[Bug tree-optimization/99739] New: [11 Regression] missing optimization of a repeated conditional

[Bug tree-optimization/99739] New: [11 Regression] missing optimization of a repeated conditional

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

            Bug ID: 99739
           Summary: [11 Regression] missing optimization of a repeated
                    conditional
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

Prior to r11-5805 both ff() and gg() in the test case below resulted in optimal
code.  With the change, the second conditional in g() is no longer recognized
as equivalent to the first and so the function isn't optimized as expected.

Incidentally, the same regression was also introduced once before: in r235653.

$ cat x.c && gcc -O1 -S -Wall -fdump-tree-optimized=/dev/stdout x.c
static inline int f (int i, int j, int k)
{
  int x = 1;

  if (i && j && k)
    x = 2;

  if (i && j && k)
    return x;

  return -1;
}

void ff (int i, int j, int k)
{
  int x = f (i, j, k);
  if (x == 1)
    __builtin_abort ();
}


static inline int g (int i, int j, int k)
{
  int x = 1;

  if (i && j && k)
    x = 2;

  if (i && k && j)
    return x;

  return -1;
}

void gg (int i, int j, int k)
{
  int x = g (i, j, k);
  if (x == 1)
    __builtin_abort ();
}

;; Function ff (ff, funcdef_no=1, decl_uid=1951, cgraph_uid=2, symbol_order=1)

void ff (int i, int j, int k)
{
  <bb 2> [local count: 1073741824]:
  return;

}



;; Function gg (gg, funcdef_no=3, decl_uid=1963, cgraph_uid=4, symbol_order=3)

Removing basic block 6
Removing basic block 7
void gg (int i, int j, int k)
{
  _Bool _7;
  _Bool _8;
  _Bool _11;
  _Bool _14;
  _Bool _16;

  <bb 2> [local count: 1073741824]:
  _7 = i_2(D) != 0;
  _8 = j_3(D) != 0;
  _14 = k_4(D) != 0;
  _11 = _7 & _14;
  _16 = _8 & _11;
  if (_16 != 0)
    goto <bb 3>; [94.27%]
  else
    goto <bb 5>; [5.73%]

  <bb 3> [local count: 1012175616]:
  if (k_4(D) != 0)
    goto <bb 5>; [100.00%]
  else
    goto <bb 4>; [0.00%]

  <bb 4> [count: 0]:
  __builtin_abort ();

  <bb 5> [local count: 1073741824]:
  return;

}

[Bug tree-optimization/99739] [11 Regression] missing optimization of a repeated conditional

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Whether we handle this or not at -O1 is quite dependent on short-circuiting
anyway - we only have jump threading at our hands at -O1 (we could consider
enabling non-iterating EVRP).

So I'm not sure this is an important regression.  At -O2 we end up with

  <bb 2> [local count: 1073741824]:
  _7 = i_2(D) != 0;
  _8 = j_3(D) != 0;
  _9 = _7 & _8;
  if (_9 != 0)
    goto <bb 5>; [50.00%]
  else
    goto <bb 3>; [50.00%]

  <bb 3> [local count: 536870911]:
  _23 = k_4(D) != 0;
  _24 = _7 & _23;
  _11 = _8 & _24;
  if (_11 != 0)
    goto <bb 4>; [94.27%]
  else
    goto <bb 5>; [5.73%]

  <bb 4> [count: 0]:
  __builtin_abort ();

  <bb 5> [local count: 1073741824]:
  return;

where reassociation leaves redundant _9 on the plate.

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.0                        |11.2

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 11.1 has been released, retargeting bugs to GCC 11.2.

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.2                        |11.3

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 11.2 is being released, retargeting bugs to GCC 11.3

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.3                        |11.4

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 11.3 is being released, retargeting bugs to GCC 11.4.

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |13.0
           Keywords|                            |needs-bisection
            Summary|[11/12/13 Regression]       |[11/12 Regression] missing
                   |missing optimization of a   |optimization of a repeated
                   |repeated conditional        |conditional

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This seems to have been fixed on the trunk ... It would be a nice idea to see
what fixed it.
Note dom3 is able to figure out they are the same.

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

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

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
r13-1268-g8c99e307b20c502e55c4258

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

--- Comment #7 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:86111e7b3027de1029718e23ee5fab0ee011e191

commit r13-6845-g86111e7b3027de1029718e23ee5fab0ee011e191
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Mar 24 09:39:59 2023 +0100

    testsuite: Add testcase for already fixed PR [PR99739]

    This PR was fixed by r13-1268-g8c99e307b20, I'm adding testcase
    to make sure we don't regress on it in the future.

    2023-03-24  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/99739
            * gcc.dg/tree-ssa/pr99739.c: New test.

[Bug tree-optimization/99739] [11/12 Regression] missing optimization of a repeated conditional

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99739

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.4                        |11.5

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 11.4 is being released, retargeting bugs to GCC 11.5.