[Bug tree-optimization/108855] New: [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1518

[Bug tree-optimization/108855] New: [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1518

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108855

            Bug ID: 108855
           Summary: [13 Regression] ICE in eliminate_unnecessary_stmts, at
                    tree-ssa-dce.cc:1518
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc 13.0.1 20230219 snapshot (g:b9c83e7789f7eec9871e370739baa55fd70be4cf) ICEs
when compiling the following testcase w/ -O1:

int m;

int
undefined (int);

__attribute__ ((pure, returns_twice)) int
bar (void)
{
  m = 1;
  while (m)
    m = 2;

  return m;
}

int
foo (void)
{
  return undefined (bar ());
}

% gcc-13 -O1 -c gl1ueszy.c
during GIMPLE pass: dce
gl1ueszy.c: In function 'foo':
gl1ueszy.c:17:1: internal compiler error: in eliminate_unnecessary_stmts, at
tree-ssa-dce.cc:1518
   17 | foo (void)
      | ^~~
0x77557c eliminate_unnecessary_stmts
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230219/work/gcc-13-20230219/gcc/tree-ssa-dce.cc:1518
0x77557c perform_tree_ssa_dce
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230219/work/gcc-13-20230219/gcc/tree-ssa-dce.cc:1951
0x102b6da tree_ssa_dce
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230219/work/gcc-13-20230219/gcc/tree-ssa-dce.cc:1986
0x102b6da execute
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230219/work/gcc-13-20230219/gcc/tree-ssa-dce.cc:2027

[Bug tree-optimization/108855] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1518

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108855

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
   Target Milestone|---                         |13.0
   Last reconfirmed|                            |2023-02-20
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Meh, another one ...

[Bug tree-optimization/108855] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1518

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108855

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
So early CD-DCE figures that there's no longjmp in this function(?) but then
late modref/pure-const discovers bar() is actually noreturn and fixup-CFG
turns foo into

int foo ()
{
  int D.2764;
  int _1(D);

  <bb 2> [local count: 1073741824]:
  bar ();

}

because the call is said to be not control altering.  But then the next DCE
chokes on this because now it _is_ control altering (fixup-CFG made it so
in fixup noreturn calls).

So this is again returns_twice + noreturn, but it also shows the per-stmt
control-altering overloading all control-altering attributes isn't fine
grained enough(?).

Note we're not setting ctrl-altering initially here, returns-twice doesn't
alter control flow but instead it receives control from elsewhere.  In
that light the previous fix for PR108691 was probably wrong.

[Bug tree-optimization/108855] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1518

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108855

--- 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:e79b9db15e410c4652438ffbbc44b6aa04e1ba61

commit r13-6152-ge79b9db15e410c4652438ffbbc44b6aa04e1ba61
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Feb 21 10:31:29 2023 +0100

    tree-optimization/108855 - new testcase

    New testcase for the fixed bug.

            PR tree-optimization/108855
            * gcc.dg/pr108855.c: New testcase.

[Bug tree-optimization/108855] [13 Regression] ICE in eliminate_unnecessary_stmts, at tree-ssa-dce.cc:1518

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108855

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

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

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
The offending patch was reverted.