[Bug tree-optimization/56501] New: gcc 4.6 ICE on noreturn function at -Os and above

[Bug tree-optimization/56501] New: gcc 4.6 ICE on noreturn function at -Os and above

[dhazeghi at yahoo dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

             Bug #: 56501
           Summary: gcc 4.6 ICE on noreturn function at -Os and above
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dhazeghi@yahoo.com


The following testcase (derived from gzip) triggers an internal compiler error
with gcc 4.6, 4.5 and 4.4 when compiled at -Os or higher on x86_64-linux.  The
problem does not occur with 4.7 or newer, or with 4.3 or older.

$ gcc-4.6 --version
gcc-4.6 (GCC) 4.6.3
$ gcc-4.6 -O1 -w small.c
$ gcc-4.6 -Os -w small.c
small.c: In function ‘main’:
small.c:24:1: internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ cat small.c

int a;
void try_help () __attribute__ ((__noreturn__));
void try_help ()
{
}

int main ()
{
    switch (a)
    {
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
        break;
    default:
        try_help ();
    }
}

[Bug tree-optimization/56501] gcc 4.6 ICE on noreturn function at -Os and above

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

Mikael Pettersson <mikpe at it dot uu.se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu.se

--- Comment #1 from Mikael Pettersson <mikpe at it dot uu.se> 2013-03-03 11:06:24 UTC ---
The original ICE stopped occurring for 4.7 in r171450, which added an FRE pass
after early SRA.  From that point on it reproduces with -Os -fno-tree-free.  It
then stopped again for 4.8 in r186901, Steven Bosscher's "Simplify
tree-switch-conversion.c a bit - prep work for gimple switch lowering" patch.

The ICE in 4.7 occurs because tree-switch-conversion.c:check_process_case calls
single_succ on a bb that has NULL succs, leading to a SEGV in
VEC_edge_base_index.

The patch in r186901 doesn't apply at all to 4.7, and I don't see any obvious
bug fix in it that could be cherry-picked and applied to 4.7.

[Bug tree-optimization/56501] [4.6/4.7 Regression] gcc 4.6 ICE on noreturn function at -Os and above

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jamborm at gcc dot gnu.org
   Target Milestone|---                         |4.6.4
            Summary|gcc 4.6 ICE on noreturn     |[4.6/4.7 Regression] gcc
                   |function at -Os and above   |4.6 ICE on noreturn
                   |                            |function at -Os and above

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-04 10:44:42 UTC ---
Which makes it a 4.6/4.7 regression.

[Bug tree-optimization/56501] [4.6/4.7 Regression] gcc 4.6 ICE on noreturn function at -Os and above

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2013-04-03
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-03 10:10:06 UTC ---
Testing

Index: gcc/tree-switch-conversion.c
===================================================================
--- gcc/tree-switch-conversion.c        (revision 197348)
+++ gcc/tree-switch-conversion.c        (working copy)
@@ -283,7 +283,12 @@ check_process_case (tree cs)
          return false;
        }

-      e = single_succ_edge (label_bb);
+      if (!single_succ_p (label_bb))
+       {
+         info.reason
+           = "  Bad case - a non-final BB without a single successor\n";
+         return false;
+       }
       following_bb = single_succ (label_bb);
     }

[Bug tree-optimization/56501] [4.6/4.7 Regression] gcc 4.6 ICE on noreturn function at -Os and above

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-03 10:29:27 UTC ---
Author: rguenth
Date: Wed Apr  3 10:28:27 2013
New Revision: 197401

URL: http://gcc.gnu.org/viewcvs?rev=197401&root=gcc&view=rev
Log:
2013-04-03  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/56501
    * gcc.dg/torture/pr56501.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr56501.c
Modified:
    trunk/gcc/testsuite/ChangeLog

Author: rguenth
Date: Wed Apr  3 10:28:59 2013
New Revision: 197402

URL: http://gcc.gnu.org/viewcvs?rev=197402&root=gcc&view=rev
Log:
2013-04-03  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/56501
    * gcc.dg/torture/pr56501.c: New testcase.

Added:
    branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr56501.c
Modified:
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog

[Bug tree-optimization/56501] [4.6 Regression] gcc 4.6 ICE on noreturn function at -Os and above

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.7.3, 4.8.0
            Summary|[4.6/4.7 Regression] gcc    |[4.6 Regression] gcc 4.6
                   |4.6 ICE on noreturn         |ICE on noreturn function at
                   |function at -Os and above   |-Os and above
      Known to fail|                            |4.7.2

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-03 12:03:29 UTC ---
Author: rguenth
Date: Wed Apr  3 12:02:56 2013
New Revision: 197405

URL: http://gcc.gnu.org/viewcvs?rev=197405&root=gcc&view=rev
Log:
2013-04-03  Richard Biener  <rguenther@suse.de>

    PR tree-optimization/56501
    * tree-switch-conversion.c (check_process_case): Properly
    handle !single_succ_p case.

    * gcc.dg/torture/pr56501.c: New testcase.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/gcc.dg/torture/pr56501.c
Modified:
    branches/gcc-4_7-branch/gcc/ChangeLog
    branches/gcc-4_7-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_7-branch/gcc/tree-switch-conversion.c

[Bug tree-optimization/56501] [4.6 Regression] gcc 4.6 ICE on noreturn function at -Os and above

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56501

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|4.6.4                       |4.7.3

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-12 16:29:06 UTC ---
The 4.6 branch has been closed, fixed in GCC 4.7.3.