[all-commits] [llvm/llvm-project] 0bc0cc: [llvm][EmbedBitcodePass] Prevent modifying the mod...

[Paul Kirth via All-commits]

  Branch: refs/heads/users/ilovepi/fatlto-wpd-fix
  Home:   https://github.com/llvm/llvm-project
  Commit: 0bc0cc2c64a7c7a347cf71888e9a57339537ce25
      https://github.com/llvm/llvm-project/commit/0bc0cc2c64a7c7a347cf71888e9a57339537ce25
  Author: Paul Kirth <paulkirth at google.com>
  Date:   2025-05-14 (Wed, 14 May 2025)

  Changed paths:
    M llvm/lib/Transforms/IPO/EmbedBitcodePass.cpp
    M llvm/test/Transforms/EmbedBitcode/embed-wpd.ll

  Log Message:
  -----------
  [llvm][EmbedBitcodePass] Prevent modifying the module with ThinLTO

Since ThinLTOBitcodeWriterPass handles many things for CFI and WPD, like
updating vtable linkage, we need to prevent those changes from
persisting in the non-LTO object code we will compile under FatLTO.

The only non-invasive way to do that is to clone the module when
serializing the module in ThinLTOBitcodeWriterPass. We may be able to
avoid cloning in the future with additional infrastructure to restore
the IR to its original state.

Fixes #139440



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