ref: e81c54ba2ecc673a4d5f8aed0e9b52841fe07b0d
dir: /os/boot.original/puma/div.s/
/* * Div/Mod taken from the Inferno 2.0 ebsit code */ Q = 0 N = 1 D = 2 CC = 3 TMP = 11 TEXT save<>(SB), 1, $0 MOVW R(Q), 0(FP) MOVW R(N), 4(FP) MOVW R(D), 8(FP) MOVW R(CC), 12(FP) MOVW R(TMP), R(Q) /* numerator */ MOVW 20(FP), R(D) /* denominator */ CMP $0, R(D) BNE s1 MOVW -1(R(D)), R(TMP) /* divide by zero fault */ s1: RET TEXT rest<>(SB), 1, $0 MOVW 0(FP), R(Q) MOVW 4(FP), R(N) MOVW 8(FP), R(D) MOVW 12(FP), R(CC) /* * return to caller * of rest<> */ MOVW 0(R13), R14 ADD $20, R13 B (R14) TEXT div<>(SB), 1, $0 MOVW $32, R(CC) /* * skip zeros 8-at-a-time */ e1: AND.S $(0xff<<24),R(Q), R(N) BNE e2 SLL $8, R(Q) SUB.S $8, R(CC) BNE e1 RET e2: MOVW $0, R(N) loop: /* * shift R(N||Q) left one */ SLL $1, R(N) CMP $0, R(Q) ORR.LT $1, R(N) SLL $1, R(Q) /* * compare numerator to denominator * if less, subtract and set quotent bit */ CMP R(D), R(N) ORR.HS $1, R(Q) SUB.HS R(D), R(N) SUB.S $1, R(CC) BNE loop RET TEXT _div(SB), 1, $16 BL save<>(SB) CMP $0, R(Q) BGE d1 RSB $0, R(Q), R(Q) CMP $0, R(D) BGE d2 RSB $0, R(D), R(D) d0: BL div<>(SB) /* none/both neg */ MOVW R(Q), R(TMP) B out d1: CMP $0, R(D) BGE d0 RSB $0, R(D), R(D) d2: BL div<>(SB) /* one neg */ RSB $0, R(Q), R(TMP) B out TEXT _mod(SB), 1, $16 BL save<>(SB) CMP $0, R(D) RSB.LT $0, R(D), R(D) CMP $0, R(Q) BGE m1 RSB $0, R(Q), R(Q) BL div<>(SB) /* neg numerator */ RSB $0, R(N), R(TMP) B out m1: BL div<>(SB) /* pos numerator */ MOVW R(N), R(TMP) B out TEXT _divu(SB), 1, $16 BL save<>(SB) BL div<>(SB) MOVW R(Q), R(TMP) B out TEXT _modu(SB), 1, $16 BL save<>(SB) BL div<>(SB) MOVW R(N), R(TMP) B out out: BL rest<>(SB) B out