[RFC] Default attributes for intrinsics

Hi all,

Recently intrinsic properties gained the ability to be declared as default and applied to all intrinsics.

Next step is to actually make some attributes default. In https://reviews.llvm.org/D86021 nofree, nosync and willreturn are made default. We also opted-out of default attributes for some intrinsics.

If there are any objections to this, please let us know in the review. If there are no objects, in about 2 weeks, we’ll go ahead and assume everyone is fine with this.



The change are ready and will land end of the week if we don't hear anything.
If you own target specific intrinsics you want to look at this and either:

\- Opt\-out for \*all intrinsics\* initially:
      sed \-i \-e 's: Intrinsic: DefaultIntrinsic'
\- Opt\-out for \*some intrinsics\* by applying the change on a case\-by\-case basis,
  this is what we did for the target independent intrinsics\.

FWIW, I'd recommend the latter though it will require you to follow changes
we apply to the "default attribute set".

~ Johannes