Re: [Qemu-devel] [PATCH v4 23/64] tcg: Allow an operand to be matching or a constant

[Alex Bennée]

Richard Henderson <address@hidden> writes:

> On 12/08/2016 09:19 AM, Alex Bennée wrote:
>>
>> Richard Henderson <address@hidden> writes:
>>
>>> This allows an output operand to match an input operand
>>> only when the input operand needs a register.
>>>
>>> Signed-off-by: Richard Henderson <address@hidden>
>>
>> It's hard to offer anything more than a mechanical review for this as
>> the constraints aren't intuitive to me (I guess not as a gcc hacker!).
>
> It's even more confusing for a gcc hacker, as we don't have a concept of
> alternatives.  You get one set of constraints.
>
>> Could we either expand the documentation of constraints in tcg/README
>> with a summary of the global ones?
>
> There's only one global constraint: 'i'.  So... sure, but I don't know how 
> much
> that will help.

So what do 0..9 and & mean? Or do you mean they are only constraints
applied by the backend?

--
Alex Bennée