[Bug tree-optimization/46561] New: [4.6 Regression] -fcompare-debug failure (length) with -O2 -ftree-vectorize -ftree-parallelize-loops

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46561

           Summary: [4.6 Regression] -fcompare-debug failure (length) with
                    -O2 -ftree-vectorize -ftree-parallelize-loops
           Product: gcc
           Version: 4.6.0
            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 22456
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22456
reduced testcase

Compiler output:
$ gcc -O2 -ftree-vectorize -ftree-parallelize-loops=2 -fcompare-debug pr46561.c 
gcc: error: pr46561.c: -fcompare-debug failure (length)

The dumps are very different, it seems the loop is not parallelized in the -g
case.

Tested revisions:
r166899 - fail
r163636 - fail
r161659 - OK
4.5 r166509 - OK