[clang] [Clang][HIP] Suppress availability diagnostics for mismatched host/device overloads (PR #93546)

[Fabian Ritter via cfe-commits]

ritter-x2a wrote:

> If we are adding a special case for handling overloads, perhaps a better approach would be to consider inferring the caller context from the enveloping function declaration attributes, and allow overload resolution to pick a device function instead. It would avoid the errors you're trying to suppress, and it will arguably make things more consistent -- the function declaration will have the same signature in both host and device compilations.


One problem I encountered when I looked into such a solution is that the host/device attribute(s) are not necessarily parsed at the time when the overload resolution in template arguments of the return type happens, because the `__attribute__((device))` can come after the return type specifier (cf. the `DeviceUserOverloadFunHostDepr2` function in the test case).
So far I haven't found an existing mechanism in clang to solve this without a bigger change that introduces some sort of backtracking. I'd be happy about pointers in that direction.

https://github.com/llvm/llvm-project/pull/93546