[Bug middle-end/43182] New: gcc could not vectorize this simple loop (un-handled data-ref)

["changpeng dot fang at amd dot com" <gcc-bugzilla@gcc.gnu.org>]

gcc 4.5 can not vectorize this simple loop:

void foo(int a[], int n) {
 int i;
 for(i=1; i< n; i++)
  a[i] = a[0];
}

"gcc -O3 -fdump-tree-vect-all -c foo.c" shows:
foo.c:3: note: not vectorized: unhandled data-ref 
foo.c:3: note: bad data references.
foo.c:1: note: vectorized 0 loops in function.

It seems gcc gets confused at a[0] and gives up vectorization. There
is no dependence in this loop, and we should teach gcc to handle a[0]
to vectorize it.


-- 
           Summary: gcc could not vectorize this simple loop (un-handled
                    data-ref)
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: changpeng dot fang at amd dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43182