[Bug tree-optimization/49496] New: [4.7 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=49496

           Summary: [4.7 Regression] -fcompare-debug failure (length) with
                    -O -ftree-vectorize
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        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 24577
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24577
reduced testcase

This still happens after fixing PR49352

Compiler output:
$ gcc -O -ftree-vectorize -fcompare-debug testcase.c
gcc: error: testcase.c: -fcompare-debug failure (length)

Generated code differs a lot with/without -g.

Tested revisions:
r175265 - fail
4.6 r175269 - OK