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From: "acoplan at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113616] [14 Regression] ICE in
 process_uses_of_deleted_def, at rtl-ssa/changes.cc:252
Date: Fri, 26 Jan 2024 11:47:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113616

--- Comment #2 from Alex Coplan <acoplan at gcc dot gnu.org> ---
I think the problem is this loop (and others that iterate over debug
uses in this way):

      // Now that we've characterized the defs involved, go through the
      // debug uses and determine how to update them (if needed).
      for (auto use : set->debug_insn_uses ())
        {
          if (*pair_dst < *use->insn () && defs[1])
            // We're re-ordering defs[1] above a previous use of the
            // same resource.
            update_debug_use (use, defs[1], writeback_pats[1]);
          else if (*pair_dst >=3D *use->insn ())
            // We're re-ordering defs[0] below its use.
            update_debug_use (use, defs[0], writeback_pats[0]);
        }

because `update_debug_use` can remove uses from the list of debug uses,
we can't use a for-range loop as the iterator will become invalidated
before getting advanced.

Should be fairly straightforward to fix, sorry for the oversight.=