On Mar 24, 2015 4:11 PM, "Nikita Popov" <nikita....@gmail.com> wrote: > > On Mon, Mar 23, 2015 at 11:41 PM, Dmitry Stogov <dmi...@zend.com> wrote: > > > Hi, > > > > Recently, Xinchen and me worked on optimization that eliminates useless > > reallocations and copying during string concatenation (ZEND_ADD_STRING and > > family + ZEND_CONCAT). > > > > The idea comes from ropes, but adopted especially for our needs. > > Rope is popular data structure in languages with immutable strings. > > http://en.wikipedia.org/wiki/Rope_%28data_structure%29 > > > > We don't try to use ropes everywhere in the engine (at least it's too > > later for 7.0), only for concatenation. > > > > The first branch uses ropes only instead of ZEND_ADD_STRING and family. > > This must be safe. The only problem is possible memory leaks on exception > > (but we already have this problem anyway). The simplest way to understand > > the patch - read code for new opcodes in zend_vm_def.h. > > > > https://github.com/php/php-src/pull/1194/files > > > > The second branch in addition uses ropes for series of ZEND_CONCAT. It > > disables calls to do_operation(ZEND_CONCAT) handler of custom internal > > classes. > > > > https://github.com/php/php-src/pull/1195/files > > > > Both make slight speed improvement (first +0.3%, second +0.6% on wordpress > > home page). > > > > We don't currently use ability to override CONCAT behavior in internal > > classes, and I'm not sure if it may be useful at all. (For example Lua > > doesn't provide concat meta-method). May be remove it? > > > > Overloading concat operator will be useful in the future for the > implementation of the UString class, for example.
Indeed :) Which will be 7.1, at best, no matter which one. Hence a bit my thoughts about waiting a bit and spend more time on that, if other ops make sense too. But again, if everyone agrees, no issue to get that part in already.
