From: Pavel Machek <pavel@ucw.cz>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Laight <David.Laight@aculab.com>,
Tom Tromey <tom@tromey.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Sparse Mailing-list <linux-sparse@vger.kernel.org>
Subject: Re: [PATCH 00/11] pragma once: treewide conversion
Date: Tue, 23 Mar 2021 11:03:56 +0100 [thread overview]
Message-ID: <20210323100356.GA20449@amd> (raw)
In-Reply-To: <CAHk-=wh8PptzH-=ak1D7C5Zp6EJ8eurYqVqGdQauupAFaNuG4g@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1126 bytes --]
Hi!
> > > (a) the traditional include guard optimization HAS NO HIDDEN SEMANTIC
> > > MEANING. It's a pure optimization that doesn't actually change
> > > anything else. If you don't do the optimization, absolutely nothing
> > > changes.
> >
> > And if the parser is well written the optimisation is probably
> > irrelevant compared to the compile time.
>
> That's actually surprisingly not even remotely true.
>
> People always think that the optimization phases of a compiler are the
> expensive ones. And yes, there are certain optimizations that can be
> *really* expensive, and people just don't even do them because they
> are _so_ expensive and are exponential in time.
Well, linux kernel can be compiled in two _seconds_ if you take
compiler optimized for fast parsing... and quick code generation.
See "SUSE Labs Conference 2018 - Compiling the Linux kernel in a
second (give or take)" on youtube.
So yes, gcc's frontend may be slow, but that does not mean job can not
be done quickly by suitable compiler.
Best regards,
Pavel
--
http://www.livejournal.com/~pavelmachek
[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]
next prev parent reply other threads:[~2021-03-23 10:04 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-28 16:57 [PATCH 00/11] pragma once: treewide conversion Alexey Dobriyan
2021-02-28 16:58 ` [PATCH 01/11] pragma once: delete include/linux/atm_suni.h Alexey Dobriyan
2021-02-28 19:05 ` Jakub Kicinski
2021-02-28 16:59 ` [PATCH 02/11] pragma once: convert arch/arm/tools/gen-mach-types Alexey Dobriyan
2021-03-01 10:19 ` Russell King - ARM Linux admin
2021-03-02 15:15 ` Alexey Dobriyan
2021-02-28 16:59 ` [PATCH 03/11] pragma once: convert arch/s390/tools/gen_facilities.c Alexey Dobriyan
2021-02-28 17:00 ` [PATCH 04/11] pragma once: convert drivers/gpu/drm/pl111/pl111_nomadik.h Alexey Dobriyan
2021-03-01 14:41 ` Linus Walleij
2021-02-28 17:01 ` [PATCH 05/11] pragma once: convert drivers/scsi/qla2xxx/qla_target.h Alexey Dobriyan
2021-02-28 22:07 ` Bart Van Assche
2021-02-28 17:02 ` [PATCH 06/11] pragma once: convert include/linux/cb710.h Alexey Dobriyan
2021-03-03 23:13 ` Michał Mirosław
2021-02-28 17:02 ` [PATCH 07/11] pragma once: convert kernel/time/timeconst.bc Alexey Dobriyan
2021-02-28 17:03 ` [PATCH 08/11] pragma once: convert scripts/atomic/ Alexey Dobriyan
2021-03-01 7:55 ` Peter Zijlstra
2021-02-28 17:04 ` [PATCH 09/11] pragma once: convert scripts/selinux/genheaders/genheaders.c Alexey Dobriyan
2021-02-28 18:37 ` Paul Moore
2021-02-28 18:57 ` Alexey Dobriyan
2021-02-28 17:05 ` [PATCH 10/11] pragma once: delete few backslashes Alexey Dobriyan
2021-03-01 8:54 ` Ido Schimmel
2021-03-02 19:00 ` Vineet Gupta
2021-03-04 14:22 ` Edward Cree
2021-03-23 10:09 ` Pavel Machek
2021-02-28 17:05 ` [PATCH 11/11] pragma once: conversion script (in Python 2) Alexey Dobriyan
2021-02-28 17:11 ` [PATCH 12/11] pragma once: scripted treewide conversion Alexey Dobriyan
2021-03-01 17:35 ` Darrick J. Wong
2021-02-28 17:46 ` [PATCH 00/11] pragma once: " Linus Torvalds
2021-02-28 19:34 ` Alexey Dobriyan
2021-02-28 20:00 ` Linus Torvalds
[not found] ` <877dmo10m3.fsf@tromey.com>
2021-03-03 20:17 ` Linus Torvalds
2021-03-04 13:55 ` David Laight
2021-03-04 20:16 ` Linus Torvalds
2021-03-05 9:19 ` David Laight
2021-03-05 21:23 ` Linus Torvalds
2021-03-06 13:07 ` Miguel Ojeda
2021-03-06 21:33 ` Linus Torvalds
2021-03-23 10:03 ` Pavel Machek [this message]
2021-03-01 0:29 ` Luc Van Oostenryck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210323100356.GA20449@amd \
--to=pavel@ucw.cz \
--cc=David.Laight@aculab.com \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-sparse@vger.kernel.org \
--cc=luc.vanoostenryck@gmail.com \
--cc=tom@tromey.com \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).