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"
30 DEBUG_ONLY(static firm_dbg_module_t *dbg);
33 * Add the new predecessor x to node node, which is either a Block or a Phi
35 static void add_pred(ir_node* node, ir_node* x)
41 assert(is_Block(node) || is_Phi(node));
43 n = get_irn_arity(node);
44 NEW_ARR_A(ir_node*, ins, n + 1);
45 for (i = 0; i < n; i++)
46 ins[i] = get_irn_n(node, i);
48 set_irn_in(node, n + 1, ins);
52 * Remove predecessor j from node, which is either a Block or a Phi
53 * returns true if only one predecessor is left
55 static int remove_pred(ir_node* node, int j)
59 assert(is_Block(node) || is_Phi(node));
61 n = get_irn_arity(node);
63 ir_node* pred = get_irn_n(node, 1 - j);
66 pred = get_nodes_block(pred);
67 edges_reroute(node, pred, current_ir_graph);
76 NEW_ARR_A(ir_node*, ins, n - 1);
77 for (i = 0; i < j; i++)
78 ins[i] = get_irn_n(node, i);
80 ins[i - 1] = get_irn_n(node, i);
82 set_irn_in(node, n - 1, ins);
87 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
95 // This is needed because we create bads sometimes
99 // already processed this block?
100 if(irn_visited(block)) {
101 ir_node *value = (ir_node*) get_irn_link(block);
105 // blocks with only 1 pred need 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);
111 set_irn_link(block, value);
112 mark_irn_visited(block);
117 in = alloca(sizeof(in[0]) * n_cfgpreds);
118 for(i = 0; i < n_cfgpreds; ++i)
119 in[i] = new_Unknown(mode);
121 irg = get_irn_irg(block);
122 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
123 set_irn_link(block, phi);
124 mark_irn_visited(block);
127 for(i = 0; i < n_cfgpreds; ++i) {
128 ir_node *pred_block = get_Block_cfgpred_block(block, i);
131 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 all users of the
140 * values (the user are determined through the out-edges of the values). Uses
141 * 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)
151 irg = get_irn_irg(vals[0]);
152 inc_irg_visited(irg);
154 mode = get_irn_mode(vals[0]);
155 for(i = 0; i < n_vals; ++i) {
156 ir_node *value = vals[i];
157 ir_node *value_block = blocks[i];
159 assert(get_irn_mode(value) == mode);
161 set_irn_link(value_block, value);
162 mark_irn_visited(value_block);
165 for(i = 0; i < n_vals; ++i) {
166 const ir_edge_t *edge, *next;
167 ir_node *value = vals[i];
169 // this can happen when fixing phi preds, we mustn't fix the users
170 if(get_nodes_block(value) != blocks[i]) {
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)
185 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
186 newval = search_def_and_create_phis(pred_block, mode);
188 newval = search_def_and_create_phis(user_block, mode);
191 // don't fix newly created phis from the SSA construction
193 set_irn_n(user, j, newval);
198 static void split_critical_edge(ir_node *block, int pos) {
199 ir_graph *irg = get_irn_irg(block);
204 in[0] = get_Block_cfgpred(block, pos);
205 new_block = new_r_Block(irg, 1, in);
206 new_jmp = new_r_Jmp(irg, new_block);
207 set_Block_cfgpred(block, pos, new_jmp);
210 typedef struct _condeval_env_t {
214 unsigned long visited_nr;
216 ir_node *cnst_pred; /**< the block before the constant */
217 int cnst_pos; /**< the pos to the constant block (needed to kill that edge later) */
220 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
221 const ir_edge_t *edge;
223 /* Look at all nodes in the cond_block and copy them into pred */
224 foreach_out_edge(block, edge) {
225 ir_node *node = get_edge_src_irn(edge);
228 /* ignore control flow */
229 if (get_irn_mode(node) == mode_X)
232 /* we can evaluate Phis right now, all other nodes get copied */
234 copy = get_Phi_pred(node, j);
236 copy = exact_copy(node);
237 set_nodes_block(copy, copy_block);
240 set_irn_link(node, copy);
241 set_irn_visited(node, env->visited_nr);
243 /* we might hit values in blocks that have already been processed by a
244 * recursive find_phi_with_const call */
245 assert(get_irn_visited(copy) <= env->visited_nr);
246 if(get_irn_visited(copy) >= env->visited_nr) {
247 ir_node *prev_copy = get_irn_link(copy);
248 if(prev_copy != NULL)
249 set_irn_link(node, prev_copy);
253 /* fix data-flow (and reconstruct SSA if needed) */
254 foreach_out_edge(block, edge) {
258 ir_node *node = get_edge_src_irn(edge);
260 if (get_irn_mode(node) == mode_X)
265 blocks[1] = copy_block;
266 vals[1] = get_irn_link(node);
267 construct_ssa(blocks, vals, 2);
271 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
272 pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
274 // does the compare evaluate to true?
