7.3.5 Invariant If Floating

When the if condition is invariant in a loop, the if statement can be floated out of the assignment loop, as shown in the following example:

for ( i=0; IPA; i++ ) {
      a[i] = b[i] + c[i];
      if ( x > 0.0 )
      a[i] *= x;
   }

Becomes:

if (x > 0.0) {
          for ( i = 0; i<n; i++ ) {
          a[i] = b[i] + c[i];
          a[i] *=  x;
             }
           } else {
           for ( i = 0; i<n; i++ ) {
           a[i] = b[i] + c[i];
      }
 }

See Chapter 4, the /eiifg and /miifg qualifiers, for information about controlling this transformation.