[Bug tree-optimization/56466] New: ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[Bug tree-optimization/56466] New: ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[antoine.balestrat at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

             Bug #: 56466
           Summary: ICE in verify_loop_structure, at cfgloop.c:1629 (loop
                    with header n not in loop tree !)
    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 20130226 :

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

void f(void)
{
    for(; b; b++)
    {
        if(0)
            for(; b < 0; b++)
                if(1 % 0)
                {
                    while(1)
                    {
                        a = 0;
lbl1:
                        c++;
                    }
lbl2:
                    ;
                }

        goto lbl1;
    }

    a = 0;
    goto lbl2;
}

$ xgcc -w -funroll-loops -O2 peel.c
peel.c: In function ‘f’:
peel.c:26:1: error: loop with header 6 not in loop tree
 }
 ^
peel.c:26:1: internal compiler error: in verify_loop_structure, at
cfgloop.c:1629
0x60ffb5 verify_loop_structure()
    ../../srcdir/gcc/cfgloop.c:1629
0x7f70af peel_loops_completely
    ../../srcdir/gcc/loop-unroll.c:310
0x7f70af unroll_and_peel_loops(int)
    ../../srcdir/gcc/loop-unroll.c:215
0x7eaed7 rtl_unroll_and_peel_loops
    ../../srcdir/gcc/loop-init.c:492
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

[Bug tree-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-02-26
                 CC|                            |mpolacek at gcc dot gnu.org
      Known to work|                            |4.7.3
   Target Milestone|---                         |4.8.0
            Summary|ICE in                      |[4.8 Regression] ICE in
                   |verify_loop_structure, at   |verify_loop_structure, at
                   |cfgloop.c:1629 (loop with   |cfgloop.c:1629 (loop with
                   |header n not in loop tree   |header n not in loop tree
                   |!)                          |!)
     Ever Confirmed|0                           |1
      Known to fail|                            |4.8.0

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-02-26 18:01:02 UTC ---
Confirmed.

[Bug tree-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-02-26 18:03:47 UTC ---
Mine.

[Bug tree-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-02-26 18:15:28 UTC ---
Unsurprisingly started with
http://gcc.gnu.org/viewcvs?view=revision&revision=195880, but must have been
latent before.

[Bug tree-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2013-02-27 09:40:09 UTC ---
RTL unrolling does excessive manual verify_loop_structure calls.  I suppose
we can either add an argument to verify_loop_structure to say whether to
check only existing loops or remove the checking, or make sure to fixup
loops.

For sure checking the whole loop tree after processing one innermost loop
is excessive:

/* Depending on FLAGS, check whether to peel loops completely and do so.  */
static void
peel_loops_completely (int flags)
{
  struct loop *loop;
  loop_iterator li;

  /* Scan the loops, the inner ones first.  */
  FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
    {
...

      if (loop->lpt_decision.decision == LPT_PEEL_COMPLETELY)
        {
          report_unroll_peel (loop, locus);
          peel_loop_completely (loop);
#ifdef ENABLE_CHECKING
          verify_loop_structure ();
#endif
        }
    }

I'd have a changed flag and do a single

  if (changed)
    fix_loop_structure (NULL);

which also does the verification at the end.  Same applies to the loop
in the caller.

[Bug rtl-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |rtl-optimization

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-02-27 11:41:24 UTC ---
Thanks, I'm testing a fix for that.

Also changing the component, we're really on the RTL level here.

[Bug rtl-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-02-28 10:13:53 UTC ---
Author: mpolacek
Date: Thu Feb 28 10:13:48 2013
New Revision: 196335

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=196335
Log:
        PR rtl-optimization/56466
        * loop-unroll.c (unroll_and_peel_loops): Call fix_loop_structure
        if we're changing a loop.
        (peel_loops_completely): Likewise.


Added:
    trunk/gcc/testsuite/gcc.dg/pr56466.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/loop-unroll.c
    trunk/gcc/testsuite/ChangeLog

[Bug rtl-optimization/56466] [4.8 Regression] ICE in verify_loop_structure, at cfgloop.c:1629 (loop with header n not in loop tree !)

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56466

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-02-28 10:15:19 UTC ---
Fixed.