[PATCH] D115283: [AMDGPU] Set "amdgpu_hostcall" module flag if an AMDGPU function has calls to device lib functions that use hostcalls.

[Konstantin Pyzhov via Phabricator via cfe-commits]

kpyzhov added a comment.

In D115283#3179651 <https://reviews.llvm.org/D115283#3179651>, @yaxunl wrote:

> One drawback of this approach is that it does not work for LLVM modules generated from assembly or programmatically e.g. Tensorflow XLA.
>
> Another drawback is that if `__ockl_call_host_function` or `__ockl_fprintf_stderr_begin` are eliminated by optimizer, the module flag is still kept. This could happen if users use printf in assert.
>
> Is there a way to detect use of hostcall later in LLVM IR not by calling of these functions?

Two other possible solutions that come to my mind:

1. Make a separate pass that would check if there is an instance of the ockl_hostcall_internal() function in the module and set the module flag if so.

2. Add a new "amdgpu_hostcall" function attribute. The "ockl_hostcall_internal()" function should be declared with __attribute__(("amdgpu_hostcall")) in the device libs. Then, in the Code Gen pass, we just set the "hidden_hostcall" kernel arg attribute if any function with "amdgpu_hostcall" is present. I think this is the best solution since we don't rely on the particular function name, and it would work ideally with any optimizations.

Please let me know what you think.


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https://reviews.llvm.org/D115283