[Bug debug/47881] New: [4.6 Regression] -fcompare-debug failure (length) with -O -fno-dce -funroll-loops -fno-web

[zsojka at seznam dot cz]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47881

           Summary: [4.6 Regression] -fcompare-debug failure (length) with
                    -O -fno-dce -funroll-loops -fno-web
           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: i686-pc-linux-gnu
            Target: i686-pc-linux-gnu


Created attachment 23452
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23452
reduced testcase

Compiler output:
$ gcc -O -fcompare-debug -fno-dce -funroll-loops -fno-web testcase.c -m32
gcc: error: testcase.c: -fcompare-debug failure (length)

$ diff testcase.*gkd
943c943
< (insn# 0 0 39 (set (reg:SI 4 si)
---
> (insn# 0 0 39 (set (reg:SI 5 di)
947,948c947,948
<             (set (reg:SI 4 si)
<                 (plus:SI (reg:SI 4 si)
---
>             (set (reg:SI 5 di)
>                 (plus:SI (reg:SI 5 di)
...

Tested revisions:
r170450 - fail
4.5 r170013 - OK
4.5.2 - OK