The code section can be really large in modules. In SpiderMonkey, we compile functions in the code section in parallel and kick off the tasks as soon as we get them off the network. So minimizing the information needed before being able to compile the first function is helpful.

If we expect many hints to be provided for the functions, then downloading and decoding the whole branch hint section before getting to the first function in the code section could delay compilation. It could be useful if the branch hints were inside the code section so that we only need to decode the hints for each function immediately before the function is compiled.

That would involve changing the code section, making this not a custom section anymore. I'm not sure if this was discussed previously and I forgot about it.