[Bug tree-optimization/108783] New: [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[Bug tree-optimization/108783] New: [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

            Bug ID: 108783
           Summary: [13 Regression] ICE: verify_flow_info failed (error:
                    returns_twice call is not first in basic block 3)
           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 20230212 snapshot (g:06ca0c9abb260266b688e2c2154c72214bb47076) ICEs
when compiling the following testcase w/ -O1:

int
bar (int x)
{
  return x;
}

__attribute__((returns_twice)) int
foo (int x, int y)
{
  int a;

  a = bar (x);
  (void) foo (x, y);

  return y && a && a;
}

% gcc-13 -O1 -c ibxb9fcz.c
ibxb9fcz.c: In function 'foo':
ibxb9fcz.c:8:1: error: returns_twice call is not first in basic block 3
    8 | foo (int x, int y)
      | ^~~
foo (x_9(D), y_12(D));
during GIMPLE pass: reassoc
ibxb9fcz.c:8:1: internal compiler error: verify_flow_info failed
0xa06a6d verify_flow_info()
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230212/work/gcc-13-20230212/gcc/cfghooks.cc:285
0xe0b153 execute_function_todo
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230212/work/gcc-13-20230212/gcc/passes.cc:2103
0xe0b69e execute_todo
       
/var/tmp/portage/sys-devel/gcc-13.0.1_p20230212/work/gcc-13-20230212/gcc/passes.cc:2145

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |needs-bisection
     Ever confirmed|0                           |1
                 CC|                            |rguenth at gcc dot gnu.org
   Target Milestone|---                         |13.0
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2023-02-14

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
reassoc1 does

   <bb 3> [local count: 966367643]:
   # a_4(ab) = PHI <x_9(D)(2), a_5(ab)(4)>
+  _14 = a_4(ab) != 0;
   foo (x_9(D), y_12(D));
   goto <bb 5>; [99.96%]

@@ -36,8 +59,7 @@
   <bb 5> [local count: 1073312329]:
   _1 = y_12(D) != 0;
   _2 = a_4(ab) != 0;
-  _3 = _1 & _2;
-  _10 = _2 & _3;
+  _10 = _14 & _1;
   _15 = (int) _10;
   return _15;

Confirmed.  It also inserts a new use of a_4(ab) which we try to generally
avoid
(but in this specific case it shouldn't be a problem).

Not sure why reassoc expands _2 and re-emits the _14 definition here.

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

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

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

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
ICEs since r13-1754-g7a158a5776f5ca95a318 when the check has been added.
Anyway, looking just at dumps, reassoc1 does this since
r5-4662-gd5e254e19c59fcc49265dda
That commit looks unrelated, but it actually changes quite a lot the generated
IL for some reason already starting with ssa dump.

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Though, the optimization that does this has been added in
r0-99848-g844381e5bc6eb515df838279 for PR28685.

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

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

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

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 54465
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54465&action=edit
gcc13-pr108783.patch

Untested fix.

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #54465|0                           |1
        is obsolete|                            |

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 54466
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54466&action=edit
gcc13-pr108783.patch

Better patch.  In the original testcase, a && a can be simplified to a despite
being (ab), and generally, there is no need to build_and_add_sum if t is the
same comparison as curr->op.

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:55db240d28d29aac90a2d2af3768283ba6288752

commit r13-6074-g55db240d28d29aac90a2d2af3768283ba6288752
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Feb 16 10:41:18 2023 +0100

    reassoc: Fix up (ab) handling in eliminate_redundant_comparison [PR108783]

    The following testcase ICEs because eliminate_redundant_comparison sees
    redundant comparisons in &&/|| where the comparison has (ab) SSA_NAME,
    maybe_fold_{and,or}_comparisons optimizes them into a single comparison
    and build_and_add_sum emits a new comparison close to the definition
    operands, which in this case is before a returns_twice call (which is
    invalid).  Generally reassoc just punts on (ab) SSA_NAMEs, declares them
    non-reassociable etc., so the second half of this patch does that.

    Though we can do better in this case; the function has special code
    when maybe_fold_{and,or}_comparisons returns INTEGER_CST (false/true)
    or when what it returns is the same as curr->op (the first of the
    comparisons we are considering) - in that case we just remove the
    second one and keep the first one.  The reason it doesn't match is that
    curr->op is a SSA_NAME whose SSA_NAME_DEF_STMT is checked to be a
    comparison, in this case _42 = a_1(ab) != 0 and the other comparison
    is also like that.  maybe_fold_{and,or}_comparisons looks through the
    definitions though and so returns a_1(ab) != 0 as tree.
    So the first part of the patch checks whether that returned comparison
    isn't the same as the curr->op comparison and if yes, it just overrides
    t back to curr->op so that its SSA_NAME is reused.  In that case we can
    handle even (ab) in {,new}op{1,2} because we don't create a new comparison
    of that, just keep using the existing one.  And t can't be (ab) because
    otherwise it wouldn't be considered a reassociable operand.

    The (ab) checks are needed say when we have a_1(ab) == 42 || a_1(ab) > 42
    kind of comparisons where maybe_fold_{and,or}_comparisons returns a new
    comparison not existing in the IL yet.

    2023-02-16  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/108783
            * tree-ssa-reassoc.cc (eliminate_redundant_comparison): If lcode
            is equal to TREE_CODE (t), op1 to newop1 and op2 to newop2, set
            t to curr->op.  Otherwise, punt if either newop1 or newop2 are
            SSA_NAME_OCCURS_IN_ABNORMAL_PHI SSA_NAMEs.

            * gcc.c-torture/compile/pr108783.c: New test.

[Bug tree-optimization/108783] [13 Regression] ICE: verify_flow_info failed (error: returns_twice call is not first in basic block 3)

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108783

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

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

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.