> On Nov 29, 2015, at 6:53 PM, David Wohlferd <[email protected]> wrote:
>
>
>
> On 11/28/2015 10:30 AM, [email protected] wrote:
>>> On Nov 28, 2015, at 2:02 AM, Bernd Edlinger <[email protected]>
>>> wrote:
>>>
>>> ...
>>> Well, I start to think that Jeff is right, and we should treat a asm ("")
>>> as if it
>>> were asm volatile ("" ::: ) but if the asm ("nonempty with optional %") we
>>> should
>>> treat it as asm volatile ("nonempty with optional %%" ::: "memory").
>> I agree. Even if that goes beyond the letter of what the manual has
>> promised before, it is the cautious answer, and it matches expectations of a
>> lot of existing code.
>
> Trying to guess what people might have been expecting is a losing game.
> There is a way for people to be clear about what they want to clobber, and
> that's to use extended asm. The way to clear up the ambiguity is to start
> deprecating basic asm, not to add to the confusion by changing its behavior
> after all these years.
>
> And the first step to do that is to provide a means of finding them. That's
> what the patch at https://gcc.gnu.org/ml/gcc/2015-11/msg00198.html does.
>
> Once they are located, people can decide for themselves what to do. If they
> favor the 'cautious' approach, they can change their asms to use :::"memory"
> (or start clobbering registers too, to be *really* safe). For people who
> require maximum backward compatibility and/or minimum impact, they can use
> :::.
>
> Have you tried that patch? How many warnings does it kick out for your
> projects?
The trouble with warnings is that they only help with projects that are
currently maintained.
paul
