From: Joseph Myers <joseph@codesourcery.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: <libc-alpha@sourceware.org>
Subject: Re: [PATCH v1 2/2] x86_64: Add {u}int_fast defs ideal for x86_64
Date: Thu, 14 Apr 2022 22:24:20 +0000 [thread overview]
Message-ID: <alpine.DEB.2.22.394.2204142221420.916201@digraph.polyomino.org.uk> (raw)
In-Reply-To: <20220411010913.1061799-2-goldstein.w.n@gmail.com>
On Sun, 10 Apr 2022, Noah Goldstein via Libc-alpha wrote:
> {u}int_fast{16|32} should never use 64-bit types. 64-bit instructions
> often use more code size (REX prefix) and a variety of instructions are
> slower on many implementations (div, bswap, etc...).
Apart from the other issues discussed with this patch, installed headers
should not be specific to either x86_64 or 32-bit x86; such headers, where
architecture-specific, should go in an x86/ sysdeps directory and contain
appropriate conditionals within the header, so a single set of installed
headers works with a multilibbed compiler.
> +# include <sysdeps/generic/int-fast.h>
And an installed header can't do that sort of thing, because only a single
version of any such header gets installed. If you want to include a
generic file it has to have a different name, with both being installed
(cf. bits/mman-*.h, for example).
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2022-04-14 22:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-11 1:09 [PATCH v1 1/2] stdlib: Refactor {u}int_fast defs in stdint Noah Goldstein
2022-04-11 1:09 ` [PATCH v1 2/2] x86_64: Add {u}int_fast defs ideal for x86_64 Noah Goldstein
2022-04-11 2:15 ` Adam Sampson
2022-04-11 6:34 ` Florian Weimer
2022-04-14 22:24 ` Joseph Myers [this message]
2022-04-14 22:44 ` Noah Goldstein
2022-04-14 22:21 ` [PATCH v1 1/2] stdlib: Refactor {u}int_fast defs in stdint Joseph Myers
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