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 struct obstack obst; /**< the obstack where data is allocated on */
45 int changed; /**< indicates whether a change was performed */
48 typedef struct case_data {
53 typedef struct ifcas_env {
56 ir_node **defusers; /**< the Projs pointing to the default case */
60 * Evaluate a switch and decide whether we should build a table switch.
62 * @param cond The Cond node representing the switch.
63 * @param spare_size Allowed spare size for table switches in machine words.
64 * (Default in edgfe: 128)
66 static int should_do_table_switch(ir_node *cond, unsigned spare_size)
71 long switch_min = LONG_MAX, switch_max = LONG_MIN;
72 unsigned long spare, num_cases = 0;
74 /* TODO: Minimum size for jump table? */
75 if(get_irn_n_outs(cond) <= 4)
78 default_pn = get_Cond_defaultProj(cond);
80 foreach_out_irn(cond, i, proj) {
81 long pn = get_Proj_proj(proj);
93 * Here we have: num_cases and [switch_min, switch_max] interval.
94 * We do an if-cascade if there are too many spare numbers.
96 spare = (unsigned long) switch_max - (unsigned long) switch_min - num_cases + 1;
97 return spare < spare_size;
100 static int casecmp(const void *a, const void *b)
102 return ((case_data_t *) a)->value - ((case_data_t *) b)->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 set_cur_block(curblock);
115 /* only one case: "if(sel == val) goto target else goto default;" */
116 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[0].value);
117 ir_node *cmp = new_Cmp(env->sel, val);
118 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
119 ir_node *cond = new_Cond(proj);
120 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
121 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
122 } else if(numcases == 2) {
123 /* only two cases: "if(sel == val[0]) goto target[0];" */
124 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[0].value);
125 ir_node *cmp = new_Cmp(env->sel, val);
126 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
127 ir_node *cond = new_Cond(proj);
131 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
132 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
133 neblock = new_Block(1, in);
135 /* second part: "else if(sel == val[1]) goto target[1] else goto default;" */
136 val = new_Const_long(get_irn_mode(env->sel), curcases[1].value);
137 cmp = new_Cmp(env->sel, val);
138 proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
139 cond = new_Cond(proj);
140 set_Block_cfgpred(curcases[1].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
141 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
143 /* recursive case: split cases in the middle */
144 int midcase = numcases / 2;
145 ir_node *val = new_Const_long(get_irn_mode(env->sel), curcases[midcase].value);
146 ir_node *cmp = new_Cmp(env->sel, val);
147 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Lt);
148 ir_node *cond = new_Cond(proj);
153 in[0] = new_Proj(cond, mode_X, pn_Cond_true);
154 ltblock = new_Block(1, in);
156 set_cur_block(curblock);
157 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
158 geblock = new_Block(1, in);
160 create_if_cascade(env, ltblock, curcases, midcase);
161 create_if_cascade(env, geblock, curcases + midcase, numcases - midcase);
166 * Block-Walker: searches for Cond nodes with a non-boolean mode
168 static void find_cond_nodes(ir_node *block, void *ctx)
170 walk_env_t *env = ctx;
176 int i, j = 0, numcases;
180 ir_node *defblock = NULL;
181 ifcas_env_t ifcas_env;
183 if(get_Block_n_cfgpreds(block) != 1)
186 projx = get_Block_cfgpred(block, 0);
189 assert(get_irn_mode(projx) == mode_X);
191 cond = get_Proj_pred(projx);
195 sel = get_Cond_selector(cond);
196 sel_mode = get_irn_mode(sel);
198 if(sel_mode == mode_b) /* not a switch? */
201 if(should_do_table_switch(cond, env->spare_size))
205 * Switch should be transformed into an if cascade.
206 * So first order the cases, so we can do a binary search on them.
209 numcases = get_irn_n_outs(cond) - 1; // does not contain default case
210 cases = obstack_alloc(&env->obst, numcases * sizeof(*cases));
212 default_pn = get_Cond_defaultProj(cond);
214 ifcas_env.defindex = 0;
215 NEW_ARR_A(ir_node*, ifcas_env.defusers, numcases);
217 foreach_out_irn(cond, i, proj) {
218 long pn = get_Proj_proj(proj);
219 ir_node *target = get_irn_out(proj, 0);
220 assert(get_Block_n_cfgpreds(target) == 1 && "Encountered critical edge in switch");
229 cases[j].target = target;
233 assert(defblock != NULL && "Switch without default proj");
234 qsort(cases, numcases, sizeof(*cases), casecmp);
236 /* Now create the if cascade */
237 condblock = get_nodes_block(cond);
238 create_if_cascade(&ifcas_env, condblock, cases, numcases);
240 /* Connect new default case users */
241 set_irn_in(defblock, ifcas_env.defindex, ifcas_env.defusers);
243 obstack_free(&env->obst, cases);
247 * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
248 * They will either remain the same or be converted into if-cascades.
250 * @param irg The ir graph to be lowered.
251 * @param spare_size Allowed spare size for table switches in machine words.
252 * (Default in edgfe: 128)
254 void lower_Switch(ir_graph *irg, unsigned spare_size)
257 ir_graph *rem = current_ir_graph;
259 current_ir_graph = irg;
261 obstack_init(&env.obst);
262 env.spare_size = spare_size;
264 remove_critical_cf_edges(irg);
265 assure_irg_outs(irg);
267 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
270 /* control flow changed */
271 set_irg_outs_inconsistent(irg);
272 set_irg_doms_inconsistent(irg);
273 set_irg_extblk_inconsistent(irg);
274 set_irg_loopinfo_inconsistent(irg);
277 obstack_free(&env.obst, NULL);
278 current_ir_graph = rem;