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
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 bool allow_out_of_bounds;
48 bool changed; /**< indicates whether a change was performed */
49 ir_nodeset_t processed;
52 typedef struct case_data_t {
57 typedef struct cond_env_t {
61 ir_node *default_block;
63 ir_node **defusers; /**< the Projs pointing to the default case */
66 static void analyse_switch(cond_env_t *env, ir_node *cond)
68 long default_pn = get_Cond_default_proj(cond);
69 long switch_min = LONG_MAX;
70 long switch_max = LONG_MIN;
71 ir_node *default_block = NULL;
72 unsigned num_cases = 0;
76 foreach_out_irn(cond, i, proj) {
77 long pn = get_Proj_proj(proj);
78 if (pn == default_pn) {
79 ir_node *target = get_irn_out(proj, 0);
80 assert(default_block == NULL || default_block == target);
81 default_block = target;
91 assert(default_block != NULL);
93 env->switch_min = switch_min;
94 env->switch_max = switch_max;
95 env->num_cases = num_cases;
96 env->default_block = default_block;
99 static int casecmp(const void *a, const void *b)
101 const case_data_t *cda = a;
102 const case_data_t *cdb = b;
105 * Enforce unsigned sorting. Signed comparison will behave differently for
106 * 32-bit values, depending on sizeof(long). This will make the resulting
107 * array deterministic.
109 return ((unsigned long)cda->value > (unsigned long)cdb->value) -
110 ((unsigned long)cda->value < (unsigned long)cdb->value);
114 * Creates an if cascade realizing binary search.
116 static void create_if_cascade(cond_env_t *env, dbg_info *dbgi, ir_node *block,
117 case_data_t *curcases, unsigned numcases)
119 ir_graph *irg = get_irn_irg(block);
124 /* Get the mode and sel node for the comparison. */
125 cmp_mode = get_irn_mode(env->sel);
127 sel_block = get_nodes_block(cmp_sel);
130 * Make sure that an unsigned comparison is used, by converting the sel
131 * node to an unsigned mode and using that mode for the constants, too.
132 * This is important, because the qsort applied to the case labels uses
133 * an unsigned comparison and both comparison methods have to match.
135 if (mode_is_signed(cmp_mode)) {
136 cmp_mode = find_unsigned_mode(cmp_mode);
137 cmp_sel = new_r_Conv(sel_block, cmp_sel, cmp_mode);
141 /* zero cases: "goto default;" */
142 ARR_APP1(ir_node*, env->defusers, new_Jmp());
143 } else if (numcases == 1) {
144 /* only one case: "if (sel == val) goto target else goto default;" */
145 ir_node *val = new_r_Const_long(irg, cmp_mode, curcases[0].value);
146 ir_node *cmp = new_rd_Cmp(dbgi, block, cmp_sel, val);
147 ir_node *proj = new_r_Proj(cmp, mode_b, pn_Cmp_Eq);
148 ir_node *cond = new_rd_Cond(dbgi, block, proj);
149 ir_node *trueproj = new_r_Proj(cond, mode_X, pn_Cond_true);
150 ir_node *falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
152 set_Block_cfgpred(curcases[0].target, 0, trueproj);
153 ARR_APP1(ir_node*, env->defusers, falseproj);
154 } else if (numcases == 2) {
155 /* only two cases: "if (sel == val[0]) goto target[0];" */
156 ir_node *val = new_r_Const_long(irg, cmp_mode, curcases[0].value);
157 ir_node *cmp = new_rd_Cmp(dbgi, block, cmp_sel, val);
158 ir_node *proj = new_r_Proj(cmp, mode_b, pn_Cmp_Eq);
159 ir_node *cond = new_rd_Cond(dbgi, block, proj);
160 ir_node *trueproj = new_r_Proj(cond, mode_X, pn_Cond_true);
161 ir_node *falseproj = new_r_Proj(cond, mode_X, pn_Cond_false);
165 set_Block_cfgpred(curcases[0].target, 0, trueproj);
168 neblock = new_r_Block(irg, 1, in);
170 /* second part: "else if (sel == val[1]) goto target[1] else goto default;" */
171 val = new_r_Const_long(irg, cmp_mode, curcases[1].value);
172 cmp = new_rd_Cmp(dbgi, neblock, cmp_sel, val);
173 proj = new_r_Proj(cmp, mode_b, pn_Cmp_Eq);
174 cond = new_rd_Cond(dbgi, neblock, proj);
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);
185 ir_node *proj = new_r_Proj(cmp, mode_b, pn_Cmp_Lt);
186 ir_node *cond = new_rd_Cond(dbgi, block, proj);
191 in[0] = new_r_Proj(cond, mode_X, pn_Cond_true);
192 ltblock = new_r_Block(irg, 1, in);
194 in[0] = new_r_Proj(cond, mode_X, pn_Cond_false);
195 geblock = new_r_Block(irg, 1, in);
197 create_if_cascade(env, dbgi, ltblock, curcases, midcase);
198 create_if_cascade(env, dbgi, geblock, curcases + midcase,
203 static void create_out_of_bounds_check(cond_env_t *env, ir_node *cond)
205 ir_graph *irg = get_irn_irg(cond);
206 dbg_info *dbgi = get_irn_dbg_info(cond);
207 ir_node *sel = get_Cond_selector(cond);
208 ir_node *block = get_nodes_block(cond);
209 ir_mode *cmp_mode = get_irn_mode(sel);
210 ir_node **default_preds = NEW_ARR_F(ir_node*, 0);
211 unsigned long default_pn = get_Cond_default_proj(cond);
225 if (mode_is_signed(cmp_mode)) {
