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
38 #define foreach_out_irn(irn, i, outirn) for(i = get_irn_n_outs(irn) - 1;\
39 i >= 0 && (outirn = get_irn_out(irn, i)); --i)
41 typedef struct walk_env {
42 unsigned spare_size; /**< the allowed spare size for table switches */
43 int changed; /**< indicates whether a change was performed */
46 typedef struct case_data {
51 typedef struct ifcas_env {
54 ir_node **defusers; /**< the Projs pointing to the default case */
58 * Evaluate a switch and decide whether we should build a table switch.
60 * @param cond The Cond node representing the switch.
61 * @param spare_size Allowed spare size for table switches in machine words.
62 * (Default in edgfe: 128)
64 static int should_do_table_switch(ir_node *cond, unsigned spare_size)
69 long switch_min = LONG_MAX, switch_max = LONG_MIN;
70 unsigned long spare, num_cases = 0;
72 /* TODO: Minimum size for jump table? */
73 if (get_irn_n_outs(cond) <= 4)
76 default_pn = get_Cond_defaultProj(cond);
78 foreach_out_irn(cond, i, proj) {
79 long pn = get_Proj_proj(proj);
91 * Here we have: num_cases and [switch_min, switch_max] interval.
92 * We do an if-cascade if there are too many spare numbers.
94 spare = (unsigned long) switch_max - (unsigned long) switch_min - num_cases + 1;
95 return spare < spare_size;
98 static int casecmp(const void *a, const void *b)
100 const case_data_t *cda = a;
101 const case_data_t *cdb = b;
102 return (cda->value > cdb->value) - (cda->value < cdb->value);
106 * Creates an if cascade realizing binary search.
108 static void create_if_cascade(ifcas_env_t *env, ir_node *curblock,
109 case_data_t *curcases, int numcases)
111 assert(numcases >= 0);
113 set_cur_block(curblock);
116 /* zero cases: "goto default;" */
117 env->defusers[env->defindex++] = new_Jmp();
118 } else if (numcases == 1) {
119 /* only one case: "if(sel == val) goto target else goto default;" */
120 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[0].value);
121 ir_node *cmp = new_Cmp(env->sel, val);
122 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
123 ir_node *cond = new_Cond(proj);
124 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
125 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
126 } else if (numcases == 2) {
127 /* only two cases: "if(sel == val[0]) goto target[0];" */
128 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[0].value);
129 ir_node *cmp = new_Cmp(env->sel, val);
130 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
131 ir_node *cond = new_Cond(proj);
135 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
136 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
137 neblock = new_Block(1, in);
138 set_cur_block(neblock);
140 /* second part: "else if(sel == val[1]) goto target[1] else goto default;" */
141 val = new_Const_long(get_irn_mode(env->sel), curcases[1].value);
142 cmp = new_Cmp(env->sel, val);
143 proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
144 cond = new_Cond(proj);
145 set_Block_cfgpred(curcases[1].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
146 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
148 /* recursive case: split cases in the middle */
149 int midcase = numcases / 2;
150 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[midcase].value);
151 ir_node *cmp = new_Cmp(env->sel, val);
152 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Lt);
153 ir_node *cond = new_Cond(proj);
158 in[0] = new_Proj(cond, mode_X, pn_Cond_true);
159 ltblock = new_Block(1, in);
161 set_cur_block(curblock);
162 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
163 geblock = new_Block(1, in);
164 set_cur_block(geblock);
166 create_if_cascade(env, ltblock, curcases, midcase);
167 create_if_cascade(env, geblock, curcases + midcase, numcases - midcase);
172 * Block-Walker: searches for Cond nodes with a non-boolean mode
174 static void find_cond_nodes(ir_node *block, void *ctx)
176 walk_env_t *env = ctx;
182 int i, j = 0, numcases;
186 ir_node *defblock = NULL;
187 ifcas_env_t ifcas_env;
189 if (get_Block_n_cfgpreds(block) != 1)
192 projx = get_Block_cfgpred(block, 0);
195 assert(get_irn_mode(projx) == mode_X);
197 cond = get_Proj_pred(projx);
201 sel = get_Cond_selector(cond);
202 sel_mode = get_irn_mode(sel);
204 if (sel_mode == mode_b) /* not a switch? */
207 if (should_do_table_switch(cond, env->spare_size))
211 * Switch should be transformed into an if cascade.
212 * So first order the cases, so we can do a binary search on them.
216 numcases = get_irn_n_outs(cond) - 1; // does not contain default case
217 NEW_ARR_A(case_data_t, cases, numcases);
219 default_pn = get_Cond_defaultProj(cond);
221 ifcas_env.defindex = 0;
222 NEW_ARR_A(ir_node*, ifcas_env.defusers, numcases);
224 foreach_out_irn(cond, i, proj) {
225 long pn = get_Proj_proj(proj);
226 ir_node *target = get_irn_out(proj, 0);
227 assert(get_Block_n_cfgpreds(target) == 1 && "Encountered critical edge in switch");
229 if (pn == default_pn) {
235 cases[j].target = target;
239 assert(defblock != NULL && "Switch without default proj");
240 qsort(cases, numcases, sizeof(*cases), casecmp);
242 /* Now create the if cascade */
243 condblock = get_nodes_block(cond);
244 create_if_cascade(&ifcas_env, condblock, cases, numcases);
246 /* Connect new default case users */
247 set_irn_in(defblock, ifcas_env.defindex, ifcas_env.defusers);
251 * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
252 * They will either remain the same or be converted into if-cascades.
254 * @param irg The ir graph to be lowered.
255 * @param spare_size Allowed spare size for table switches in machine words.
256 * (Default in edgfe: 128)
258 void lower_switch(ir_graph *irg, unsigned spare_size)
261 ir_graph *rem = current_ir_graph;
263 current_ir_graph = irg;
266 env.spare_size = spare_size;
268 remove_critical_cf_edges(irg);
269 assure_irg_outs(irg);
271 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
274 /* control flow changed */
275 set_irg_outs_inconsistent(irg);
276 set_irg_doms_inconsistent(irg);
277 set_irg_extblk_inconsistent(irg);
278 set_irg_loopinfo_inconsistent(irg);
280 current_ir_graph = rem;