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4 * This file is part of libFirm.
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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
21 * @file ir/opt/ifconv.c
22 * @brief If conversion
23 * @author Christoph Mallon
31 #include "iroptimize.h"
48 * Environment for if-conversion.
50 typedef struct walker_env {
51 arch_allow_ifconv_func allow_ifconv;
52 bool changed; /**< Set if the graph was changed. */
55 DEBUG_ONLY(static firm_dbg_module_t *dbg);
58 * Returns non-zero if a Block can be emptied.
60 * @param block the block
62 static bool can_empty_block(ir_node *block)
64 return get_Block_mark(block) == 0;
68 * Find the ProjX node leading from block dependency to block start.
70 * @param start a block that is control depended on dependency
71 * @param dependency the block that decides whether start is executed
73 * @return a ProjX node that represent the decision control flow or
74 * NULL is start is not dependent at all or a block on the way
77 static ir_node* walk_to_projx(ir_node* start, const ir_node* dependency)
82 /* No need to find the conditional block if this block cannot be emptied and
83 * therefore not moved */
84 if (!can_empty_block(start)) return NULL;
86 arity = get_irn_arity(start);
87 for (i = 0; i < arity; ++i) {
88 ir_node* pred = get_irn_n(start, i);
89 ir_node* pred_block = get_nodes_block(skip_Proj(pred));
91 if (pred_block == dependency) {
93 assert(get_irn_mode(pred) == mode_X);
97 /* Not a Proj? Should not happen. */
102 assert(get_irn_mode(pred) == mode_X);
103 /* another Proj but not from the control block */
107 if (is_cdep_on(pred_block, dependency)) {
108 return walk_to_projx(pred_block, dependency);
116 * Recursively copies the DAG starting at node to the i-th predecessor
118 * - if node isn't in the src_block, recursion ends and node is returned
119 * - if node is a Phi in the src_block, the i-th predecessor of this Phi is
120 * returned and recursion ends
121 * otherwise returns a copy of the passed node created in the i-th predecessor of
124 * @param node a root of a DAG
125 * @param src_block the block of the DAG
126 * @param i the position of the predecessor the DAG
129 * @return the root of the copied DAG
131 static ir_node* copy_to(ir_node* node, ir_node* src_block, int i)
137 if (get_nodes_block(node) != src_block) {
138 /* already outside src_block, do not copy */
142 /* move through the Phi to the i-th predecessor */
143 return get_irn_n(node, i);
146 /* else really need a copy */
147 copy = exact_copy(node);
148 dst_block = get_nodes_block(get_irn_n(src_block, i));
149 set_nodes_block(copy, dst_block);
151 DB((dbg, LEVEL_1, "Copying node %+F to block %+F, copy is %+F\n",
152 node, dst_block, copy));
154 /* move recursively all predecessors */
155 for (j = get_irn_arity(node) - 1; j >= 0; --j) {
156 set_irn_n(copy, j, copy_to(get_irn_n(node, j), src_block, i));
157 DB((dbg, LEVEL_2, "-- pred %d is %+F\n", j, get_irn_n(copy, j)));
164 * Remove predecessors i and j (i < j) from a node and
165 * add an additional predecessor new_pred.
