Replacing Nested if Statement With AND

Question

I am wondering whether nested if is better than AND statement. I have a loop that goes so many times so I am thinking of faster execution available. Below is the code that has same logic with my code. The nested if statement is inside a loop.

   for ( int i = 0; i < array.length; i++)
   {
      // do stuff
      if (x == 5)
      {
         if (y == 3)
         {
             // do stuff
         }
      }
   }  

Will my code be faster by a significant difference if I replace the nested if with this And STATEMENT?

     if ((x == 5) && (y == 3))
           // do stuff

I have read this link but I didn't find the answer. I am a student and still learning, thanks for all the feedback!

Answer 1

No, it will not have a significant difference on performance, but there may be a difference in readability.

Both of those will generate the same IL when compiled with optimization/release(Tested with LINQPad):

IL_0000:  ldc.i4.5    
IL_0001:  stloc.0     
IL_0002:  ldc.i4.s    0A 
IL_0004:  stloc.1     
IL_0005:  ldloc.0     
IL_0006:  ldc.i4.5    
IL_0007:  bne.un.s    IL_000D
IL_0009:  ldloc.1     
IL_000A:  ldc.i4.3    
IL_000B:  pop         

Even without optimization the difference is not that significant:

Nested statements:

IL_0001:  ldc.i4.5    
IL_0002:  stloc.0     
IL_0003:  ldc.i4.s    0A 
IL_0005:  stloc.1     
IL_0006:  ldloc.0     
IL_0007:  ldc.i4.5    
IL_0008:  ceq         
IL_000A:  ldc.i4.0    
IL_000B:  ceq         
IL_000D:  stloc.2     
IL_000E:  ldloc.2     
IL_000F:  brtrue.s    IL_0020
IL_0011:  nop         
IL_0012:  ldloc.1     
IL_0013:  ldc.i4.3    
IL_0014:  ceq         
IL_0016:  ldc.i4.0    
IL_0017:  ceq         
IL_0019:  stloc.2     
IL_001A:  ldloc.2     
IL_001B:  brtrue.s    IL_001F
IL_001D:  nop         
IL_001E:  nop 

Not Nested statements:

IL_0001:  ldc.i4.5    
IL_0002:  stloc.0     
IL_0003:  ldc.i4.s    0A 
IL_0005:  stloc.1     
IL_0006:  ldloc.0     
IL_0007:  ldc.i4.5    
IL_0008:  bne.un.s    IL_0013
IL_000A:  ldloc.1     
IL_000B:  ldc.i4.3    
IL_000C:  ceq         
IL_000E:  ldc.i4.0    
IL_000F:  ceq         
IL_0011:  br.s        IL_0014
IL_0013:  ldc.i4.1    
IL_0014:  nop         
IL_0015:  stloc.2     
IL_0016:  ldloc.2     
IL_0017:  brtrue.s    IL_001B
IL_0019:  nop 

Answer 2

.NET will stop checking if the first part of the conditional is false, so there will be no performance difference between the two.