FETCH_DIM_TMP_VAR is used especiualy for list(). It expects array, don't check for objects and strings. It doesn't remove the operand and allow it's reuse in next opcode.
FETCH_DIM_R is used for list() only in some cases (when operand IS_VAR). To work in list() context it has to keep operand not destroyed, and to do it FETCH_DIM_R has to check for (opline->extended_value & ZEND_FETCH_ADD_LOCK). Note that this check has to be executed for each array access operation unrelated to list() handling. Thanks. Dmitry. On Fri, Sep 26, 2014 at 12:32 AM, Nikita Popov <nikita....@gmail.com> wrote: > On Thu, Sep 25, 2014 at 1:15 PM, Dmitry Stogov <dmi...@zend.com> wrote: > >> disabling string handling would allow make operation simpler and would >> improve regular access to array elements. >> We won't need to check for (opline->extended_value & ZEND_FETCH_ADD_LOCK) >> in FETCH_DIM_R handler. >> However, it's going to be very small improvement, and I don't care a lot. >> :) >> >> enabling string handling would require complication of >> ZEND_FETCH_DIM_TMP_VAR handler (for strings support). >> It's going to make list() handling a bit slower, but not significantly. >> >> my choice +1 for disabling. >> > > Could you please clarify why removing string support would make the > operation simpler? I voted for always supporting strings because I thought > that is the option that simplifies things - in particular it would allow > use to drop the FETCH_DIM_TMP_VAR opcode and always go through FETCH_DIM_R > instead. Sample patch here: > https://github.com/nikic/php-src/compare/stringOffsetsInList Or did I > miss something and we can't do that? > > Nikita >
