2 * Copyright (C) 1995-2008 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
21 * @file ir/opt/ifconv.c
22 * @brief If conversion
23 * @author Christoph Mallon
31 #include "iroptimize.h"
43 #include "opt_manage.h"
49 * Environment for if-conversion.
51 typedef struct walker_env {
52 arch_allow_ifconv_func allow_ifconv;
53 bool changed; /**< Set if the graph was changed. */
56 DEBUG_ONLY(static firm_dbg_module_t *dbg);
59 * Returns non-zero if a Block can be emptied.
61 * @param block the block
63 static bool can_empty_block(ir_node *block)
65 return get_Block_mark(block) == 0;
69 * Find the ProjX node leading from block dependency to block start.
71 * @param start a block that is control depended on dependency
72 * @param dependency the block that decides whether start is executed
74 * @return a ProjX node that represent the decision control flow or
75 * NULL is start is not dependent at all or a block on the way
78 static ir_node* walk_to_projx(ir_node* start, const ir_node* dependency)
83 /* No need to find the conditional block if this block cannot be emptied and
84 * therefore not moved */
85 if (!can_empty_block(start)) return NULL;
87 arity = get_irn_arity(start);
88 for (i = 0; i < arity; ++i) {
89 ir_node* pred = get_irn_n(start, i);
90 ir_node* pred_block = get_nodes_block(skip_Proj(pred));
92 if (pred_block == dependency) {
94 assert(get_irn_mode(pred) == mode_X);
98 /* Not a Proj? Should not happen. */
103 assert(get_irn_mode(pred) == mode_X);
104 /* another Proj but not from the control block */
108 if (is_cdep_on(pred_block, dependency)) {
109 return walk_to_projx(pred_block, dependency);
117 * Recursively copies the DAG starting at node to the i-th predecessor
119 * - if node isn't in the src_block, recursion ends and node is returned
120 * - if node is a Phi in the src_block, the i-th predecessor of this Phi is
121 * returned and recursion ends
122 * otherwise returns a copy of the passed node created in the i-th predecessor of
125 * @param node a root of a DAG
126 * @param src_block the block of the DAG
127 * @param i the position of the predecessor the DAG
130 * @return the root of the copied DAG
132 static ir_node* copy_to(ir_node* node, ir_node* src_block, int i)
138 if (get_nodes_block(node) != src_block) {
139 /* already outside src_block, do not copy */
143 /* move through the Phi to the i-th predecessor */
144 return get_irn_n(node, i);
147 /* else really need a copy */
148 copy = exact_copy(node);
149 dst_block = get_nodes_block(get_irn_n(src_block, i));
150 set_nodes_block(copy, dst_block);
152 DB((dbg, LEVEL_1, "Copying node %+F to block %+F, copy is %+F\n",
153 node, dst_block, copy));
155 /* move recursively all predecessors */
156 for (j = get_irn_arity(node) - 1; j >= 0; --j) {
157 set_irn_n(copy, j, copy_to(get_irn_n(node, j), src_block, i));
158 DB((dbg, LEVEL_2, "-- pred %d is %+F\n", j, get_irn_n(copy, j)));
165 * Remove predecessors i and j (i < j) from a node and
166 * add an additional predecessor new_pred.
