LLVM ERROR: Attributes 'readnone and readonly' are incompatible!

[TyOverby]

When I use cargo to set [profile.dev] to use opt-level = 1, cargo build fails with this error. Any other opt-level and it's fine.

Attributes 'readnone and readonly' are incompatible!
void ({ i8*, void (i8*)** }*, { i8*, void (i8*)** }*)* @"_ZN25Box$LT$CloneAny$GT$.Clone5clone20hea41b2e97e38689bjhaE"
LLVM ERROR: Broken function found, compilation aborted!

The project that I'm getting this error on is private for now, but it is breaking when compiling typemap v0.2.1.

[nagisa]

Minimized case

#![feature(box_syntax)]
#![crate_type="lib"]

trait Clone2 {
    fn clone_convert(&self) -> Box<Clone3>;
}
trait Clone3: Clone2 {}
impl<T: Clone + 'static> Clone3 for T {}
impl<T: Clone + 'static> Clone2 for T {
    fn clone_convert(&self) -> Box<Clone3> {
        box self.clone()
    }
}
impl Clone for Box<Clone3> {
    fn clone(&self) -> Self {
        self.clone_convert()
    }
}

This is bug in our codegen, I fear (especially because we do dereference pointers we get), since we indeed emit both readonly and readnone. Interesting this is only caught by an optimisation pass, though...

[dotdash]

We do not emit readnone.

This is a bug in LLVM. There are two functions that call each other and have a pointer argument that is only used in the mutual calls. In that case, the pointer argument gets the readnone attribute, but if there's already a readonly attribute present, that is not removed and the verifier complains.

This triggers the error:

define void @bar(i8* readonly) {
  call void @foo(i8* %0)
    ret void
}

define void @foo(i8* readonly) {
  call void @bar(i8* %0)
  ret void
}

Patch submitted at http://reviews.llvm.org/D9995

[sanxiyn]

Can this be closed now?

[apasel422]

This no longer appears to be an issue.