[Bug c/108449] New: [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[Bug c/108449] New: [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[gscfq@t-online.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

            Bug ID: 108449
           Summary: [13 Regression] ICE in eliminate_unnecessary_stmts, at
                    tree-ssa-dce.cc:1512
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gscfq@t-online.de
  Target Milestone: ---

Started between 20220904 and 20220911, at -O1+ :


$ cat z1.c
static int vfork();
void f() { vfork(); }


$ gcc-13-20230115 -c z1.c -O2
z1.c:1:12: warning: 'vfork' used but never defined
    1 | static int vfork();
      |            ^~~~~
during GIMPLE pass: cddce
z1.c: In function 'f':
z1.c:2:1: internal compiler error: in eliminate_unnecessary_stmts, at
tree-ssa-dce.cc:1512
    2 | void f() { vfork(); }
      | ^~~~
0xe0f0dc eliminate_unnecessary_stmts
        ../../gcc/tree-ssa-dce.cc:1512
0xe108bf perform_tree_ssa_dce
        ../../gcc/tree-ssa-dce.cc:1945
0xe11e55 tree_ssa_cd_dce
        ../../gcc/tree-ssa-dce.cc:1986
0xe11e55 execute
        ../../gcc/tree-ssa-dce.cc:2069

[Bug tree-optimization/108449] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.0
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-01-18
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=106866

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The assert that is being hit was added by r13-2518-ga262f969d6fd93 .

Confirmed.

[Bug tree-optimization/108449] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, so early we still have vfork() 'static' and maybe_special_function_p
returns false.  But then check_global_declaration () comes along and does

  /* Warn about any function declared static but not defined.  We don't
     warn about variables, because many programs have static variables
     that exist only to get some text into the object file.  */
  if (TREE_CODE (decl) == FUNCTION_DECL
      && DECL_INITIAL (decl) == 0
      && DECL_EXTERNAL (decl)
      && ! DECL_ARTIFICIAL (decl)
      && ! TREE_PUBLIC (decl))
    {
      if (warning_suppressed_p (decl, OPT_Wunused))
        ;
      else if (snode->referred_to_p (/*include_self=*/false))
        pedwarn (input_location, 0, "%q+F used but never defined", decl);
      else
        warning (OPT_Wunused_function, "%q+F declared %<static%> but never "
                                       "defined", decl);
      /* This symbol is effectively an "extern" declaration now.  */
      TREE_PUBLIC (decl) = 1;

which will result in maybe_special_function_p to return true.

I suppose leaving the decl static might have an effect on the linker errors
emitted for targets that require special asm ops for undefined external
references, but then you should still get an error here.

This mangling dates back to RMS at r0-3845-g7d429c41c5953f

[Bug tree-optimization/108449] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug tree-optimization/108449] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:106f99406312d7ed47434de53c180718225ffa5e

commit r13-5285-g106f99406312d7ed47434de53c180718225ffa5e
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Jan 19 08:44:25 2023 +0100

    tree-optimization/108449 - keep maybe_special_function_p behavior

    When we have a static declaration without definition we diagnose
    that and turn it into an extern declaration.  That can alter
    the outcome of maybe_special_function_p here and there's really
    no point in doing that, so don't.

            PR tree-optimization/108449
            * cgraphunit.cc (check_global_declaration): Do not turn
            undefined statics into externs.

            * gcc.dg/pr108449.c: New testcase.

[Bug tree-optimization/108449] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

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

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

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.

[Bug tree-optimization/108449] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1512

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108449

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=108511

--- Comment #5 from Martin Liška <marxin at gcc dot gnu.org> ---
Caused: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108511