Incorrect asm constraints or GCC bug?

[Florian Weimer]

On 11/19/2012 12:44 PM, Andrew Haley wrote:
> On 11/19/2012 11:28 AM, Florian Weimer wrote:
>> Note how %0 and %3 are assigned the same register.  Changing "=r" to
>> "+r" fixes this.  If an output-only operand must be modified last, the
>> original register assignment would be correct, but the Extended Asm
>> documentation does not require such a thing.
>
> It does.
>
> "Unless an output operand has the `&' constraint modifier, GCC may
> allocate it in the same register as an unrelated input operand, on the
> assumption the inputs are consumed before the outputs are produced."

Oh, thanks, that settles it.  I've submitted a fix for OpenSSL.  (This 
was a recent regression on their part.)

-- 
Florian Weimer / Red Hat Product Security Team