CHAPTER 12. CONDITIONAL JUMPS CHAPTER 12. CONDITIONAL JUMPS
12.4 Getting minimal and maximal values.
12.4.1 32-bit.
int my_max(int a, int b)
{
if (a>b)
return a;
else
return b;
};
int my_min(int a, int b)
{
if (a<b)
return a;
else
return b;
};
Listing 12.26: Non-optimizing MSVC 2013_a$ = 8
_b$ = 12
_my_min PROC
push ebp
mov ebp, esp
mov eax, DWORD PTR _a$[ebp]
; compare A and B:
cmp eax, DWORD PTR _b$[ebp]
; jump, if A is greater or equal to B:
jge SHORT $LN2@my_min
; reload A to EAX if otherwise and jump to exit
mov eax, DWORD PTR _a$[ebp]
jmp SHORT $LN3@my_min
jmp SHORT $LN3@my_min ; this is redundant JMP
$LN2@my_min:
; return B
mov eax, DWORD PTR _b$[ebp]
$LN3@my_min:
pop ebp
ret 0
_my_min ENDP
_a$ = 8
_b$ = 12
_my_max PROC
push ebp
mov ebp, esp
mov eax, DWORD PTR _a$[ebp]
; compare A and B:
cmp eax, DWORD PTR _b$[ebp]
; jump if A is less or equal to B:
jle SHORT $LN2@my_max
; reload A to EAX if otherwise and jump to exit
mov eax, DWORD PTR _a$[ebp]
jmp SHORT $LN3@my_max
jmp SHORT $LN3@my_max ; this is redundant JMP
$LN2@my_max:
; return B
mov eax, DWORD PTR _b$[ebp]
$LN3@my_max:
pop ebp
ret 0
_my_max ENDP
These two functions differ only in the conditional jump instruction: JGE (“Jump if Greater or Equal”) is used in the first one
and JLE (“Jump if Less or Equal”) in the second.