[Bug tree-optimization/79958] Missed tree DSE

[Bug tree-optimization/79958] Missed tree DSE

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79958

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2017-03-10 00:00:00         |2021-8-14
           Severity|normal                      |enhancement

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
With the reduced testcase in comment #2 and -O2 -fno-tree-dce we still get:
  x.i = 1;
  if (b_3(D) != 0)
    goto <bb 3>; [0.04%]
  else
    goto <bb 4>; [99.96%]

  <bb 3> [local count: 429496]:
  bar ();
  __builtin_abort ();

  <bb 4> [local count: 1073312329]:
  bar (); [tail call]
  x ={v} {CLOBBER};

As Richi mentioned tree level DCE can figure it out for the reduced testcase
while DSE cannot.

[Bug tree-optimization/79958] Missed tree DSE

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79958

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

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

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Testing a patch.

[Bug tree-optimization/79958] Missed tree DSE

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79958

--- Comment #6 from GCC 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:1e0ae1f52741f7e0133661659ed2d210f939a398

commit r15-571-g1e0ae1f52741f7e0133661659ed2d210f939a398
Author: Richard Biener <rguenther@suse.de>
Date:   Wed May 15 18:32:37 2024 +0200

    tree-optimization/79958 - make DSE track multiple paths

    DSE currently gives up when the path we analyze forks.  This leads
    to multiple missed dead store elimination PRs.  The following fixes
    this by recursing for each path and maintaining the visited bitmap
    to avoid visiting CFG re-merges multiple times.  The overall cost
    is still limited by the same bound, it's just more likely we'll hit
    the limit now.  The patch doesn't try to deal with byte tracking
    once a path forks but drops info on the floor and only handling
    fully dead stores in that case.

            PR tree-optimization/79958
            PR tree-optimization/109087
            PR tree-optimization/100314
            PR tree-optimization/114774
            * tree-ssa-dse.cc (dse_classify_store): New forwarder.
            (dse_classify_store): Add arguments cnt and visited, recurse
            to track multiple paths when we end up with multiple defs.

            * gcc.dg/tree-ssa/ssa-dse-48.c: New testcase.
            * gcc.dg/tree-ssa/ssa-dse-49.c: Likewise.
            * gcc.dg/tree-ssa/ssa-dse-50.c: Likewise.
            * gcc.dg/tree-ssa/ssa-dse-51.c: Likewise.
            * gcc.dg/graphite/pr80906.c: Avoid DSE of last data reference
            in loop.
            * g++.dg/ipa/devirt-24.C: Adjust for extra DSE.
            * g++.dg/warn/Wuninitialized-pr107919-1.C: Use more important
            -O2 optimization level, -O1 regresses.

[Bug tree-optimization/79958] Missed tree DSE

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79958

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |15.0
         Resolution|---                         |FIXED

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Should be fixed for GCC 15.