[all-commits] [llvm/llvm-project] 4ac79a: [lld-macho] Use Symbols as branch target for safe_...

[alx32 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4ac79a8c988ff74984b78c13d489eafcce9189e5
      https://github.com/llvm/llvm-project/commit/4ac79a8c988ff74984b78c13d489eafcce9189e5
  Author: alx32 <103613512+alx32 at users.noreply.github.com>
  Date:   2025-02-13 (Thu, 13 Feb 2025)

  Changed paths:
    M lld/MachO/Arch/ARM64.cpp
    M lld/MachO/ICF.cpp
    M lld/MachO/Target.h
    M lld/test/MachO/arm64-thunks.s

  Log Message:
  -----------
  [lld-macho] Use Symbols as branch target for safe_thunks ICF (#126835)

## Problem

The `safe_thunks` ICF optimization in `lld-macho` was creating thunks
that pointed to `InputSection`s instead of `Symbol`s. While, generally,
branch relocations can point to symbols or input sections, in this case
we need them to point to symbols as subsequently the branch extension
algorithm expects branches to always point to `Symbol`'s.

## Solution
This patch changes the ICF implementation so that safe thunks point to
`Symbol`'s rather than `InputSection`s.

## Testing
The existing `arm64-thunks.s` test is modified to include
`--icf=safe_thunks` to explicitly verify the interaction between ICF and
branch range extension thunks. Two functions were added that will be
merged together via a thunk. Before this patch, this test would generate
an assert - now this scenario is correctly handled.



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