pred_block = get_Block_cfgpred_block(block, i);
116 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
118 set_irn_n(phi, i, pred_val);
125 * Given a set of values this function constructs SSA-form for the users of the
126 * first value (the users are determined through the out-edges of the value).
127 * Uses the irn_visited flags. Works without using the dominance tree.
129 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
134 const ir_edge_t *edge;
135 const ir_edge_t *next;
140 irg = get_irn_irg(vals[0]);
141 inc_irg_visited(irg);
143 mode = get_irn_mode(vals[0]);
144 for(i = 0; i < n_vals; ++i) {
145 ir_node *value = vals[i];
146 ir_node *value_block = blocks[i];
148 assert(get_irn_mode(value) == mode || is_Bad(value));
150 set_irn_link(value_block, value);
151 mark_irn_visited(value_block);
154 /* Only fix the users of the first, i.e. the original node */
157 foreach_out_edge_safe(value, edge, next) {
158 ir_node *user = get_edge_src_irn(edge);
159 int j = get_edge_src_pos(edge);
160 ir_node *user_block = get_nodes_block(user);
167 if (user_block == blocks[1])
170 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
173 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
174 newval = search_def_and_create_phis(pred_block, mode);
176 newval = search_def_and_create_phis(user_block, mode);
179 /* don't fix newly created Phis from the SSA construction */
180 if (newval != user) {
181 DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
182 set_irn_n(user, j, newval);
187 static void split_critical_edge(ir_node *block, int pos) {
188 ir_graph *irg = get_irn_irg(block);
193 in[0] = get_Block_cfgpred(block, pos);
194 new_block = new_r_Block(irg, 1, in);
195 new_jmp = new_r_Jmp(irg, new_block);
196 set_Block_cfgpred(block, pos, new_jmp);
199 typedef struct condeval_env_t {
201 ir_node *cmp; /**< The Compare node that might be partial evaluated */
202 pn_Cmp pnc; /**< The Compare mode of the Compare node. */
205 ir_visited_t visited_nr;
207 ir_node *cnst_pred; /**< the block before the constant */
208 int cnst_pos; /**< the pos to the constant block (needed to
209 kill that edge later) */
212 static ir_node *copy_and_fix_node(const condeval_env_t *env, ir_node *block,
213 ir_node *copy_block, int j, ir_node *node) {
217 /* we can evaluate Phis right now, all other nodes get copied */
219 copy = get_Phi_pred(node, j);
220 /* we might have to evaluate a Phi-cascade */
221 if(get_irn_visited(copy) >= env->visited_nr) {
222 copy = get_irn_link(copy);
225 copy = exact_copy(node);
226 set_nodes_block(copy, copy_block);
228 assert(get_irn_mode(copy) != mode_X);
230 arity = get_irn_arity(copy);
231 for(i = 0; i < arity; ++i) {
232 ir_node *pred = get_irn_n(copy, i);
235 if(get_nodes_block(pred) != block)
238 if(get_irn_visited(pred) >= env->visited_nr) {
239 new_pred = get_irn_link(pred);
241 new_pred = copy_and_fix_node(env, block, copy_block, j, pred);
243 set_irn_n(copy, i, new_pred);
247 set_irn_link(node, copy);
248 set_irn_visited(node, env->visited_nr);
253 static void copy_and_fix(const condeval_env_t *env, ir_node *block,
254 ir_node *copy_block, int j) {
255 const ir_edge_t *edge;
257 /* Look at all nodes in the cond_block and copy them into pred */
