From: "Jan Beulich" <JBeulich@suse.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: "Binutils" <binutils@sourceware.org>
Subject: Re: [committed, PATCH] Remove Disp16|Disp32 from 64-bit direct branches
Date: Tue, 12 May 2015 12:20:00 -0000 [thread overview]
Message-ID: <55520C440200007800079718@mail.emea.novell.com> (raw)
In-Reply-To: <CAMe9rOpDbkeFbmNbQh0a1AKhAQy-cH4HJu20o_ERQaoR6sTxbQ@mail.gmail.com>
>>> On 12.05.15 at 13:54, <hjl.tools@gmail.com> wrote:
> On Tue, May 12, 2015 at 3:41 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>> On 11.05.15 at 23:23, <hongjiu.lu@intel.com> wrote:
>>> Disp16 and Disp32 aren't supported by direct branches in 64-bit mode.
>>> This patch removes them from 64-bit direct branches.
>>
>> See the recent discussion regarding callw - these can certainly have
>> 16-bit displacements on AMD CPUs. And while disassembly may just
>> get "disturbed" by getting this wrong, assembly will produce bad
>> code if you don't account for both cases (or refuse to assemble
>> such mnemonics if they would require size overrides to be added).
>>
>> Apart from that I wonder why you do this for CALL and JMP, but not
>> for Jcc, JCXZ, JRCXZ, LOOP, and LOOPcc.
>>
>> But first of all - please don't bias x86 binutils towards only supporting
>> Intel hardware.
>
> Can you generate call/jmp with 16-bit displacement in 64-bit mode?
Didn't check whether there is a mechanism currently; of course I
would expect "data16 jmp <label>" to do precisely that.
Jan
next prev parent reply other threads:[~2015-05-12 12:20 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-11 21:23 H.J. Lu
2015-05-12 10:41 ` Jan Beulich
2015-05-12 11:54 ` H.J. Lu
2015-05-12 12:20 ` Jan Beulich [this message]
2015-05-12 12:37 ` H.J. Lu
2015-05-12 13:03 ` Jan Beulich
2015-05-12 13:37 ` H.J. Lu
2015-05-12 13:49 ` Michael Matz
2015-05-12 13:57 ` H.J. Lu
2015-05-12 14:31 ` Michael Matz
2015-05-12 14:49 ` H.J. Lu
2015-05-12 15:14 ` Michael Matz
2015-05-12 15:21 ` H.J. Lu
2015-05-12 15:32 ` Michael Matz
2015-05-12 14:59 ` Jan Beulich
2015-05-12 15:03 ` H.J. Lu
2015-05-12 15:09 ` Jan Beulich
2015-05-12 15:11 ` H.J. Lu
2015-05-12 15:17 ` Jan Beulich
2015-05-12 15:37 ` Michael Matz
2015-05-12 15:43 ` H.J. Lu
2015-05-12 15:47 ` Michael Matz
2015-05-12 16:00 ` H.J. Lu
2015-05-12 16:03 ` Michael Matz
2015-05-12 16:08 ` H.J. Lu
2015-05-13 6:18 ` Jan Beulich
2015-05-13 11:35 ` H.J. Lu
2015-05-13 12:27 ` Jan Beulich
2015-05-13 13:15 ` H.J. Lu
2015-05-13 12:34 ` Michael Matz
2015-05-13 13:32 ` H.J. Lu
2015-05-13 16:50 ` Maciej W. Rozycki
2015-05-13 16:53 ` H.J. Lu
2015-05-15 6:39 ` Jan Beulich
2015-05-15 16:52 ` H.J. Lu
2015-05-18 7:05 ` Jan Beulich
2015-05-18 11:22 ` H.J. Lu
2015-05-18 11:48 ` Jan Beulich
2015-05-18 12:18 ` H.J. Lu
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