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Date: Thu, 6 Aug 2020 09:50:35 +0300
Message-ID: <CAPVMwwvmHM56mHMQvc8BjirmJn+moiuEexmn9seXTtUy3P1shA@mail.gmail.com>
To: Benjamin Eberlei <kontakt@beberlei.de>
Cc: PHP Internals <internals@lists.php.net>, Dmitry Stogov <dmitry@zend.com>, 
	Nikita Popov <nikita.ppv@gmail.com>
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Subject: Re: [PHP-DEV] Re: @@Jit Attribute Considerations
From: dmitrystogov@gmail.com (Dmitry Stogov)

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My solution:

- remove doc-comment trigger. It doesn't make sense.
- add @@Jit("off") only. Later we may extend this.


On Tue, Aug 4, 2020 at 11:11 AM Benjamin Eberlei <kontakt@beberlei.de>
wrote:

> On Mon, Aug 3, 2020 at 7:44 PM Benjamin Eberlei <kontakt@beberlei.de>
> wrote:
>
> > Hi,
> >
> > I am going to pick up a discussion from
> > https://github.com/php/php-src/pull/5915 about the @@Jit attribute.
> >
> > Nikita mentioned he is still not 100% clear what the usecase is for @@Jit
> > attribute and asked to discuss here.
> >
> > The reason is that the default tracing JIT is clever to decide itself
> when
> > to JIT or not, better not interfere with that. In case you run the
> tracing
> > JIT, only @@Jit("off") has an effect the others @@Jit("tracing") and
> > @@Jit("function") get ignored.
> >
> > Only the trigger mode 4 (attributes) is actually using @@Jit("tracing")
> > and "function". This trigger mode feels like micro-management for
> > developers and since it has virtually no spotlight in discussions and
> blog
> > posts about the JIT at the moment, we don't know if it brings benefits.
> >
> > Maybe for now it would be better to remove docblock / attribute support
> > for the JIT, and take a new attempt at it in 8.1? That prevents us from
> > rolling something we regret having to maintain later.
> >
>
> I updated the PR https://github.com/php/php-src/pull/5915 with the
> following things:
>
> - Removed attribute trigger mode for now.
> - Removed obsolete doc comment trigger mode
> - Add @@Jit("off") to disable JIT for an op_array or script
>
> Open questions:
> - Are we ok with removing @Jit("on"), @@Jit("tracing") and
> @@Jit("function") for now to thoroughly discuss best approach for 8.1?
> - Rename @@Jit to something more specific like @@JitOptions or @@JitHint?
> - Remove the attribute trigger constant 4, and move tracing JIT to use 4
> instead of 5?
>
> Outlook:
>
> We need to think about what the @@Jit attribute should actually mean in
> context of the function or tracing JIT. Personally it probably means
> "Always Jit this function regardless of hot counter or tracing results".
> I believe we don't need the attributes trigger mode, as everything happens
> either in context of function or tracing JIT.
>
>
> > greetings
> > Benjamin
> >
>

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