[erlang-questions] Is there a good source for documentation on BEAM?

[James Hague]

When there was some documentation long ago, the bulk of it was about
the dozens and dozens of BEAM opcodes, and that's not actually the
important part.

What *really* matters are all the undocumented assumptions in the
system. What are the rules about floating point registers? Which BIFs
can cause garbage collection and how are they treated differently than
non-GC BIFs? When should registers be marked as unused? When are
destructive tuple updates allowed? What inefficient-looking sequences
are improved by the BEAM loader?

I can learn BEAM by disassembling code (anyone who is interested can
can use http://prog21.dadgum.com/127.html as a starting point), but I
can't learn the underlying rules and philosophies of the VM.

BEAM documentation can be as simple as:
* One-line-per-instruction description of opcodes.
* Couple of pages of VM architecture and rules.
* Two HOWTO docs: adding a BIF and adding a VM instruction.
* List of transformations done by the loader.