[all-commits] [llvm/llvm-project] ebb326: [ELF] Fix unnecessary inclusion of unreferenced pr...

[partaror via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ebb326a51fec37b5a47e5702e8ea157cd4f835cd
      https://github.com/llvm/llvm-project/commit/ebb326a51fec37b5a47e5702e8ea157cd4f835cd
  Author: Parth Arora <quic_partaror at quicinc.com>
  Date:   2024-03-25 (Mon, 25 Mar 2024)

  Changed paths:
    M lld/ELF/Driver.cpp
    M lld/ELF/LinkerScript.cpp
    M lld/ELF/LinkerScript.h
    M lld/ELF/ScriptParser.cpp
    M lld/ELF/SymbolTable.cpp
    M lld/ELF/SymbolTable.h
    A lld/test/ELF/gc-sections-with-provide.s
    M lld/test/ELF/linkerscript/symbolreferenced.s

  Log Message:
  -----------
  [ELF] Fix unnecessary inclusion of unreferenced provide symbols

Previously, linker was unnecessarily including a PROVIDE symbol which
was referenced by another unused PROVIDE symbol. For example, if a
linker script contained the below code and 'not_used_sym' provide symbol
is not included, then linker was still unnecessarily including 'foo' PROVIDE
symbol because it was referenced by 'not_used_sym'. This commit fixes
this behavior.

PROVIDE(not_used_sym = foo)
PROVIDE(foo = 0x1000)

This commit fixes this behavior by using dfs-like algorithm to find
all the symbols referenced in provide expressions of included provide
symbols.

This commit also fixes the issue of unused section not being garbage-collected
if a symbol of the section is referenced by an unused PROVIDE symbol.

Closes #74771
Closes #84730

Co-authored-by: Fangrui Song <i at maskray.me>



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