lld, part of the LLVM family of projects, is a high-performance linker for the ELF, COFF, and Mach-O object formats. This page describes the ongoing project to use lld as FreeBSD's base system linker.

FreeBSD-CURRENT contains LLD 6.0.0. As of r334391, LLD is the default system linker on amd64 and aarch64.

On other architectures, to build world and kernel with LLD and install LLD as /usr/bin/ld, add to /etc/src.conf:

WITH_LLD_IS_LD=yes
WITH_LLD_BOOTSTRAP=yes

WITH_LLD_BOOTSTRAP=yes uses lld as the linker for building the FreeBSD world, and has no effect on the linker installed in /usr/bin/ld. WITH_LLD_IS_LD=yes installes lld as /usr/bin/ld, and has no effect on the linker used for building world.

git clone https://github.com/llvm-mirror/llvm
cd llvm/tools
git clone https://github.com/llvm-mirror/lld
mkdir ../build && cd ../build
cmake -G "Unix Makefiles" ../
make -j8

cd build/bin
ln -s lld ld
setenv PATH /path/to/llvm/build/bin:$PATH
setenv LD /path/to/llvm/build/bin
rehash

To check if the changes took effect:

davide@rabbit1:/home/davide/llvm/build/bin $ ld --help | head -n 1
OVERVIEW: LLVM Linker

• Create reserved symbols early so they can be versioned

MIPS

• MIPS Multi-GOT implementation (2017-03-31)

ARM

• Record created ThunkSections in InputSectionDescription (2017-09-12)
• Pre-create ThunkSections at Target specific intervals (2017-06-27)
• Introduce range extension thunks for ARM (2017-06-27)
• Add support for multiple passes to createThunks (2017-06-27)

A FreeBSD ports exp-run is tracked in PR214864.

• go crashes on startup go Github issue 19018
• print/gl2ps needs explicit -L/usr/lib PR218399.

1. Passing compiler flags, such as -fPIC, to the linker.
2. lld has no built-in search paths (/lib, /usr/lib). Normally the linker is invoked from the compiler driver, which adds the library search paths. If lld is invoked directly then library search paths must be explicitly specified, with -L/lib -L/usr/lib.
3. Shared library protected symbol preemption.
4. lld does not have a built-in default output target. For the most common use of the linker (linking individual .o objects in to an executable or shared object) lld infers the target from the first object file. However, when the linker is used to convert an arbitrary binary file into an ELF object (via -r -b binary) lld must have the output target specified explicitly with -m.

• Rui Ueyama's New LLD linker for ELF talk
• Linking the FreeBSD base system with LLD status update from March 2016
• lld as the FreeBSD base system linker Google Doc