Problem 3
---------

        Observe the  dumps generated by Liveness  based pointer analysis
        pass for the two programs given below :

        1) Why is the  occurrence of variable `q' removed  from the code
           in basic block 2 of program 1? Which optimization is this and
           why it it correct?

        2) Why is the optimization that  you observed in program 1 (ref:
           question 2 above) suppressed in program 2 for pointer `q'?

Program 1
---------

        #include <stdio.h>
        int main ()
        {
          int w, x, y, z;
          int *p, *q, *r, *s;
          q = &z;
          if (*q)
             p = &x;
          else if (y>2)
             p = &y;
          else
             p = &z;
         
          y = *p;
          printf ("%d%d%d%d%d%d", w, x, y, z, p, q, r, s);
        
        }

Program 2
---------

        int main ()
        {
          int w, x, y, z;
          int *p, *q, *r, *s;
          if(x)
        	q = &z;
          else
        	q = &y;
          if (*q)
             p = &x;
          else if (y>2)
             p = &y;
          else
             p = &z;
         
          y = *p;
          printf ("%d%d%d%d%d%d", w, x, y, z, p, q, r, s);
        
        }


Procedure 
---------

        1) Compile   the   test    program   with   following   command 
           $(INSTALL)/bin/gcc -O2 -flipta -fdump-ipa-lipta test.c       

        2) Observe the *.lipta dump generated 
 
        3) `livein' and `liveout' represent  the liveness information at
           a  basic block.  `mayin' and  `mayout' represent  the pointer
           information of the basic block.