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);
68 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
76 // This is needed because we create bads sometimes
80 // already processed this block?
81 if(irn_visited(block)) {
82 ir_node *value = (ir_node*) get_irn_link(block);
86 // blocks with only 1 pred need no phi
87 n_cfgpreds = get_Block_n_cfgpreds(block);
89 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
90 ir_node *value = search_def_and_create_phis(pred_block, mode);
92 set_irn_link(block, value);
93 mark_irn_visited(block);
98 NEW_ARR_A(ir_node*, in, n_cfgpreds);
99 for(i = 0; i < n_cfgpreds; ++i)
100 in[i] = new_Unknown(mode);
102 irg = get_irn_irg(block);
103 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
104 set_irn_link(block, phi);
105 mark_irn_visited(block);
108 for(i = 0; i < n_cfgpreds; ++i) {
109 ir_node *pred_block = get_Block_cfgpred_block(block, i);
110 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
112 set_irn_n(phi, i, pred_val);
119 * Given a set of values this function constructs SSA-form for the users of the
120 * first value (the users are determined through the out-edges of the value).
121 * Uses the irn_visited flags. Works without using the dominance tree.
123 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
128 const ir_edge_t *edge;
129 const ir_edge_t *next;
134 irg = get_irn_irg(vals[0]);
135 inc_irg_visited(irg);
137 mode = get_irn_mode(vals[0]);
138 for(i = 0; i < n_vals; ++i) {
139 ir_node *value = vals[i];
140 ir_node *value_block = blocks[i];
142 assert(get_irn_mode(value) == mode);
144 set_irn_link(value_block, value);
145 mark_irn_visited(value_block);
148 // Only fix the users of the first, i.e. the original node
151 // this can happen when fixing phi preds, we mustn't fix the users
152 if(get_nodes_block(value) != blocks[0]) return;
154 foreach_out_edge_safe(value, edge, next) {
155 ir_node *user = get_edge_src_irn(edge);
156 int j = get_edge_src_pos(edge);
157 ir_node *user_block = get_nodes_block(user);
161 if(get_irn_op(user) == op_End)
164 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
167 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
168 newval = search_def_and_create_phis(pred_block, mode);
170 newval = search_def_and_create_phis(user_block, mode);
173 // don't fix newly created phis from the SSA construction
174 if (newval != user) {
175 DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
176 set_irn_n(user, j, newval);
181 static void split_critical_edge(ir_node *block, int pos) {
182 ir_graph *irg = get_irn_irg(block);
187 in[0] = get_Block_cfgpred(block, pos);
188 new_block = new_r_Block(irg, 1, in);
189 new_jmp = new_r_Jmp(irg, new_block);
190 set_Block_cfgpred(block, pos, new_jmp);
193 typedef struct _condeval_env_t {
197 unsigned long visited_nr;
199 ir_node *cnst_pred; /**< the block before the constant */
200 int cnst_pos; /**< the pos to the constant block (needed to kill that edge later) */
203 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
204 const ir_edge_t *edge;
206 /* Look at all nodes in the cond_block and copy them into pred */
207 foreach_out_edge(block, edge) {
208 ir_node *node = get_edge_src_irn(edge);
210 ir_mode *mode = get_irn_mode(node);
212 /* ignore control flow */
215 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
216 be handled in all backends. Instead we duplicate the node and move it to it's users */
217 if (mode == mode_b) {
218 const ir_edge_t *edge, *next;
222 assert(is_Proj(node));
224 pred = get_Proj_pred(node);
225 pn = get_Proj_proj(node);
227 foreach_out_edge_safe(node, edge, next) {
229 ir_node *user = get_edge_src_irn(edge);
230 int pos = get_edge_src_pos(edge);
231 ir_node *user_block = get_nodes_block(user);
233 if(user_block == block)
236 cmp_copy = exact_copy(pred);
237 set_nodes_block(cmp_copy, user_block);
238 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
239 set_irn_n(user, pos, copy);
244 /* we can evaluate Phis right now, all other nodes get copied */
246 copy = get_Phi_pred(node, j);
248 copy = exact_copy(node);
249 set_nodes_block(copy, copy_block);
252 set_irn_link(node, copy);
253 set_irn_visited(node, env->visited_nr);
255 /* we might hit values in blocks that have already been processed by a
256 * recursive find_phi_with_const call */
257 assert(get_irn_visited(copy) <= env->visited_nr);
258 if(get_irn_visited(copy) >= env->visited_nr) {
259 ir_node *prev_copy = get_irn_link(copy);
260 if(prev_copy != NULL)
261 set_irn_link(node, prev_copy);
265 /* fix data-flow (and reconstruct SSA if needed) */
266 foreach_out_edge(block, edge) {
269 ir_node *node = get_edge_src_irn(edge);
270 ir_mode *mode = get_irn_mode(node);
277 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
281 blocks[1] = copy_block;
282 vals[1] = get_irn_link(node);
283 construct_ssa(blocks, vals, 2);
287 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
288 pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
290 // does the compare evaluate to true?
