[Bug tree-optimization/96695] New: Failure to optimize combination of pointer comparison to nullptr and another pointer

[Bug tree-optimization/96695] New: Failure to optimize combination of pointer comparison to nullptr and another pointer

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

            Bug ID: 96695
           Summary: Failure to optimize combination of pointer comparison
                    to nullptr and another pointer
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

bool f(char *x, char *y)
{
    return (x == 0) && (x > y);
}

This can be optimized to `return false;`. This transformation is done by LLVM,
but not by GCC.

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

--- Comment #1 from Gabriel Ravier <gabravier at gmail dot com> ---
PS: Very similar transformations can be done with alike patterns like `(x == 0)
&& (x <= y)`, which can be optimized to `x == 0`.

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-08-25

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, so we can optimize 0 > y to false, likewise 0 <= y to true.  I guess we
already do that so VRP should handle

 if (x == 0)
   if (x > y)

already.

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu.org
           Severity|normal                      |enhancement

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

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

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

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We handle:
bool f2(unsigned x, unsigned y)
{
    return (x == 0) && (x > y);
}

via:

/* x >  y  &&  x != XXX_MIN  -->  x > y
   x >  y  &&  x == XXX_MIN  -->  false . */

min_value is defined as:
(match min_value
 INTEGER_CST
 (if (INTEGRAL_TYPE_P (type)
      && wi::eq_p (wi::to_wide (t), wi::min_value (type)))))

I suspect we could add POINTER_TYPE_P there and it will work.

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 55694
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55694&action=edit
Patch which I am testing

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2023-August/
                   |                            |626402.html

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Patch posted:
https://gcc.gnu.org/pipermail/gcc-patches/2023-August/626402.html

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Andrew Pinski <pinskia@gcc.gnu.org>:

https://gcc.gnu.org/g:58f1e185ff6d108171b9c8ea043796c85a65fcec

commit r14-3014-g58f1e185ff6d108171b9c8ea043796c85a65fcec
Author: Andrew Pinski <apinski@marvell.com>
Date:   Sat Aug 5 09:23:26 2023 -0700

    MATCH: Extend min_value/max_value to pointer types

    Since we already had the infrastructure to optimize
    `(x == 0) && (x > y)` to false for integer types,
    this extends the same to pointer types as indirectly
    requested by PR 96695.

    OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

    gcc/ChangeLog:

            PR tree-optimization/96695
            * match.pd (min_value, max_value): Extend to
            pointer types too.

    gcc/testsuite/ChangeLog:

            PR tree-optimization/96695
            * gcc.dg/pr96695-1.c: New test.
            * gcc.dg/pr96695-10.c: New test.
            * gcc.dg/pr96695-11.c: New test.
            * gcc.dg/pr96695-12.c: New test.
            * gcc.dg/pr96695-2.c: New test.
            * gcc.dg/pr96695-3.c: New test.
            * gcc.dg/pr96695-4.c: New test.
            * gcc.dg/pr96695-5.c: New test.
            * gcc.dg/pr96695-6.c: New test.
            * gcc.dg/pr96695-7.c: New test.
            * gcc.dg/pr96695-8.c: New test.
            * gcc.dg/pr96695-9.c: New test.

[Bug tree-optimization/96695] Failure to optimize combination of pointer comparison to nullptr and another pointer

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96695

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed.