what is the role of ZEND_FASTCALL in Zend source code?
the following is zend_vm_execute.h: in zend source code
`static int ZEND_FASTCALL ZEND_ASSIGN_SPEC_CV_CONST_HANDLER (ZEND_OPCODE_HANDLER_ARGS)
{
USE_OPLINE
zval *value;
zval **variable_ptr_ptr;
SAVE_OPLINE();
value = opline->op2.zv;
variable_ptr_ptr = _get_zval_ptr_ptr_cv_BP_VAR_W(execute_data, opline->op1.var TSRMLS_CC);
if (IS_CV == IS_VAR && UNEXPECTED(variable_ptr_ptr == NULL)) {
if (zend_assign_to_string_offset(&EX_T(opline->op1.var), value, IS_CONST TSRMLS_CC)) {
if (RETURN_VALUE_USED(opline)) {
PZVAL_LOCK(&EG(uninitialized_zval));
EX_T(opline->result.var).var.ptr = &EG(uninitialized_zval);
}
} else {
if (IS_CONST == IS_TMP_VAR) {
value = zend_assign_tmp_to_variable(variable_ptr_ptr, value TSRMLS_CC);
} else if (IS_CONST == IS_CONST) {
value = zend_assign_const_to_variable(variable_ptr_ptr, value TSRMLS_CC);
} else {
value = zend_assign_to_variable(variable_ptr_ptr, value TSRMLS_CC);
}
if (RETURN_VALUE_USED(opline)) {
PZVAL_LOCK(value);
EX_T(opline->result.var).var.ptr = value;
}
}
if (IS_CV == IS_VAR && 0) {
zval_ptr_dtor_nogc(&value);
}
/* zend_assign_to_variable() always takes care of op2, never free it! */
CHECK_EXCEPTION();
ZEND_VM_NEXT_OPCODE();
}