mailing list of musl libc
 help / color / mirror / code / Atom feed
From: Rich Felker <dalias@libc.org>
To: "Luís Marques" <luismarques@lowrisc.org>
Cc: musl@lists.openwall.com
Subject: Re: [musl] Re: [PATCH] Fix RISC-V a_cas inline asm operand sign extension
Date: Wed, 22 Jan 2020 09:46:20 -0500	[thread overview]
Message-ID: <20200122144620.GA30412@brightrain.aerifal.cx> (raw)
In-Reply-To: <CAPhv3nof+aodqqwwnX8aqGCcEf83y9AK0exxmWLNGCs3Wa+1+w@mail.gmail.com>

On Wed, Jan 22, 2020 at 02:31:25PM +0000, Luís Marques wrote:
> On Wed, Jan 15, 2020 at 1:33 PM Luís Marques <luismarques@lowrisc.org> wrote:
> > This patch adds an explicit cast to the int arguments passed to the inline asm
> > used in the RISC-V's implementation of `a_cas`, to ensure that they are properly
> > sign extended to 64 bits. They aren't automatically sign extended by Clang, and
> > GCC technically also doesn't guarantee that they will be sign extended.
> 
> Does anyone have any feedback regarding this patch?
> If not, perhaps it could be merged?

Thanks for pinging this again. It's unfortunate that clang doesn't do
this right to begin with, but the patch is not terribly ugly and
probably okay.

Can you clarify why it's needed and why sign-extending is the right
thing to do, though? Does lr.w sign-extend the loaded value (vs
zero-extend or something else)?

Rich

  reply	other threads:[~2020-01-22 14:46 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15 13:24 [musl] " Luís Marques
2020-01-15 13:50 ` Florian Weimer
2020-01-15 14:18   ` Luís Marques
2020-01-22 14:31 ` [musl] " Luís Marques
2020-01-22 14:46   ` Rich Felker [this message]
2020-01-22 16:57     ` Luís Marques

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=20200122144620.GA30412@brightrain.aerifal.cx \
    --to=dalias@libc.org \
    --cc=luismarques@lowrisc.org \
    --cc=musl@lists.openwall.com \
    /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. 
Code repositories for project(s) associated with this public inbox

	https://git.vuxu.org/mirror/musl/

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).