micro optimisation in for loop c++ -

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Assume C ++ for loop as 

  Integer should be allocated initially and after that, each phase should be increased. So it will not be fast enough to do something:  
  variables since f or (int i; i ++ <10;)   
 Do not need to be reloaded in storage? When is this  unstable ?   
 is making this small example code the same result for all the cases, whether the loop is optimized anyway or am I missing something?  
  # include & lt; Iostream & gt; # Include & lt; Ctime & gt; Int main () {time_t start, ende; Unstable intimate dummy = 1; Const int rep = 1000000000; // method 1 start = time (0); For (int i = 0; i & lt; rep; i ++) dummy = 1; End = time (0); Std :: cout & lt; & Lt; "Method 1:" & lt; & Lt; Fifthme (End, Beginning) * 1000 & lt; & Lt; "MS" & lt; & Lt; Std :: endl; // method2 start = time (0); For (int i = 0; i ++> lie; representative;) dummy = 1; End = time (0); Std :: cout & lt; & Lt; "Method 2:" & lt; & Lt; Fifthme (End, Beginning) * 1000 & lt; & Lt; "MS" & lt; & Lt; Std :: endl; // method 3 start = time (0); For (Unstable int i = 0; i   
 OS: Linux compiler: G ++ optimization: standart (no flag)   
 
 
 Compiler A  lot  is more efficient than you think.    will not produce duplicate loads

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