x=x+1 vs. x +=1

Question

I\'m under the impression that these two commands result in the same end, namely incrementing X by 1 but that the latter is probably more efficient.

If this is not c

Answer 1

i thought the differences are due to the additional clock cycles used for memory references, but i turned out to be wrong! can't understand this thing myself

instruction type        example                      cycles

===================================================================

ADD reg,reg             add ax,bx                       1
ADD mem,reg             add total, cx                   3
ADD reg,mem             add cx,incr                     2
ADD reg,immed           add bx,6                        1
ADD mem,immed           add pointers[bx][si],6          3
ADD accum,immed         add ax,10                       1

INC reg                 inc bx                          1
INC mem                 inc vpage                       3

MOV reg,reg             mov bp,sp                       1
MOV mem,reg             mov array[di],bx                1
MOV reg,mem             mov bx,pointer                  1
MOV mem,immed           mov [bx],15                     1
MOV reg,immed           mov cx,256                      1
MOV mem,accum           mov total,ax                    1
MOV accum,mem           mov al,string                   1
MOV segreg,reg16        mov ds,ax                       2, 3
MOV segreg,mem16        mov es,psp                      2, 3
MOV reg16,segreg        mov ax,ds                       1
MOV mem16,segreg        mov stack_save,ss               1
MOV reg32,controlreg    mov eax,cr0                     22
                        mov eax,cr2                     12
                        mov eax,cr3                     21, 46
                        mov eax,cr4                     14
MOV controlreg,reg32    mov cr0,eax                     4
MOV reg32,debugreg      mov edx,dr0                     DR0-DR3,DR6,DR7=11;
                                                        DR4,DR5=12 
MOV debugreg,reg32      mov dr0,ecx                     DR0-DR3,DR6,DR7=11;
                                                        DR4,DR5=12 

source:http://turkish_rational.tripod.com/trdos/pentium.txt

the instructions may be tranlated as:

;for i = i+1   ; cycles
mov  ax,   [i]  ; 1
add  ax,   1    ; 1
mov  [i],  ax   ; 1

;for i += 1
; dunno the syntax of instruction. it should be the pointers one :S     

;for i++
inc  i          ; 3
;or
mov  ax,   [i]  ; 1
inc  ax         ; 1
mov  [i],  ax   ; 1

;for ++i
mov  ax,   [i]  ; 1
;do  stuff      ; matters not
inc  ax         ; 1
mov  [i],  ax   ; 1

all turn out to be same :S its just some data that may be helpful. please comment!