168 * @param node the node whose inputs are changed
169 * @param i the first index to remove
170 * @param j the second index to remove
171 * @param new_pred a node that is added as a new input to node
173 static void rewire(ir_node* node, int i, int j, ir_node* new_pred)
175 int arity = get_irn_arity(node);
180 NEW_ARR_A(ir_node *, ins, arity - 1);
183 for (k = 0; k < i; ++k) ins[l++] = get_irn_n(node, k);
184 for (++k; k < j; ++k) ins[l++] = get_irn_n(node, k);
185 for (++k; k < arity; ++k) ins[l++] = get_irn_n(node, k);
187 assert(l == arity - 1);
188 set_irn_in(node, l, ins);
193 * Remove the j-th predecessor from the i-th predecessor of block and add it to block
195 static void split_block(ir_node* block, int i, int j)
197 ir_node *pred_block = get_nodes_block(get_irn_n(block, i));
198 int arity = get_irn_arity(block);
199 ir_node **ins = ALLOCAN(ir_node*, arity + 1);
206 DB((dbg, LEVEL_1, "Splitting predecessor %d of predecessor %d of %+F\n", j, i, block));
208 for (phi = get_Block_phis(block); phi != NULL; phi = get_Phi_next(phi)) {
209 ir_node* copy = copy_to(get_irn_n(phi, i), pred_block, j);
211 for (k = 0; k < i; ++k) ins[k] = get_irn_n(phi, k);
213 for (; k < arity; ++k) ins[k] = get_irn_n(phi, k);
214 ins[k++] = get_irn_n(phi, i);
215 set_irn_in(phi, k, ins);
218 for (k = 0; k < i; ++k) ins[k] = get_irn_n(block, k);
219 ins[k++] = get_irn_n(pred_block, j);
220 for (; k < arity; ++k) ins[k] = get_irn_n(block, k);
221 ins[k++] = get_irn_n(block, i);
222 set_irn_in(block, k, ins);
224 new_pred_arity = get_irn_arity(pred_block) - 1;
225 pred_ins = ALLOCAN(ir_node*, new_pred_arity);
227 for (phi = get_Block_phis(pred_block); phi != NULL; phi = next) {
228 next = get_Phi_next(phi);
229 for (k = 0; k != j; ++k) pred_ins[k] = get_irn_n(phi, k);
230 for (; k != new_pred_arity; ++k) pred_ins[k] = get_irn_n(phi, k + 1);
232 exchange(phi, pred_ins[0]);
234 set_irn_in(phi, k, pred_ins);
238 for (k = 0; k != j; ++k) pred_ins[k] = get_irn_n(pred_block, k);
239 for (; k != new_pred_arity; ++k) pred_ins[k] = get_irn_n(pred_block, k + 1);
241 exchange(pred_block, get_nodes_block(pred_ins[0]));
243 set_irn_in(pred_block, k, pred_ins);
248 static void prepare_path(ir_node* block, int i, const ir_node* dependency)
250 ir_node* pred = get_nodes_block(get_irn_n(block, i));
254 DB((dbg, LEVEL_1, "Preparing predecessor %d of %+F\n", i, block));
256 pred_arity = get_irn_arity(pred);
257 for (j = 0; j < pred_arity; ++j) {
258 ir_node* pred_pred = get_nodes_block(get_irn_n(pred, j));
260 if (pred_pred != dependency && is_cdep_on(pred_pred, dependency)) {
261 prepare_path(pred, j, dependency);
262 split_block(block, i, j);
269 * Block walker: Search for diamonds and do the if conversion.
271 static void if_conv_walker(ir_node *block, void *ctx)
273 walker_env *env = (walker_env*)ctx;
277 /* Bail out, if there are no Phis at all */
278 if (get_Block_phis(block) == NULL) return;
281 arity = get_irn_arity(block);
282 for (i = 0; i < arity; ++i) {
286 pred0 = get_Block_cfgpred_block(block, i);
287 if (pred0 == block) continue;
289 for (cdep = find_cdep(pred0); cdep != NULL; cdep = get_cdep_next(cdep)) {
290 const ir_node* dependency = get_cdep_node(cdep);
291 ir_node* projx0 = walk_to_projx(pred0, dependency);
295 if (projx0 == NULL) continue;
297 cond = get_Proj_pred(projx0);
301 /* We only handle boolean decisions, no switches */
302 if (get_irn_mode(get_Cond_selector(cond)) != mode_b) continue;
304 for (j = i + 1; j < arity; ++j) {
315 pred1 = get_Block_cfgpred_block(block, j);
316 if (pred1 == block) continue;
318 if (!is_cdep_on(pred1, dependency)) continue;
320 projx1 = walk_to_projx(pred1, dependency);
322 if (projx1 == NULL) continue;
324 sel = get_Cond_selector(cond);
325 phi = get_Block_phis(block);
327 negated = get_Proj_proj(projx0) == pn_Cond_false;
328 for (p = phi; p != NULL; p = get_Phi_next(p)) {
332 mux_true = get_Phi_pred(p, j);
