3 * File name: ir/opt/cfopt.c
4 * Purpose: Partial condition evaluation
5 * Author: Christoph Mallon, Matthias Braun
6 * Created: 10. Sep. 2006
8 * Copyright: (c) 1998-2006 Universität Karlsruhe
9 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
26 #include "iredges_t.h"
31 DEBUG_ONLY(static firm_dbg_module_t *dbg);
34 * Add the new predecessor x to node node, which is either a Block or a Phi
36 static void add_pred(ir_node* node, ir_node* x)
42 assert(is_Block(node) || is_Phi(node));
44 n = get_irn_arity(node);
45 NEW_ARR_A(ir_node*, ins, n + 1);
46 for (i = 0; i < n; i++)
47 ins[i] = get_irn_n(node, i);
49 set_irn_in(node, n + 1, ins);
53 * Remove predecessor j from node, which is either a Block or a Phi
54 * returns true if only one predecessor is left
56 static int remove_pred(ir_node* node, int j)
60 assert(is_Block(node) || is_Phi(node));
62 n = get_irn_arity(node);
64 ir_node* pred = get_irn_n(node, 1 - j);
67 pred = get_nodes_block(pred);
68 edges_reroute(node, pred, current_ir_graph);
77 NEW_ARR_A(ir_node*, ins, n - 1);
78 for (i = 0; i < j; i++)
79 ins[i] = get_irn_n(node, i);
81 ins[i - 1] = get_irn_n(node, i);
83 set_irn_in(node, n - 1, ins);
88 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
96 // This is needed because we create bads sometimes
100 // already processed this block?
101 if(irn_visited(block)) {
102 ir_node *value = (ir_node*) get_irn_link(block);
106 // blocks with only 1 pred need 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);
112 set_irn_link(block, value);
113 mark_irn_visited(block);
118 NEW_ARR_A(ir_node*, in, n_cfgpreds);
119 for(i = 0; i < n_cfgpreds; ++i)
120 in[i] = new_Unknown(mode);
122 irg = get_irn_irg(block);
123 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
124 set_irn_link(block, phi);
125 mark_irn_visited(block);
128 for(i = 0; i < n_cfgpreds; ++i) {
129 ir_node *pred_block = get_Block_cfgpred_block(block, i);
130 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
132 set_irn_n(phi, i, pred_val);
139 * Given a set of values this function constructs SSA-form for the users of the
140 * first value (the users are determined through the out-edges of the value).
141 * Uses the irn_visited flags. Works without using the dominance tree.
143 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
148 const ir_edge_t *edge;
149 const ir_edge_t *next;
154 irg = get_irn_irg(vals[0]);
155 inc_irg_visited(irg);
157 mode = get_irn_mode(vals[0]);
158 for(i = 0; i < n_vals; ++i) {
159 ir_node *value = vals[i];
160 ir_node *value_block = blocks[i];
162 assert(get_irn_mode(value) == mode);
164 set_irn_link(value_block, value);
165 mark_irn_visited(value_block);
168 // Only fix the users of the first, i.e. the original node
171 // this can happen when fixing phi preds, we mustn't fix the users
172 if(get_nodes_block(value) != blocks[0]) return;
174 foreach_out_edge_safe(value, edge, next) {
175 ir_node *user = get_edge_src_irn(edge);
176 int j = get_edge_src_pos(edge);
177 ir_node *user_block = get_nodes_block(user);
181 if(get_irn_op(user) == op_End)
184 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
187 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
188 newval = search_def_and_create_phis(pred_block, mode);
190 newval = search_def_and_create_phis(user_block, mode);
193 // don't fix newly created phis from the SSA construction
194 if (newval != user) {
195 DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
196 set_irn_n(user, j, newval);
201 static void split_critical_edge(ir_node *block, int pos) {
202 ir_graph *irg = get_irn_irg(block);
207 in[0] = get_Block_cfgpred(block, pos);
208 new_block = new_r_Block(irg, 1, in);
209 new_jmp = new_r_Jmp(irg, new_block);
210 set_Block_cfgpred(block, pos, new_jmp);
213 typedef struct _condeval_env_t {
217 unsigned long visited_nr;
219 ir_node *cnst_pred; /**< the block before the constant */
220 int cnst_pos; /**< the pos to the constant block (needed to kill that edge later) */
223 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
224 const ir_edge_t *edge;
226 /* Look at all nodes in the cond_block and copy them into pred */
227 foreach_out_edge(block, edge) {
228 ir_node *node = get_edge_src_irn(edge);
230 ir_mode *mode = get_irn_mode(node);
232 /* ignore control flow */
235 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
236 be handled in all backends. Instead we duplicate the node and move it to it's users */
237 if (mode == mode_b) {
238 const ir_edge_t *edge, *next;
242 assert(is_Proj(node));
244 pred = get_Proj_pred(node);
245 pn = get_Proj_proj(node);
247 foreach_out_edge_safe(node, edge, next) {
249 ir_node *user = get_edge_src_irn(edge);
250 int pos = get_edge_src_pos(edge);
251 ir_node *user_block = get_nodes_block(user);
253 if(user_block == block)
256 cmp_copy = exact_copy(pred);
257 set_nodes_block(cmp_copy, user_block);
258 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
259 set_irn_n(user, pos, copy);
264 /* we can evaluate Phis right now, all other nodes get copied */
266 copy = get_Phi_pred(node, j);
268 copy = exact_copy(node);
269 set_nodes_block(copy, copy_block);
272 set_irn_link(node, copy);
273 set_irn_visited(node, env->visited_nr);
275 /* we might hit values in blocks that have already been processed by a
276 * recursive find_phi_with_const call */
277 assert(get_irn_visited(copy) <= env->visited_nr);
278 if(get_irn_visited(copy) >= env->visited_nr) {
279 ir_node *prev_copy = get_irn_link(copy);
280 if(prev_copy != NULL)
281 set_irn_link(node, prev_copy);
285 /* fix data-flow (and reconstruct SSA if needed) */
286 foreach_out_edge(block, edge) {
289 ir_node *node = get_edge_src_irn(edge);
290 ir_mode *mode = get_irn_mode(node);
297 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
301 blocks[1] = copy_block;
302 vals[1] = get_irn_link(node);
303 construct_ssa(blocks, vals, 2);
307 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
308 pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
310 // does the compare evaluate to true?
