LCID-Fire/emscripten — comment on commit 12b2162a58a06615caa634b25207cb4de562850c
File: emscripten.py line 159
By kripken:

Emscripten needs to parse .ll files that were generated with annotations. It's a common mistake to forget them, and get weird errors. So emscripten.py checks for the existence of annotations here, and if they are not present, will recompile the .ll with annotations.

It reads the whole .ll file to check, but in general that shouldn't be too bad because you are about to load it anyhow to compile it, so it'll be cached by the OS.