Gen 3's LCRNG in GBZ80

__addsi3:
    ; *hl = *bc + *de
    push hl
    ld h, d
    ld l, e
    pop de
    ld a, [bc]
    add [hl]
    ld [de], a
    inc bc
    inc de
    inc hl
    ld a, [bc]
    adc [hl]
    ld [de], a
    inc bc
    inc de
    inc hl
    ld a, [bc]
    adc [hl]
    ld [de], a
    inc bc
    inc de
    inc hl
    ld a, [bc]
    adc [hl]
    ld [de], a
    ret

__shlsi3:
    ; *hl = *de << b
    ld a, b
    and a
    jr z, .sh0
    cp 32
    jr c, .proceed
    xor a
    ld [hli], a
    ld [hli], a
    ld [hli], a
    ld [hl], a
    scf
    ret
.sh0:
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hl], a
    and a
    ret
.proceed:
    xor a ; reset carry
    push af
    add sp, -4
    push hl
    ld hl, sp + 2
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hl], a
.loop:
    ld hl, sp + 2
    sla [hl]
    inc hl
    rla [hl]
    inc hl
    rla [hl]
    inc hl
    rla [hl]
    push af
    ld hl, sp + 1
    ld a, [hl]
    and $10
    ld hl, sp + 9
    or [hl]
    ld [hl], a
    pop af
    dec b
    jr nz, .loop
    ld hl, sp + 2
    pop de
    ld a, [hli]
    ld [de], a
    inc de
    ld a, [hli]
    ld [de], a
    inc de
    ld a, [hli]
    ld [de], a
    inc de
    ld a, [hl]
    ld [de], a
    add sp, 4
    pop af
    ret

__mulsi3:
    ; *hl = *bc * *de
    xor a
    push af
    add sp, -8
    push hl
    ld hl, sp + 2
    xor a
    ld [hli], a
    ld [hli], a
    ld [hli], a
    ld [hli], a
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hli], a
    inc de
    ld a, [de]
    ld [hl], a
    ld d, 4
.loop:
    ld a, [bc]
    ld e, 8
.loop2:
    push bc
    push de
    rrca
    jr nc, .skip
    ld hl, sp + 10
    ld b, h
    ld c, l
    ld hl, sp + 6
    ld d, h
    ld e, l
    call __addsi3
    push af
    ld hl, sp + 1
    ld a, [hl]
    and $10
    ld hl, sp + 17
    or [hl]
    ld [hl], a
    pop af
.skip:
    ld hl, sp + 10
    ld d, h
    ld e, l
    ld b, 1
    call __shlsi3
    pop de
    pop bc
    dec e
    jr nz, .loop2
    inc bc
    dec b
    jr nz, .loop
    pop de
    ld hl, sp + 0
    ld a, [hli]
    ld [de], a
    inc de
    ld a, [hli]
    ld [de], a
    inc de
    ld a, [hli]
    ld [de], a
    inc de
    ld a, [hl]
    ld [de], a
    add sp, 8
    pop af
    ret

Random:
    ld hl, wRngValue
    ld d, h
    ld e, l
    ld bc, .multiplicand
    call __mulsi3
    ld hl, wRngValue
    ld d, h
    ld e, l
    ld bc, .addend
    call __addsi3
    ld hl, wRngValue + 2
    ld a, [hli]
    ld h, [hl]
    ld l, a
    ret
.multiplicand: dl 1103515245
.addend: dl 24691