258 foreach_out_edge(block, edge) {
259 ir_node *node = get_edge_src_irn(edge);
263 if (is_Block(node)) {
264 /* Block->Block edge, should be the MacroBlock edge */
265 assert(get_Block_MacroBlock(node) == block && "Block->Block edge found");
269 /* ignore control flow */
270 mode = get_irn_mode(node);
271 if (mode == mode_X || is_Cond(node))
274 /* we may not copy mode_b nodes, because this could produce Phi with
275 * mode_bs which can't be handled in all backends. Instead we duplicate
276 * the node and move it to its users */
277 if (mode == mode_b) {
278 const ir_edge_t *edge, *next;
282 assert(is_Proj(node));
284 pred = get_Proj_pred(node);
285 pn = get_Proj_proj(node);
287 foreach_out_edge_safe(node, edge, next) {
289 ir_node *user = get_edge_src_irn(edge);
290 int pos = get_edge_src_pos(edge);
291 ir_node *user_block = get_nodes_block(user);
293 if(user_block == block)
296 cmp_copy = exact_copy(pred);
297 set_nodes_block(cmp_copy, user_block);
298 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
299 set_irn_n(user, pos, copy);
305 copy = copy_and_fix_node(env, block, copy_block, j, node);
307 /* we might hit values in blocks that have already been processed by a
308 * recursive find_phi_with_const() call */
309 assert(get_irn_visited(copy) <= env->visited_nr);
310 if(get_irn_visited(copy) >= env->visited_nr) {
311 ir_node *prev_copy = get_irn_link(copy);
312 if(prev_copy != NULL)
313 set_irn_link(node, prev_copy);
317 /* fix data-flow (and reconstruct SSA if needed) */
318 foreach_out_edge(block, edge) {
321 ir_node *node = get_edge_src_irn(edge);
324 if (is_Block(node)) {
325 /* Block->Block edge, should be the MacroBlock edge */
326 assert(get_Block_MacroBlock(node) == block && "Block->Block edge found");
330 mode = get_irn_mode(node);
331 if (mode == mode_X || is_Cond(node))
338 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
342 blocks[1] = copy_block;
343 vals[1] = get_irn_link(node);
344 construct_ssa(blocks, vals, 2);
349 * returns whether the cmp evaluates to true or false, or can't be evaluated!
350 * 1: true, 0: false, -1: can't evaluate
352 * @param pnc the compare mode of the Compare
353 * @param tv_left the left tarval
354 * @param tv_right the right tarval
356 static int eval_cmp_tv(pn_Cmp pnc, tarval *tv_left, tarval *tv_right) {
357 pn_Cmp cmp_result = tarval_cmp(tv_left, tv_right);
359 /* does the compare evaluate to true? */
360 if (cmp_result == pn_Cmp_False)
362 if ((cmp_result & pnc) != cmp_result)
369 * returns whether the cmp evaluates to true or false, or can't be evaluated!
370 * 1: true, 0: false, -1: can't evaluate
372 * @param env the environment
373 * @param cand the candidate node, either a Const or a Confirm
375 static int eval_cmp(condeval_env_t *env, ir_node *cand) {
376 if (is_Const(cand)) {
377 tarval *tv_cand = get_Const_tarval(cand);
378 tarval *tv_cmp = get_Const_tarval(env->cnst);
380 return eval_cmp_tv(env->pnc, tv_cand, tv_cmp);
381 } else { /* a Confirm */
382 tarval *res = computed_value_Cmp_Confirm(env->cmp, cand, env->cnst, env->pnc);
384 if (res == tarval_bad)
386 return res == tarval_b_true;
391 * Check for Const or Confirm with Const.
