Chap#4 Pentium Instructions, Part 2 : Arithmetic, Logical, Bit Manipulation, Program Transfer, and Processor Control Instructions
Objectives :

• The arithmetic, logical, and bit manipulation instruction
• The program transfer instructions
• The processor control instructions
• How an assembler generates machine code
• The special properties of relocatable code

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4.1  Introduction

• Pentium's instruction set. Part II

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4.2  Arithmetic Instructions

• 1)  ADD    D, S (Add byte, W, DW)

    e.g.    ADD    BX,AX
• 2)  ADC    D, S (Add byte, W, DW with carry)

    e.g.    ADC    AX, BX  (P100)
• 3)  INC     D, S (Increment byte, W, DW by 1)

    e.g.     INC    AX
• 4)  SUB   D, S (Subtract byte, W, DW)

    e.g.     SUB    AL, BL
• 5)  SBB    D, S (Subtrac byte, W, DW with Borrow)

    e.g.     SBB    BH, CH
• 6)  DEC     D, S (Decrement byte, W, DW by 1)

    e.g.    DEC    BYTE PTR [200H] (P101)
• 7)  CMP    D, S (Compare byte, W, DW)

    e.g.    CMP    AX, 3B2EH
• 8)  CMPXCHG    D, S (Compare and Exchange)

    e.g.    CMPXCHG    BL, CL (P103)
• 9)  CMPXCHG8B    D (Compare and Exchange 8 Bytes)

    e.g.    MOV    EDX, 12345678H
             MOV    EAX, 9ABCDEF0H
             MOV    ECX, 01020304H
             MOV    EBX, 05060708H
             CMPXCHG8B    VAL64BIT
                - - -
VAL64BIT    DQ    123456789ABCDEF0H
                - - -
• 10) MUL    Sourse (Multiply Byte, W, DW Unsigned)

e.g.  MUL    CL  ==> CL * AL = AX
       MUL    BX ==> BX * AX = DX:AX
MUL    EBX ==> EBX * EAX = EDX:EAX
• 11) IMUL  Sourse (Integer Multiply Byte, W, DW)

e.g.1)  IMUL    CL    ;if CL=80H,  AL=20, then         AX=F000H(2's complement)
e.g.2)  IMUL    CX, -12    ; CX=CX * -12
           IMUL    EAX, EBX    ; EAX=EAX * EBX
e.g.3)  IMUL    AX, BX, 5    ; AX=BX * 5
           IMUL    EBX, [SI], -23    ; EBX= [SI] * -23
• 12) DIV    Sourse (Divide Byte, W, DW Unsigned)

e.g.  DIV    CL ==> AX/CL =AL ---(AH: remainder)
       DIV    CX ==> DX:AX/CX =AX ---(DX: remainder)
       DIV    EBX ==> EDX:EAX/EBX = EAX ---(EDX: remainder)
• 13) IDIV  Sourse (Integer Divide Byte, W, DW)

    Random number generator :
        RANDHI    DD    12345678H
        RANDLO    DD    9ABCDEF0H
        GTERM    DD    5A5A5A5AH
            - - -
        MOV    EDX, RANDHI
        MOV    EAX, RANDLO
        MOV    EBX, GTERM
        IDIV    EBX
        MOV    RANDHI, EDX
        MOV    RANDLO, EAX
            - - -
• 14) NEG    D (Negate Byte, W, DW)

        NEG    AX    ==> AX = 0 - AX (2'S Complement)
• 15) CBW    (Convert Byte to Word)

            AL Convert to AX
       before    IDIV or IMUL
• 16) CWD/CWDE    (Convert Word to DW)

       CWD ---AX Convert to DX:AX
       CWDE --- AX Convert to EAX
      Preparing for IDIV or IMUL
• 17) CDQ    (Convert DW to Quadword)

       CWQ --- EAX Convert to EDX:EAX
      Preparing for IDIV or IMUL
• 18) DAA    (Decimal Adjust for Addition)

  e.g.  ADD    AL, BL    ;AL=15H, BL=25H
                                           ;AL=3AH
          DAA                   ;AL=40H
• 19) DAS    (Decimal Adjust for Subtraction)

  e.g.    SUB    AL,CL    ;AL=10H, CL=02H
                                            ;AL=0EH
            DAS                   ;AL=08H
• 20) AAA    (ASCII Adjust for Addition)

  e.g.    ADD    AL, BL    ;AL=34H, BL=38H
                                       ;AL=6CH
           AAA                    ;AX=0102H
           OR    AX,3030H  ;AX=3132H
• 21) AAS   (ASCII Adjust for Subtraction)

                ;ASC1=38H,   ASC2=34H
   MOV    AL,ASC1    ;AL=38H
    SUB     AL,ASC2    ;AL=04H
    AAS                       ;AX=0004
    OR        AL,30H    ;AL=34H
    - - -
   MOV    AL,ASC2    ;AL=34H
    SUB     AL,ASC1    ;AL=FCH
    AAS                       ;AX=FF06H
• 22) AAM    (ASCII Adjust for Multiply)