291 if(cmp_result == pn_Cmp_False)
293 if((cmp_result & pnc) != cmp_result)
299 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
300 ir_node *block = get_nodes_block(jump);
302 if(irn_visited(value))
304 mark_irn_visited(value);
306 if(is_Const(value)) {
307 tarval *tv_const = get_Const_tarval(env->cnst);
308 tarval *tv = get_Const_tarval(value);
310 if(!eval_cmp(env->pnc, tv, tv_const))
315 "> Found condition evaluation candidate %+F->%+F\n",
316 env->true_block, block
319 // adjust true_block to point directly towards our jump
320 add_pred(env->true_block, jump);
322 split_critical_edge(env->true_block, 0);
324 // we need a bigger visited nr when going back
333 // the phi has to be in the same block as the jump
334 if(get_nodes_block(value) != block)
337 arity = get_irn_arity(value);
338 for(i = 0; i < arity; ++i) {
340 ir_node *phi_pred = get_Phi_pred(value, i);
341 ir_node *cfgpred = get_Block_cfgpred(block, i);
343 copy_block = find_phi_with_const(cfgpred, phi_pred, env);
344 if(copy_block == NULL)
347 /* copy duplicated nodes in copy_block and fix SSA */
348 copy_and_fix(block, copy_block, i, env);
350 if(copy_block == get_nodes_block(cfgpred)) {
351 env->cnst_pred = block;
355 // return now as we can't process more possibilities in 1 run
365 * Block-walker: searches for the following construct
367 * Const or Phi with constants
377 static void cond_eval(ir_node* block, void* data)
381 ir_graph *irg = current_ir_graph;
392 if(get_Block_n_cfgpreds(block) != 1)
395 projx = get_Block_cfgpred(block, 0);
398 assert(get_irn_mode(projx) == mode_X);
400 cond = get_Proj_pred(projx);
404 pred = get_Cond_selector(cond);
405 // TODO handle switches
406 if (get_irn_mode(pred) != mode_b)
410 pnc = get_Proj_proj(pred);
412 cmp = get_Proj_pred(pred);
415 left = get_Cmp_left(cmp);
416 right = get_Cmp_right(cmp);
417 assert(get_irn_mode(left) == get_irn_mode(right));
419 /* we assume that the cond_block is the true case */
420 if (get_Proj_proj(projx) == pn_Cond_false) {
421 pnc = get_negated_pnc(pnc, get_irn_mode(left));
424 /* we assume that the constant is on the right side, swap left/right
431 pnc = get_inversed_pnc(pnc);
437 cond_block = get_nodes_block(cond);
439 // special case: comparing a constant with a constant
441 tarval *tv1 = get_Const_tarval(left);
442 tarval *tv2 = get_Const_tarval(right);
444 if(eval_cmp(pnc, tv1, tv2)) {
445 pred = new_r_Jmp(irg, cond_block);
449 set_Block_cfgpred(block, 0, pred);
451 set_irg_doms_inconsistent(irg);
452 set_irg_extblk_inconsistent(irg);
453 set_irg_loopinfo_inconsistent(irg);
455 if(get_nodes_block(left) != cond_block)
458 // (recursively) look if a pred of a phi is a constant
459 env.true_block = block;
462 inc_irg_visited(current_ir_graph);
463 env.visited_nr = get_irg_visited(irg);
465 copy_block = find_phi_with_const(projx, left, &env);
467 if(copy_block != NULL) {
468 /* we have to remove the edge towards the pred as the pred now
469 * jumps into the true_block. We also have to shorten phis
470 * in our block because of this */
471 const ir_edge_t *edge, *next;
472 ir_node* bad = new_Bad();
473 size_t cnst_pos = env.cnst_pos;
476 foreach_out_edge_safe(env.cnst_pred, edge, next) {
477 ir_node *node = get_edge_src_irn(edge);
480 set_Phi_pred(node, cnst_pos, bad);
483 set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
485 /* the graph is changed now */
491 void opt_cond_eval(ir_graph* irg)
495 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
497 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
499 remove_critical_cf_edges(irg);
500 normalize_proj_nodes(irg);
503 set_using_irn_link(irg);
504 set_using_visited(irg);
509 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
514 /* control flow changed, some blocks may become dead */
515 set_irg_doms_inconsistent(irg);
516 set_irg_extblk_inconsistent(irg);
517 set_irg_loopinfo_inconsistent(irg);
520 clear_using_visited(irg);
521 clear_using_irn_link(irg);