; MACROGROK — INFER4 (4-input fixed-point binary decision)
; AGC-inspired pseudo-ISA. Not authentic yaYUL. 15 data bits + parity.
; See README.md for Q formats and memory map.

; ===== FIXED / ROM =====
WEIGHTS_Q1_14: DC 2458, -1638, 819, 3277   ; Q1.14
BIAS_Q3_12: DC -256                         ; Q3.12
ALPHA_Q1_14: DC 12288                       ; 0.75 Q1.14
ONE_Q1_14: DC 16384
OUT_MIN_Q1_14: DC -16384
OUT_MAX_Q1_14: DC 16383
SCORE_MIN_Q3_12: DC -8192
SCORE_MAX_Q3_12: DC 8191

; ===== ERASABLE / RAM =====
INPUT: DS 4
STATE: DS 1
OUTPUT: DS 1
ACC_HI: DS 1
ACC_LO: DS 1
PROD_HI: DS 1
PROD_LO: DS 1
TMP0: DS 1
TMP1: DS 1
FLAGS: DS 1
FLAG_VALID EQU 0001
FLAG_SAT EQU 0002
FLAG_POSITIVE EQU 0004

; ===== PRIMITIVE MACROS =====
; LOAD/STORE/ADD/SUB/MUL16/ADD32/ASR32/CMP/BR* assumed.

MACRO CLR_ACC
    CLR ACC_HI
    CLR ACC_LO
ENDM

MACRO MAC_Q1_14 a, b
    LOAD R0, a
    LOAD R1, b
    MUL16 R0, R1         ; PROD_HI:PROD_LO
    LOAD R2, PROD_HI
    LOAD R3, PROD_LO
    ASR32 R2:R3, 4
    ADD32 ACC_HI:ACC_LO, R2:R3
ENDM

MACRO ACC_TO_Q3_12 dest
    ASR32 ACC_HI:ACC_LO, 12
    STORE dest, ACC_LO
ENDM

MACRO SAT_Q3_12 value, lo, hi
    LOAD R0, value
    LOAD R1, lo
    CMP R0, R1
    BRLT %%LOW
    LOAD R1, hi
    CMP R0, R1
    BRGT %%HIGH
    BR %%DONE
%%LOW:
    LOAD R0, lo
    STORE value, R0
    LOAD R1, FLAGS
    OR R1, FLAG_SAT
    STORE FLAGS, R1
    BR %%DONE
%%HIGH:
    LOAD R0, hi
    STORE value, R0
    LOAD R1, FLAGS
    OR R1, FLAG_SAT
    STORE FLAGS, R1
%%DONE:
ENDM

MACRO DOT4_Q1_14
    CLR_ACC
    MAC_Q1_14 INPUT+0, WEIGHTS_Q1_14+0
    MAC_Q1_14 INPUT+1, WEIGHTS_Q1_14+1
    MAC_Q1_14 INPUT+2, WEIGHTS_Q1_14+2
    MAC_Q1_14 INPUT+3, WEIGHTS_Q1_14+3
ENDM

MACRO THRESHOLD_Q3_12
    LOAD R0, TMP0
    CLR R1
    CMP R0, R1
    BRLT %%NEG
    LOAD R0, ONE_Q1_14
    STORE TMP1, R0
    LOAD R0, FLAGS
    OR R0, FLAG_POSITIVE
    STORE FLAGS, R0
    BR %%DONE
%%NEG:
    LOAD R0, OUT_MIN_Q1_14
    STORE TMP1, R0
%%DONE:
ENDM

MACRO UPDATE_STATE_3_4
    LOAD R0, STATE
    ADD R1, R0
    ADD R1, R0
    ADD R1, R0          ; R1=3*STATE
    LOAD R2, TMP1
    ADD R1, R2          ; 3*STATE+TARGET
    ASR R1, 2           ; /4
    STORE STATE, R1
ENDM

; ===== MAIN =====
INFER4:
    CLR FLAGS
    DOT4_Q1_14
    ACC_TO_Q3_12 TMP0
    LOAD R0, TMP0
    LOAD R1, BIAS_Q3_12
    ADD R0, R1
    STORE TMP0, R0
    SAT_Q3_12 TMP0, SCORE_MIN_Q3_12, SCORE_MAX_Q3_12
    THRESHOLD_Q3_12
    UPDATE_STATE_3_4
    LOAD R0, STATE
    STORE OUTPUT, R0
    LOAD R0, FLAGS
    OR R0, FLAG_VALID
    STORE FLAGS, R0
    RET