Jumps and branches

Efficiently moving the instruction pointer(s) around.

There are three types of jump instructions used in various scenarios:

• jmp - jumps to an 11 bit absolute address (32 byte aligned, full range)
• jmpr - jumps to an 11 bit relative offset (2 byte aligned, +- 2 KiB range)
• jmpd - jumps to a 15 bit register address (2 byte aligned, full range)

Each jump type has a ‘link’ variant, resulting in a jump-and-link calling convention by setting the rp (r1) register to the instruction pointer one after the link instruction.

jmpd rp returns back to the invoking call site (pseudo-instruction ret). A dynamic jump instruction discards the LSB due to the 2 byte aligned instruction pointer. There is no exception given if the LSB is high when using jmpd.

1 Branches

Branches are conditional, non-callable jumps. The brh instruction takes an 8 bit offset address (2 byte aligned, +- 256 byte range).