C FE question: Is this test even valid?

[Mike Stump]

On May 19, 2006, at 12:01 PM, Diego Novillo wrote:

> Mark Mitchell wrote on 05/19/06 14:54:
>
>> Yes, this test case is valid; the code is ill-formed GNU C, since the
>> machine in question know not have a register named "unknown  
>> register".
>>                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> I can't parse this.

known to not have a register named...