We can, if we so choose, not mention errno at all for math intrinsics.
If we do so, we could always use the intrinsics, and get rid of the library call handling for good.
If the frontend/user is aware errno is to be ignored (-fno-math-errno), readnone is placed on the call site.
This does not solve the issue that we might pick an errno setting implementation for a non-errno setting intrinsic, but it also doesn’t make it worse.
What this would do is to unify our handling of “math” in the IR.
FWIW, I always advocated against more intrinsic and in favor of removing the ones we have.
Since that never got enough traction, I am happy to support the “all intrinsic” approach.