[PATCH] D26716: DAG: Ignore call site attributes when emitting target intrinsic

[Matt Arsenault via llvm-commits]

arsenm added a comment.

In https://reviews.llvm.org/D26716#601584, @arsenm wrote:

> In https://reviews.llvm.org/D26716#597575, @efriedma wrote:
>
> > Why can't you just compute whether the intrinsic has a chain based on the IntrinsicInfo?  Checking for a readnone attribute in the IR seems dubious at best; an intrinsic can be both readnone and require a chain (for example, it could have undefined behavior for some inputs).
>
>
>
>
> In https://reviews.llvm.org/D26716#601558, @efriedma wrote:
>
> > llvm.sqrt is a readnone intrinsic which can exhibit undefined behavior, but I think we don't actually generate a chain for it at the moment, so maybe we can get away with querying whether the intrinsic is readnone.  But the right way to do that is to call Intrinsic::getAttributes; we can't trust the IR to have the right attributes on the declaration (it's not something the verifier checks).
>
>
> Intrinsic declarations do have the right attributes on the declaration. The Function constructor ensures they are added.


As a special case,you can have intrinsics defined in the backend which are just generally broken right now. The TargetIntrinsicInfo interface does exist to fix this, but needs work to make actually usable (and probably not worth the effort).


https://reviews.llvm.org/D26716