393 static int is_Const_or_Confirm(const ir_node *node) {
394 if (is_Confirm(node))
395 node = get_Confirm_bound(node);
396 return is_Const(node);
400 * get the tarval of a Const or Confirm with
402 static tarval *get_Const_or_Confirm_tarval(const ir_node *node) {
403 if (is_Confirm(node)) {
404 if (get_Confirm_bound(node))
405 node = get_Confirm_bound(node);
407 return get_Const_tarval(node);
410 static ir_node *find_const_or_confirm(condeval_env_t *env, ir_node *jump, ir_node *value)
412 ir_node *block = get_nodes_block(jump);
414 if (irn_visited(value))
416 mark_irn_visited(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(value)) {
482 mark_irn_visited(value);
484 if (is_Const_or_Confirm(value)) {
485 tarval *tv = get_Const_or_Confirm_tarval(value);
492 "> Found condition evaluation candidate %+F->%+F\n",
493 env->true_block, block
496 /* adjust true_block to point directly towards our jump */
497 add_pred(env->true_block, jump);
499 split_critical_edge(env->true_block, 0);
501 /* we need a bigger visited nr when going back */
509 /* the Phi has to be in the same Block as the Jmp */
510 if(get_nodes_block(value) != block)
513 arity = get_irn_arity(value);
514 for(i = 0; i < arity; ++i) {
516 ir_node *phi_pred = get_Phi_pred(value, i);
517 ir_node *cfgpred = get_Block_cfgpred(block, i);
519 copy_block = find_candidate(env, cfgpred, phi_pred);
520 if(copy_block == NULL)
523 /* copy duplicated nodes in copy_block and fix SSA */
524 copy_and_fix(env, block, copy_block, i);
526 if(copy_block == get_nodes_block(cfgpred)) {
527 env->cnst_pred = block;
531 /* return now as we can't process more possibilities in 1 run */
539 ir_node *cmp = get_Proj_pred(value);
543 left = get_Cmp_left(cmp);
544 right = get_Cmp_right(cmp);
545 pnc = get_Proj_proj(value);
547 /* we assume that the constant is on the right side, swap left/right
554 pnc = get_inversed_pnc(pnc);
560 if(get_nodes_block(left) != block) {
564 /* negate condition when we're looking for the false block */
565 if(env->tv == tarval_b_false) {
566 pnc = get_negated_pnc(pnc, get_irn_mode(right));
569 /* (recursively) look if a pred of a Phi is a constant or a Confirm */
574 return find_const_or_confirm(env, jump, left);
581 * Block-walker: searches for the following construct
583 * Const or Phi with constants
593 static void cond_eval(ir_node* block, void* data)
601 int selector_evaluated;
602 const ir_edge_t *edge, *next;
606 if(get_Block_n_cfgpreds(block) != 1)
609 projx = get_Block_cfgpred(block, 0);
612 assert(get_irn_mode(projx) == mode_X);
614 cond = get_Proj_pred(projx);
618 selector = get_Cond_selector(cond);
619 /* TODO handle switch Conds */
620 if (get_irn_mode(selector) != mode_b)
623 /* handle cases that can be immediately evaluated */
624 selector_evaluated = -1;
625 if(is_Proj(selector)) {
626 ir_node *cmp = get_Proj_pred(selector);
628 ir_node *left = get_Cmp_left(cmp);
629 ir_node *right = get_Cmp_right(cmp);
630 if(is_Const(left) && is_Const(right)) {
631 int pnc = get_Proj_proj(selector);
632 tarval *tv_left = get_Const_tarval(left);
633 tarval *tv_right = get_Const_tarval(right);
635 selector_evaluated = eval_cmp_tv(pnc, tv_left, tv_right);
636 if(selector_evaluated < 0)
640 } else if (is_Const_or_Confirm(selector)) {
641 tarval *tv = get_Const_or_Confirm_tarval(selector);
642 if(tv == tarval_b_true) {
643 selector_evaluated = 1;
645 assert(tv == tarval_b_false);
646 selector_evaluated = 0;
650 env.cnst_pred = NULL;
651 if (get_Proj_proj(projx) == pn_Cond_false) {
652 env.tv = tarval_b_false;
653 if(selector_evaluated >= 0)
654 selector_evaluated = !selector_evaluated;
656 env.tv = tarval_b_true;
659 if(selector_evaluated == 0) {
661 exchange(projx, bad);
664 } else if(selector_evaluated == 1) {
665 dbg_info *dbgi = get_irn_dbg_info(selector);
666 ir_node *jmp = new_rd_Jmp(dbgi, current_ir_graph, get_nodes_block(projx));
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. */