LLVM Bytecode Loader

This package allows you to require() LLVM bytecode files, automatically compiling them to JS + WebAssembly using Emscripten.

Installation & Requirements

This loader itself can be installed via npm or Yarn:

npm install llvmbc-wasm-loader

You'll also need a working Emscripten installation, as the loader shells out to emcc to convert the bytecode files to JS/WASM.

Basic usage

Create a simple C++ file:

// mylibrary.cpp
#include <emscripten.h>

extern "C" EMSCRIPTEN_KEEPALIVE int add(int x, int y) {
  return x + y;
}

Use em++ to compile it to LLVM Intermediate Representation bytecode:

$ em++ mylibrary.cpp -o mylibrary.bc

require() it from your JS file:

// mylibrary.js
var lib = require('llvmbc-wasm-loader!./mylibrary.bc')

// You need to wait for this Promise to complete:
lib.ready.then(function() {
  console.log("1 + 2 = " + lib._add(1, 2));
}

Write a webpack config:

// webpack.config.js
module.exports = {
  target: 'node',
  entry: './mylibrary.js',
  output: {
    filename: 'bundle.js'
  }
}

Compile with webpack:

$ webpack

And run the bundle with node:

$ node bundle.js
1 + 2 = 3

Loader Options

emscriptenCommand

This should be a list representing the emcc command line to be invoked to produce the .js and .wasm files for a given input. The default is:

[
  'emcc',
  // Prevents the runtime from being shutdown after invocation of a
  // `main()` function, if any. This allows for library usage.
  '-s', 'NO_EXIT_RUNTIME=1',
]

To all command lines, the following necessary arguments will be appended:

[
  '-s', 'WASM=1', // Necessary to produce WASM output
  INFILE,
  '-o', OUTFILE
]

If you're using multiple distinct emcc invocations in your application, we recommend using resourceQuery to differentiate between them, rather than specifying rather unwieldy commands in the loader query syntax. In your webpack.config.js:

module.exports = {
  // ...
  module: {
    rules: {
      {
        test: /\.bc$/,
        // `oneOf` will pick the first matching rule:
        oneOf: [
          // `import '.../foo.bc?withFunctionPointers'` will resolve to these options:
          {
            resourceQuery: /^\?withFunctionPointers$/,
            use: {
              loader: 'llvmbc-wasm-loader',
              options: {
                command: ['emcc', '-s', 'NO_EXIT_RUNTIME=1', '-s', 'RESERVED_FUNCTION_POINTERS=1']
              }
            }
          },
          // All other imports will resolve to the default config:
          {
            use: 'llvmbc-wasm-loader'
          }
        ]
      }
    }
  }
}

Then, from your application:

import lib1 from './lib1.bc?withFunctionPointers'
import lib2 from './lib2.bc'

// ...

License

This library is released under the Unlicense:

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to http://unlicense.org/