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 assert(!is_Bad(block));
97 // already processed this block?
98 if(irn_visited(block)) {
99 ir_node *value = (ir_node*) get_irn_link(block);
103 // blocks with only 1 pred need no phi
104 n_cfgpreds = get_Block_n_cfgpreds(block);
105 if(n_cfgpreds == 1) {
106 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
107 ir_node *value = search_def_and_create_phis(pred_block, mode);
109 set_irn_link(block, value);
110 mark_irn_visited(block);
115 in = alloca(sizeof(in[0]) * n_cfgpreds);
116 for(i = 0; i < n_cfgpreds; ++i)
117 in[i] = new_Unknown(mode);
119 irg = get_irn_irg(block);
120 phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
121 set_irn_link(block, phi);
122 mark_irn_visited(block);
125 for(i = 0; i < n_cfgpreds; ++i) {
126 ir_node *pred_block = get_Block_cfgpred_block(block, i);
129 pred_val = search_def_and_create_phis(pred_block, mode);
130 set_irn_n(phi, i, pred_val);
137 * Given a set of values this function constructs SSA-form for all users of the
138 * values (the user are determined through the out-edges of the values). Uses
139 * the irn_visited flags. Works without using the dominance tree.
141 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
149 irg = get_irn_irg(vals[0]);
150 inc_irg_visited(irg);
152 mode = get_irn_mode(vals[0]);
153 for(i = 0; i < n_vals; ++i) {
154 ir_node *value = vals[i];
155 ir_node *value_block = blocks[i];
157 assert(get_irn_mode(value) == mode);
159 set_irn_link(value_block, value);
160 mark_irn_visited(value_block);
163 for(i = 0; i < n_vals; ++i) {
164 const ir_edge_t *edge, *next;
165 ir_node *value = vals[i];
167 // this can happen when fixing phi preds, we mustn't fix the users
168 if(get_nodes_block(value) != blocks[i]) {
172 foreach_out_edge_safe(value, edge, next) {
173 ir_node *user = get_edge_src_irn(edge);
174 int j = get_edge_src_pos(edge);
175 ir_node *user_block = get_nodes_block(user);
179 if(get_irn_op(user) == op_End)
183 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
184 newval = search_def_and_create_phis(pred_block, mode);
186 newval = search_def_and_create_phis(user_block, mode);
189 // don't fix newly created phis from the SSA construction
191 set_irn_n(user, j, newval);
196 static void split_critical_edge(ir_node *block, int pos) {
197 ir_graph *irg = get_irn_irg(block);
202 in[0] = get_Block_cfgpred(block, pos);
203 new_block = new_r_Block(irg, 1, in);
204 new_jmp = new_r_Jmp(irg, new_block);
205 set_Block_cfgpred(block, pos, new_jmp);
208 typedef struct _condeval_env_t {
212 unsigned long visited_nr;
214 ir_node *cnst_pred; /**< the block before the constant */
215 int cnst_pos; /**< the pos to the constant block (needed to kill that edge later) */
218 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
219 const ir_edge_t *edge;
221 /* Look at all nodes in the cond_block and copy them into pred */
222 foreach_out_edge(block, edge) {
223 ir_node *node = get_edge_src_irn(edge);
226 /* ignore control flow */
227 if (get_irn_mode(node) == mode_X)
230 /* we can evaluate Phis right now, all other nodes get copied */
232 copy = get_Phi_pred(node, j);
234 copy = exact_copy(node);
235 set_nodes_block(copy, copy_block);
238 set_irn_link(node, copy);
239 set_irn_visited(node, env->visited_nr);
241 /* we might hit values in blocks that have already been processed by a
242 * recursive find_phi_with_const call */
243 assert(get_irn_visited(copy) <= env->visited_nr);
244 if(get_irn_visited(copy) >= env->visited_nr) {
245 ir_node *prev_copy = get_irn_link(copy);
246 if(prev_copy != NULL)
247 set_irn_link(node, prev_copy);
251 /* fix data-flow (and reconstruct SSA if needed) */
252 foreach_out_edge(block, edge) {
256 ir_node *node = get_edge_src_irn(edge);
258 if (get_irn_mode(node) == mode_X)
263 blocks[1] = copy_block;
264 vals[1] = get_irn_link(node);
265 construct_ssa(blocks, vals, 2);
269 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
270 pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
272 // does the compare evaluate to true?
