what if the compiler doesnt know ??
If you mean those 2 diff. variables of same type.
The below is going to take somewhat less cycyle in some cases
Code:
printf("%i", CPY);
But how much less is going to depend upon some other factors & implementation details
Like what kind of variable? Whether compiler decide to store local variable in CPU register or not? How the C++ class structure implemented by compiler?


Here code generated by VC compiler.
It generating following code for local variable


Code:
00411AEA  mov         eax,dword ptr [CPY] 
00411AED  push        eax
& Its generating below code for class member access

Code:
00411AFB  mov         eax,dword ptr [this] 
00411AFE  mov         ecx,dword ptr [eax] 
00411B00  push        ecx
Note its doing one extra move to get first member
Some aggressive optimized compiler might give you same cycles for both

Vinod