diff --git a/ext/opcache/Optimizer/zend_dfg.c b/ext/opcache/Optimizer/zend_dfg.c
index b45aac41fbd..c1972128d54 100644
--- a/ext/opcache/Optimizer/zend_dfg.c
+++ b/ext/opcache/Optimizer/zend_dfg.c
@@ -25,21 +25,19 @@ int zend_build_dfg(const zend_op_array *op_array, const zend_cfg *cfg, zend_dfg
 	int set_size;
 	zend_basic_block *blocks = cfg->blocks;
 	int blocks_count = cfg->blocks_count;
-	zend_bitset tmp, gen, def, use, in, out;
+	zend_bitset tmp, def, use, in, out;
 	zend_op *opline;
 	uint32_t k, var_num;
 	int j;
 
-	/* FIXME: can we use "gen" instead of "def" for flow analyzing? */
 	set_size = dfg->size;
 	tmp = dfg->tmp;
-	gen = dfg->gen;
 	def = dfg->def;
 	use = dfg->use;
 	in  = dfg->in;
 	out = dfg->out;
 
-	/* Collect "gen", "def" and "use" sets */
+	/* Collect "def" and "use" sets */
 	for (j = 0; j < blocks_count; j++) {
 		if ((blocks[j].flags & ZEND_BB_REACHABLE) == 0) {
 			continue;
@@ -84,6 +82,9 @@ int zend_build_dfg(const zend_op_array *op_array, const zend_cfg *cfg, zend_dfg
 							goto op1_def;
 						}
 						goto op1_use;
+					case ZEND_UNSET_VAR:
+						ZEND_ASSERT(opline->extended_value & ZEND_QUICK_SET);
+						/* break missing intentionally */
 					case ZEND_ASSIGN:
 					case ZEND_ASSIGN_REF:
 					case ZEND_BIND_GLOBAL:
@@ -92,17 +93,6 @@ int zend_build_dfg(const zend_op_array *op_array, const zend_cfg *cfg, zend_dfg
 					case ZEND_SEND_REF:
 					case ZEND_SEND_VAR_NO_REF:
 					case ZEND_FE_RESET_RW:
-op1_def:
-						if (!DFG_ISSET(use, set_size, j, var_num)) {
-							// FIXME: include into "use" to ...?
-							DFG_SET(use, set_size, j, var_num);
-							DFG_SET(def, set_size, j, var_num);
-						}
-						DFG_SET(gen, set_size, j, var_num);
-						break;
-					case ZEND_UNSET_VAR:
-						ZEND_ASSERT(opline->extended_value & ZEND_QUICK_SET);
-						/* break missing intentionally */
 					case ZEND_ASSIGN_ADD:
 					case ZEND_ASSIGN_SUB:
 					case ZEND_ASSIGN_MUL:
@@ -132,7 +122,11 @@ op1_def:
 					case ZEND_FETCH_OBJ_FUNC_ARG:
 					case ZEND_FETCH_OBJ_UNSET:
 					case ZEND_VERIFY_RETURN_TYPE:
-						DFG_SET(gen, set_size, j, var_num);
+op1_def:
+						// FIXME: include into "use" too ...?
+						DFG_SET(use, set_size, j, var_num);
+						DFG_SET(def, set_size, j, var_num);
+						break;
 					default:
 op1_use:
 						if (!DFG_ISSET(def, set_size, j, var_num)) {
@@ -142,9 +136,9 @@ op1_use:
 				} else if (opline->op1_type & (IS_VAR|IS_TMP_VAR)) {
 					var_num = EX_VAR_TO_NUM(opline->op1.var);
 					if (opline->opcode == ZEND_VERIFY_RETURN_TYPE) {
-						DFG_SET(gen, set_size, j, var_num);
-					}
-					if (!DFG_ISSET(def, set_size, j, var_num)) {
+						DFG_SET(use, set_size, j, var_num);
+						DFG_SET(def, set_size, j, var_num);
+					} else if (!DFG_ISSET(def, set_size, j, var_num)) {
 						DFG_SET(use, set_size, j, var_num);
 					}
 				}
@@ -165,12 +159,9 @@ op1_use:
 						case ZEND_FE_FETCH_R:
 						case ZEND_FE_FETCH_RW:
 op2_def:
-							if (!DFG_ISSET(use, set_size, j, var_num)) {
-								// FIXME: include into "use" to ...?
-								DFG_SET(use, set_size, j, var_num);
-								DFG_SET(def, set_size, j, var_num);
-							}
-							DFG_SET(gen, set_size, j, var_num);
+							// FIXME: include into "use" too ...?
+							DFG_SET(use, set_size, j, var_num);
+							DFG_SET(def, set_size, j, var_num);
 							break;
 						default:
 op2_use:
@@ -182,10 +173,7 @@ op2_use:
 				} else if (opline->op2_type & (IS_VAR|IS_TMP_VAR)) {
 					var_num = EX_VAR_TO_NUM(opline->op2.var);
 					if (opline->opcode == ZEND_FE_FETCH_R || opline->opcode == ZEND_FE_FETCH_RW) {
-						if (!DFG_ISSET(use, set_size, j, var_num)) {
-							DFG_SET(def, set_size, j, var_num);
-						}
-						DFG_SET(gen, set_size, j, var_num);
+						DFG_SET(def, set_size, j, var_num);
 					} else {
 						if (!DFG_ISSET(def, set_size, j, var_num)) {
 							DFG_SET(use, set_size, j, var_num);
@@ -194,10 +182,7 @@ op2_use:
 				}
 				if (opline->result_type & (IS_CV|IS_VAR|IS_TMP_VAR)) {
 					var_num = EX_VAR_TO_NUM(opline->result.var);
-					if (!DFG_ISSET(use, set_size, j, var_num)) {
-						DFG_SET(def, set_size, j, var_num);
-					}
-					DFG_SET(gen, set_size, j, var_num);
+					DFG_SET(def, set_size, j, var_num);
 				}
 			}
 		}
diff --git a/ext/opcache/Optimizer/zend_dfg.h b/ext/opcache/Optimizer/zend_dfg.h
index 9d864992cac..5ed8cfc5d0d 100644
--- a/ext/opcache/Optimizer/zend_dfg.h
+++ b/ext/opcache/Optimizer/zend_dfg.h
@@ -26,7 +26,6 @@ typedef struct _zend_dfg {
 	int         vars;
 	uint32_t    size;
 	zend_bitset tmp;
-	zend_bitset gen;
 	zend_bitset def;
 	zend_bitset use;
 	zend_bitset in;
diff --git a/ext/opcache/Optimizer/zend_dump.c b/ext/opcache/Optimizer/zend_dump.c
index ba5fb8a0ce5..986e4703457 100644
--- a/ext/opcache/Optimizer/zend_dump.c
+++ b/ext/opcache/Optimizer/zend_dump.c
@@ -1143,7 +1143,6 @@ void zend_dump_dfg(const zend_op_array *op_array, const zend_cfg *cfg, const zen
 
