[Bug debug/46375] New: [4.6 Regression] -fcompare-debug failure (length) with -O -fgcse -fno-tree-dominator-opts

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46375

           Summary: [4.6 Regression] -fcompare-debug failure (length) with
                    -O -fgcse -fno-tree-dominator-opts
           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 22327
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22327
reduced testcase

Compiler output:
$ gcc -fgcse -fno-tree-dominator-opts -fcompare-debug -O pr46375.c 
gcc: error: pr46375.c: -fcompare-debug failure (length)
$ diff pr46375.*gkd
53a54
> (code_label 5 0 0 5 "" [0 uses])

Tested revisions:
r166414 - fail
r165699 - OK
4.5 r165781 - OK