                ; AL=35H,   CL=39H
    AND    CL,0FH
    AND    AL,0FH
    MUL    CL
    AAM                          ;AX=0405H
    OR        AX,3030H    ;AX=3435H
• 23) AAD    (ASCII Adjust for Division)

                ;AX=3238H,    CL=37H
    AND    CL, 0FH
    AND    AX,0F0FH
    AAD                            ;AX=001CH
    DIV       CL                  ;AX=0004H
• 24) XADD    D, S (Exchange and ADD Byte, W, DW)

                ;AX=2000H,    BX=3000H
        XADD    AX, BX     ;AX=5000H,  BX=2000H

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4.3  Logical Instructions

• 1)  NOT   Dest. ("NOT" Byte, W, DW)
• 2)  AND   D, S  ("AND" Byte, W, DW) (P112)
• 3)  OR     D, S  ("OR" Byte, W, DW) (P113)
• 4)  XOR   D, S  ("Exclusive-OR" Byte, W, DW) (P114)
• 5)  TEST   D, S  ("TEST" Byte, W, DW)

      e.g. AND    DX, 2000H    ;DX change, Set Flag
      e.g. TEST    DX, 2000H    ;DX not-change, Set Flag
6)  BSF/BSR   D, S (Bit Scan Forward/Reverse) (P115)
• 7)  BT/BTC/BTS/BTR  D, S

        (Bit Test and Complement/Set/Reset) (P116)
        * Bit are 0 ~ 31
• 8)  SETcc   Dest. (Set Byte on Condition) (P117)

    e.g.  SETNZ    AL    ; if true then AL = 01H
                                     : if false then AL = 00H

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4.4  Bit Manipulation Instructions

• 1) SHL/SAL  D, S

        (Shift Logical/Arithmetic Left Byte, W, DW)
• 2) SHR  D, Count

        (Shift Logical Right Byte, W, DW) (P118)
• 3) SAR  D, Count

        (Shift Arithmetic Right Byte, W, DW) (P119)
• 4) SHLD/SHRD  D, S, Count

        (Shift Left/Right Double Precision) (P120)
• 5) ROL  D, Count

        (Rotate Left Byte, W, DW) (P121)
• 6) ROR  D, Count

        (Rotate Right Byte, W, DW) (P122)
• 7) RCL  D, Count

        (Rotate Left Through Carry Byte, W, DW) (P123)
• 8) RCR  D, Count

        (Rotate Right Through Carry Byte, W, DW)

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4.5  Program Transfer Instructions

• 1) JMP  Target

            (Unconditional Jump to Target) (P126)
• 2) Conditional Jumps (P127)
• 3) LOOP  Short-Label (Loop) (P129)
• 4) LOOPE/LOOPZ    Short-Label

            (Loop if Equal, Loop if Zero)
• 5) LOOPNE/LOOPNZ    Short-Label

            (Loop if not Equal, Loop if not Zero)
• 6) JCXZ/JECXZ    Short-Label

            (Jump if CX/ECX = 0) (P130)
• 7) CALL    Procedure-Name

            (Call Procedure) (P131) (P132)
• 8) RET    Optional-Pop-Value

            (Return from Procedure) (P133)
• 9) INT    Interrupt-Type

            (Interrupt) (P134)
• 10) IRET/IRETD

            (Interrupt Return) (P135)
• 11) INTO

            (Interrupt on Overflow)
• 12) BOUND    Index, Range

            (Check Array Index Against Bounds)
• 13) ENTER/LEAVE

            (Enter/Leave a Procedure) (P137)
• @ Assembler Directive PROC and ENDP (P138)

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4.6  Processor Control Instructions

• 1) CLC    (Clear Carry Flag)
• 2) STC     (Set Carry Flag)
• 3) CMC   (Complement Carry Flag)
• 4) CLD    (Clear Direction Flag)
• 5) STD    (Set Direction Flag)
• 6) CLI     (Clear Intrrupt-Enable Flag)
• 7) STI     (Set Intrrupt-Enable Flag)
• 8) HLT    (Halt Until Interrpt or Reset)
• 9) NOP    (No Operation)
• 10) LOCK    ( Lock Bus During Next Instruction)

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4.7  How an Assembler Generates Machine Code

• MOVSB : m/c code : 1010 010w (0)
  MOVSW : m/c code : 1010 010w (1)
• MUL    CX : m/c code : 1111 0111 1110 0r/w(=001)
  MUL    SI : m/c code : 1111 0111 1110 0r/w(=110)
• Refer to P452 ~ P458

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4.8 The Beauty of Relocatable Code

• A relocatable program is a program that can be loaded into memory at any address and the executed normally.

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4.9  Summary

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