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386. mikroprocesora aritmētika

386. mikroprocesora aritmētika. Direktīva .386. . code .startup .386. Operanda paplašināšana ( MovSx ). NegTwo DB -2 ... Mov Al, NegTwo ;Al = ?? FE MovSx Cx, Al ;Cx = FFFE MovSx Bx, NegTwo ;Bx = FFFE MovSx EDx, NegTwo ;EDx = FFFF FFFE.

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386. mikroprocesora aritmētika

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  1. 386. mikroprocesora aritmētika Direktīva .386 .code .startup .386 Operanda paplašināšana (MovSx) NegTwo DB -2 ... Mov Al, NegTwo;Al = ??FE MovSx Cx, Al;Cx = FFFE MovSx Bx, NegTwo;Bx = FFFE MovSx EDx, NegTwo;EDx = FFFF FFFE

  2. Operanda paplašināšana (MovZx) NegTwo DB -2 ... Mov Al, NegTwo;Al = ??FE MovZx Cx, Al;Cx = 00FE MovZx Bx, NegTwo;Bx = 00FE MovZx EDx, NegTwo;EDx = 000000FE Kļūdas MovSx Cl, Bl;operandu izmēri sakrīt MovSx Cx, Bx;operandu izmēri sakrīt MovSx ECx, EBx;operandu izmēri sakrīt MovSx MemW, MemB ;formāts “atmiņa” – “atmiņa”

  3. Divu operandu reizināšana (IMul) Var izmantot ne tikai akumulatoru. MovBx, 3;Bx= 0003 MovCx, -2;Cx = FFFE IMulBx, Cx;Bx = FFFA (-6) Mov Bx, -2;Bx = FFFE IMul Bx, X;Bx = FFFA, ja vārds X = 3 Kļūdas IMul Bl, Cl;operandi nav vārdi MulBx, Cx ;bez zīmju reizināšana

  4. Trīs operandu reizināšana (IMul). Trešais operands vienmēr ir tiešais operands. Rezultāts atrodas pirmajā operandā-reģistrā. Mov Bx, 2;Bx = 2 IMul Bx, Bx, 3;Bx = 6 Mov Bx, 2;Bx = 2 IMul Cx, Bx, 3;Cx =6 X Dw 2 ... IMul Cx, X, 3;Cx =6 Mov EBx, 2;EBx = 2 IMul ECx, EBx, 3;ECx = 6

  5. Operandu paplašināšana līdz četrkāršotām vārdam (Cwde, Cdq). Mov Ax, -3;Ax = FFFD (-3) Cwde;EAx = FFFFFFFD (-3) Cdq;EDx:EAx = FFFFFFFF:FFFFFFFD Alternatīvais risinājums: Mov EAx, -3 Cdq Piezīme: neder MovSx EAx, -3 Dalīšana: Mov EBx, 3;EBx = 3 IDiv EBx;EAx = FFFF (-1), EDx = 0

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