C/C++ bindings

[yuanming-hu]

Concisely describe the proposed feature
A few users want to ship compiled Taichi kernels, so that they can run it without Python

Describe the solution you'd like
We can add a method like ti.export_all(lang='C'/'C++'), to dump

• A header that contains all the interfaces
• A shared object with all compiled kernels

Then users can basically do something like

#include "mpm99_exported.h"

int main() {
  initialize_taichi();
  mpm99_substep();
  finalize_taichi();
}

... or using a more OOP C++ version.

Additional comments
If you also need this or have any suggestions, please feel free to comment! :-)

[samuela]

I would really like the ability to do this, esp. with rust support.

[yuanming-hu]

Yeah I think we can start with a standard C interface and most other languages like C++/rust/go/Ruby can make use of it as well.

[samuela]

Makes sense. I'd be happy to help out with this but I'm personally not sure where to start.

[yuanming-hu]

For CPU code we can just dump LLVM IR and use llc to compile it into a .obj. Not sure what else we should do to make it a loadable shared object. The place where the optimized LLVM IR is emitted:

taichi/taichi/backends/codegen_llvm_x86.cpp

Line 104 in abbf5b1

module->print(llvm::errs(), nullptr);

We should explore this direction and a good starting point is to compile a simple taichi kernel, such as

for i in range(n):
  a[i] += 1

Some related discussions on SO: https://stackoverflow.com/questions/22956761/generate-binary-code-shared-library-from-embedded-llvm-in-c

For GPU code we can simply dump the compiled PTX and invoke the CUDA runtime to load and run the PTX code.

[archibate]

Possible solution:
First, dump llvm::errs() into /tmp/a.ll.
Second, call llc /tmp/a.ll -o /tmp/a.o.
Third, call gcc -fPIC -shared -o /tmp/a.so /tmp/a.o.

[archibate]

How to convert llvm::errs() into std::string?

[github-actions]

Warning: The issue has been out-of-update for 50 days, marking stale.

[archibate]

#1332 could be a systematic solution for this.
Note: Currently the experimental C backend is already capable of creating .so, which could be later linked into user programs.