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From: Junio C Hamano <gitster@pobox•com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail•com>
Cc: Git Mailing List <git@vger•kernel.org>, Jeff King <peff@peff•net>,
	Jeffrey Walton <noloader@gmail•com>
Subject: Re: Very promising results with libpcre2
Date: Sat, 01 Apr 2017 11:24:39 -0700	[thread overview]
Message-ID: <xmqqbmsgugt4.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <CACBZZX416M3YFDAACGAWCjJ4Xt0g78zpFF+iusMCarKb7SSfVw@mail.gmail.com> ("Ævar Arnfjörð Bjarmason"'s message of "Sat, 1 Apr 2017 10:55:11 +0200")

Ævar Arnfjörð Bjarmason <avarab@gmail•com> writes:

> On Sat, Apr 1, 2017 at 12:48 AM, Junio C Hamano <gitster@pobox•com> wrote:
>> Ævar Arnfjörð Bjarmason <avarab@gmail•com> writes:
>>
>>> That enables the new JIT support in pcre v2:
>>>
>>>       s/iter    rx fixed   prx
>>> rx      2.19    --  -33%  -44%
>>> fixed   1.47   49%    --  -17%
>>> prx     1.22   79%   20%    --
>>
>> The numbers with JIT does look "interesting".
>>
>> I couldn't quite tell if there are major incompatibilities in the
>> regex language itself between two versions from their documentation,
>> but assuming that there isn't (modulo bugfixes and enhancements) and
>> assuming that we are going to use their standard matcher, it may be
>> OK to just use the newer one without linking both.
>
> There's no incompatibilities in the regex language itself (modulo bugs
> etc). So yeah, I'll prepare some patch to use v2.

Just to make sure that we are on the same page.  While I do not see
the need to link with both variants and allow users to choose
between them at runtime, I do not know if the whole world is ready
to drop pcre1 and use pcre2 (the latter of which has only been
around for a bit over two years).

So we'd probably want to do 

 (1) keep USE_LIBPCRE and enable v1 when set;
 (2) add USE_LIBPCRE2 and enable v2 when set;
 (3) make sure to error out when both are set.

or something like that.  It is tempting to allow us to say

    make USE_LIBPCRE=2

but the existing builds are likely to be depending on "is it set to
anything? then use PCRE1" behaviour, so we unfortunately cannot take
that route.

Thanks.

next prev parent reply	other threads:[~2017-04-01 18:24 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-31 21:23 Very promising results with libpcre2 Ævar Arnfjörð Bjarmason
2017-03-31 22:48 ` Junio C Hamano
2017-04-01  8:55   ` Ævar Arnfjörð Bjarmason
2017-04-01 18:24     ` Junio C Hamano [this message]
2017-04-01 19:11       ` Ævar Arnfjörð Bjarmason
2017-04-02  3:45         ` Junio C Hamano
2017-04-01 23:33       ` Jeffrey Walton
2017-04-02  3:45         ` Junio C Hamano

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