 	for (j = 0; j < cfg->blocks_count; j++) {
 		fprintf(stderr, "  BB%d:\n", j);
-		zend_dump_var_set(op_array, "gen", DFG_BITSET(dfg->gen, dfg->size, j));
 		zend_dump_var_set(op_array, "def", DFG_BITSET(dfg->def, dfg->size, j));
 		zend_dump_var_set(op_array, "use", DFG_BITSET(dfg->use, dfg->size, j));
 		zend_dump_var_set(op_array, "in ", DFG_BITSET(dfg->in,  dfg->size, j));
diff --git a/ext/opcache/Optimizer/zend_ssa.c b/ext/opcache/Optimizer/zend_ssa.c
index 9d5f5a8e184..c70ecc52fc6 100644
--- a/ext/opcache/Optimizer/zend_ssa.c
+++ b/ext/opcache/Optimizer/zend_ssa.c
@@ -765,7 +765,7 @@ int zend_build_ssa(zend_arena **arena, const zend_op_array *op_array, uint32_t b
 	zend_ssa_block *ssa_blocks;
 	int blocks_count = ssa->cfg.blocks_count;
 	uint32_t set_size;
-	zend_bitset tmp, gen, in;
+	zend_bitset tmp, def, in;
 	int *var = NULL;
 	int i, j, k, changed;
 	zend_dfg dfg;
@@ -784,8 +784,7 @@ int zend_build_ssa(zend_arena **arena, const zend_op_array *op_array, uint32_t b
 	dfg.size = set_size = zend_bitset_len(dfg.vars);
 	dfg.tmp = do_alloca((set_size * sizeof(zend_ulong)) * (blocks_count * 5 + 1), dfg_use_heap);
 	memset(dfg.tmp, 0, (set_size * sizeof(zend_ulong)) * (blocks_count * 5 + 1));
-	dfg.gen = dfg.tmp + set_size;
-	dfg.def = dfg.gen + set_size * blocks_count;
+	dfg.def = dfg.tmp + set_size;
 	dfg.use = dfg.def + set_size * blocks_count;
 	dfg.in  = dfg.use + set_size * blocks_count;
 	dfg.out = dfg.in  + set_size * blocks_count;
@@ -800,10 +799,10 @@ int zend_build_ssa(zend_arena **arena, const zend_op_array *op_array, uint32_t b
 	}
 
