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Date: Tue, 5 Apr 2016 10:15:06 +0100
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To: Derick Rethans <derick@php.net>
Cc: Dmitry Stogov <dmitry@zend.com>, Nikita Popov <nikita.ppv@gmail.com>, 
	Bob Weinand <bobwei9@hotmail.com>, Xinchen Hui <xinchen.h@zend.com>, Eran Ifrah <eran@zend.com>, 
	internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] RETURN micro optimization
From: pthreads@pthreads.org (Joe Watkins)

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Morning Derick,

    I don't think it does make anything impossible, it's just a more
efficient copying method in the EXPECTED branch is all.

Cheers
Joe

On Tue, Apr 5, 2016 at 10:04 AM, Derick Rethans <derick@php.net> wrote:

> On Tue, 5 Apr 2016, Dmitry Stogov wrote:
>
> > I propose a micro optimization for RETURN statement.
> >
> > Currently "return $x" increments reference counter of $x, then in
> > zend_leave_helper() we perform zval_ptr_dtor() on the same $x.
> >
> > The patch sets the original value of $x to null in first place, so
> > zval_ptr_dtor() is not going to be called.
> >
> > https://gist.github.com/dstogov/36f68b206242a39691ac539c2fc85d40
> >
> > the performance impact is invisible (0.1% less instruction retired on
> > Wordpress).
> >
> > It breaks sapi/phpdbg/tests/breakpoints_005.phpt, but this is probably
> > not a big deal.
> >
> > BTW: this change may affect debuggers in some other way.
>
> I'd like to know why this breaks before saying something. It'd be a PITA
> if this micro optimisation wouldn't actually do a lot performance wise,
> but makes some debugging not possible.
>
> cheers,
> Derick
>
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