167 * @param node the node whose inputs are changed
168 * @param i the first index to remove
169 * @param j the second index to remove
170 * @param new_pred a node that is added as a new input to node
172 static void rewire(ir_node* node, int i, int j, ir_node* new_pred)
174 int arity = get_irn_arity(node);
179 NEW_ARR_A(ir_node *, ins, arity - 1);
182 for (k = 0; k < i; ++k) ins[l++] = get_irn_n(node, k);
183 for (++k; k < j; ++k) ins[l++] = get_irn_n(node, k);
184 for (++k; k < arity; ++k) ins[l++] = get_irn_n(node, k);
186 assert(l == arity - 1);
187 set_irn_in(node, l, ins);
192 * Remove the j-th predecessor from the i-th predecessor of block and add it to block
194 static void split_block(ir_node* block, int i, int j)
196 ir_node *pred_block = get_nodes_block(get_irn_n(block, i));
197 int arity = get_irn_arity(block);
198 ir_node **ins = ALLOCAN(ir_node*, arity + 1);
205 DB((dbg, LEVEL_1, "Splitting predecessor %d of predecessor %d of %+F\n", j, i, block));
207 for (phi = get_Block_phis(block); phi != NULL; phi = get_Phi_next(phi)) {
208 ir_node* copy = copy_to(get_irn_n(phi, i), pred_block, j);
210 for (k = 0; k < i; ++k) ins[k] = get_irn_n(phi, k);
212 for (; k < arity; ++k) ins[k] = get_irn_n(phi, k);
213 ins[k++] = get_irn_n(phi, i);
214 set_irn_in(phi, k, ins);
217 for (k = 0; k < i; ++k) ins[k] = get_irn_n(block, k);
218 ins[k++] = get_irn_n(pred_block, j);
219 for (; k < arity; ++k) ins[k] = get_irn_n(block, k);
220 ins[k++] = get_irn_n(block, i);
221 set_irn_in(block, k, ins);
223 new_pred_arity = get_irn_arity(pred_block) - 1;
224 pred_ins = ALLOCAN(ir_node*, new_pred_arity);
226 for (phi = get_Block_phis(pred_block); phi != NULL; phi = next) {
227 next = get_Phi_next(phi);
228 for (k = 0; k != j; ++k) pred_ins[k] = get_irn_n(phi, k);
229 for (; k != new_pred_arity; ++k) pred_ins[k] = get_irn_n(phi, k + 1);
231 exchange(phi, pred_ins[0]);
233 set_irn_in(phi, k, pred_ins);
237 for (k = 0; k != j; ++k) pred_ins[k] = get_irn_n(pred_block, k);
238 for (; k != new_pred_arity; ++k) pred_ins[k] = get_irn_n(pred_block, k + 1);
240 exchange(pred_block, get_nodes_block(pred_ins[0]));
242 set_irn_in(pred_block, k, pred_ins);
247 static void prepare_path(ir_node* block, int i, const ir_node* dependency)
249 ir_node* pred = get_nodes_block(get_irn_n(block, i));
253 DB((dbg, LEVEL_1, "Preparing predecessor %d of %+F\n", i, block));
255 pred_arity = get_irn_arity(pred);
256 for (j = 0; j < pred_arity; ++j) {
257 ir_node* pred_pred = get_nodes_block(get_irn_n(pred, j));
259 if (pred_pred != dependency && is_cdep_on(pred_pred, dependency)) {
260 prepare_path(pred, j, dependency);
261 split_block(block, i, j);
268 * Block walker: Search for diamonds and do the if conversion.
270 static void if_conv_walker(ir_node *block, void *ctx)
272 walker_env *env = (walker_env*)ctx;
276 /* Bail out, if there are no Phis at all */
277 if (get_Block_phis(block) == NULL) return;
280 arity = get_irn_arity(block);
281 for (i = 0; i < arity; ++i) {
285 pred0 = get_Block_cfgpred_block(block, i);
286 for (cdep = find_cdep(pred0); cdep != NULL; cdep = get_cdep_next(cdep)) {
287 const ir_node* dependency = get_cdep_node(cdep);
288 ir_node* projx0 = walk_to_projx(pred0, dependency);
292 if (projx0 == NULL) continue;
294 cond = get_Proj_pred(projx0);
298 /* We only handle boolean decisions, no switches */
299 if (get_irn_mode(get_Cond_selector(cond)) != mode_b) continue;
301 for (j = i + 1; j < arity; ++j) {
312 pred1 = get_Block_cfgpred_block(block, j);
314 if (!is_cdep_on(pred1, dependency)) continue;
316 projx1 = walk_to_projx(pred1, dependency);
318 if (projx1 == NULL) continue;
320 sel = get_Cond_selector(cond);
321 phi = get_Block_phis(block);
323 negated = get_Proj_proj(projx0) == pn_Cond_false;
324 for (p = phi; p != NULL; p = get_Phi_next(p)) {
328 mux_true = get_Phi_pred(p, j);
