Re: [PHP-DEV] Compiler Optimizations

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September 15, 2020 14:03 chasepeeler@gmail.com (Chase Peeler)
On Tue, Sep 15, 2020 at 9:51 AM Benas IML iml@gmail.com> wrote:

> Ah, sorry! Misread your post. Anyways, the compiler doesn't transform > `\array_keys()` yet, so there's no optimization for that. > > As for other compiler optimizations, 2 that I know that the compiler does > is: > > 1. Binary OP evaluation i. e. `2 * 2` does not yield `ZEND_ADD` opcode but > is instead computed by the compiler directly. > > 2. There are special functions that have their own opcodes. You can learn > more about those here: > > https://phpinternals.net/articles/optimising_internal_functions_via_new_opcode_instructions >
That's a good starting point, thanks.
> > Best regards, > Benas > > On Tue, Sep 15, 2020, 4:44 PM Chase Peeler <chasepeeler@gmail.com> wrote: > >> I wasn't proposing that my example be supported. I'm totally okay with >> the fact that it doesn't. My question was about whether or not those kinds >> of optimizations are documented anywhere so that developers can make sure >> they don't miss out on them by not fitting the proper pattern. >> >> On Tue, Sep 15, 2020 at 9:40 AM Benas IML iml@gmail.com> >> wrote: >> >>> Hey, >>> >>> During my free time, I'm implementing that specific `array_keys` >>> optimization. I'm not planning on supporting cases like yours (i. e. >>> indirection through a variable) since there's no point in doing that. And >>> also, it's not feasible to support every use case. Should we also support >>> cases like this? >>> >>> ```php >>> $a = 'array_keys'; >>> $b = $a(...); >>> $c = 'b'; >>> >>> foreach ($$c as $key) { >>> ... >>> } >>> ``` >>> >>> Obviously not. `\array_keys` optimization will work the same way as an >>> optimized `strlen` function works. >>> >>> That means that the optimization is only going to be applied if the >>> `array_keys` function is used directly in the `foreach` loop and only if a) >>> either the namespace is global b) or `\array_keys(...)`/`use function >>> array_keys` is used. >>> >>> >>> Best regards, >>> Benas >>> >>> On Tue, Sep 15, 2020, 4:23 PM Chase Peeler <chasepeeler@gmail.com> >>> wrote: >>> >>>> I brought this up on another thread, but it wasn't addressed (which is >>>> fine, since it was somewhat off-topic). I thought it might be >>>> worth bringing up in its own thread, though. >>>> >>>> In the other thread, someone had mentioned the following compiler >>>> optimization >>>> >>>> foreach(\array_keys($arr) as $key) { >>>> >>>> and quietly transform that into: >>>> >>>> foreach ($arr as $key => >>>> $_unusedVariableNameThatIsntEvenSpilledToTheScope) >>>> { >>>> >>>> I would be more likely to write: >>>> $keys = array_keys($arr); >>>> foreach($keys as $key){ >>>> Which would prevent me from being able to take advantage of the >>>> optimization. >>>> >>>> So, what I was wondering, is if there are other optimizations I might be >>>> missing out on, and if so, are they documented anywhere? >>>> >>>> >>>> -- >>>> Chase Peeler >>>> chasepeeler@gmail.com >>>> >>> >> >> -- >> Chase Peeler >> chasepeeler@gmail.com >> >
-- Chase Peeler chasepeeler@gmail.com