Omit free for frameless calls returning non-RC types

Author: iluuu1994

Zend/zend_compile.c

@@ -795,6 +795,17 @@ static void zend_do_free(znode *op1) /* {{{ */
 				case ZEND_PRE_DEC:
 					SET_UNUSED(opline->result);
 					return;
+				case ZEND_FRAMELESS_ICALL_0:
+				case ZEND_FRAMELESS_ICALL_1:
+				case ZEND_FRAMELESS_ICALL_2:
+				case ZEND_FRAMELESS_ICALL_3: {
+					const zend_type return_type = ZEND_FLF_FUNC(opline)->common.arg_info[-1].type;
+					if (!ZEND_TYPE_IS_COMPLEX(return_type)
+					 && !(ZEND_TYPE_PURE_MASK(return_type) & (MAY_BE_STRING|MAY_BE_ARRAY|MAY_BE_OBJECT|MAY_BE_RESOURCE|MAY_BE_REF))) {
+						return;
+					}
+					break;
+				}
 			}
 		}
 
@@ -816,9 +827,11 @@ static void zend_do_free(znode *op1) /* {{{ */
 			} else {
 				/* Frameless calls usually use the return value, so always emit a free. This should be
 				 * faster than checking RETURN_VALUE_USED inside the handler. */
-				// FIXME: We may actually look at the function signature to determine whether a free
-				// is necessary.
-				zend_emit_op(NULL, ZEND_FREE, op1, NULL);
+				const zend_type return_type = ZEND_FLF_FUNC(opline)->common.arg_info[-1].type;
+				if (ZEND_TYPE_IS_COMPLEX(return_type)
+				 || (ZEND_TYPE_PURE_MASK(return_type) & (MAY_BE_STRING|MAY_BE_ARRAY|MAY_BE_OBJECT|MAY_BE_RESOURCE|MAY_BE_REF))) {
+					zend_emit_op(NULL, ZEND_FREE, op1, NULL);
+				}
 			}
 		} else {
 			while (opline >= CG(active_op_array)->opcodes) {

ext/opcache/tests/frameless_omit_free.phpt

@@ -0,0 +1,37 @@
+--TEST--
+Frameless returning non-RC types can omit free at compile-time
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.opt_debug_level=0x10000
+--FILE--
+<?php
+
+function test(array $array) {
+    class_exists('Foo');
+    preg_match('(foo)', 'foo');
+    implode(', ', $array);
+}
+
+?>
+--EXPECTF--
+$_main:
+     ; (lines=%d, args=0, vars=0, tmps=%d)
+     ; (before optimizer)
+     ; %s
+     ; return  [] RANGE[0..0]
+0000 RETURN int(1)
+
+test:
+     ; (lines=%d, args=1, vars=1, tmps=%d)
+     ; (before optimizer)
+     ; %s
+     ; return  [] RANGE[0..0]
+0000 CV0($array) = RECV 1
+0001 T1 = FRAMELESS_ICALL_1(class_exists) string("Foo")
+0002 T2 = FRAMELESS_ICALL_2(preg_match) string("(foo)") string("foo")
+0003 T3 = FRAMELESS_ICALL_2(implode) string(", ") CV0($array)
+0004 FREE T3
+0005 RETURN null