Bug#1116585: amd_hip_bf16.h: bf16 functions need to be static

[Cordell Bloor <cgmb@slerp.xyz>]

Control: tags -1 - pending

Whoa there, Christian. Changing the definition of __HOST_DEVICE__ to 
implicitly be static inline is using a bazooka to kill a housefly.

That would have knock-on effects on any code that uses the 
__HOST_DEVICE__ macro, not just the handful of functions defined in the 
bf16 header. That header is indeed quite difficult to use without static 
or inline qualifiers on all the functions it defines and those functions 
were clearly always intended to have inline and/or static qualifiers. 
However, if we want to backport a fix to trixie, changing the macro is 
not going to be acceptable. User code might be using that 
__HOST_DEVICE__ macro, in which case the impact may be much larger than 
just bf16 if we change that definition.

For this specific patch, there is also the problem that the 
__HOST_DEVICE__ macro is defined in multiple different headers, but 
you've only changed the definition in one. That will result in a warning 
when both headers are included in the same translation unit (and 
inconsistent definitions if different translation units include 
different headers).

I would recommend that we consider narrowly adding the appropriate 
static and/or inline qualifiers to the specific functions in 
amd_hip_bf16.h where they are needed.

Sincerely,
Cory Bloor