The new Darwin backend for LLD is now able to link reasonably large
real-world programs on x86_64. For instance, we have achieved
self-hosting for the X86_64 target, where all LLD tests pass when
building lld with itself on macOS. As such, we would like to make it the
default back-end.
The new port is now named `ld64.lld`, and the old port remains
accessible as `ld64.lld.darwinold`
This [annoucement email][1] has some context. (But note that, unlike
what the email says, we are no longer doing this as part of the LLVM 12
branch cut -- instead we will go into LLVM 13.)
Numerous mechanical test changes were required to make this change; in
the interest of creating something that's reviewable on Phabricator,
I've split out the boring changes into a separate diff (D95905). I plan to
merge its contents with those in this diff before landing.
(@gkm made the original draft of this diff, and he has agreed to let me
take over.)
[1]: https://lists.llvm.org/pipermail/llvm-dev/2021-January/147665.html
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D95204
An upcoming commit will change how we choose to reference a dylib. Currently
dylibs are only given an LC_LOAD_DYLIB in the final image if an atom is used.
This is different from ld64 which adds the load command when the dylib is referenced
on the cmdline.
In order to change this behaviour, we need libSystem.yaml to actually contain a mach header
so that it is parsed as a dylib, instead of currently being parsed as a normalised file.
To get a mach header, we also require an arch, so now we have one libsystem per arch and
all the tests have been updated to choose the correct one.
llvm-svn: 278372
Jez Ng