2 * Copyright (C) 1995-2011 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
22 * @brief Lowering of Switches if necessary or advantageous.
23 * @author Moritz Kroll
40 #include "irnodeset.h"
42 #define foreach_out_irn(irn, i, outirn) for (i = get_irn_n_outs(irn) - 1;\
43 i >= 0 && (outirn = get_irn_out(irn, i)); --i)
45 typedef struct walk_env_t {
46 unsigned spare_size; /**< the allowed spare size for table switches */
47 unsigned small_switch;
48 bool allow_out_of_bounds;
49 bool changed; /**< indicates whether a change was performed */
50 ir_nodeset_t processed;
53 typedef struct case_data_t {
58 typedef struct cond_env_t {
62 ir_node *default_block;
64 ir_node **defusers; /**< the Projs pointing to the default case */
67 static void analyse_switch(cond_env_t *env, ir_node *cond)
69 long default_pn = get_Cond_default_proj(cond);
70 long switch_min = LONG_MAX;
71 long switch_max = LONG_MIN;
72 ir_node *default_block = NULL;
73 unsigned num_cases = 0;
77 foreach_out_irn(cond, i, proj) {
78 long pn = get_Proj_proj(proj);
79 if (pn == default_pn) {
80 ir_node *target = get_irn_out(proj, 0);
81 assert(default_block == NULL || default_block == target);
82 default_block = target;
92 assert(default_block != NULL);
94 env->switch_min = switch_min;
95 env->switch_max = switch_max;
96 env->num_cases = num_cases;
97 env->default_block = default_block;
100 static int casecmp(const void *a, const void *b)
102 const case_data_t *cda = (const case_data_t*)a;
103 const case_data_t *cdb = (const case_data_t*)b;
106 * Enforce unsigned sorting. Signed comparison will behave differently for
107 * 32-bit values, depending on sizeof(long). This will make the resulting
108 * array deterministic.
110 return ((unsigned long)cda->value > (unsigned long)cdb->value) -
111 ((unsigned long)cda->value < (unsigned long)cdb->value);
115 * Creates an if cascade realizing binary search.
117 static void create_if_cascade(cond_env_t *env, dbg_info *dbgi, ir_node *block,
118 case_data_t *curcases, unsigned numcases)
120 ir_graph *irg = get_irn_irg(block);
125 /* Get the mode and sel node for the comparison. */
126 cmp_mode = get_irn_mode(env->sel);
128 sel_block = get_nodes_block(cmp_sel);
131 * Make sure that an unsigned comparison is used, by converting the sel
132 * node to an unsigned mode and using that mode for the constants, too.
133 * This is important, because the qsort applied to the case labels uses
134 * an unsigned comparison and both comparison methods have to match.
136 if (mode_is_signed(cmp_mode)) {
137 cmp_mode = find_unsigned_mode(cmp_mode);
138 cmp_sel = new_r_Conv(sel_block, cmp_sel, cmp_mode);
142 /* zero cases: "goto default;" */
143 ARR_APP1(ir_node*, env->defusers, new_r_Jmp(block));
144 } else if (numcases == 1) {
145 /* only one case: "if (sel == val) goto target else goto default;" */
146 ir_node *val = new_r_Const_long(irg, cmp_mode, curcases[0].value);
147 ir_node *cmp = new_rd_Cmp(dbgi, block, cmp_sel, val,
149 ir_node *cond = new_rd_Cond(dbgi, block, cmp);
150 ir_node *trueproj = new_r_Proj(cond, mode_X, pn_Cond_true);
151 ir_node *falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
153 set_Block_cfgpred(curcases[0].target, 0, trueproj);
154 ARR_APP1(ir_node*, env->defusers, falseproj);
155 } else if (numcases == 2) {
156 /* only two cases: "if (sel == val[0]) goto target[0];" */
