You Can Now Run LLVM Assembly In Your Web-Browser

Thanks to some experimental and innovative work done on LLVM, it's now possible to parse and execute LLVM Assembly within your web-browser. This Assembly code from the LLVM compiler infrastructure is then translated to JavaScript using EmScripten.

EmScripten is the project that was first talked about at the end of 2011 for translating LLVM bit-code into JavaScript. With EmScripten, in theory any major code-base with a compiler front-end for LLVM could then be translated to JavaScript and run within a modern web-browser. There's been various experimental plays with EmScripten but nothing too exciting that's been picked up mainstream. Python has been made to run within the browser using EmScripten as was the Cube 2 game and various other "toy" projects.

In a new developer mailing list thread entitled LLVM IR execution in JavaScript, parts of LLVM itself were translated using EmScripten into JavaScript. With parts of the LLVM compiler itself being translated into JavaScript, LLVM Assembly can then be parsed and executed via the JavaScript-powered compiler in the web-browser. Basically you enter some LLVM IR, press a button and see the output of compiling and running it, directly in the browser.

The GitHub demo page goes on to explain, "This demo works by using parts of the LLVM toolchain (llvm-dis and llvm-as), compiled by emscripten from C++ to JavaScript, to check the assembly for errors and pretty-print it. Then the emscripten compiler (originally written in JavaScript, but ported from the normal batch/shell mode to the browser environment) is run on the output, and the code executed directly. This demo was done as a fun hacking project over a holiday vacation, so there are some caveats: The generated code is not optimized at all, so benchmarking is pointless; if you want to benchmark, run emscripten normally with -O2. Compilation speed has also not been optimized at all. Also, this demo has hardly been tested and glues together several codebases in ways they were not originally intended, there might be things that do not work."