[PATCH] D80237: [hip] Ensure pointer in struct argument has proper `addrspacecast`.

Fri May 29 07:34:30 PDT 2020

arsenm added a comment.

In D80237#2058108 <https://reviews.llvm.org/D80237#2058108>, @rjmccall wrote:

> In D80237#2055902 <https://reviews.llvm.org/D80237#2055902>, @arsenm wrote:
>
> > In D80237#2051933 <https://reviews.llvm.org/D80237#2051933>, @rjmccall wrote:
> >
> > > Okay.  Can you explain why we need to coerce in the first place, though?  Especially if the representation is the same, why is your target-lowering requiring parameters to be coerced to involve pointers in a different address space?
> >
> >
> > It's not a requirement, but an optimization. The pointer representation is the same, but there's a penalty to using the generic pointer. From the language context here, we know the flat pointer can never alias the non-global address spaces.
>
>
> Is that because it's a kernel argument?  I don't understand how the coercion can work in general for structs that just contain pointers.

Yes, there's no valid way to pass a non-global address space pointer through a flat pointer into a kernel. This doesn't apply in other contexts

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