157 ir_node *val = new_r_Const_long(irg, cmp_mode, curcases[0].value);
158 ir_node *cmp = new_rd_Cmp(dbgi, block, cmp_sel, val,
160 ir_node *cond = new_rd_Cond(dbgi, block, cmp);
161 ir_node *trueproj = new_r_Proj(cond, mode_X, pn_Cond_true);
162 ir_node *falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
166 set_Block_cfgpred(curcases[0].target, 0, trueproj);
169 neblock = new_r_Block(irg, 1, in);
171 /* second part: "else if (sel == val[1]) goto target[1] else goto default;" */
172 val = new_r_Const_long(irg, cmp_mode, curcases[1].value);
173 cmp = new_rd_Cmp(dbgi, neblock, cmp_sel, val, ir_relation_equal);
174 cond = new_rd_Cond(dbgi, neblock, cmp);
175 trueproj = new_r_Proj(cond, mode_X, pn_Cond_true);
176 falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
177 set_Block_cfgpred(curcases[1].target, 0, trueproj);
178 ARR_APP1(ir_node*, env->defusers, falseproj);
180 /* recursive case: split cases in the middle */
181 int midcase = numcases / 2;
182 ir_node *val = new_r_Const_long(irg, cmp_mode,
183 curcases[midcase].value);
184 ir_node *cmp = new_rd_Cmp(dbgi, block, cmp_sel, val, ir_relation_less);
185 ir_node *cond = new_rd_Cond(dbgi, block, cmp);
190 in[0] = new_r_Proj(cond, mode_X, pn_Cond_true);
191 ltblock = new_r_Block(irg, 1, in);
193 in[0] = new_r_Proj(cond, mode_X, pn_Cond_false);
194 geblock = new_r_Block(irg, 1, in);
196 create_if_cascade(env, dbgi, ltblock, curcases, midcase);
197 create_if_cascade(env, dbgi, geblock, curcases + midcase,
202 static void create_out_of_bounds_check(cond_env_t *env, ir_node *cond)
204 ir_graph *irg = get_irn_irg(cond);
205 dbg_info *dbgi = get_irn_dbg_info(cond);
206 ir_node *sel = get_Cond_selector(cond);
207 ir_node *block = get_nodes_block(cond);
208 ir_mode *cmp_mode = get_irn_mode(sel);
209 ir_node **default_preds = NEW_ARR_F(ir_node*, 0);
210 long default_pn = get_Cond_default_proj(cond);
219 size_t n_default_preds;
223 if (mode_is_signed(cmp_mode)) {
224 cmp_mode = find_unsigned_mode(cmp_mode);
225 sel = new_r_Conv(block, sel, cmp_mode);
228 /* normalize so switch_min is at 0 */
229 if (env->switch_min != 0) {
230 ir_node *min_const = new_r_Const_long(irg, cmp_mode, env->switch_min);
231 sel = new_rd_Sub(dbgi, block, sel, min_const, cmp_mode);
233 delta = env->switch_min;
235 env->switch_max -= delta;
236 set_Cond_selector(cond, sel);
239 /* check for out-of-bounds */
240 max_const = new_r_Const_long(irg, cmp_mode, env->switch_max);
241 cmp = new_rd_Cmp(dbgi, block, sel, max_const, ir_relation_less_equal);
242 oob_cond = new_rd_Cond(dbgi, block, cmp);
243 proj_true = new_r_Proj(oob_cond, mode_X, pn_Cond_true);
244 proj_false = new_r_Proj(oob_cond, mode_X, pn_Cond_false);
246 ARR_APP1(ir_node*, default_preds, proj_false);
248 /* create new block containing the cond */
250 new_block = new_r_Block(irg, 1, in);
251 set_nodes_block(cond, new_block);
254 foreach_out_irn(cond, i, proj) {
255 long pn = get_Proj_proj(proj);
256 long new_pn = pn - delta;
257 if (pn == default_pn) {
258 set_Cond_default_proj(cond, new_pn);
259 ARR_APP1(ir_node*, default_preds, proj);
262 set_Proj_proj(proj, new_pn);
263 set_nodes_block(proj, new_block);
266 /* adapt default block */
267 n_default_preds = ARR_LEN(default_preds);
268 if (n_default_preds > 1) {
271 /* create new intermediate blocks so we don't have critical edges */
272 for (p = 0; p < n_default_preds; ++p) {
