php-5.2.3: zend_opcode.c: pass_two() question

An example assignment such as: $x = 10; doesn't seem to get handled as a simple ref-count incrementing assignment (in zend_assign_to_variable()). Instead, $x ends up getting a new "zval" into which a copy of the RHS (10) is made. This seems to be because the zval/znode corresponding to the literal 10 is an IS_CONST operand of the assignment opcode. And, during the end of compilation of a function, the IS_CONST operands in the function's op_array are patched up as "references" (is_ref is set to 1). zend_opcode.c:pass_two() ... while (opline < end) { if (opline->op1.op_type == IS_CONST) { opline->op1.u.constant.is_ref = 1; opline->op1.u.constant.refcount = 2; /* Make sure is_ref won't be reset */ } if (opline->op2.op_type == IS_CONST) { opline->op2.u.constant.is_ref = 1; opline->op2.u.constant.refcount = 2; } ... And zend_assign_to_variable(), when it sees the RHS to be a reference ("is_ref == 1") ends up doing a copy rather than a ref-count incrementing assignment. It seems like performance would be better if we didn't mark constant operands as "references" in pass_two(). But presumably it is required to handle some cases that'll otherwise break? I am trying to understand what those cases are. If someone can shed further light on this issue, it is much appreciated... regards, Kannan Muthukkaruppan