333 mux_false = get_Phi_pred(p, i);
335 mux_true = get_Phi_pred(p, i);
336 mux_false = get_Phi_pred(p, j);
338 if (!env->allow_ifconv(sel, mux_false, mux_true)) {
346 DB((dbg, LEVEL_1, "Found Cond %+F with proj %+F and %+F\n",
350 /* remove critical edges */
352 prepare_path(block, i, dependency);
353 prepare_path(block, j, dependency);
354 arity = get_irn_arity(block);
356 mux_block = get_nodes_block(cond);
357 cond_dbg = get_irn_dbg_info(cond);
358 do { /* generate Mux nodes in mux_block for Phis in block */
359 ir_node* val_i = get_irn_n(phi, i);
360 ir_node* val_j = get_irn_n(phi, j);
364 if (val_i == val_j) {
366 DB((dbg, LEVEL_2, "Generating no Mux, because both values are equal\n"));
370 /* Something is very fishy if two predecessors of a PhiM point into
371 * one block, but not at the same memory node
373 assert(get_irn_mode(phi) != mode_M);
382 mux = new_rd_Mux(cond_dbg, mux_block, sel, f, t, get_irn_mode(phi));
383 DB((dbg, LEVEL_2, "Generating %+F for %+F\n", mux, phi));
386 next_phi = get_Phi_next(phi);
391 rewire(phi, i, j, mux);
394 } while (phi != NULL);
396 /* move mux operands into mux_block */
397 exchange(get_nodes_block(get_irn_n(block, i)), mux_block);
398 exchange(get_nodes_block(get_irn_n(block, j)), mux_block);
403 DB((dbg, LEVEL_1, "Welding block %+F and %+F\n", block, mux_block));
404 /* copy the block-info from the Mux-block to the block before merging */
406 mark = get_Block_mark(mux_block) | get_Block_mark(block);
407 set_Block_mark(block, mark);
408 set_Block_phis(block, get_Block_phis(mux_block));
410 set_irn_in(block, get_irn_arity(mux_block), get_irn_in(mux_block) + 1);
411 exchange_cdep(mux_block, block);
412 exchange(mux_block, block);
414 DB((dbg, LEVEL_1, "Welding block %+F to %+F\n", block, mux_block));
415 mark = get_Block_mark(mux_block) | get_Block_mark(block);
416 /* mark both block just to be sure, should be enough to mark mux_block */
417 set_Block_mark(mux_block, mark);
418 exchange(block, mux_block);
422 rewire(block, i, j, new_r_Jmp(mux_block));
431 * Block walker: clear block marks and Phi lists.
433 static void init_block_link(ir_node *block, void *env)
436 set_Block_mark(block, 0);
437 set_Block_phis(block, NULL);
442 * Daisy-chain all Phis in a block.
443 * If a non-movable node is encountered set the has_pinned flag in its block.
445 static void collect_phis(ir_node *node, void *env)
450 ir_node *block = get_nodes_block(node);
452 add_Block_phi(block, node);
454 if (!is_Block(node) && get_irn_pinned(node) == op_pin_state_pinned) {
456 * Ignore control flow nodes (except Raise), these will be removed.
458 if (!is_cfop(node) && !is_Raise(node)) {
459 ir_node *block = get_nodes_block(node);
461 DB((dbg, LEVEL_2, "Node %+F in block %+F is unmovable\n", node, block));
462 set_Block_mark(block, 1);
468 static ir_graph_state_t do_ifconv(ir_graph *irg)
471 const backend_params *be_params = be_get_backend_param();
473 /* get the parameters */
474 env.allow_ifconv = be_params->allow_ifconv;
477 FIRM_DBG_REGISTER(dbg, "firm.opt.ifconv");
479 DB((dbg, LEVEL_1, "Running if-conversion on %+F\n", irg));
483 ir_reserve_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_PHI_LIST);
485 irg_block_walk_graph(irg, init_block_link, NULL, NULL);
486 irg_walk_graph(irg, collect_phis, NULL, NULL);
487 irg_block_walk_graph(irg, NULL, if_conv_walker, &env);
489 ir_free_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_PHI_LIST);
492 local_optimize_graph(irg);
497 return IR_GRAPH_STATE_NO_CRITICAL_EDGES | IR_GRAPH_STATE_ONE_RETURN;
500 optdesc_t opt_ifconv = {
502 IR_GRAPH_STATE_NO_CRITICAL_EDGES | IR_GRAPH_STATE_NO_UNREACHABLE_BLOCKS | IR_GRAPH_STATE_NO_BAD_BLOCKS | IR_GRAPH_STATE_ONE_RETURN,
506 void opt_if_conv(ir_graph *irg)
508 perform_irg_optimization(irg, &opt_ifconv);
511 ir_graph_pass_t *opt_if_conv_pass(const char *name)
513 return def_graph_pass(name ? name : "ifconv", opt_if_conv);