273 if(cmp_result == pn_Cmp_False)
275 if((cmp_result & pnc) != cmp_result)
281 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
282 ir_node *block = get_nodes_block(jump);
284 if(irn_visited(value))
286 mark_irn_visited(value);
288 if(is_Const(value)) {
289 tarval *tv_const = get_Const_tarval(env->cnst);
290 tarval *tv = get_Const_tarval(value);
292 if(!eval_cmp(env->pnc, tv, tv_const))
297 "> Found condition evaluation candidate %+F->%+F\n",
298 env->true_block, block
301 // adjust true_block to point directly towards our jump
302 add_pred(env->true_block, jump);
304 split_critical_edge(env->true_block, 0);
306 // we need a bigger visited nr when going back
315 // the phi has to be in the same block as the jump
316 if(get_nodes_block(value) != block)
319 arity = get_irn_arity(value);
320 for(i = 0; i < arity; ++i) {
322 ir_node *phi_pred = get_Phi_pred(value, i);
323 ir_node *cfgpred = get_Block_cfgpred(block, i);
325 copy_block = find_phi_with_const(cfgpred, phi_pred, env);
326 if(copy_block == NULL)
329 /* copy duplicated nodes in copy_block and fix SSA */
330 copy_and_fix(block, copy_block, i, env);
332 if(copy_block == get_nodes_block(cfgpred)) {
333 env->cnst_pred = block;
337 // return now as we can't process more possibilities in 1 run
347 * Block-walker: searchs for the following construct
349 * Const or Phi with constants
359 static void cond_eval(ir_node* block, void* data)
363 ir_graph *irg = current_ir_graph;
374 if(get_Block_n_cfgpreds(block) != 1)
377 projx = get_Block_cfgpred(block, 0);
380 assert(get_irn_mode(projx) == mode_X);
382 cond = get_Proj_pred(projx);
386 pred = get_Cond_selector(cond);
387 // TODO handle switches
388 if (get_irn_mode(pred) != mode_b)
392 pnc = get_Proj_proj(pred);
394 cmp = get_Proj_pred(pred);
397 left = get_Cmp_left(cmp);
398 right = get_Cmp_right(cmp);
399 assert(get_irn_mode(left) == get_irn_mode(right));
401 /* we assume that the cond_block is the true case */
402 if (get_Proj_proj(projx) == pn_Cond_false) {
403 pnc = get_negated_pnc(pnc, get_irn_mode(left));
406 /* we assume that the constant is on the right side, swap left/right
413 pnc = get_inversed_pnc(pnc);
419 cond_block = get_nodes_block(cond);
421 // special case: comparing a constant with a constant
423 tarval *tv1 = get_Const_tarval(left);
424 tarval *tv2 = get_Const_tarval(right);
425 if(eval_cmp(pnc, tv1, tv2)) {
426 ir_node *jmp = new_r_Jmp(irg, cond_block);
427 set_Block_cfgpred(block, 0, jmp);
429 set_Block_cfgpred(block, 0, new_Bad());
432 set_irg_doms_inconsistent(irg);
433 set_irg_extblk_inconsistent(irg);
434 set_irg_loopinfo_inconsistent(irg);
436 if(get_nodes_block(left) != cond_block)
439 // (recursively) look if a pred of a phi is a constant
440 env.true_block = block;
443 inc_irg_visited(current_ir_graph);
444 env.visited_nr = get_irg_visited(irg);
446 copy_block = find_phi_with_const(projx, left, &env);
448 if(copy_block != NULL) {
449 /* we have to remove the edge towards the pred as the pred now
450 * jumps into the true_block. We also have to shorten phis
451 * in our block because of this */
452 const ir_edge_t *edge, *next;
455 foreach_out_edge_safe(env.cnst_pred, edge, next) {
456 ir_node *node = get_edge_src_irn(edge);
459 remove_pred(node, env.cnst_pos);
462 remove_pred(env.cnst_pred, env.cnst_pos);
464 // the graph is changed now
466 set_irg_doms_inconsistent(irg);
467 set_irg_extblk_inconsistent(irg);
468 set_irg_loopinfo_inconsistent(irg);
473 void opt_cond_eval(ir_graph* irg)
477 FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
478 //firm_dbg_set_mask(dbg, SET_LEVEL_5);
480 DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
483 remove_critical_cf_edges(irg);
485 normalize_proj_nodes(irg);
489 irg_block_walk_graph(irg, cond_eval, NULL, &changed);