KAP recognizes loops with invariant-IFs. To avoid repeatedly performing the same IF test, KAP generates two versions of the loop and places the IF test outside, as shown in the following example:
DO 1 I=1,N IF (ADD) THEN X(I) = X(I) + Y(I) ELSE X(I) = X(I) - Y(I) ENDIF 1 CONTINUE 10 CONTINUE
Becomes:
IF (ADD) THEN DO 3 I=1,N X(I) = X(I) + Y(I) 3 CONTINUE ELSE DO 4 I=1,N X(I) = X(I) - Y(I) 4 CONTINUE ENDIF
This transformation is enabled only when -scalaropt
>2. See the command switches -each_invariant_if_growth
and -max_invariant_if_growth for ways to restrict this
transformation.