273 ir_node *pred = default_preds[p];
274 ir_node *split_block;
275 ir_node *block_in[1];
278 split_block = new_r_Block(irg, 1, block_in);
280 default_preds[p] = new_r_Jmp(split_block);
283 set_irn_in(env->default_block, n_default_preds, default_preds);
285 DEL_ARR_F(default_preds);
289 * Block-Walker: searches for Cond nodes with a non-boolean mode
291 static void find_cond_nodes(ir_node *block, void *ctx)
293 walk_env_t *env = (walk_env_t *)ctx;
305 ir_node *defblock = NULL;
309 bool lower_switch = false;
311 /* because we split critical blocks only blocks with 1 predecessors may
312 * contain Proj->Cond nodes */
313 if (get_Block_n_cfgpreds(block) != 1)
316 projx = get_Block_cfgpred(block, 0);
319 assert(get_irn_mode(projx) == mode_X);
321 cond = get_Proj_pred(projx);
325 sel = get_Cond_selector(cond);
326 sel_mode = get_irn_mode(sel);
328 if (sel_mode == mode_b)
331 if (ir_nodeset_contains(&env->processed, cond))
333 ir_nodeset_insert(&env->processed, cond);
335 /* the algorithms here don't work reliable for modes bigger than 32
336 * since we operate with long numbers */
337 assert(get_mode_size_bits(sel_mode) <= 32);
339 analyse_switch(&cond_env, cond);
342 * Here we have: num_cases and [switch_min, switch_max] interval.
343 * We do an if-cascade if there are too many spare numbers.
345 spare = (unsigned long) cond_env.switch_max
346 - (unsigned long) cond_env.switch_min
347 - (unsigned long) cond_env.num_cases + 1;
348 lower_switch |= spare >= env->spare_size;
349 lower_switch |= cond_env.num_cases <= env->small_switch;
352 /* we won't decompose the switch. But we might have to add
353 * out-of-bounds checking */
354 if (!env->allow_out_of_bounds) {
355 create_out_of_bounds_check(&cond_env, cond);
362 * Switch should be transformed into an if cascade.
363 * So first order the cases, so we can do a binary search on them.
367 numcases = get_irn_n_outs(cond) - 1; /* does not contain default case */
368 cases = XMALLOCN(case_data_t, numcases);
370 default_pn = get_Cond_default_proj(cond);
372 cond_env.defusers = NEW_ARR_F(ir_node*, 0);
374 foreach_out_irn(cond, i, proj) {
375 long pn = get_Proj_proj(proj);
376 ir_node *target = get_irn_out(proj, 0);
377 assert(get_Block_n_cfgpreds(target) == 1);
379 if (pn == default_pn) {
385 cases[j].target = target;
388 assert(j == numcases);
390 if (defblock == NULL)
391 panic("Switch %+F has no default proj", cond);
393 qsort(cases, numcases, sizeof(cases[0]), casecmp);
395 /* Now create the if cascade */
396 condblock = get_nodes_block(cond);
397 dbgi = get_irn_dbg_info(cond);
398 create_if_cascade(&cond_env, dbgi, condblock, cases, numcases);
400 /* Connect new default case users */
401 set_irn_in(defblock, ARR_LEN(cond_env.defusers), cond_env.defusers);
404 DEL_ARR_F(cond_env.defusers);
407 void lower_switch(ir_graph *irg, unsigned small_switch, unsigned spare_size,
408 int allow_out_of_bounds)
412 env.spare_size = spare_size;
413 env.small_switch = small_switch;
414 env.allow_out_of_bounds = allow_out_of_bounds;
415 ir_nodeset_init(&env.processed);
417 remove_critical_cf_edges(irg);
418 assure_irg_outs(irg);
420 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
421 ir_nodeset_destroy(&env.processed);
424 /* control flow changed */
425 clear_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_DOMINANCE
426 | IR_GRAPH_STATE_VALID_EXTENDED_BLOCKS);