[all-commits] [llvm/llvm-project] 4d575e: [ELF] Sort forward thunks by destination to preven...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4d575e790fef3995b23d6838e4ce557d2f9b5b98
      https://github.com/llvm/llvm-project/commit/4d575e790fef3995b23d6838e4ce557d2f9b5b98
  Author: Fangrui Song <i at maskray.me>
  Date:   2026-07-28 (Tue, 28 Jul 2026)

  Changed paths:
    M lld/ELF/Config.h
    M lld/ELF/Driver.cpp
    M lld/ELF/Relocations.cpp
    M lld/ELF/SyntheticSections.cpp
    M lld/ELF/SyntheticSections.h
    M lld/test/ELF/aarch64-thunk-align.s
    M lld/test/ELF/aarch64-thunk-bti-execute-only.s
    M lld/test/ELF/aarch64-thunk-bti-multipass.s
    M lld/test/ELF/aarch64-thunk-bti.s
    M lld/test/ELF/aarch64-thunk-script.s
    A lld/test/ELF/aarch64-thunk-sort.s
    M lld/test/ELF/arm-bl-v4t.s
    M lld/test/ELF/arm-branch-rangethunk.s
    M lld/test/ELF/arm-force-pi-thunk.s
    M lld/test/ELF/arm-thumb-condbranch-thunk.s
    M lld/test/ELF/arm-thumb-interwork-shared.s
    M lld/test/ELF/arm-thumb-interwork-thunk.s
    M lld/test/ELF/arm-thumb-mix-range-thunk-os.s
    M lld/test/ELF/arm-thumb-plt-range-thunk-os.s
    M lld/test/ELF/arm-thumb-range-thunk-os-no-ext.s
    M lld/test/ELF/arm-thumb-range-thunk-os.s
    M lld/test/ELF/arm-thunk-arm-thumb-reuse.s
    M lld/test/ELF/arm-thunk-linkerscript-dotexpr.s
    M lld/test/ELF/arm-thunk-linkerscript-orphan.s
    M lld/test/ELF/arm-thunk-linkerscript.s
    M lld/test/ELF/arm-thunk-re-add.s
    M lld/test/ELF/hexagon-thunk-range-b22rel.s
    M lld/test/ELF/ppc32-call-stub-nopic.s
    M lld/test/ELF/ppc32-call-stub-pic.s
    M lld/test/ELF/ppc32-long-thunk.s
    M lld/test/ELF/ppc64-call-reach.s
    M lld/test/ELF/ppc64-ifunc.s
    M lld/test/ELF/ppc64-long-branch-pi.s
    M lld/test/ELF/ppc64-long-branch-rel14.s
    M lld/test/ELF/ppc64-long-branch.s

  Log Message:
  -----------
  [ELF] Sort forward thunks by destination to prevent convergence failures (#211721)

A thunk's distance to a forward destination grows when a thunk after it
grows.

For
```
[forward A B C] dstA dstB dstC
```

When all thunks are initially short, promoting C can push B to be
enlarged on the following pass, which in turn pushes A to be promoted on
the following pass. Promoting just one thunk on a pass can therefore
trigger "address assignment did not converge".

Sort each ThunkSection once pass 0 has created its thunks. A forward
thunk's distance grows only when a thunk after it grows, so order
forward thunks by descending destination. A backward thunk's distance
grows only with a promotion before it, already applied when we reach
it, so backward thunks need no ordering; partition them ahead of the
forward thunks in creation order.

Tests that depend on creation order are pinned with -z nosort-thunks;
they can be migrated individually, after which the option can be
removed.

Fixes #61250

Co-authored-by: Pranav Kant <prka at google.com>



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