Re: i686 quirk for AMD Geode

H. Peter Anvin
2009-11-10T20:08:56Z

On 11/10/2009 11:50 AM, Avi Kivity wrote:
>>
>> Consider SSE3, for example. Why should the same concept not apply to
>> SSE3 instructions as to CMOV?
>
> Because then user programs would run 20x or more slower than the user
> expects. Better to terminate early (and teach userspace how to choose
> the instruction subset correctly).
>

I picked the example carefully: SSE3 is a small set of instructions
which probably aren't used very heavily. In that sense, it has
*exactly* the same properties as CMOV - if you have the source, you're
better off recompiling, but it *might* help you if you happen to only
have a binary.

What I want people to understand is that this is a *huge* rathole, and
it doesn't have any obvious bottom that I can see.

-hpa