[Build] [RISC-V]: issues on cross-compiling for RISC-V target

[BHbean]

OpenVINO Version

tag 2024.0.0

Operating System

Ubuntu 22.04 (LTS)

Hardware Architecture

RISC-V

Target Platform

No response

Build issue description

Hi there!

I have been trying to cross-compile openvino for RISC-V target with rv64gcv arch recently, and I finally succeeded. However, it took me much effort due to unexpected issues on its submodules. Therefore, I want to open a new issue here to discuss the problems I met and give basic guidance for those who have the same problems.

Modification Guidance

The problems mainly lie in two submodules: oneDNN and FlatBuffers.

oneDNN

1. Due to the evolution of the RVV intrinsic spec, the new compilers DO NOT support the old definitions of RVV intrinsics, presented in src/plugins/intel_cpu/thirdparty/onednn/src/cpu/rv64/rvv_nchw_pooling.cpp. Therefore. it is a must to add compatible headers to make old ones effective again. These headers can take OpenCV as a reference and be added to the afore-mentioned file.

2. When the compiling process meets the src/plugins/intel_cpu/thirdparty/onednn/src/cpu/rv64/rvv_nchw_pooling.hpp file, it will prompt an error: error: base class has incomplete type. This problem can be solved by introducing the header file containing the definition of primitive_t class, like the following:

   // src/plugins/intel_cpu/thirdparty/onednn/src/cpu/rv64/rvv_nchw_pooling.hpp
   
   #ifndef RV64_NCHW_POOLING_HPP
   #define RV64_NCHW_POOLING_HPP
   
   #include "cpu/cpu_pooling_pd.hpp"
   #include "common/primitive.hpp"   // <== add here
   
   ...

FlatBuffers

3. The newest version of FlatBuffers compiler will generate some files under the build dir automatically, like build/src/frontends/tensorflow_lite/src/schema_generated.h. Inside these files, the flatbuffers/flatbuffers.h head file is included, which can be easily found under /usr/include path in common linux systems. However, it does not exsit in the target sysroot, so we have to copy the whole /usr/include/flatbuffers dir into our target sysroot:

   $ sudo cp /usr/include/flatbuffers <RISCV_TOOLCHAIN_ROOT>/sysroot/usr/include -r

Following the above steps, openvino can be successfully build for RISC-V target using this toolchain file.

Discussion

• I want to contribute the above guidance to existing docs, what should I do?
• I want to make PRs for the oneDNN repo to adapt the above changes, but there are a upstream repo and a fork made by openvinotoolkit. Which one should I contribute to?
• Someone is also bothered by FlatBuffers (see this issue). It does not seem to be elegant to copy some head files. How to solve this issue?

Build scrip or step-by-step to reproduce

No response

Relevant log output

No response

Issue submission checklist

• I'm reporting an issue. It's not a question.
• I checked the problem with the documentation, FAQ, open issues, Stack Overflow, etc., and have not found a solution.

[ilya-lavrenov]

Hi @BHbean
Could you please send those suggestions as PR to https://github.com/oneapi-src/oneDNN ?

Inside these files, the flatbuffers/flatbuffers.h head file is included, which can be easily found under /usr/include path in common linux systems

I did not quite follow this problem, it was an intention that even during cross-compilation we use headers from native system (e.g. /usr/include), see https://github.com/openvinotoolkit/openvino/blob/master/thirdparty/dependencies.cmake#L397. Why do you need to copy to <RISCV_TOOLCHAIN_ROOT>/sysroot/usr/include if it can work with /usr/include ?

[BHbean]

@ilya-lavrenov Thanks for your reply!

Could you please send those suggestions as PR to https://github.com/oneapi-src/oneDNN ?

Of course! I will propose a PR to https://github.com/oneapi-src/oneDNN later.

I did not quite follow this problem, it was an intention that even during cross-compilation we use headers from native system (e.g. /usr/include), see https://github.com/openvinotoolkit/openvino/blob/master/thirdparty/dependencies.cmake#L397. Why do you need to copy to <RISCV_TOOLCHAIN_ROOT>/sysroot/usr/include if it can work with /usr/include ?

I am not so sure why this was happening, probably due to the sysroot set in the toolchain file? The command used for my build is:

$ cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=<openvino_repo>/cmake/toolchains/riscv64-gnu.toolchain.cmake ..

Note: BTW, simply cross-compiling the thirdparty/flatbuffers/flatbuffers lib and installing it under <RISCV_TOOLCHAIN_ROOT>/sysroot/usr/include does not work, due to mismatch of versions.

[ilya-lavrenov]

Note: BTW, simply cross-compiling the thirdparty/flatbuffers/flatbuffers lib and installing it under <RISCV_TOOLCHAIN_ROOT>/sysroot/usr/include does not work, due to mismatch of versions.

We don't need to cross-compile flatbuffers, because it's used as build system tool:

• we use flatc to compile .fs files to .cpp
• headers (either on build or host system) are used during compilation