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From: "antoine.balestrat at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/55833] New: ICE in verify_loop_structure, at cfgloop.c:1582 (BB should be marked irreducible !)
Date: Mon, 31 Dec 2012 14:56:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D55833

             Bug #: 55833
           Summary: ICE in verify_loop_structure, at cfgloop.c:1582 (BB
                    should be marked irreducible !)
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: antoine.balestrat@gmail.com


Using GCC 4.8.0 as of 20121231 :

$ cat bb.c
int a, b, c;

void foo()
{
    unsigned d, l, *p, k =3D 1;

    if(bar())
    {
label:
        if((a =3D a <=3D 0))
        {
            if(c)
                d =3D b;

            if (b || d ? l : k ? : 0)
                a =3D d =3D 0;

            goto label;
        }
    }

    while(*p++)
        goto label;
}

$ xgcc -w -O3 bb.c
bb.c: In function =E2=80=98foo=E2=80=99:
bb.c:24:1: error: edge from 27 to 29 should be marked irreducible
 }
 ^
bb.c:24:1: error: basic block 29 should be marked irreducible
bb.c:24:1: error: edge from 29 to 7 should be marked irreducible
bb.c:24:1: internal compiler error: in verify_loop_structure, at cfgloop.c:=
1582
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.