[Bug tree-optimization/115256] New: [15 Regression] 502.gcc_r Run failed with '-march=native -Ofast -funroll-loops -flto' since r15-571-g1e0ae1f52741f7

["admin at levyhsu dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115256

            Bug ID: 115256
           Summary: [15 Regression] 502.gcc_r Run failed with
                    '-march=native -Ofast -funroll-loops -flto' since
                    r15-571-g1e0ae1f52741f7
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: admin at levyhsu dot com
  Target Milestone: ---

Bisect down to r15-571-g1e0ae1f52741f7
(1e0ae1f52741f7e0133661659ed2d210f939a398)

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.

Observed on 
Ice Lake
Cascade Lake
AlderLake
Zen3 Server/Client
Also failed on Aarch64 (But didn't bisect)