Optimize Traversable unpacking in zend_vm_def.h

The C compiler sees that a dynamic function is being called, so it cannot infer
that iter->funcs has not changed.

This results in more assembly instructions and slightly more time to execute that code
path.

Unpacking traversables to arrays(`ZEND_ADD_ARRAY_UNPACK`),
starting foreach loops (`ZEND_FE_FETCH*`), etc. are affected.

```
<?php
/*
 * Before: 1.576 seconds
 * After:  1.474 seconds
 */
function example() {
    $start = hrtime(true);
    $it = new SplFixedArray(1000);
    $total = 0;
    for ($i = 0; $i < 100000; $i++) {
        $total += count([...$it]);
    }
    $end = hrtime(true);
    printf("Elapsed: %.6f\n", ($end - $start) / 1_000_000_000);
}
example();
```

1 files changed, 28 insertions, 24 deletions

diff --git a/Zend/zend_vm_execute.h b/Zend/zend_vm_execute.h
index 0fe4fb5bb5..b170b9ab47 100644
--- a/Zend/zend_vm_execute.h
+++ b/Zend/zend_vm_execute.h
@@ -2203,26 +2203,27 @@ send_again:
 				HANDLE_EXCEPTION();
 			}
 
-			if (iter->funcs->rewind) {
-				iter->funcs->rewind(iter);
+			const zend_object_iterator_funcs *funcs = iter->funcs;
+			if (funcs->rewind) {
+				funcs->rewind(iter);
 			}
 
-			for (; iter->funcs->valid(iter) == SUCCESS; ++arg_num) {
+			for (; funcs->valid(iter) == SUCCESS; ++arg_num) {
 				zval *arg, *top;
 
 				if (UNEXPECTED(EG(exception) != NULL)) {
 					break;
 				}
 
-				arg = iter->funcs->get_current_data(iter);
+				arg = funcs->get_current_data(iter);
 				if (UNEXPECTED(EG(exception) != NULL)) {
 					break;
 				}
 
 				zend_string *name = NULL;
-				if (iter->funcs->get_current_key) {
+				if (funcs->get_current_key) {
 					zval key;
-					iter->funcs->get_current_key(iter, &key);
+					funcs->get_current_key(iter, &key);
 					if (UNEXPECTED(EG(exception) != NULL)) {
 						break;
 					}
@@ -2284,7 +2285,7 @@ send_again:
 					ZEND_CALL_NUM_ARGS(EX(call))++;
 				}
 
-				iter->funcs->move_forward(iter);
+				funcs->move_forward(iter);
 			}
 
 			zend_iterator_dtor(iter);
@@ -2544,25 +2545,26 @@ add_unpack_again:
 				HANDLE_EXCEPTION();
 			}
 
-			if (iter->funcs->rewind) {
-				iter->funcs->rewind(iter);
+			const zend_object_iterator_funcs *funcs = iter->funcs;
+			if (funcs->rewind) {
+				funcs->rewind(iter);
 			}
 
-			for (; iter->funcs->valid(iter) == SUCCESS; ) {
+			for (; funcs->valid(iter) == SUCCESS; ) {
 				zval *val;
 
 				if (UNEXPECTED(EG(exception) != NULL)) {
 					break;
 				}
 
-				val = iter->funcs->get_current_data(iter);
+				val = funcs->get_current_data(iter);
 				if (UNEXPECTED(EG(exception) != NULL)) {
 					break;
 				}
 
 				zval key;
-				if (iter->funcs->get_current_key) {
-					iter->funcs->get_current_key(iter, &key);
+				if (funcs->get_current_key) {
+					funcs->get_current_key(iter, &key);
 					if (UNEXPECTED(EG(exception) != NULL)) {
 						break;
 					}
@@ -2592,7 +2594,7 @@ add_unpack_again:
 					}
 				}
 
