Node:VM disassembler, Next:VM profiler, Previous:Peephole optimization, Up:Using the generated code
A VM code disassembler is optional for an interpretive system, but highly recommended during its development and maintenance, because it is very useful for detecting bugs in the front end (and for distinguishing them from VM interpreter bugs).
Vmgen supports VM code disassembling by generating
file-disasm.i. This code has to be wrapped into a
function, as is done in vmgen-ex/disasm.c. You can use this file
almost verbatim. In addition to vm_A2B(a,b),
vm_out, printarg_type(value), which are
explained above, the following macros and variables are used in
file-disasm.i (and you have to define them):
ip
IP IPTOS
IPTOS is the first argument of the current VM instruction, and
IP points to it; this is just as in the engine, but here
ip points to the opcode of the VM instruction (in contrast to the
engine, where ip points to the next cell, or even one further).
VM_IS_INST(Inst i, int n)
i is the same as the nth entry in the
VM instruction table.