Description:
------------
Variants of that code (dependent on where execute_data->prev_execute_data is first needed) may also crash.

My longer analysis resumed:
EG(vm_stack_top) is reset to generator->stack->top in the next resume after zend_vm_stack_push_call_frame was called in the ZEND_INIT_FCALL_BY_NAME, that stack frame is now equal to EG(vm_stack_top), which is then returned in the next stack frame allocation (the var_dump one in the example) and prev_execute_data is set there to the address of the stack frame itself.

Adding generator->stack->top = EG(vm_stack_top); on line 330 of zend_generators.c fixed the bug for me, but not sure if that's safe...

Test script:
---------------
function a($x) {
    var_dump($x);
}

function gen() {
     a(yield);
}

$g = gen();
$g->send(1);

Expected result:
----------------
int(1)

Actual result:
--------------
Infinite loop: execute_data->prev_execute_data == execute_data