cyx-6 commented on code in PR #254: URL: https://github.com/apache/tvm-ffi/pull/254#discussion_r2986565483
########## addons/tvm-ffi-orcjit/examples/quick-start/README.md: ########## @@ -0,0 +1,92 @@ +<!--- Licensed to the Apache Software Foundation (ASF) under one --> +<!--- or more contributor license agreements. See the NOTICE file --> +<!--- distributed with this work for additional information --> +<!--- regarding copyright ownership. The ASF licenses this file --> +<!--- to you under the Apache License, Version 2.0 (the --> +<!--- "License"); you may not use this file except in compliance --> +<!--- with the License. You may obtain a copy of the License at --> + +<!--- http://www.apache.org/licenses/LICENSE-2.0 --> + +<!--- Unless required by applicable law or agreed to in writing, --> +<!--- software distributed under the License is distributed on an --> +<!--- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY --> +<!--- KIND, either express or implied. See the License for the --> +<!--- specific language governing permissions and limitations --> +<!--- under the License. --> + +# Quick Start Example + +Demonstrates basic usage of tvm-ffi-orcjit: compile functions to object files, +load them into the ORC JIT at runtime, and call them from Python. + +## Files + +| File | Description | +| ------ | ------------- | +| `add.cc` | C++ source using `TVM_FFI_DLL_EXPORT_TYPED_FUNC` (automatic type marshaling, supports `std::string`) | +| `add_c.c` | Pure C source using `TVMFFISafeCallType` ABI (`__tvm_ffi_` prefix). No C++ runtime needed. | +| `run.py` | Python script that loads and calls the compiled functions | +| `CMakeLists.txt` | Build configuration for both variants | + +## Prerequisites + +- Python 3.10+, CMake 3.18+, C/C++ compiler +- `apache-tvm-ffi` and `tvm-ffi-orcjit` packages installed + +## Steps + +### 1. Build the object files + +```bash +cmake -B build +cmake --build build +``` + +This produces `add.o` (C++) and `add_c.o` (pure C). On Windows, only the C +variant is built (C++ is not supported for ORC JIT on Windows). + +### 2. Run + +```bash +# C++ variant (Linux/macOS) +python run.py + +# Pure C variant (all platforms including Windows) +python run.py --lang c +``` + +## How It Works + +**C++ variant** (`add.cc`): Functions are exported with +`TVM_FFI_DLL_EXPORT_TYPED_FUNC`, which wraps a typed C++ lambda/function into +TVM-FFI's packed calling convention. Supports C++ types like `std::string`. + +**C variant** (`add_c.c`): Functions follow the `TVMFFISafeCallType` ABI +directly — each function is named `__tvm_ffi_<name>` and manually packs +arguments/results via `TVMFFIAny`. Zero C++ dependencies, works on all +platforms including Windows with MSVC or clang-cl. + +**Python side** (`run.py`): + +```python +from tvm_ffi_orcjit import ExecutionSession + +session = ExecutionSession() # Create ORC JIT session +lib = session.create_library() # Create a JITDylib +lib.add("add_c.o") # Load object file into JIT +add = lib.get_function("add") # Look up symbol +print(add(10, 20)) # Call like a normal function → 30 +``` + +## Platform Notes + +| Platform | C++ (`add.o`) | C (`add_c.o`) | +| ---------- | :-: | :-: | +| Linux (Clang/GCC) | yes | yes | +| macOS (Clang/Apple Clang) | yes | yes | +| Windows (all compilers) | no | yes | + +C++ is not supported for ORC JIT on Windows. The `TVM_FFI_DLL_EXPORT_TYPED_FUNC` +macro uses `try`/`catch` which requires Itanium exception ABI symbols that the +MSVC-built host process cannot provide. Use the pure C variant on Windows. Review Comment: It is ORC JIT-specific problem on Windows. When building a normal DLL, the linker resolves exception handling symbols against the CRT. In ORC JIT, we skip `COFFPlatform` because it requires MSVC CRT symbols (_CxxThrowException, RTTI vtables, etc.) that are difficult to provide in the JIT environment. Without `COFFPlatform`, the exception handling symbols from try/catch in `TVM_FFI_DLL_EXPORT_TYPED_FUNC` can't be resolved. The pure C variant avoids exception handling entirely. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
