Mach-O LLD Port¶
LLD is a linker from the LLVM project that is a drop-in replacement for system linkers and runs much faster than them. It also provides features that are useful for toolchain developers. This document will describe the Mach-O port.
Features¶
LLD is a drop-in replacement for Apple’s Mach-O linker, ld64, that accepts the same command line arguments.
LLD is very fast. When you link a large program on a multicore machine, you can expect that LLD runs more than twice as fast as the ld64 linker.
Download¶
LLD is available as a pre-built binary by going to the latest release,
downloading the appropriate bundle (clang+llvm-<version>-<your architecture>-<your platform>.tar.xz
),
decompressing it, and locating the binary at bin/ld64.lld
. Note
that if ld64.lld
is moved out of bin
, it must still be accompanied
by its sibling file lld
, as ld64.lld
is technically a symlink to lld
.
Build¶
The easiest way to build LLD is to
check out the entire LLVM projects/sub-projects from a git mirror and
build that tree. You need cmake
and of course a C++ compiler.
$ git clone https://github.com/llvm/llvm-project llvm-project
$ mkdir build
$ cd build
$ cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS='lld' ../llvm-project/llvm
$ ninja check-lld-macho
Then you can find output binary at build/bin/ld64.lld
. Note
that if ld64.lld
is moved out of bin
, it must still be accompanied
by its sibling file lld
, as ld64.lld
is technically a symlink to lld
.
Using LLD¶
LLD can be used by adding -fuse-ld=/path/to/ld64.lld
to the linker flags.
For Xcode, this can be done by adding it to “Other linker flags” in the build
settings. For Bazel, this can be done with --linkopt
or with
rules_apple_linker.
See also
ld64 vs LLD-MachO has more info on the differences between the two linkers.