[Bug tree-optimization/66794] New: ICE at -O2 and -O3 on x86_64-linux-gnu

[Bug tree-optimization/66794] New: ICE at -O2 and -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66794

            Bug ID: 66794
           Summary: ICE at -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The following code causes an ICE when compiled with the current gcc trunk at
-O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes. 

It is a regression from 5.1.x. 

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20150707 (experimental) [trunk revision 225501] (GCC) 
$ 
$ gcc-trunk -Os -c small.c
small.c: In function ‘fn1’:
small.c:18:10: warning: function returns address of local variable
[-Wreturn-local-addr]
   return *c;
          ^
small.c:12:7: note: declared here
   int f, **g = &b;
       ^
$ gcc-5.1 -O2 -c small.c
small.c: In function ‘fn1’:
small.c:18:10: warning: function may return address of local variable
[-Wreturn-local-addr]
   return *c;
          ^
small.c:12:7: note: declared here
   int f, **g = &b;
       ^
$ 
$ gcc-trunk -O2 -c small.c
small.c: In function ‘fn1’:
small.c:18:10: warning: function may return address of local variable
[-Wreturn-local-addr]
   return *c;
          ^
small.c:12:7: note: declared here
   int f, **g = &b;
       ^
small.c:10:1: error: dominator of 4 status unknown
 fn1 ()
 ^
small.c:10:1: internal compiler error: Segmentation fault
0xbb296f crash_signal
        ../../gcc-trunk/gcc/toplev.c:360
0x76ac43 verify_dominators(cdi_direction)
        ../../gcc-trunk/gcc/dominance.c:1059
0x76aed7 calculate_dominance_info(cdi_direction)
        ../../gcc-trunk/gcc/dominance.c:685
0xcd85e4 execute
        ../../gcc-trunk/gcc/tree-ssa-dse.c:404
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.
$ 


------------------------------


int a, *b, e;
static int **c = &b;

struct
{
  int f0;
} d;

int *
fn1 ()
{
  int f, **g = &b;
  e = a;
  for (; a;)
    for (; d.f0; d.f0++)
      ;
  *g = &f;
  return *c;
}
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From: "marcus at jet dot franken.de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/66782] Unable to run 64-bit wine after MS->SYSV register changes
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf782

--- Comment #4 from marcus at jet dot franken.de ---
(actually not sure this is the same issue that my wine colleagueds are seeing,
but it also a miscompilation)

[Bug tree-optimization/66794] [6 Regression] ICE at -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66794

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2015-07-08
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
   Target Milestone|---                         |6.0
            Summary|ICE at -O2 and -O3 on       |[6 Regression] ICE at -O2
                   |x86_64-linux-gnu            |and -O3 on x86_64-linux-gnu
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
So this means post-dominators are corrupt at then entry to DSE.  Usually passes
should always release post-dominators - it seems there is at least one that
fails to do that.  isolate-paths in this case.  Passes are not good at making
sure
to release post-dom-info when they invalidate it.

The regression is due to extra checking.

Index: gcc/gimple-ssa-isolate-paths.c
===================================================================
--- gcc/gimple-ssa-isolate-paths.c      (revision 225504)
+++ gcc/gimple-ssa-isolate-paths.c      (working copy)
@@ -501,10 +501,10 @@ gimple_ssa_isolate_erroneous_paths (void
   /* We scramble the CFG and loop structures a bit, clean up
      appropriately.  We really should incrementally update the
      loop structures, in theory it shouldn't be that hard.  */
+  free_dominance_info (CDI_POST_DOMINATORS);
   if (cfg_altered)
     {
       free_dominance_info (CDI_DOMINATORS);
-      free_dominance_info (CDI_POST_DOMINATORS);
       loops_state_set (LOOPS_NEED_FIXUP);
       return TODO_cleanup_cfg | TODO_update_ssa;
     }

fixes it.

[Bug tree-optimization/66794] [6 Regression] ICE at -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66794

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Wed Jul  8 11:47:42 2015
New Revision: 225545

URL: https://gcc.gnu.org/viewcvs?rev=225545&root=gcc&view=rev
Log:
2015-07-08  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66794
        * passes.c (execute_function_todo): Assert that post-dominators
        are not computed.
        * gimple-ssa-isolate-paths.c (gimple_ssa_isolate_erroneous_paths):
        Free post-dominators.

        * gcc.dg/torture/pr66794.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr66794.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple-ssa-isolate-paths.c
    trunk/gcc/passes.c
    trunk/gcc/testsuite/ChangeLog

[Bug tree-optimization/66794] [4.9/5 Regression] ICE at -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66794

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |6.0
   Target Milestone|6.0                         |4.9.4
            Summary|[6 Regression] ICE at -O2   |[4.9/5 Regression] ICE at
                   |and -O3 on x86_64-linux-gnu |-O2 and -O3 on
                   |                            |x86_64-linux-gnu

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed on trunk.  The issue is latent on the branches though, possibly using
broken post-dom info.

[Bug tree-optimization/66794] [4.9/5 Regression] ICE at -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66794
Bug 66794 depends on bug 66807, which changed state.

Bug 66807 Summary: [6 Regression] --enable-libmpx failed
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66807

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

[Bug tree-optimization/66794] [4.9/5 Regression] ICE at -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66794

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Fri Jul 10 12:33:28 2015
New Revision: 225671

URL: https://gcc.gnu.org/viewcvs?rev=225671&root=gcc&view=rev
Log:
2015-07-10  Richard Biener  <rguenther@suse.de>

        Backport from mainline
        2015-07-10  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66823
        * tree-if-conv.c (memrefs_read_or_written_unconditionally): Fix
        inverted predicate.

        * gcc.dg/vect/pr61194.c: Remove -ftree-loop-if-convert-stores
        which should not be necessary.  XFAIL.

        2015-07-08  Richard Biener  <rguenther@suse.de>

        PR middle-end/43341
        * toplev.c (compile_file): Reset maximum_field_alignment after parsing.

        2015-07-08  Richard Biener  <rguenther@suse.de>

        PR tree-optimization/66794
        * gimple-ssa-isolate-paths.c (gimple_ssa_isolate_erroneous_paths):
        Free post-dominators.

        * gcc.dg/torture/pr66794.c: New testcase.

Added:
    branches/gcc-5-branch/gcc/testsuite/gcc.dg/torture/pr66794.c
Modified:
    branches/gcc-5-branch/gcc/ChangeLog
    branches/gcc-5-branch/gcc/gimple-ssa-isolate-paths.c
    branches/gcc-5-branch/gcc/testsuite/ChangeLog
    branches/gcc-5-branch/gcc/testsuite/gcc.dg/vect/pr61194.c
    branches/gcc-5-branch/gcc/toplev.c
    branches/gcc-5-branch/gcc/tree-if-conv.c