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RE: PATCH: Move operand/address-size override prefixes before SIMD prefix
- From: "Dave Korn" <dave dot korn at artimi dot com>
- To: "'malc'" <av1474 at comtv dot ru>
- Cc: "'Menezes, Evandro'" <evandro dot menezes at amd dot com>, "'Jan Beulich'" <jbeulich at novell dot com>, "'H. J. Lu'" <hjl at lucon dot org>, <binutils at sourceware dot org>
- Date: Thu, 7 Dec 2006 20:36:04 -0000
- Subject: RE: PATCH: Move operand/address-size override prefixes before SIMD prefix
On 07 December 2006 12:34, malc wrote:
> 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.
That's not quite correct, from a logical reasoning / experimental design
point of view.
I agree that if it did *not* cause an exception, that would in no way
guarantee that it was legal or valid or safe to use or that it would remain so
in any future revisions.
OTOH, if it *did* cause an exception, it *would* prove that the instruction
was *not* valid.
So, it could have proved it one way but not the other.
cheers,
DaveK
--
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