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4 * This file is part of libFirm.
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12 * this file in accordance with the libFirm Commercial License.
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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 Alternative extended basic block computation
23 * @author Matthias Braun
27 * Alternative algorithm for computing extended basic blocks (using out edges
28 * and execution frequencies)
32 #include "irextbb_t.h"
35 #include "irgraph_t.h"
36 #include "iredges_t.h"
43 struct obstack *obst; /**< the obstack where allocations took place */
44 ir_extblk *head; /**< head of the list of all extended blocks */
45 ir_exec_freq *execfreqs;
49 * allocate a new extended block header.
51 static ir_extblk *allocate_extblk(ir_node *block, env_t *env)
53 ir_extblk *extblk = OALLOC(env->obst, ir_extblk);
55 extblk->kind = k_ir_extblk;
57 extblk->blks = (ir_node **)env->head;
61 set_Block_extbb(block, extblk);
62 set_irn_link(block, NULL);
68 * add a block to an extended block
70 static void addto_extblk(ir_extblk *extblk, ir_node *block)
72 /* link all blocks belonging to this extended block */
73 set_irn_link(block, extblk->link);
78 set_Block_extbb(block, extblk);
82 * Returns the number of block successors.
83 * we are interested only in 1, 2 and >2.
85 static int get_block_n_succs(ir_node *block)
87 if (edges_activated(current_ir_graph)) {
88 const ir_edge_t *edge;
90 edge = get_block_succ_first(block);
94 edge = get_block_succ_next(block, edge);
98 edge = get_block_succ_next(block, edge);
102 return get_Block_n_cfg_outs(block);
105 static void pick_successor(ir_node *block, ir_extblk *extblk, env_t *env);
107 static void create_extblk(ir_node *block, env_t *env)
111 if (irn_visited_else_mark(block))
114 extblk = allocate_extblk(block, env);
116 pick_successor(block, extblk, env);
119 static void pick_successor(ir_node *block, ir_extblk *extblk, env_t *env)
121 const ir_edge_t *edge;
122 ir_node *best_succ = NULL;
123 double best_execfreq = -1;
126 More than two successors means we have a jump table.
127 we cannot include a jump target into the current extended
128 basic block, so create a new one here.
130 if (get_block_n_succs(block) > 2) {
131 const ir_edge_t *edge;
133 foreach_block_succ(block, edge) {
134 ir_node *succ = get_edge_src_irn(edge);
135 create_extblk(succ, env);
141 foreach_block_succ(block, edge) {
142 ir_node *succ = get_edge_src_irn(edge);
145 if (irn_visited(succ))
148 if (get_Block_n_cfgpreds(succ) > 1) {
149 create_extblk(succ, env);
153 execfreq = get_block_execfreq(env->execfreqs, succ);
156 Remember best successor and make non best successor with only 1
157 pred block to new extbb leaders.
159 if (execfreq > best_execfreq) {
160 if (best_succ != NULL) {
161 create_extblk(best_succ, env);
164 best_execfreq = execfreq;
168 create_extblk(succ, env);
172 /* add best successor and recursively try to pick more */
173 if (best_succ != NULL) {
174 addto_extblk(extblk, best_succ);
175 mark_irn_visited(best_succ);
176 pick_successor(best_succ, extblk, env);
181 * Compute the extended basic blocks for a graph
183 void compute_extbb_execfreqs(ir_graph *irg, ir_exec_freq *execfreqs)
186 ir_extblk *extbb, *next;
189 if (irg->extbb_obst) {
190 obstack_free(irg->extbb_obst, NULL);
193 irg->extbb_obst = XMALLOC(struct obstack);
195 obstack_init(irg->extbb_obst);
197 env.obst = irg->extbb_obst;
199 env.execfreqs = execfreqs;
201 assure_irg_outs(irg);
203 /* we must mark nodes, so increase the visited flag */
204 inc_irg_visited(irg);
205 create_extblk(get_irg_start_block(irg), &env);
207 /* the end block needs a extbb assigned (even for endless loops) */
208 endblock = get_irg_end_block(irg);
209 create_extblk(endblock, &env);
212 Ok, we have now the list of all extended blocks starting with env.head
213 every extended block "knowns" the number of blocks in visited and
214 the blocks are linked in link.
215 Now we can create arrays that hold the blocks, some kind of "out" edges
216 for the extended block
218 for (extbb = env.head; extbb; extbb = next) {
219 int i, len = (int)extbb->visited;
222 next = (ir_extblk *)extbb->blks;
224 extbb->blks = NEW_ARR_D(ir_node *, env.obst, len);
226 for (block = extbb->link, i = 0; i < len; ++i) {
227 ir_node *nblock = get_irn_link(block);
229 /* ensure that the leader is the first one */
230 extbb->blks[len - 1 - i] = block;
231 set_irn_link(block, NULL);
236 for (i = 0; i < len; ++i) {
239 ir_printf("%+F", extbb->blks[i]);
248 irg->extblk_state = extblk_valid;