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Date: Tue, 14 Apr 2020 09:02:55 -0500
References: <0ddd2987-644b-6fec-2670-2b6f366290e2@php.net>
To: PHP internals <internals@lists.php.net>
In-Reply-To: <0ddd2987-644b-6fec-2670-2b6f366290e2@php.net>
Message-ID: <55096EBD-4A01-43A6-A41A-843C8C5657A1@benramsey.com>
Subject: Re: [PHP-DEV] opcache.jit directive should be split up
From: ben@benramsey.com (Ben Ramsey)

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> On Apr 14, 2020, at 08:53, Sebastian Bergmann <sebastian@php.net> =
wrote:
>=20
> PHP 8's JIT is currently mainly controlled through the opcache.jit =
configuration directive [1].
>=20
> The value for opcache.jit is currently a sequence of four digits, =
"5021" for instance. This would activate JIT optimizations based on =
static type inference and inner procedure analyses (Optimization Level), =
JIT optimization of all functions on load of the respective sourcecode =
file (Trigger), global linear-scan register allocator (Register =
Allocation), and AVX instruction generation (CPU-Specific Optimization =
Flags).
>=20
> I think that using a single configuration directive for these four =
distinct aspects of just-in-compilation is a bad idea. Many will, at =
least at first glance, mistake the value for a bitmask.
>=20
> I think it would be best to split up opcache.jit into five separate =
configuration directives and propose the following names:
>=20
> * opcache.jit for (de)activating JIT
> * opcache.jit_optimization_level for setting the optimization level
> * opcache.jit_trigger for configuring the JIT trigger
> * opcache.jit_register_allocation for configuring register allocation
> * opcache.jit_cpu_flags for configuring CPU-specific flags
>=20
> What do you think?
>=20
> --
> [1] https://wiki.php.net/rfc/jit#phpini_defaults


+1 for improving developer experience. Now=E2=80=99s the time to make =
this easier for folks to use. If we wait until after GA, we=E2=80=99ll =
have to support the harder-to-use sequence of digits for at least the =
rest of 8.x.

Cheers,
Ben



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