-				iter->funcs->move_forward(iter);
+				funcs->move_forward(iter);
 				if (UNEXPECTED(EG(exception))) {
 					break;
 				}
@@ -21692,15 +21694,16 @@ fe_fetch_r_exit:
 				}
 			}
 		} else {
+			const zend_object_iterator_funcs *funcs = iter->funcs;
 			if (EXPECTED(++iter->index > 0)) {
 				/* This could cause an endless loop if index becomes zero again.
 				 * In case that ever happens we need an additional flag. */
-				iter->funcs->move_forward(iter);
+				funcs->move_forward(iter);
 				if (UNEXPECTED(EG(exception) != NULL)) {
 					UNDEF_RESULT();
 					HANDLE_EXCEPTION();
 				}
-				if (UNEXPECTED(iter->funcs->valid(iter) == FAILURE)) {
+				if (UNEXPECTED(funcs->valid(iter) == FAILURE)) {
 					/* reached end of iteration */
 					if (UNEXPECTED(EG(exception) != NULL)) {
 						UNDEF_RESULT();
@@ -21709,7 +21712,7 @@ fe_fetch_r_exit:
 					goto fe_fetch_r_exit;
 				}
 			}
-			value = iter->funcs->get_current_data(iter);
+			value = funcs->get_current_data(iter);
 			if (UNEXPECTED(EG(exception) != NULL)) {
 				UNDEF_RESULT();
 				HANDLE_EXCEPTION();
@@ -21719,8 +21722,8 @@ fe_fetch_r_exit:
 				goto fe_fetch_r_exit;
 			}
 			if (RETURN_VALUE_USED(opline)) {
-				if (iter->funcs->get_current_key) {
-					iter->funcs->get_current_key(iter, EX_VAR(opline->result.var));
+				if (funcs->get_current_key) {
+					funcs->get_current_key(iter, EX_VAR(opline->result.var));
 					if (UNEXPECTED(EG(exception) != NULL)) {
 						UNDEF_RESULT();
 						HANDLE_EXCEPTION();
@@ -21845,15 +21848,16 @@ static ZEND_OPCODE_HANDLER_RET ZEND_FASTCALL ZEND_FE_FETCH_RW_SPEC_VAR_HANDLER(Z
 				}
 			}
 		} else {
+			const zend_object_iterator_funcs *funcs = iter->funcs;
 			if (++iter->index > 0) {
 				/* This could cause an endless loop if index becomes zero again.
 				 * In case that ever happens we need an additional flag. */
-				iter->funcs->move_forward(iter);
+				funcs->move_forward(iter);
 				if (UNEXPECTED(EG(exception) != NULL)) {
 					UNDEF_RESULT();
 					HANDLE_EXCEPTION();
 				}
-				if (UNEXPECTED(iter->funcs->valid(iter) == FAILURE)) {
+				if (UNEXPECTED(funcs->valid(iter) == FAILURE)) {
 					/* reached end of iteration */
 					if (UNEXPECTED(EG(exception) != NULL)) {
 						UNDEF_RESULT();
@@ -21862,7 +21866,7 @@ static ZEND_OPCODE_HANDLER_RET ZEND_FASTCALL ZEND_FE_FETCH_RW_SPEC_VAR_HANDLER(Z
 					goto fe_fetch_w_exit;
 				}
 			}
-			value = iter->funcs->get_current_data(iter);
+			value = funcs->get_current_data(iter);
 			if (UNEXPECTED(EG(exception) != NULL)) {
 				UNDEF_RESULT();
 				HANDLE_EXCEPTION();
@@ -21872,8 +21876,8 @@ static ZEND_OPCODE_HANDLER_RET ZEND_FASTCALL ZEND_FE_FETCH_RW_SPEC_VAR_HANDLER(Z
 				goto fe_fetch_w_exit;
 			}
 			if (RETURN_VALUE_USED(opline)) {
-				if (iter->funcs->get_current_key) {
-					iter->funcs->get_current_key(iter, EX_VAR(opline->result.var));
+				if (funcs->get_current_key) {
+					funcs->get_current_key(iter, EX_VAR(opline->result.var));
 					if (UNEXPECTED(EG(exception) != NULL)) {
 						UNDEF_RESULT();
 						HANDLE_EXCEPTION();