Function b_imm

crates/virtual-machine/src/cpu/decoder.rs:914–920

B-type immediate: [31]<<12 | [7]<<11 | [30:25]<<5 | [11:8]<<1, sign-extended to 13 bits.

(word: u32)

fn j_imm(word: u32) -> i64 {
    let bit20 = field(word, 31, 31) << 20;
    let bits19_12 = field(word, 19, 12) << 12;
    let bit11 = field(word, 20, 20) << 11;
    let bits10_1 = field(word, 30, 21) << 1;
    sign_ext(bit20 | bits19_12 | bit11 | bits10_1, 21)
}