Fixed CFG/SSA construction (avoid multiple identical predecessors)

ext/opcache/Optimizer/zend_cfg.c

@@ -649,9 +649,18 @@ int zend_cfg_build_predecessors(zend_arena **arena, zend_cfg *cfg) /* {{{ */
 
 	for (j = 0; j < cfg->blocks_count; j++) {
 		if (blocks[j].flags & ZEND_BB_REACHABLE) {
+			/* SWITCH_STRING/LONG may have few identical successors */
 			for (s = 0; s < blocks[j].successors_count; s++) {
-				/* SWITCH_STRING/LONG may have few following identical successors */
-				if (s == 0 || blocks[j].successors[s-1] != blocks[j].successors[s]) {
+				int duplicate = 0;
+				int p;
+
+				for (p = 0; p < s; p++) {
+					if (blocks[j].successors[p] == blocks[j].successors[s]) {
+						duplicate = 1;
+						break;
+					}
+				}
+				if (!duplicate) {
 					zend_basic_block *b = blocks + blocks[j].successors[s];
 
 					predecessors[b->predecessor_offset + b->predecessors_count] = j;