311 if(cmp_result == pn_Cmp_False)
313 if((cmp_result & pnc) != cmp_result)
319 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
320 ir_node *block = get_nodes_block(jump);
322 if(irn_visited(value))
324 mark_irn_visited(value);
326 if(is_Const(value)) {
327 tarval *tv_const = get_Const_tarval(env->cnst);
328 tarval *tv = get_Const_tarval(value);
330 if(!eval_cmp(env->pnc, tv, tv_const))
335 "> Found condition evaluation candidate %+F->%+F\n",
336 env->true_block, block
339 // adjust true_block to point directly towards our jump
340 add_pred(env->true_block, jump);
342 split_critical_edge(env->true_block, 0);
344 // we need a bigger visited nr when going back
353 // the phi has to be in the same block as the jump
354 if(get_nodes_block(value) != block)
357 arity = get_irn_arity(value);
358 for(i = 0; i < arity; ++i) {
360 ir_node *phi_pred = get_Phi_pred(value, i);
361 ir_node *cfgpred = get_Block_cfgpred(block, i);
363 copy_block = find_phi_with_const(cfgpred, phi_pred, env);
364 if(copy_block == NULL)
367 /* copy duplicated nodes in copy_block and fix SSA */
368 copy_and_fix(block, copy_block, i, env);
370 if(copy_block == get_nodes_block(cfgpred)) {
371 env->cnst_pred = block;
375 // return now as we can't process more possibilities in 1 run
385 * Block-walker: searchs for the following construct
387 * Const or Phi with constants
397 static void cond_eval(ir_node* block, void* data)
401 ir_graph *irg = current_ir_graph;
412 if(get_Block_n_cfgpreds(block) != 1)
415 projx = get_Block_cfgpred(block, 0);
418 assert(get_irn_mode(projx) == mode_X);
420 cond = get_Proj_pred(projx);
424 pred = get_Cond_selector(cond);
425 // TODO handle switches
426 if (get_irn_mode(pred) != mode_b)
430 pnc = get_Proj_proj(pred);
432 cmp = get_Proj_pred(pred);
435 left = get_Cmp_left(cmp);
436 right = get_Cmp_right(cmp);
437 assert(get_irn_mode(left) == get_irn_mode(right));
439 /* we assume that the cond_block is the true case */
440 if (get_Proj_proj(projx) == pn_Cond_false) {
441 pnc = get_negated_pnc(pnc, get_irn_mode(left));
444 /* we assume that the constant is on the right side, swap left/right
451 pnc = get_inversed_pnc(pnc);
457 cond_block = get_nodes_block(cond);
459 // special case: comparing a constant with a constant
461 tarval *tv1 = get_Const_tarval(left);
462 tarval *tv2 = get_Const_tarval(right);
464 if(eval_cmp(pnc, tv1, tv2)) {
465 pred = new_r_Jmp(irg, cond_block);
469 set_Block_cfgpred(block, 0, pred);
471 set_irg_doms_inconsistent(irg);
472 set_irg_extblk_inconsistent(irg);
473 set_irg_loopinfo_inconsistent(irg);
475 if(get_nodes_block(left) != cond_block)
478 // (recursively) look if a pred of a phi is a constant
479 env.true_block = block;
482 inc_irg_visited(current_ir_graph);
483 env.visited_nr = get_irg_visited(irg);
485 copy_block = find_phi_with_const(projx, left, &env);
487 if(copy_block != NULL) {
488 /* we have to remove the edge towards the pred as the pred now
489 * jumps into the true_block. We also have to shorten phis
490 * in our block because of this */
491 const ir_edge_t *edge, *next;
494 foreach_out_edge_safe(env.cnst_pred, edge, next) {
495 ir_node *node = get_edge_src_irn(edge);
498 remove_pred(node, env.cnst_pos);
501 remove_pred(env.cnst_pred, env.cnst_pos);
503 // the graph is changed now
505 set_irg_doms_inconsistent(irg);
506 set_irg_extblk_inconsistent(irg);
507 set_irg_loopinfo_inconsistent(irg);
512 void opt_cond_eval(ir_graph* irg)
516 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
518 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
521 remove_critical_cf_edges(irg);
523 normalize_proj_nodes(irg);
525 set_using_irn_link(irg);
526 set_using_visited(irg);
530 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
533 clear_using_visited(irg);
534 clear_using_irn_link(irg);