[Bug tree-optimization/49038] New: -ftree-vectorise introduces reads past end of array

[rsandifo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49038

           Summary: -ftree-vectorise introduces reads past end of array
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rsandifo@gcc.gnu.org


Created attachment 24276
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24276
Test case

The vectoriser has support for interleaved loads with gaps,
such as:

   ...a[n*4]
   ...a[n*4+1]
   ...a[n*4+2]

It implements this by loading blocks of 4*vectfactor elements
from a[], then permuting them.  However, it doesn't seem to
check whether the gap elements are provably loadable.

The attached testcase segfaults on x86_64-linux-gnu with
-O2 -ftree-vectorize, but works with plain -O2.