Problem with tree pass pre

[shmeel gutl]

When dealing with an array with known values, pre will evaluate the 
first iteration of a loop over the elements. The code generator with 
then jump into the loop. This is at best increasing the size of the 
code. It also creates inferior code when the hardware supports zero 
overhead loops. The attached code demonstrates the difference between an 
unknown array and a known array. The loop size has been picked large 
enough for cunrolli to not fully unroll the loop. The problem did not 
exist in gcc 4.8.


extern int B[27];
int foo()
{
        int i;
        int t=0;
        for(i=0;i<27;i++)
                t+=B[i];
        return t;
}
int boo()
{
        int i;
        int t=0;
        static int A[] = 
{1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9};
        for(i=0;i<27;i++)
                t+=A[i];
        return t;
}