[flang] [llvm] [flang][OpenMP] Parse `bind` clause for `loop` direcitve. (PR #113662)

[Michael Klemm via llvm-commits]

mjklemm wrote:

>  If teams is specified as binding then the corresponding loop region must be strictly nested inside a teams region.

Yes, that's a runtime requirement and not a compile-time requirement.  Thus, it will be hard to check.

> If teams is specified as binding and the corresponding loop region executes on a non-host device then the behavior of a 
reduction clause that appears on the corresponding loop construct is unspecified if the construct is not nested inside a teams 
construct.

This we should be able to check at compile time.

> If parallel is specified as binding, the behavior is unspecified if the corresponding loop region is closely nested inside a simd 
region.

Runtime condition.


The good thing is that OpenMP makes this unspecified, so we can have any failure mode that we desire, incl. just computing something useless.  However, somehow producing a sensible error will increase the user experience with all this.

https://github.com/llvm/llvm-project/pull/113662