The DECLARE_(ANON_)INHERITED_CLASS(_DELAYED) opcodes were
referencing the parent ce VAR through extended_value. This is
hacky and we can't track the def-use chain in SSA.
To avoid this, the layout of declaration opcodes is changed
as follows: op1 points to the lcname and rtd_key literals, in
that order. (For anon/lambda declarations only one of lcname or
rtd_key is present.) This frees up op2, which is now used to
reference the parent ce VAR in inheriting declarations. The
jmp offset for anon class declarations is moved frop op2 to
extended_value.
The changes were applied both to class and function declarations
to keep everything symmetric.
This is generalized solution for Bob's idea of speed up self::method() calls without ZEND_FETCH_CLASS.
At first, it adds few new opcodes to separate class related behaviour:
FETCH_STATIC_PROP_R
FETCH_STATIC_PROP_W
FETCH_STATIC_PROP_RW
FETCH_STATIC_PROP_FUNC_ARG
FETCH_STATIC_PROP_UNSET
FETCH_STATIC_PROP_IS
UNSET_STATIC_PROP
ISSET_ISEMPTY_STATIC_PROP
FETCH_CLASS_CONSTANT
At seconds, it enables IS_UNUSED operand to fetch (self, parent or static without separate FETCH_CLASS) for new opcodes and the following ones:
INIT_STATIC_METHOD_CALL
NEW
END_INSTANCEOF
Finaly, opcache optimizer had to be fixed to support new opcodes.
In PHP-5.6 and below each argument passed to user function was copies on VM stack twice.
Now we always have ZEND_INIT_FCALL (or simular) opcode that pushes "call frame" on top of VM stack.
"Call frame" is actually the same zend_execute_data structure.
All the following ZEND_SEND instructions push arguments on top of the stack in a way that they directly comes into corresponding CV variables of the called frame. Extra arguments are copied at the end of stack frame (after all CV and TMP variables) on function enterance.
There are two minor incompatibilities:
1) It's not allowed to decalre functions redefining arguments e.g. "function foo($a,$a) {}".
2) func_get_arg() and func_get args() return the current value of argument and not the original value that was sent.
It should be accessed using Z_CACHE_SLOT() macro.
zend_literal structure is removed.
API functions that accepted pointer to zend_literal now accept pointer to zval or cache_slot directly.
Calls of such functiond that now accept cache_slot need to be changed to pass -1 instead of NULL.
