LLD 7.0.0 Release Notes


lld is a high-performance linker that supports ELF (Unix), COFF (Windows), Mach-O (macOS), MinGW and WebAssembly. lld is command-line-compatible with GNU linkers and Microsoft link.exe, and is significantly faster than the system default linkers.

lld 7 for ELF, COFF and MinGW are production-ready.

  • lld/ELF can build the entire FreeBSD/{AMD64,ARMv7} and will be the default linker of the next version of the operating system.
  • lld/COFF is being used to create official builds of large popular programs such as Chrome and Firefox.
  • lld/MinGW is being used by Firefox for their MinGW builds. lld/MinGW still needs a sysroot specifically built for lld, with llvm-dlltool, though.
  • lld/WebAssembly is used as the default (only) linker in Emscripten when using the upstream LLVM compiler.
  • lld/Mach-O is still experimental.

Non-comprehensive list of changes in this release

ELF Improvements

  • Fixed a lot of long-tail compatibility issues with GNU linkers.
  • Added -z retpolineplt to emit a PLT entry that doesn’t contain an indirect jump instruction to mitigate Spectre v2 vulnerability.
  • Added experimental support for SHT_RELR sections to create a compact dynamic relocation table.
  • Added support for split stacks.
  • Added support for address significance table (section with type SHT_LLVM_ADDRSIG) to improve Identical Code Folding (ICF). Combined with the -faddrsig compiler option added to Clang 7, lld’s --icf=all can now safely merge functions and data to generate smaller outputs than before.
  • Improved --gdb-index so that it is faster (r336790) and uses less memory (r336672).
  • Reduced memory usage of --compress-debug-sections (r338913).
  • Added linker script OVERLAY support (r335714).
  • Added --warn-backref to make it easy to identify command line option order that doesn’t work with GNU linkers (r329636)
  • Added ld.lld.1 man page (r324512).
  • Added support for multi-GOT.
  • Added support for MIPS position-independent executable (PIE).
  • Fixed MIPS TLS GOT entries for local symbols in shared libraries.
  • Fixed calculation of MIPS GP relative relocations in case of relocatable output.
  • Added support for PPCv2 ABI.
  • Removed an incomplete support of PPCv1 ABI.
  • Added support for Qualcomm Hexagon ISA.
  • Added the following flags: --apply-dynamic-relocs, --check-sections, --cref, --just-symbols, --keep-unique, --no-allow-multiple-definition, --no-apply-dynamic-relocs, --no-check-sections, --no-gnu-unique, ``--no-pic-executable, --no-undefined-version, --no-warn-common, --pack-dyn-relocs=relr, --pop-state, --print-icf-sections, --push-state, --thinlto-index-only, --thinlto-object-suffix-replace, --thinlto-prefix-replace, --warn-backref, -z combreloc, -z copyreloc, -z initfirst, -z keep-text-section-prefix, -z lazy, -z noexecstack, -z relro, -z retpolineplt, -z text

COFF Improvements

  • Improved correctness of exporting mangled stdcall symbols.
  • Completed support for ARM64 relocations.
  • Added support for outputting PDB debug info for MinGW targets.
  • Improved compatibility of output binaries with GNU binutils objcopy/strip.
  • Sped up PDB file creation.
  • Changed section layout to improve compatibility with link.exe.
  • /subsystem inference is improved to cover more corner cases.
  • Added the following flags: --color-diagnostics={always,never,auto}, --no-color-diagnostics, /brepro, /debug:full, /debug:ghash, /guard:cf, /guard:longjmp, /guard:nolongjmp, /integritycheck, /order, /pdbsourcepath, /timestamp