10.2.7 Unswitching

LOOP FOR I := 1 TO 1000

IF (Test) THEN


X (I) := A(I) + B(I)

ELSE

X(I) := A(I) - B(I)

ENDLOOP

Here, the test is performed each time through the loop. The following performs the test once:

IF (Test) THEN


LOOP FOR I := 1 to 1000

X(I) = A(I) + B(I)

ENDLOOP
ELSE

LOOP FOR I := 1 to 100

X(I) = A(I) - B(I)

ENDLOOP

The second version here reduces the number of instructions executed, but the code takes more space.