x86: Support Intel UINTR

[Jan Beulich]

On 13.10.2020 11:00, Cui, Lili wrote:
>> On 13.10.2020 08:11, Cui, Lili wrote:
>>> --- a/gas/testsuite/gas/i386/prefix.s
>>> +++ b/gas/testsuite/gas/i386/prefix.s
>>> @@ -367,14 +367,6 @@
>>>
>>>  	nop
>>>
>>> -# repz; rdrand %eax
>>> -	.byte 0xf3
>>> -	.byte 0x0f
>>> -	.byte 0xc7
>>> -	.byte 0xf0
>>> -
>>> -	nop
>>> -
>>
>> Instead of outright dropping this, can you see about finding a suitable
>> replacement encoding to retain what's being tested here?
> 
> Thanks for your review, I tried but didn't find a replaceable encoding here，
> as RDRAND not support F2/F3 prefixes, so H.J added an invalid test case(repz rdrand %eax) here,
> "repz rdrand" encoding is same with "senduipi",  so I have to delete this testcase.
> 
> 
> Rdrand  NFx REX.W + 0F C7 /6 
> 
> NFx ? Indicates the use of F2/F3 prefixes (beyond those already part of the instructions opcode) are not
> allowed with the instruction. Such use will either cause an invalid-opcode exception (#UD) or result in the
> encoding for a different instruction.

Question is whether HJ really mean to test the RDRAND major opcode
specifically, or whether some other one could be use in its stead.
HJ?

Jan