The Hexagon runtime implements the functionality necessary for executing ML models on Hexagon hardware (or emulation).
The prerequisite is to have Hexagon SDK installed, version 4.0.0 or later.
It is also recommended to use as recent version of LLVM as possible, version 7.0.0 being the minimum (based on community feedback).
TVM running on host can serve as a cross-compiler that produces machine code for Hexagon. To enable that, certain elements of both, the compiler and the runtime need to include Hexagon-specific functionality. For the compiler, it is code generation, and for the runtime, it is the ability to represent modules with Hexagon code. Since Hexagon codegen is based on LLVM, LLVM codegen needs to be enabled as well. The set of cmake options to enable Hexagon support is
USE_LLVM=llvm-config USE_HEXAGON=ON USE_HEXAGON_SDK=/path/to/sdk
Aside from x86, there are two other platforms where support for Hexagon may be relevant. One of them is obviously Hexagon itself, the other one is Android. Neither of these platforms supports the compiler side of TVM, only runtime, and so the only compiler-related cmake option from the x86 build above can be omitted: USE_LLVM.
Additionally, for Android, set the toolchain and target flags:
ANDROID_ABI=aarch64-v8a ANDROID_PLATFORM=android-28 CMAKE_TOOLCHAIN_FILE=/path/to/android-ndk/build/cmake/android.toolchain.cmake USE_HEXAGON=ON USE_HEXAGON_ARCH=v65|v66|v68|v69|v73 USE_HEXAGON_SDK=/path/to/sdk
Building for Hexagon requires setting the C/C++ compiler to hexagon-clang/++:
CMAKE_C_COMPILER=hexagon-clang CMAKE_CXX_COMPILER=hexagon-clang++ USE_HEXAGON=ON USE_HEXAGON_ARCH=v65|v66|v68|v69|v73 USE_HEXAGON_SDK=/path/to/sdk
As mentioned before, only build the runtime component (e.g. make runtime).
Please note that the Hexagon SDK version needs to support the architecture specified in USE_HEXAGON_ARCH.