From: Segher Boessenkool <segher@kernel.crashing.org>
To: "Kewen.Lin" <linkw@linux.ibm.com>
Cc: HAO CHEN GUI <guihaoc@linux.ibm.com>, David <dje.gcc@gmail.com>,
Peter Bergner <bergner@linux.ibm.com>,
gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH, rs6000] Use bcdsub. instead of bcdadd. for bcd invalid number checking
Date: Thu, 18 Apr 2024 05:35:41 -0500 [thread overview]
Message-ID: <20240418103541.GR19790@gate.crashing.org> (raw)
In-Reply-To: <e5c42135-7dbd-6e75-775c-f990e69e111a@linux.ibm.com>
On Thu, Apr 18, 2024 at 11:14:42AM +0800, Kewen.Lin wrote:
> on 2024/4/18 10:01, HAO CHEN GUI wrote:
> > This patch replace bcdadd. with bcdsub. for bcd invalid number checking.
> > bcdadd on two same numbers might cause overflow which also set
> > overflow/invalid bit so that we can't distinguish it's invalid or overflow.
> > The bcdsub doesn't have the problem as subtracting on two same number never
> > causes overflow.
> >
> > Bootstrapped and tested on powerpc64-linux BE and LE with no
> > regressions. Is it OK for the trunk?
>
> Considering that this issue affects some basic functionality of bcd bifs
> and the fix itself is simple and very safe, OK for trunk, thanks for fixing!
Yup. If a number X is invalid the X-X calculation might set the
overflow flag as well, but we cannot see that difference at all anyway,
it always has set the invalid flag after all.
Thanks!
Segher
prev parent reply other threads:[~2024-04-18 10:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 2:01 HAO CHEN GUI
2024-04-18 3:14 ` Kewen.Lin
2024-04-18 10:35 ` Segher Boessenkool [this message]
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=20240418103541.GR19790@gate.crashing.org \
--to=segher@kernel.crashing.org \
--cc=bergner@linux.ibm.com \
--cc=dje.gcc@gmail.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=guihaoc@linux.ibm.com \
--cc=linkw@linux.ibm.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.
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 read-only IMAP folder(s) and NNTP newsgroup(s).