Use worklist for DFG construction

About 40x faster.

diff --git a/ext/opcache/Optimizer/zend_dfg.c b/ext/opcache/Optimizer/zend_dfg.c
index 1266ae5e542c372505b0818838befcf6074bb999..65c19b21d99cbd6fc5b9f020f10c213a3cc4e710 100644 (file)
--- a/ext/opcache/Optimizer/zend_dfg.c
+++ b/ext/opcache/Optimizer/zend_dfg.c
@@ -28,7 +28,7 @@ int zend_build_dfg(const zend_op_array *op_array, const zend_cfg *cfg, zend_dfg
        zend_bitset tmp, gen, def, use, in, out;
        zend_op *opline;
        uint32_t k;
-       int j, changed;
+       int j;
 
        /* FIXME: can we use "gen" instead of "def" for flow analyzing? */
        set_size = dfg->size;
@@ -205,9 +205,20 @@ int zend_build_dfg(const zend_op_array *op_array, const zend_cfg *cfg, zend_dfg
        }
 
        /* Calculate "in" and "out" sets */
-       do {
-               changed = 0;
+       {
+               uint32_t worklist_len = zend_bitset_len(blocks_count);
+               ALLOCA_FLAG(use_heap);
+               zend_bitset worklist = ZEND_BITSET_ALLOCA(worklist_len, use_heap);
+               memset(worklist, 0, worklist_len * ZEND_BITSET_ELM_SIZE);
                for (j = 0; j < blocks_count; j++) {
+                       zend_bitset_incl(worklist, j);
+               }
+               while (!zend_bitset_empty(worklist, worklist_len)) {
+                       /* We use the last block on the worklist, because predecessors tend to be located
+                        * before the succeeding block, so this converges faster. */
+                       j = zend_bitset_last(worklist, worklist_len);
+                       zend_bitset_excl(worklist, j);
+
                        if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
                                continue;
                        }
@@ -222,10 +233,19 @@ int zend_build_dfg(const zend_op_array *op_array, const zend_cfg *cfg, zend_dfg
                        zend_bitset_union_with_difference(tmp, DFG_BITSET(use, set_size, j), DFG_BITSET(out, set_size, j), DFG_BITSET(def, set_size, j), set_size);
                        if (!zend_bitset_equal(DFG_BITSET(in, set_size, j), tmp, set_size)) {
                                zend_bitset_copy(DFG_BITSET(in, set_size, j), tmp, set_size);
-                               changed = 1;
+
+                               /* Add predecessors of changed block to worklist */
+                               {
+                                       int *predecessors = &cfg->predecessors[blocks[j].predecessor_offset];
+                                       for (k = 0; k < blocks[j].predecessors_count; k++) {
+                                               zend_bitset_incl(worklist, predecessors[k]);
+                                       }
+                               }
                        }
                }
-       } while (changed);
+
+               free_alloca(worklist, use_heap);
+       }
 
        return SUCCESS;
 }