inline asm and multi-alternative constraints

[Jeff Law]

On 10/25/2015 09:41 PM, David Wohlferd wrote:
> Does gcc's inline asm support multi-alternative constraints?  Or are
> they only supported for md?
>
> The fact that it is doc'ed with the other constraints
> (https://gcc.gnu.org/onlinedocs/gcc/Constraints.html) says it works for
> inline.  But https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10396#c17 says
> it only works for md.
>
> I've got a patch ready to remove this section from the non-md docs
> (attached).  But there probably needs to be more support than a 11 year
> old comment to approve it.
>
> Dropping a supported feature is always controversial.  But if it doesn't
> work, perhaps less so.  After all, doc'ing something that doesn't work
> is just as bad.
>
> dw
>
> PS If it *is* supported, then the docs need some work.
I think Richard corrected me last I spoke on this topic :-)  They *are* 
supported.  ie, something like this should work on a ciscy target.

   asm("add %0,%1" : "=r,m"(x) : "rim,ri"(y))