Inner loop unable to compute sufficient information during vectorization

[Abhishek Shrivastav <abhishek dot shrivastav24 at gmail dot com>]

for a loop like

1         for(i=0;i<N;i++)
2           for(j=0;j<N;j++)
3               a[i][j] = a[i][j]+b[i][j];

GCC 4.3.* is unable to get the information for the inner loop that
array reference 'a'  is alias of each other and generates code for
runtime aliasing check during vectorization. Is it necessary to
recompute all information in loop_vec_info in function
vect_analyze_ref for analysis of inner loop also, as most of the
information is similar for the outer loop for the program.

Similarly, outer loop is able to compute correct chrec i.e. NULL , for
array 'a' reference, while innerloop has chrec as chrec_dont_know, and
therfore complaint about runtime alias check.