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Date: Wed, 20 Nov 2013 21:17:53 +0100
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To: Yasuo Ohgaki <yohgaki@ohgaki.net>
Subject: Re: [PHP-DEV] [RFC] [VOTE] Constant scalar expressions
From: bobwei9@hotmail.com (Bob Weinand)

Am 20.11.2013 um 21:06 schrieb Yasuo Ohgaki <yohgaki@ohgaki.net>:
> Hi Bob,
>=20
> On Thu, Nov 21, 2013 at 1:54 AM, Bob Weinand <bobwei9@hotmail.com> =
wrote:
>=20
>> I just have moved the RFC to vote as there was no negative feedback =
nor
>> unresolved issues.
>>=20
>> Find the vote (and the RFC) at:
>>=20
>> https://wiki.php.net/rfc/const_scalar_exprs#vote
>>=20
>> Vote will last for one week.
>>=20
>=20
> It's nice feature, but I concerned about op caching.
> Currently, const is "constant". Therefore, constant value can be =
cached
> (i.e. hard coded in ops)
>=20
> This feature seems break op caching (or close the door for constant
> optimization at least)
>=20
> Is this a issue? I would like hear opinions from opcache/apc =
developers.
>=20
> Regards,
>=20
> --
> Yasuo Ohgaki
> yohgaki@ohgaki.net

As noted in the RFC "The patch is ready to be merged. (Opcache support =
is included, thanks to Dmitry)".

So, Dmitry already did the patch for opcache and I assume he has done =
the best possible for that.

Btw. opcache doesn't affect constants if I'm not wrong, because, what =
would you optimize here (already possible):

a.php:
if ($argv[1] =3D=3D "include")
    include 'b.php';
const B =3D A;

b.php:
const A =3D 10;

Here we can't cache anything because the constant B depends on a =
conditional inclusion: same problem.

It's that same way resolved with the current patch.

Also constant expressions (like 2+2 without constants involved) are =
resolved at compile time.

So I can't detect any impact related to opcache.

Bob