[PATCH] D93783: [ELFObjectWriter] emit STT_SECTION symbols for sections

[Nick Desaulniers via Phabricator via llvm-commits]

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Effectively a revert of r239045 ("Omit unused section symbols from the symbol table.")

By not emitted STT_SECTION symbols for each section, external utilities
that rely on address calculations from these symbols break when moving
from GNU `as` (via `-no-integrated-as`) to Clang's integrated assembler.

Particularly, the Linux kernel's `objtool` utility which is used to
embed custom format unwind info for x86 into the kernel image.

To improve compatibility with GAS, do not intentionally omit these
section symbols.

Increases binary sizes slightly due to additional symbol entries in the
symbol table.

Link: https://github.com/ClangBuiltLinux/linux/issues/669
Link: https://github.com/ClangBuiltLinux/linux/issues/872
Link: https://github.com/ClangBuiltLinux/linux/issues/1209


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93783

Files:
  lld/test/ELF/icf-safe.s
  lld/test/ELF/lto/thinlto-single-module.ll
  llvm/lib/MC/ELFObjectWriter.cpp
  llvm/test/CodeGen/PowerPC/pcrel-tls-general-dynamic.ll
  llvm/test/CodeGen/PowerPC/pcrel-tls-initial-exec.ll
  llvm/test/MC/AArch64/size-directive.s
  llvm/test/MC/ELF/alias.s
  llvm/test/MC/ELF/cgprofile.s
  llvm/test/MC/ELF/comdat.s
  llvm/test/MC/ELF/empty.s
  llvm/test/MC/ELF/reloc-same-name-section.s
  llvm/test/MC/ELF/relocation-alias.s
  llvm/test/MC/ELF/section-sym.s
  llvm/test/MC/ELF/undef.s
  llvm/test/tools/llvm-objdump/X86/demangle.s
  llvm/test/tools/llvm-readobj/ELF/many-sections2.s

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