275 if(cmp_result == pn_Cmp_False)
277 if((cmp_result & pnc) != cmp_result)
283 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
284 ir_node *block = get_nodes_block(jump);
286 if(irn_visited(value))
288 mark_irn_visited(value);
290 if(is_Const(value)) {
291 tarval *tv_const = get_Const_tarval(env->cnst);
292 tarval *tv = get_Const_tarval(value);
294 if(!eval_cmp(env->pnc, tv, tv_const))
299 "> Found condition evaluation candidate %+F->%+F\n",
300 env->true_block, block
303 // adjust true_block to point directly towards our jump
304 add_pred(env->true_block, jump);
306 split_critical_edge(env->true_block, 0);
308 // we need a bigger visited nr when going back
317 // the phi has to be in the same block as the jump
318 if(get_nodes_block(value) != block)
321 arity = get_irn_arity(value);
322 for(i = 0; i < arity; ++i) {
324 ir_node *phi_pred = get_Phi_pred(value, i);
325 ir_node *cfgpred = get_Block_cfgpred(block, i);
327 copy_block = find_phi_with_const(cfgpred, phi_pred, env);
328 if(copy_block == NULL)
331 /* copy duplicated nodes in copy_block and fix SSA */
332 copy_and_fix(block, copy_block, i, env);
334 if(copy_block == get_nodes_block(cfgpred)) {
335 env->cnst_pred = block;
339 // return now as we can't process more possibilities in 1 run
349 * Block-walker: searchs for the following construct
351 * Const or Phi with constants
361 static void cond_eval(ir_node* block, void* data)
365 ir_graph *irg = current_ir_graph;
376 if(get_Block_n_cfgpreds(block) != 1)
379 projx = get_Block_cfgpred(block, 0);
382 assert(get_irn_mode(projx) == mode_X);
384 cond = get_Proj_pred(projx);
388 pred = get_Cond_selector(cond);
389 // TODO handle switches
390 if (get_irn_mode(pred) != mode_b)
394 pnc = get_Proj_proj(pred);
396 cmp = get_Proj_pred(pred);
399 left = get_Cmp_left(cmp);
400 right = get_Cmp_right(cmp);
401 assert(get_irn_mode(left) == get_irn_mode(right));
403 /* we assume that the cond_block is the true case */
404 if (get_Proj_proj(projx) == pn_Cond_false) {
405 pnc = get_negated_pnc(pnc, get_irn_mode(left));
408 /* we assume that the constant is on the right side, swap left/right
415 pnc = get_inversed_pnc(pnc);
421 cond_block = get_nodes_block(cond);
423 // special case: comparing a constant with a constant
425 tarval *tv1 = get_Const_tarval(left);
426 tarval *tv2 = get_Const_tarval(right);
428 if(eval_cmp(pnc, tv1, tv2)) {
429 pred = new_r_Jmp(irg, cond_block);
433 set_Block_cfgpred(block, 0, pred);
435 set_irg_doms_inconsistent(irg);
436 set_irg_extblk_inconsistent(irg);
437 set_irg_loopinfo_inconsistent(irg);
439 if(get_nodes_block(left) != cond_block)
442 // (recursively) look if a pred of a phi is a constant
443 env.true_block = block;
446 inc_irg_visited(current_ir_graph);
447 env.visited_nr = get_irg_visited(irg);
449 copy_block = find_phi_with_const(projx, left, &env);
451 if(copy_block != NULL) {
452 /* we have to remove the edge towards the pred as the pred now
453 * jumps into the true_block. We also have to shorten phis
454 * in our block because of this */
455 const ir_edge_t *edge, *next;
458 foreach_out_edge_safe(env.cnst_pred, edge, next) {
459 ir_node *node = get_edge_src_irn(edge);
462 remove_pred(node, env.cnst_pos);
465 remove_pred(env.cnst_pred, env.cnst_pos);
467 // the graph is changed now
469 set_irg_doms_inconsistent(irg);
470 set_irg_extblk_inconsistent(irg);
471 set_irg_loopinfo_inconsistent(irg);
476 void opt_cond_eval(ir_graph* irg)
480 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
481 //firm_dbg_set_mask(dbg, SET_LEVEL_5);
483 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
486 remove_critical_cf_edges(irg);
488 normalize_proj_nodes(irg);
492 irg_block_walk_graph(irg, cond_eval, NULL, &changed);