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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 = obstack_alloc(env->obst, sizeof(*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) {
86 if (edges_activated(current_ir_graph)) {
87 const ir_edge_t *edge;
89 edge = get_block_succ_first(block);
93 edge = get_block_succ_next(block, edge);
97 edge = get_block_succ_next(block, edge);
101 return get_Block_n_cfg_outs(block);
104 static void pick_successor(ir_node *block, ir_extblk *extblk, env_t *env);
106 static void create_extblk(ir_node *block, env_t *env)
110 if (irn_visited_else_mark(block))
113 extblk = allocate_extblk(block, env);
115 pick_successor(block, extblk, env);
118 static void pick_successor(ir_node *block, ir_extblk *extblk, env_t *env)
120 const ir_edge_t *edge;
121 ir_node *best_succ = NULL;
122 double best_execfreq = -1;
125 More than two successors means we have a jump table.
126 we cannot include a jump target into the current extended
127 basic block, so create a new one here.
129 if (get_block_n_succs(block) > 2) {
130 const ir_edge_t *edge;
132 foreach_block_succ(block, edge) {
133 ir_node *succ = get_edge_src_irn(edge);
134 create_extblk(succ, env);
140 foreach_block_succ(block, edge) {
141 ir_node *succ = get_edge_src_irn(edge);
144 if(irn_visited(succ))
147 if(get_Block_n_cfgpreds(succ) > 1) {
148 create_extblk(succ, env);
152 execfreq = get_block_execfreq(env->execfreqs, succ);
155 Remember best successor and make non best successor with only 1
156 pred block to new extbb leaders.
158 if (execfreq > best_execfreq) {
159 if (best_succ != NULL) {
160 create_extblk(best_succ, env);
163 best_execfreq = execfreq;
167 create_extblk(succ, env);
171 /* add best successor and recursively try to pick more */
172 if(best_succ != NULL) {
173 addto_extblk(extblk, best_succ);
174 mark_irn_visited(best_succ);
175 pick_successor(best_succ, extblk, env);
180 * Compute the extended basic blocks for a graph
182 void compute_extbb_execfreqs(ir_graph *irg, ir_exec_freq *execfreqs) {
184 ir_extblk *extbb, *next;
187 if (irg->extbb_obst) {
188 obstack_free(irg->extbb_obst, NULL);
191 irg->extbb_obst = XMALLOC(struct obstack);
193 obstack_init(irg->extbb_obst);
195 env.obst = irg->extbb_obst;
197 env.execfreqs = execfreqs;
199 assure_irg_outs(irg);
201 /* we must mark nodes, so increase the visited flag */
202 inc_irg_visited(irg);
203 create_extblk(get_irg_start_block(irg), &env);
205 /* the end block needs a extbb assigned (even for endless loops) */
206 endblock = get_irg_end_block(irg);
207 create_extblk(endblock, &env);
210 Ok, we have now the list of all extended blocks starting with env.head
211 every extended block "knowns" the number of blocks in visited and
212 the blocks are linked in link.
213 Now we can create arrays that hold the blocks, some kind of "out" edges
214 for the extended block
216 for (extbb = env.head; extbb; extbb = next) {
217 int i, len = (int)extbb->visited;
220 next = (ir_extblk *)extbb->blks;
222 extbb->blks = NEW_ARR_D(ir_node *, env.obst, len);
224 for (block = extbb->link, i = 0; i < len; ++i) {
225 ir_node *nblock = get_irn_link(block);
227 /* ensure that the leader is the first one */
228 extbb->blks[len - 1 - i] = block;
229 set_irn_link(block, NULL);
234 for(i = 0; i < len; ++i) {
237 ir_printf("%+F", extbb->blks[i]);
246 irg->extblk_state = extblk_valid;