More accurate reference-counter inference

Author: dstogov

ext/opcache/Optimizer/zend_inference.c

@@ -3398,10 +3398,26 @@ static zend_always_inline int _zend_update_type_info(
 		case ZEND_FETCH_OBJ_UNSET:
 		case ZEND_FETCH_OBJ_FUNC_ARG:
 			if (ssa_op->result_def >= 0) {
-				tmp = zend_fetch_prop_type(script,
-					zend_fetch_prop_info(op_array, ssa, opline, ssa_op), &ce);
+				zend_property_info *prop_info = zend_fetch_prop_info(op_array, ssa, opline, ssa_op);
+
+				tmp = zend_fetch_prop_type(script, prop_info, &ce);
 				if (opline->result_type != IS_TMP_VAR) {
 					tmp |= MAY_BE_REF | MAY_BE_INDIRECT;
+				} else if (prop_info) {
+					/* FETCH_OBJ_R/IS for plain property increments reference counter,
+					   so it can't be 1 */
+					tmp &= ~MAY_BE_RC1;
+				} else {
+					zend_class_entry *ce = NULL;
+
+					if (opline->op1_type == IS_UNUSED) {
+						ce = op_array->scope;
+					} else if (ssa_op->op1_use >= 0 && !ssa->var_info[ssa_op->op1_use].is_instanceof) {
+						ce = ssa->var_info[ssa_op->op1_use].ce;
+					}
+					if (ce && !ce->create_object && !ce->__get) {
+						tmp &= ~MAY_BE_RC1;
+					}
 				}
 				UPDATE_SSA_TYPE(tmp, ssa_op->result_def);
 				if (ce) {
@@ -3419,6 +3435,8 @@ static zend_always_inline int _zend_update_type_info(
 				zend_fetch_static_prop_info(script, op_array, ssa, opline), &ce);
 			if (opline->result_type != IS_TMP_VAR) {
 				tmp |= MAY_BE_REF | MAY_BE_INDIRECT;
+			} else {
+				tmp &= ~MAY_BE_RC1;
 			}
 			UPDATE_SSA_TYPE(tmp, ssa_op->result_def);
 			if (ce) {
@@ -3523,7 +3541,11 @@ static zend_always_inline int _zend_update_type_info(
 			if (ssa_op->result_def >= 0) {
 				tmp = MAY_BE_ANY | MAY_BE_ARRAY_KEY_ANY | MAY_BE_ARRAY_OF_ANY | MAY_BE_ARRAY_OF_REF;
 				if (opline->result_type == IS_TMP_VAR) {
-					tmp |= MAY_BE_RC1 | MAY_BE_RCN;
+					if (opline->opcode == ZEND_FETCH_R || opline->opcode == ZEND_FETCH_IS) {
+						tmp |= MAY_BE_RCN;
+					} else {
+						tmp |= MAY_BE_RC1 | MAY_BE_RCN;
+					}
 				} else {
 					tmp |= MAY_BE_REF | MAY_BE_RC1 | MAY_BE_RCN;
 					switch (opline->opcode) {