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RE: PATCH: Move operand/address-size override prefixes before SIMD prefix
- From: "Jan Beulich" <jbeulich at novell dot com>
- To: "malc" <av1474 at comtv dot ru>
- Cc: "Evandro' 'Menezes" <evandro dot menezes at amd dot com>, "Dave Korn" <dave dot korn at artimi dot com>, "'H. J. Lu'" <hjl at lucon dot org>,<binutils at sourceware dot org>
- Date: Thu, 07 Dec 2006 13:17:21 +0000
- Subject: RE: PATCH: Move operand/address-size override prefixes before SIMD prefix
- References: <00f301c719fa$2d30a6b0$a501a8c0@CAM.ARTIMI.COM> <Pine.LNX.4.64.0612071532220.694@home.oyster.ru>
>>> malc <av1474@comtv.ru> 07.12.06 13:34 >>>
>On Thu, 7 Dec 2006, Dave Korn wrote:
>
>> On 07 December 2006 11:50, malc wrote:
>>
>>
>>> So your position is that it's #UD. Objdump disagrees with you, whether
>>> rightfully or not is an open question (or original question if you will)
>>
>>
>> Well, can't you just try single-stepping over one in the debugger and see if
>> it executes something or blows up with an illegal instruction trap?
>
>I can. This will proove exactly nothing though. I want an official
>position of Intel and AMD, even if the position is that the behaviour
>is unspecified that will suit me just fine.
It is undefined - the manuals say nothing about it being valid. And if you tried
this on hardware (I did a while ago), you'd see that it also behaves like that
(i.e. depending on count and order of prefixes you get different results).
Jan