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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/96564] [11/12/13/14/15 Regression] New maybe use of
 uninitialized variable warning since r11-959
Date: Thu, 16 May 2024 11:23:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96564

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2020-08-11 00:00:00         |2024-5-16
                 CC|                            |aldyh at gcc dot gnu.org

--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
Handling pointer-vs-pointer in ptrs_compare_unequal isn't enough since we h=
ave

  # PT =3D nonlocal null
  unsigned int * x_7(D) =3D x;
...
  # PT =3D null { D.2785 }
  a_9 =3D malloc (_2);
  if (a_9 =3D=3D 0B)=20
    goto <bb 7>; [0.04%]
  else
    goto <bb 3>; [99.96%]

  <bb 7> [local count: 429496]:
  goto <bb 6>; [100.00%]

  <bb 3> [local count: 1073312328]:
  if (x_7(D) !=3D a_9)

so querying points-to only has to consider both pointers being NULL.  Now,
I'm not sure how prange handles the above and whether or how it integrates
knowledge from flow-insensitive points-to analysis.

Aldy might know.

I'm testing a patch enhancing ptrs_compare_unequal right now, also filling
in a missing bit in points-to info.=