 	tmp = dfg.tmp;
-	gen = dfg.gen;
+	def = dfg.def;
 	in  = dfg.in;
 
-	/* SSA construction, Step 1: Propagate "gen" sets in merge points */
+	/* SSA construction, Step 1: Propagate "def" sets in merge points */
 	do {
 		changed = 0;
 		for (j = 0; j < blocks_count; j++) {
@@ -811,16 +810,16 @@ int zend_build_ssa(zend_arena **arena, const zend_op_array *op_array, uint32_t b
 				continue;
 			}
 			if (j >= 0 && (blocks[j].predecessors_count > 1 || j == 0)) {
-				zend_bitset_copy(tmp, gen + (j * set_size), set_size);
+				zend_bitset_copy(tmp, def + (j * set_size), set_size);
 				for (k = 0; k < blocks[j].predecessors_count; k++) {
 					i = ssa->cfg.predecessors[blocks[j].predecessor_offset + k];
 					while (i != -1 && i != blocks[j].idom) {
-						zend_bitset_union_with_intersection(tmp, tmp, gen + (i * set_size), in + (j * set_size), set_size);
+						zend_bitset_union_with_intersection(tmp, tmp, def + (i * set_size), in + (j * set_size), set_size);
 						i = blocks[i].idom;
 					}
 				}
-				if (!zend_bitset_equal(gen + (j * set_size), tmp, set_size)) {
-					zend_bitset_copy(gen + (j * set_size), tmp, set_size);
+				if (!zend_bitset_equal(def + (j * set_size), tmp, set_size)) {
+					zend_bitset_copy(def + (j * set_size), tmp, set_size);
 					changed = 1;
 				}
 			}
@@ -850,7 +849,7 @@ int zend_build_ssa(zend_arena **arena, const zend_op_array *op_array, uint32_t b
 				for (k = 0; k < blocks[j].predecessors_count; k++) {
 					i = ssa->cfg.predecessors[blocks[j].predecessor_offset + k];
 					while (i != -1 && i != blocks[j].idom) {
-						zend_bitset_union_with_intersection(tmp, tmp, gen + (i * set_size), in + (j * set_size), set_size);
+						zend_bitset_union_with_intersection(tmp, tmp, def + (i * set_size), in + (j * set_size), set_size);
 						i = blocks[i].idom;
 					}
 				}
@@ -907,7 +906,7 @@ int zend_build_ssa(zend_arena **arena, const zend_op_array *op_array, uint32_t b
 							if (p) {
 								if (p->pi >= 0) {
 									if (zend_bitset_in(in + (j * set_size), p->var) &&
-									    !zend_bitset_in(gen + (i * set_size), p->var)) {
+									    !zend_bitset_in(def + (i * set_size), p->var)) {
 										zend_bitset_incl(tmp, p->var);
 									}
 								} else {