329 mux_false = get_Phi_pred(p, i);
331 mux_true = get_Phi_pred(p, i);
332 mux_false = get_Phi_pred(p, j);
334 if (!env->allow_ifconv(sel, mux_false, mux_true)) {
342 DB((dbg, LEVEL_1, "Found Cond %+F with proj %+F and %+F\n",
346 /* remove critical edges */
348 prepare_path(block, i, dependency);
349 prepare_path(block, j, dependency);
350 arity = get_irn_arity(block);
352 mux_block = get_nodes_block(cond);
353 cond_dbg = get_irn_dbg_info(cond);
354 do { /* generate Mux nodes in mux_block for Phis in block */
355 ir_node* val_i = get_irn_n(phi, i);
356 ir_node* val_j = get_irn_n(phi, j);
360 if (val_i == val_j) {
362 DB((dbg, LEVEL_2, "Generating no Mux, because both values are equal\n"));
366 /* Something is very fishy if two predecessors of a PhiM point into
367 * one block, but not at the same memory node
369 assert(get_irn_mode(phi) != mode_M);
378 mux = new_rd_Mux(cond_dbg, mux_block, sel, f, t, get_irn_mode(phi));
379 DB((dbg, LEVEL_2, "Generating %+F for %+F\n", mux, phi));
382 next_phi = get_Phi_next(phi);
387 rewire(phi, i, j, mux);
390 } while (phi != NULL);
392 /* move mux operands into mux_block */
393 exchange(get_nodes_block(get_irn_n(block, i)), mux_block);
394 exchange(get_nodes_block(get_irn_n(block, j)), mux_block);
399 DB((dbg, LEVEL_1, "Welding block %+F and %+F\n", block, mux_block));
400 /* copy the block-info from the Mux-block to the block before merging */
402 mark = get_Block_mark(mux_block) | get_Block_mark(block);
403 set_Block_mark(block, mark);
404 set_Block_phis(block, get_Block_phis(mux_block));
406 set_irn_in(block, get_irn_arity(mux_block), get_irn_in(mux_block) + 1);
407 exchange_cdep(mux_block, block);
408 exchange(mux_block, block);
410 DB((dbg, LEVEL_1, "Welding block %+F to %+F\n", block, mux_block));
411 mark = get_Block_mark(mux_block) | get_Block_mark(block);
412 /* mark both block just to be sure, should be enough to mark mux_block */
413 set_Block_mark(mux_block, mark);
414 exchange(block, mux_block);
418 rewire(block, i, j, new_r_Jmp(mux_block));
427 * Block walker: clear block marks and Phi lists.
429 static void init_block_link(ir_node *block, void *env)
432 set_Block_mark(block, 0);
433 set_Block_phis(block, NULL);
438 * Daisy-chain all Phis in a block.
439 * If a non-movable node is encountered set the has_pinned flag in its block.
441 static void collect_phis(ir_node *node, void *env)
446 ir_node *block = get_nodes_block(node);
448 add_Block_phi(block, node);
450 if (!is_Block(node) && get_irn_pinned(node) == op_pin_state_pinned) {
452 * Ignore control flow nodes (except Raise), these will be removed.
454 if (!is_cfop(node) && !is_Raise(node)) {
455 ir_node *block = get_nodes_block(node);
457 DB((dbg, LEVEL_2, "Node %+F in block %+F is unmovable\n", node, block));
458 set_Block_mark(block, 1);
464 void opt_if_conv(ir_graph *irg)
467 const backend_params *be_params = be_get_backend_param();
469 /* get the parameters */
470 env.allow_ifconv = be_params->allow_ifconv;
473 FIRM_DBG_REGISTER(dbg, "firm.opt.ifconv");
475 DB((dbg, LEVEL_1, "Running if-conversion on %+F\n", irg));
477 normalize_one_return(irg);
478 remove_critical_cf_edges(irg);
482 ir_reserve_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_PHI_LIST);
484 irg_block_walk_graph(irg, init_block_link, NULL, NULL);
485 irg_walk_graph(irg, collect_phis, NULL, NULL);
486 irg_block_walk_graph(irg, NULL, if_conv_walker, &env);
488 ir_free_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_PHI_LIST);
491 local_optimize_graph(irg);
493 /* graph has changed, invalidate analysis info */
494 set_irg_outs_inconsistent(irg);
495 set_irg_extblk_inconsistent(irg);
496 set_irg_loopinfo_inconsistent(irg);
497 set_irg_doms_inconsistent(irg);
503 ir_graph_pass_t *opt_if_conv_pass(const char *name)
505 return def_graph_pass(name ? name : "ifconv", opt_if_conv);