From: Roland McGrath <mcgrathr@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: binutils@sourceware.org
Subject: Re: [PATCH] i386-dis: fix decoding of reserved "prefetch" encodings
Date: Tue, 07 Aug 2012 18:00:00 -0000 [thread overview]
Message-ID: <CAB=4xhrEY+cWK4vTKzPr7njQrYEKi8VGSVcvjSy0UGZxLHwQXA@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOrADoEYCH2-=toQX_=NJF5sRq6uX47UKUPey1DGToDUjQ@mail.gmail.com>
On Tue, Aug 7, 2012 at 10:34 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> Those are marked as NOPs in AMD manual and reserved in Intel
> manual. I don't like "prefetch(bad)". I can live with "nop/reserved".
Can you cite the manuals you are looking at?
I'm looking at http://support.amd.com/us/Processor_TechDocs/24594_APM_v3.pdf
on page 254:
The reserved PREFETCH types do not result in an invalid-opcode
exception if executed. Instead, for forward compatibility with
future processors that may implement additional forms of the
PREFETCH instruction, all reserved PREFETCH types are implemented
as synonyms of the basic PREFETCH type (the PREFETCH instruction
with type 000b).
That says they are prefetch, not nop. That's for the 0f 0d set.
For 0f 18, the same AMD manual's Table A-7 (page 430, in the "Group 16"
row) says "NOP[4]" for these excess encodings but the footnote is:
4. Reserved prefetch encodings are aliases to the /0 encoding
(PREFETCH Exclusive) for future compatibility.
So these Intel reserved opcodes are in fact also prefetch on AMD, not nop,
despite the appearance of "NOP" in the table grid.
So it seems to me the mnemonic ought to have "prefetch" in it somewhere.
How about "prefetch/reserved"?
Thanks,
Roland
next prev parent reply other threads:[~2012-08-07 17:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-06 22:51 Roland McGrath
2012-08-07 17:36 ` H.J. Lu
2012-08-07 18:00 ` Roland McGrath [this message]
2012-08-07 18:23 ` H.J. Lu
2012-08-08 7:07 ` Roland McGrath
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='CAB=4xhrEY+cWK4vTKzPr7njQrYEKi8VGSVcvjSy0UGZxLHwQXA@mail.gmail.com' \
--to=mcgrathr@google.com \
--cc=binutils@sourceware.org \
--cc=hjl.tools@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).