[all-commits] [llvm/llvm-project] d12bae: [BOLT] Make .debug_names emission reproducible

[Rafael Auler via All-commits]

  Branch: refs/heads/users/rafaelauler/bolt-fix-nondeterminism-debugstr
  Home:   https://github.com/llvm/llvm-project
  Commit: d12baec56a90148db5f7538cdda9d2bbe6439c57
      https://github.com/llvm/llvm-project/commit/d12baec56a90148db5f7538cdda9d2bbe6439c57
  Author: Rafael Auler <rafaelauler at fb.com>
  Date:   2026-09-21 (Mon, 21 Sep 2026)

  Changed paths:
    M bolt/include/bolt/Core/DebugNames.h
    M bolt/lib/Core/DebugNames.cpp

  Log Message:
  -----------
  [BOLT] Make .debug_names emission reproducible

Summary:
--update-debug-sections does not produce the same binary twice when the
input has a .debug_names section, or is given one with
--create-debug-names-section. Three sections vary from run to run:
.debug_str, .debug_names and .debug_str_offsets. On a two-CU
split-DWARF test binary, ten runs of the same llvm-bolt produced three
different outputs.

PR #197859 made the per-bucket work merge in partition order precisely so
the output would be reproducible, but missed this section. Two issues:

 - .debug_str offsets were handed out from the workers, so main.dwo.dwo
   added by the merge step lands in a different place in each
   run. The string offsets stored in .debug_names follow from it, and
   so does .debug_str_offsets;
 - hash colliding names were ordered by insertion (worker) order, also
   non-deterministic.

We now determine string positions in the non-concurrent finalize step(),
and order collisions.



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