From: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
To: Michael.Collison@arm.com
Cc: gcc-patches@gcc.gnu.org, nd@arm.com, pinskia@gmail.com
Subject: RE: [PATCH] [Aarch64] Optimize subtract in shift counts
Date: Tue, 08 Aug 2017 01:56:00 -0000 [thread overview]
Message-ID: <20170808015616.1386833CA8@vlsi1.gnat.com> (raw)
In-Reply-To: <HE1PR0802MB2377C331B4FC7BDA5C2C429795B50@HE1PR0802MB2377.eurprd08.prod.outlook.com>
> On Aarc64 SHIFT_COUNT_TRUNCATED is only true if SIMD code generation
> is disabled. This is because the simd instructions can be used for
> shifting but they do not truncate the shift count.
In that case, the change isn't safe! Consider if the value was
negative, for example. Yes, it's technically undefined, but I'm not
sure I'd want to rely on that.
next prev parent reply other threads:[~2017-08-08 1:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-07 20:36 Michael Collison
2017-08-07 20:44 ` Andrew Pinski
2017-08-07 21:02 ` Richard Kenner
2017-08-07 23:44 ` Michael Collison
2017-08-08 1:56 ` Richard Kenner [this message]
2017-08-08 4:06 ` Michael Collison
2017-08-08 12:13 ` Richard Kenner
2017-08-08 19:46 ` Michael Collison
2017-08-08 19:52 ` Richard Kenner
2017-08-08 19:59 ` Michael Collison
2017-08-08 20:04 ` Richard Kenner
2017-08-08 20:18 ` Michael Collison
2017-08-08 20:20 ` Richard Kenner
2017-08-08 20:33 ` Michael Collison
2017-08-14 8:58 ` Richard Biener
2017-08-15 7:28 ` Michael Collison
2017-08-21 19:11 ` Richard Sandiford
2017-08-21 19:14 ` Richard Biener
2017-08-22 8:17 ` Richard Sandiford
2017-08-22 8:46 ` Richard Biener
2017-08-22 8:50 ` Richard Sandiford
2017-09-06 9:11 ` Michael Collison
2017-09-06 10:32 ` Richard Sandiford
2017-09-06 15:41 ` Michael Collison
2017-09-06 16:53 ` Richard Sandiford
2017-09-06 16:56 ` Richard Sandiford
2017-09-06 17:21 ` Richard Sandiford
2017-09-15 8:15 ` Michael Collison
2017-09-29 23:01 ` James Greenhalgh
2017-08-07 20:58 ` Richard Kenner
2017-08-08 10:04 Wilco Dijkstra
2017-08-22 11:01 Wilco Dijkstra
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=20170808015616.1386833CA8@vlsi1.gnat.com \
--to=kenner@vlsi1.ultra.nyu.edu \
--cc=Michael.Collison@arm.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=nd@arm.com \
--cc=pinskia@gmail.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).