[Bug debug/46771] New: [4.6 Regression] -fcompare-debug failure (length) with -O -ftree-vectorize

["zsojka at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46771

           Summary: [4.6 Regression] -fcompare-debug failure (length) with
                    -O -ftree-vectorize
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: zsojka@seznam.cz
                CC: aoliva@gcc.gnu.org
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu


Created attachment 22607
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22607
reduced testcase

Output:
$ gcc -O -ftree-vectorize -fcompare-debug pr46771.c             
gcc: error: pr46771.c: -fcompare-debug failure (length)
$ diff pr46771.*gkd
11c11
...(long output)
There's a difference in generated code with(out) -g.

Tested revisions:
r167383 - fail
r165699 - fail
r161659 - OK
4.5 r166509 - OK