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 struct obstack obst; /**< the obstack where data is allocated on */
44 int changed; /**< indicates whether a change was performed */
47 typedef struct case_data {
53 * Add the new predecessor x to node node, which is either a Block or a Phi
55 static void add_pred(ir_node* node, ir_node* x)
61 assert(is_Block(node) || is_Phi(node));
63 n = get_irn_arity(node);
64 NEW_ARR_A(ir_node*, ins, n + 1);
65 for (i = 0; i < n; i++)
66 ins[i] = get_irn_n(node, i);
68 set_irn_in(node, n + 1, ins);
72 * Remove the predecessor x from node node one time, which is either a Block or a Phi
74 static void remove_pred(ir_node* node, ir_node* x)
80 assert(is_Block(node) || is_Phi(node));
82 n = get_irn_arity(node);
83 NEW_ARR_A(ir_node*, ins, n - 1);
84 for (i = 0, j = -1; i < n - 1; i++)
86 ins[++j] = get_irn_n(node, i);
89 assert(i == j + 1 && "x is not a pred of node");
90 set_irn_in(node, n - 1, ins);
94 * Evaluate a switch and decide whether we should build a table switch.
96 * @param cond The Cond node representing the switch.
97 * @param spare_size Allowed spare size for table switches in machine words.
98 * (Default in edgfe: 128)
100 static int should_do_table_switch(ir_node *cond, unsigned spare_size)
105 long switch_min = LONG_MAX, switch_max = LONG_MIN;
106 unsigned long spare, num_cases = 0;
108 /* TODO: Minimum size for jump table? */
109 if(get_irn_n_outs(cond) <= 4)
112 default_pn = get_Cond_defaultProj(cond);
114 foreach_out_irn(cond, i, proj) {
115 long pn = get_Proj_proj(proj);
127 * Here we have: num_cases and [switch_min, switch_max] interval.
128 * We do an if-cascade if there are too many spare numbers.
130 spare = (unsigned long) switch_max - (unsigned long) switch_min - num_cases + 1;
131 return spare < spare_size;
134 static int casecmp(const void *a, const void *b)
136 return ((case_data_t *) a)->value - ((case_data_t *) b)->value;
140 * Creates an if cascade realizing binary search.
142 static void create_if_cascade(ir_node *sel, ir_node *curblock, ir_node *defblock,
143 case_data_t *curcases, int numcases)
145 set_cur_block(curblock);
149 /* only one case: "if(sel == val) goto target else goto default;" */
150 ir_node *val = new_Const_long(get_irn_mode(sel), curcases[0].value);
151 ir_node *cmp = new_Cmp(sel, val);
152 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
153 ir_node *cond = new_Cond(proj);
154 add_pred(curcases[0].target, new_Proj(cond, mode_X, pn_Cond_true));
155 add_pred(defblock, new_Proj(cond, mode_X, pn_Cond_false));
157 } else if(numcases == 2) {
158 /* only two cases: "if(sel == val[0]) goto target[0];" */
159 ir_node *val = new_Const_long(get_irn_mode(sel), curcases[0].value);
160 ir_node *cmp = new_Cmp(sel, val);
161 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
162 ir_node *cond = new_Cond(proj);
166 add_pred(curcases[0].target, new_Proj(cond, mode_X, pn_Cond_true));
167 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
168 neblock = new_Block(1, in);
170 /* second part: "else if(sel == val[1]) goto target[1] else goto default;" */
171 val = new_Const_long(get_irn_mode(sel), curcases[1].value);
172 cmp = new_Cmp(sel, val);
173 proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
174 cond = new_Cond(proj);
175 add_pred(curcases[1].target, new_Proj(cond, mode_X, pn_Cond_true));
176 add_pred(defblock, new_Proj(cond, mode_X, pn_Cond_false));
179 /* recursive case: split cases in the middle */
180 int midcase = numcases / 2;
181 ir_node *val = new_Const_long(get_irn_mode(sel), curcases[midcase].value);
182 ir_node *cmp = new_Cmp(sel, val);
183 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Lt);
184 ir_node *cond = new_Cond(proj);
189 in[0] = new_Proj(cond, mode_X, pn_Cond_true);
190 ltblock = new_Block(1, in);
192 set_cur_block(curblock);
193 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
194 geblock = new_Block(1, in);
196 create_if_cascade(sel, ltblock, defblock, curcases, midcase);
197 create_if_cascade(sel, geblock, defblock, curcases + midcase, numcases - midcase);
202 * Block-Walker: searches for Cond nodes with a non-boolean mode
204 static void find_cond_nodes(ir_node *block, void *ctx)
206 walk_env_t *env = ctx;
212 int i, j = 0, numcases;
216 ir_node *defblock = NULL;
218 if(get_Block_n_cfgpreds(block) != 1)
221 projx = get_Block_cfgpred(block, 0);
224 assert(get_irn_mode(projx) == mode_X);
226 cond = get_Proj_pred(projx);
230 sel = get_Cond_selector(cond);
231 sel_mode = get_irn_mode(sel);
233 if(sel_mode == mode_b) /* not a switch? */
236 if(should_do_table_switch(cond, env->spare_size))
240 * Switch should be transformed into an if cascade.
241 * So first order the cases, so we can do a binary search on them.
244 numcases = get_irn_n_outs(cond) - 1; // does not contain default case
245 cases = obstack_alloc(&env->obst, numcases * sizeof(*cases));
247 default_pn = get_Cond_defaultProj(cond);
249 foreach_out_irn(cond, i, proj) {
250 long pn = get_Proj_proj(proj);
253 defblock = get_irn_out(proj, 0);
254 remove_pred(defblock, proj);
259 cases[j].target = get_irn_out(proj, 0);
260 remove_pred(cases[j].target, proj);
263 assert(defblock != NULL && "Switch without default proj");
264 qsort(cases, numcases, sizeof(*cases), casecmp);
266 /* Now create the if cascade */
267 condblock = get_nodes_block(cond);
268 create_if_cascade(sel, condblock, defblock, cases, numcases);
270 obstack_free(&env->obst, cases);
274 * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
275 * They will either remain the same or be converted into if-cascades.
277 * @param irg The ir graph to be lowered.
278 * @param spare_size Allowed spare size for table switches in machine words.
279 * (Default in edgfe: 128)
281 void lower_Switch(ir_graph *irg, unsigned spare_size)
284 ir_graph *rem = current_ir_graph;
286 current_ir_graph = irg;
288 obstack_init(&env.obst);
289 env.spare_size = spare_size;
291 assure_irg_outs(irg);
293 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
296 /* control flow changed */
297 set_irg_outs_inconsistent(irg);
298 set_irg_doms_inconsistent(irg);
299 set_irg_extblk_inconsistent(irg);
300 set_irg_loopinfo_inconsistent(irg);
303 obstack_free(&env.obst, NULL);
304 current_ir_graph = rem;