HIP platform selection

hip-build-platform.md

1. In the install script, determine the build platform by querying hipconfig --platform
   • This is necessary, as the install script needs to know the build platform so it can to choose what dependencies to install.
   • hipconfig --platform determines the platform by reading the contents of the .hipInfo file installed as part of the hip runtime.
   • If the platform is autodetected incorrectly, it can be be set explicitly via an environment variable, e.g., export HIP_PLATFORM=amd or export HIP_PLATFORM=nvidia.
2. In CMake, find_package(hip REQUIRED) will be used for both the AMD and NVIDIA platforms.
   • There will be no need for a different find_package call on each platform; the same call will be used for both platforms.
   • find_package(hip) will set HIP_PLATFORM so the rest of the build rules can branch on if(HIP_PLATFORM STREQUAL amd) or if(HIP_PLATFORM STREQUAL nvidia).
   • find_package(hip) will create the imported interface target hip::host, which will have all necessary defines, dependencies and include paths for using the HIP library with a normal C or C++ compiler. For example, anything linked with hip::host will be passed -D__HIP_PLATFORM_AMD__ when HIP_PLATFORM=amd and -D__HIP_PLATFORM_NVIDIA__ when HIP_PLATFORM=nvidia.
3. find_package(hip) will be implemented in cmake/Findhip.cmake. This file will be copied into each project that needs to support the NVIDIA platform.
   • Findhip.cmake will use hipconfig --platform to set the HIP_PLATFORM CMake variable. This behaviour will be copied directly from FindHIP.cmake.
   • On the AMD platform, Findhip.cmake will be a thin wrapper around hip-config.cmake
   • On the NVIDIA platform, Findhip.cmake will find the HIP include directories and create the hip::host target.
   • Once hip-config.cmake defines HIP_PLATFORM and adds hip::host to the NVIDIA platform, Findhip.cmake can be deleted. It's just a compatibility shim to add features that have not been implemented in HIP yet. Once they are implemented, the shim can be removed without any further changes required to the libraries.

Currently, valid values are as follows:

 HIP_PLATFORM={ amd, nvidia }
      and
 { __HIP_PLATFORM_AMD__, __HIP_PLATFORM_NVIDIA__ }

Does it make sense to consider an extension:

 HIP_PLATFORM={ amd, xilinx, nvidia }
      and
 { __HIP_PLATFORM_AMD__, __HIP_PLATFORM_XILINX__, __HIP_PLATFORM_NVIDIA__ }

 and of course 'hipconfig' utility should support it.