To add to that, in principle Emscripten could use gcc and this backend instead of clang and an LLVM backend. Emscripten itself abstracts over the backend detail

To add to that, in principle Emscripten could use gcc and this backend instead of clang and an LLVM backend. Emscripten itself abstracts over the backend details (it's supported 3 different backends in its history, and currently supports 2). Most of the code in Emscripten is in the libraries, like OpenGL=>WebGL, etc., and JS integration code, which shouldn't depend on the backend. It would be interesting to get that working and do some code comparisons on the output.