226 cmp_mode = find_unsigned_mode(cmp_mode);
227 sel = new_r_Conv(block, sel, cmp_mode);
230 /* normalize so switch_min is at 0 */
231 if (env->switch_min != 0) {
232 ir_node *min_const = new_r_Const_long(irg, cmp_mode, env->switch_min);
233 sel = new_rd_Sub(dbgi, block, sel, min_const, cmp_mode);
235 delta = env->switch_min;
237 env->switch_max -= delta;
240 /* check for out-of-bounds */
241 max_const = new_r_Const_long(irg, cmp_mode, env->switch_max);
242 cmp = new_rd_Cmp(dbgi, block, sel, max_const);
243 proj_cmp = new_r_Proj(cmp, mode_b, pn_Cmp_Le);
244 oob_cond = new_rd_Cond(dbgi, block, proj_cmp);
245 proj_true = new_r_Proj(oob_cond, mode_X, pn_Cond_true);
246 proj_false = new_r_Proj(oob_cond, mode_X, pn_Cond_false);
248 ARR_APP1(ir_node*, default_preds, proj_false);
250 /* create new block containing the cond */
252 new_block = new_r_Block(irg, 1, in);
253 set_nodes_block(cond, new_block);
256 foreach_out_irn(cond, i, proj) {
257 unsigned long pn = get_Proj_proj(proj);
258 unsigned long new_pn = pn - delta;
259 if (pn == default_pn) {
260 /* we might have to choose a new default_pn */
261 if (pn < (unsigned long) env->switch_max) {
262 new_pn = env->switch_max + 1;
263 set_Cond_default_proj(cond, new_pn);
267 ARR_APP1(ir_node*, default_preds, proj);
270 set_Proj_proj(proj, new_pn);
271 set_nodes_block(proj, new_block);
274 /* adapt default block */
275 n_default_preds = ARR_LEN(default_preds);
276 if (n_default_preds > 1) {
279 /* create new intermediate blocks so we don't have critical edges */
280 for (i = 0; i < n_default_preds; ++i) {
281 ir_node *proj = default_preds[i];
286 block = new_r_Block(irg, 1, in);
288 default_preds[i] = new_r_Jmp(block);
291 set_irn_in(env->default_block, n_default_preds, default_preds);
293 DEL_ARR_F(default_preds);
297 * Block-Walker: searches for Cond nodes with a non-boolean mode
299 static void find_cond_nodes(ir_node *block, void *ctx)
301 walk_env_t *env = ctx;
313 ir_node *defblock = NULL;
318 /* because we split critical blocks only blocks with 1 predecessors may
319 * contain Proj->Cond nodes */
320 if (get_Block_n_cfgpreds(block) != 1)
323 projx = get_Block_cfgpred(block, 0);
326 assert(get_irn_mode(projx) == mode_X);
328 cond = get_Proj_pred(projx);
332 sel = get_Cond_selector(cond);
333 sel_mode = get_irn_mode(sel);
335 if (sel_mode == mode_b)
338 if (ir_nodeset_contains(&env->processed, cond))
340 ir_nodeset_insert(&env->processed, cond);
342 /* the algorithms here don't work reliable for modes bigger than 32
343 * since we operate with long numbers */
344 assert(get_mode_size_bits(sel_mode) <= 32);
346 analyse_switch(&cond_env, cond);
349 * Here we have: num_cases and [switch_min, switch_max] interval.
350 * We do an if-cascade if there are too many spare numbers.
352 spare = (unsigned long) cond_env.switch_max
353 - (unsigned long) cond_env.switch_min
354 - (unsigned long) cond_env.num_cases + 1;
355 if (spare < env->spare_size) {
356 /* we won't decompose the switch. But we might have to add
357 * out-of-bounds checking */
358 if (!env->allow_out_of_bounds) {
359 create_out_of_bounds_check(&cond_env, cond);
366 * Switch should be transformed into an if cascade.
367 * So first order the cases, so we can do a binary search on them.
371 numcases = get_irn_n_outs(cond) - 1; /* does not contain default case */
372 cases = XMALLOCN(case_data_t, numcases);
374 default_pn = get_Cond_default_proj(cond);
376 cond_env.defusers = NEW_ARR_F(ir_node*, 0);
378 foreach_out_irn(cond, i, proj) {
379 long pn = get_Proj_proj(proj);
380 ir_node *target = get_irn_out(proj, 0);
381 assert(get_Block_n_cfgpreds(target) == 1);
383 if (pn == default_pn) {
389 cases[j].target = target;
392 assert(j == numcases);
394 if (defblock == NULL)
395 panic("Switch %+F has no default proj", cond);
397 qsort(cases, numcases, sizeof(cases[0]), casecmp);
399 /* Now create the if cascade */
400 condblock = get_nodes_block(cond);
401 dbgi = get_irn_dbg_info(cond);
402 create_if_cascade(&cond_env, dbgi, condblock, cases, numcases);
404 /* Connect new default case users */
405 set_irn_in(defblock, ARR_LEN(cond_env.defusers), cond_env.defusers);
408 DEL_ARR_F(cond_env.defusers);
411 void lower_switch(ir_graph *irg, unsigned spare_size, int allow_out_of_bounds)
415 env.spare_size = spare_size;
416 env.allow_out_of_bounds = allow_out_of_bounds;
417 ir_nodeset_init(&env.processed);
419 remove_critical_cf_edges(irg);
420 assure_irg_outs(irg);
422 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
423 ir_nodeset_destroy(&env.processed);
426 /* control flow changed */
427 set_irg_outs_inconsistent(irg);
428 set_irg_doms_inconsistent(irg);
429 set_irg_extblk_inconsistent(irg);
430 set_irg_loopinfo_inconsistent(irg);