[Frug]: R5900 `viaddi` instruction is improperly decoded

[Mc-muffin]

Explain the problem.

There's a decoding bug in the VU instruction viaddi, the imm5 is signed but it's decoded as unsigned.

Reproducer

Decode B207034A, it should decode as viaddi $vi3, $vi0, -0x2 but it's decoding as viaddi $vi3, $vi0, 0x1E instead.

Is this issue related to an specific MIPS extension?

R5900 EE (Emotion Engine, A Sony PlayStation 2 extension)

rabbitizer version

1.12.5

Optional: splat/spimdisasm version

No response

Optional: Version of other stuff

No response

Extra comments?

No response