Updated BEAM spec?

Bjorn Gustavsson <>
Tue Aug 15 12:53:00 CEST 2000


There is still no BEAM document. I've been busy working with the R7 release.
Perhaps after R7...

Are you referrering to {'%live',N}? This is not a real instruction
(meaning that the assembler will discard it and you will not find it
in the .beam file). N indicates the number of live X registers at that
point in the code. The code generator emits one such %live instruction
at the end of every basic block. The beam_block modules uses the information
to optimize basic blocks.

/Björn

James Hague <> writes:

> I asked this a ways back, before the latest Erlang release:  Is there a
> document outlining the generic BEAM opcodes used by the emulator?  The
> basic opcodes aren't too hard to figure out, but there are other opcode
> bits I don't understand (related to register lifetime, perhaps?).  The BEAM
> doc on the web is terribly outdated.
> 
> James
> 

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