学 Win32 汇编[26] - 加减指令: INC、DEC、NEG、ADD、ADC、SUB、SBB、CMP

;INC(Increment): 加一

;DEC(Decrement): 减一

;NEG(Negate):    求补(求反)

;ADD(Add):       加

;ADC(Add Carry): 带进位加

;SUB(Subtract):  减

;SBB(Subtract With Borrow): 带进位减

;CMP(Compare):   比较



;INC、DEC、NEG 的指令格式:

;INC r/m



;ADD、ADC、SUB、SBB、CMP 的指令格式:

;ADD r/m, r/m/i



;它们的结果影响 OF、SF、ZF、AF、PF、CF


 
   

INC、DEC、NEG

---

; Test26_1.asm

.386

.model flat, stdcall



include    windows.inc

include    kernel32.inc

include    masm32.inc

include    debug.inc

includelib kernel32.lib

includelib masm32.lib

includelib debug.lib



.code

main proc

    mov eax, 6

    inc eax

    PrintDec eax ;7

    dec eax

    PrintDec eax ;6

    neg eax      ;NEG 就是加个负号

    PrintDec eax ;-6

    neg eax

    PrintDec eax ;6

    ret

main endp

end main


 
   

ADD、ADC

---

; Test26_2.asm

.386

.model flat, stdcall



include    windows.inc

include    kernel32.inc

include    masm32.inc

include    debug.inc

includelib kernel32.lib

includelib masm32.lib

includelib debug.lib



.code

main proc

    mov eax, 5

    add eax, 1

    PrintDec eax ;6

    

    stc          ;CF=1

    mov eax, 5

    adc eax, 1   ;ADC 比 ADD 还要多加上 CF

    PrintDec eax ;7

    

    clc          ;CF=0

    mov eax, 5

    adc eax, 1

    PrintDec eax ;6

    ret

main endp

end main


 
   

SUB、SBB

---

; Test26_3.asm

.386

.model flat, stdcall



include    windows.inc

include    kernel32.inc

include    masm32.inc

include    debug.inc

includelib kernel32.lib

includelib masm32.lib

includelib debug.lib



.code

main proc

    mov eax, 5

    sub eax, 1

    PrintDec eax ;4

    

    stc

    mov eax, 5

    sbb eax, 1   ;SBB 比 SUB 还要多减去 CF

    PrintDec eax ;3

    

    clc

    mov eax, 5

    sbb eax, 1

    PrintDec eax ;4

    ret

main endp

end main


 
   

CMP

---

;CMP 隐含执行 SUB, 但并不改写操作数, 只是影响标志位;

;零标志位标识着两个数是否相等, 符号标志位标识着两个数的大小. 

;它后面经常跟着跳转指令



; Test26_4.asm

.386

.model flat, stdcall



include    windows.inc

include    kernel32.inc

include    masm32.inc

include    debug.inc

includelib kernel32.lib

includelib masm32.lib

includelib debug.lib



.code

main proc

    mov eax, 3

    cmp eax, 3

    lahf

    PrintHex ah ;46 - 01000110b(ZF=1 说明两个数相等)

    

    mov eax, 3

    cmp eax, 2

    lahf

    PrintHex ah ;02 - 00000010b(SF=0、ZF=0 说明前者 > 后者)

    

    mov eax, 3

    cmp eax, 4

    lahf

    PrintHex ah ;76 - 10010111b(SF=1、ZF=0 说明前者 < 后者)    

    ret

main endp

end main


 
   

辨析 NEG 与 NOT

---

; Test26_5.asm

.386

.model flat, stdcall



include    windows.inc

include    kernel32.inc

include    masm32.inc

include    debug.inc

includelib kernel32.lib

includelib masm32.lib

includelib debug.lib



.data?

    val sword ?

.code

main proc

    ;求补运算: 取反+1

    mov val, 44

    PrintDec val  ;44

    PrintHex val  ;002C - 00000000 00101100b

    

    not val

    inc val

    PrintDec val  ;-44

    PrintHex val  ;FFD4 - 11111111 11010100b

    

    not val

    inc val

    PrintDec val  ;44

    PrintHex val  ;002C - 00000000 00101100b

    

    ;NEG 就相当于: 取反+1

    mov val, 44

    neg val

    PrintDec val  ;-44

    PrintHex val  ;FFD4 - 11111111 11010100b

    

    neg val

    PrintDec val  ;44

    PrintHex val  ;002C - 00000000 00101100b

    ret

main endp

end main