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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/100314] missed optimization for dead code elimination at
 -O3 (vs. -O1)  (inlining differences due to missed dse)
Date: Thu, 16 May 2024 09:04:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100314

--- Comment #7 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.=