[Scummvm-devel] Decompiler survey: Jump opcodes

Jordi Vilalta jvprat at jvprat.com
Sat Jun 12 15:35:40 CEST 2010


Hi,

2010/6/12 Michael Madsen:
> I'm about to start working on the code flow part of my decompiler, and I would like to request some information on jump opcodes in various engines. Specifically, I am interested in knowing if there are any engines that have a jump opcode which takes something other than a single argument containing the destination as part of the instruction bytes.
>
> It doesn't matter if it's a conditional jump or an unconditional jump - the question concerns *all* jumps. Calls to subroutines are not included.
>
> If the argument to your jump opcodes is anything other than an absolute address, or an address relative to the PC, I would like to hear about that as well.

The Groovie engine has several conditional jumps that perform the
condition test themselves based on arguments provided to them. I think
all of them have this look:
JumpIfMatch ArrayOfValues, AbsoluteDestAddress

The ArrayOfValues is a single argument.

Regards,
Jordi




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