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 #define foreach_out_irn(irn, i, outirn) for (i = get_irn_n_outs(irn) - 1;\
41 i >= 0 && (outirn = get_irn_out(irn, i)); --i)
43 typedef struct walk_env {
44 unsigned spare_size; /**< the allowed spare size for table switches */
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_default_proj(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 const case_data_t *cda = a;
103 const case_data_t *cdb = b;
106 * Enforce unsigned sorting. Signed comparison will behave differently for
107 * 32-bit values, depending on sizeof(long). This will make the resulting
108 * array deterministic.
110 return ((unsigned long)cda->value > (unsigned long)cdb->value) -
111 ((unsigned long)cda->value < (unsigned long)cdb->value);
115 * Creates an if cascade realizing binary search.
117 static void create_if_cascade(ifcas_env_t *env, ir_node *curblock,
118 case_data_t *curcases, int numcases)
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))
137 cmp_mode = find_unsigned_mode(cmp_mode);
138 cmp_sel = new_r_Conv(sel_block, cmp_sel, cmp_mode);
141 assert(numcases >= 0);
143 set_cur_block(curblock);
146 /* zero cases: "goto default;" */
147 env->defusers[env->defindex++] = new_Jmp();
148 } else if (numcases == 1) {
149 /* only one case: "if (sel == val) goto target else goto default;" */
150 ir_node *val = new_Const_long(cmp_mode, curcases[0].value);
151 ir_node *cmp = new_Cmp(cmp_sel, val);
152 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
153 ir_node *cond = new_Cond(proj);
154 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
155 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
156 } else if (numcases == 2) {
157 /* only two cases: "if (sel == val[0]) goto target[0];" */
158 ir_node *val = new_Const_long(cmp_mode, curcases[0].value);
159 ir_node *cmp = new_Cmp(cmp_sel, val);
160 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
161 ir_node *cond = new_Cond(proj);
165 set_Block_cfgpred(curcases[0].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
166 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
167 neblock = new_Block(1, in);
168 set_cur_block(neblock);
170 /* second part: "else if (sel == val[1]) goto target[1] else goto default;" */
171 val = new_Const_long(cmp_mode, curcases[1].value);
172 cmp = new_Cmp(cmp_sel, val);
173 proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
174 cond = new_Cond(proj);
175 set_Block_cfgpred(curcases[1].target, 0, new_Proj(cond, mode_X, pn_Cond_true));
176 env->defusers[env->defindex++] = new_Proj(cond, mode_X, pn_Cond_false);
178 /* recursive case: split cases in the middle */
179 int midcase = numcases / 2;
180 ir_node *val = new_Const_long(cmp_mode, curcases[midcase].value);
181 ir_node *cmp = new_Cmp(cmp_sel, val);
182 ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Lt);
183 ir_node *cond = new_Cond(proj);
188 in[0] = new_Proj(cond, mode_X, pn_Cond_true);
189 ltblock = new_Block(1, in);
191 set_cur_block(curblock);
192 in[0] = new_Proj(cond, mode_X, pn_Cond_false);
193 geblock = new_Block(1, in);
194 set_cur_block(geblock);
196 create_if_cascade(env, ltblock, curcases, midcase);
197 create_if_cascade(env, geblock, 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;
217 ifcas_env_t ifcas_env;
219 if (get_Block_n_cfgpreds(block) != 1)
222 projx = get_Block_cfgpred(block, 0);
225 assert(get_irn_mode(projx) == mode_X);
227 cond = get_Proj_pred(projx);
231 sel = get_Cond_selector(cond);
232 sel_mode = get_irn_mode(sel);
234 if (sel_mode == mode_b) /* not a switch? */
237 if (should_do_table_switch(cond, env->spare_size))
241 * Switch should be transformed into an if cascade.
242 * So first order the cases, so we can do a binary search on them.
246 numcases = get_irn_n_outs(cond) - 1; // does not contain default case
247 NEW_ARR_A(case_data_t, cases, numcases);
249 default_pn = get_Cond_default_proj(cond);
251 ifcas_env.defindex = 0;
252 NEW_ARR_A(ir_node*, ifcas_env.defusers, numcases);
254 foreach_out_irn(cond, i, proj) {
255 long pn = get_Proj_proj(proj);
256 ir_node *target = get_irn_out(proj, 0);
257 assert(get_Block_n_cfgpreds(target) == 1 && "Encountered critical edge in switch");
259 if (pn == default_pn) {
265 cases[j].target = target;
269 assert(defblock != NULL && "Switch without default proj");
270 qsort(cases, numcases, sizeof(*cases), casecmp);
272 /* Now create the if cascade */
273 condblock = get_nodes_block(cond);
274 create_if_cascade(&ifcas_env, condblock, cases, numcases);
276 /* Connect new default case users */
277 set_irn_in(defblock, ifcas_env.defindex, ifcas_env.defusers);
281 * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
282 * They will either remain the same or be converted into if-cascades.
284 * @param irg The ir graph to be lowered.
285 * @param spare_size Allowed spare size for table switches in machine words.
286 * (Default in edgfe: 128)
288 void lower_switch(ir_graph *irg, unsigned spare_size)
291 ir_graph *rem = current_ir_graph;
293 current_ir_graph = irg;
296 env.spare_size = spare_size;
298 remove_critical_cf_edges(irg);
299 assure_irg_outs(irg);
301 irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
304 /* control flow changed */
305 set_irg_outs_inconsistent(irg);
306 set_irg_doms_inconsistent(irg);
307 set_irg_extblk_inconsistent(irg);
308 set_irg_loopinfo_inconsistent(irg);
310 current_ir_graph = rem;
314 ir_graph_pass_t pass;
319 * Wrapper for running lower_switch() as a pass.
321 static int pass_wrapper(ir_graph *irg, void *context)
323 struct pass_t *pass = context;
325 lower_switch(irg, pass->spare_size);
329 /* creates a pass for lower_switch */
330 ir_graph_pass_t *lower_switch_pass(const char *name, unsigned spare_size)
332 struct pass_t *pass = XMALLOCZ(struct pass_t);
334 pass->spare_size = spare_size;
335 return def_graph_pass_constructor(
336 &pass->pass, name ? name : "lower_switch", pass_wrapper);