Chapter 54

mov ax, simu1 bxmov bx.axadd cx.dxPOP axmu1 diadd bx.axadc cx.dxmov ax, simu1 diif MUL-ROUNDING-ONadd ax.8000hadc bx.dxelse :!MUL-ROUNDING-ONadd bx.dxendif ;MUL-ROUNDING-ONadc cx.0mov dx.cxmov ax.bxPOP cxand cx,cxjz Fi xedMul Doneneg dxneg axsbb dx.0FixedMulDone::low word M1 times high word M2:accumulate result in CX:BX;retrieve high word of M1;high word M1 times low word MZ:accumulate result in CX:BX:low word M1 times low word M2;round by adding 2^(-17):don't round;accumulate result in:is the result negative?;no. we're all set;yes. so negate DX:AXCX:BXpoppopdisi:restore C register variablesendif :USE386POP bPret- FixedMul endp: Divides one fixed-point value by another.: C near-callable as:; Fixedpoint FixedDiv(Fixedp0int Dividend, Fixedpoint Divisor);FDparms strucdw 2 dup(?) :return address & pushed BPDividend dd ?Divisor dd ?FDparms endsa1 i gn ALIGNMENTpublic JixedOivJixedDi v proc nearpush bpmov bP SSPif USE386if DIV-ROUNDING-ONsub cx.cx ;assume positive resultmov eax.[bp+Oividendland eax,eax ;positive dividend?jns FOP1 :yesinc cx :mark it's a negative dividendneg eax :make the dividend positive101 0 Chapter 54