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
39 #define foreach_out_irn(irn, i, outirn) for(i = get_irn_n_outs(irn) - 1;\
40 i >= 0 && (outirn = get_irn_out(irn, i)); --i)
42 typedef struct walk_env {
43 unsigned spare_size; /**< the allowed spare size for table switches */
44 int changed; /**< indicates whether a change was performed */
47 typedef struct case_data {
52 typedef struct ifcas_env {
55 ir_node **defusers; /**< the Projs pointing to the default case */
59 * Evaluate a switch and decide whether we should build a table switch.
61 * @param cond The Cond node representing the switch.
62 * @param spare_size Allowed spare size for table switches in machine words.
63 * (Default in edgfe: 128)
65 static int should_do_table_switch(ir_node *cond, unsigned spare_size)
70 long switch_min = LONG_MAX, switch_max = LONG_MIN;
71 unsigned long spare, num_cases = 0;
73 /* TODO: Minimum size for jump table? */
74 if (get_irn_n_outs(cond) <= 4)
77 default_pn = get_Cond_defaultProj(cond);
79 foreach_out_irn(cond, i, proj) {
80 long pn = get_Proj_proj(proj);
92 * Here we have: num_cases and [switch_min, switch_max] interval.
93 * We do an if-cascade if there are too many spare numbers.
95 spare = (unsigned long) switch_max - (unsigned long) switch_min - num_cases + 1;
96 return spare < spare_size;
99 static int casecmp(const void *a, const void *b)
101 const case_data_t *cda = a;
102 const case_data_t *cdb = b;
103 return cda->value - cdb->value;
107 * Creates an if cascade realizing binary search.
109 static void create_if_cascade(ifcas_env_t *env, ir_node *curblock,
110 case_data_t *curcases, int numcases)
112 assert(numcases >= 0);
114 set_cur_block(curblock);
117 /* zero cases: "goto default;" */
118 env->defusers[env->defindex++] = new_Jmp();
119 } else if (numcases == 1) {
120 /* only one case: "if(sel == val) goto target else goto default;" */
121 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[0].value);
122 ir_node *cmp = new_Cmp(env->sel, val);
123 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
124 ir_node *cond = new_Cond(proj);
125 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
126 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
127 } else if (numcases == 2) {
128 /* only two cases: "if(sel == val[0]) goto target[0];" */
129 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[0].value);
130 ir_node *cmp = new_Cmp(env->sel, val);
131 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
132 ir_node *cond = new_Cond(proj);
136 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
137 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
138 neblock = new_Block(1, in);
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);
165 create_if_cascade(env, ltblock, curcases, midcase);
166 create_if_cascade(env, geblock, curcases + midcase, numcases - midcase);
171 * Block-Walker: searches for Cond nodes with a non-boolean mode
173 static void find_cond_nodes(ir_node *block, void *ctx)
175 walk_env_t *env = ctx;
181 int i, j = 0, numcases;
185 ir_node *defblock = NULL;
186 ifcas_env_t ifcas_env;
188 if (get_Block_n_cfgpreds(block) != 1)
191 projx = get_Block_cfgpred(block, 0);
194 assert(get_irn_mode(projx) == mode_X);
196 cond = get_Proj_pred(projx);
200 sel = get_Cond_selector(cond);
201 sel_mode = get_irn_mode(sel);
203 if (sel_mode == mode_b) /* not a switch? */
206 if (should_do_table_switch(cond, env->spare_size))
210 * Switch should be transformed into an if cascade.
211 * So first order the cases, so we can do a binary search on them.
215 numcases = get_irn_n_outs(cond) - 1; // does not contain default case
216 NEW_ARR_A(case_data_t, cases, numcases);
218 default_pn = get_Cond_defaultProj(cond);
220 ifcas_env.defindex = 0;
221 NEW_ARR_A(ir_node*, ifcas_env.defusers, numcases);
223 foreach_out_irn(cond, i, proj) {
224 long pn = get_Proj_proj(proj);
225 ir_node *target = get_irn_out(proj, 0);
226 assert(get_Block_n_cfgpreds(target) == 1 && "Encountered critical edge in switch");
228 if (pn == default_pn) {
234 cases[j].target = target;
238 assert(defblock != NULL && "Switch without default proj");
239 qsort(cases, numcases, sizeof(*cases), casecmp);
241 /* Now create the if cascade */
242 condblock = get_nodes_block(cond);
243 create_if_cascade(&ifcas_env, condblock, cases, numcases);
245 /* Connect new default case users */
246 set_irn_in(defblock, ifcas_env.defindex, ifcas_env.defusers);
250 * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
251 * They will either remain the same or be converted into if-cascades.
253 * @param irg The ir graph to be lowered.
254 * @param spare_size Allowed spare size for table switches in machine words.
255 * (Default in edgfe: 128)
257 void lower_switch(ir_graph *irg, unsigned spare_size)
260 ir_graph *rem = current_ir_graph;
262 current_ir_graph = irg;
265 env.spare_size = spare_size;
267 remove_critical_cf_edges(irg);
268 assure_irg_outs(irg);
270 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
273 /* control flow changed */
274 set_irg_outs_inconsistent(irg);
275 set_irg_doms_inconsistent(irg);
276 set_irg_extblk_inconsistent(irg);
277 set_irg_loopinfo_inconsistent(irg);
279 current_ir_graph = rem;