/scalaropt level is 1 or higher, KAP performs
dead-code elimination. The following optimizations are performed:
Each of the following code examples illustrates one of the optimizations:
goto hop; x=2.0; hop: y=13.0;
hop:; y = 13.0;
forloops. For example, the following would be deleted completely:
for (i=10;i<2;i++) x = x+y;
#define NNN 12 if ( NNN > 10 ) x = 1.0; else x = 2.0;
x = 1.0;
The true branch will always be taken.
/scalaropt qualifier set to 2 and
/optimize set > 2, the additional optimization
explained in 4. is performed.
KAP performs lifetime analysis to determine the reaching definitions of variables and removes unused definitions, as shown in the following example:
y = 5.0; /* no subsequent use */ x = 3.0; /* variable redefined */ x = 4.0; printf("%g \n",x);
x = 4.0; printf("%g \n",x);
The full effect of dead-code elimination is realized when combined with other optimizations, such as subprogram inlining and forward substitution, which help in exposing useless or unreachable code.