Re: Design of the Zend Engine's Instruction Set

Hi Stefan, On Sat, Aug 15, 2009 at 8:52 PM, Stefan Marr<php@stefan-marr.de> wrote: > Sometimes, it would be really interesting to know > where some of the used ideas are coming from > and what the reasoning was. I tend to think that its rather unlikely that > they > are pulled out of thin air. Some parts of the model remind me of CISC > instruction > sets... 3-address form, register-memory model... I think they are pulled out of thin air. More specifically, I think there are optimizations heaped upon optimizations heaped upon an initial implementation. It seems that each new release of PHP has a small speed improvement based on some optimization performed, but that there has been no major rearchitecture since the addition of a bytecode based interpreter in PHP 4. I do not know how that was designed though, maybe others do? One thing I do find interesting is that the register machine nature of PHP comes from an optimization called "compiled variables". CVs point to symbol-table entries, but without them, I'm not sure whether we would still call PHP a register machine. Any thoughts? Thanks, Paul -- Paul Biggar paul.biggar@gmail.com