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
The darwin linker has an option, heavily used by Xcode, in which, instead
of listing all input files on the command line, the input file paths are
written to a text file and the path of that text file is passed to the linker
with the -filelist option (similar to @file).
In order to make test cases for this, I generalized the -test_libresolution
option to become -test_file_usage.
llvm-svn: 215762
These behave slightly idiosyncratically in the best of cases, and have
additional hacks layered on top of that for compatibility with badly behaved
build systems (via ld64).
For -lXYZ:
+ If XYZ is actually XY.o then search all library paths for XY.o
+ Otherwise search all library paths, first for libXYZ.dylib, then libXYZ.a
+ By default the library paths are /usr/lib and /usr/local/lib in that order.
For -syslibroot:
+ -syslibroot options apply to absolute paths in the search order.
+ All -syslibroot prefixes that exist are added to the search path *instead*
of the original.
+ If no -syslibroot prefixed path exists, the original is kept.
+ Hacks^WExceptions:
+ If only 1 -syslibroot is given and doesn't contain /usr/lib or
/usr/local/lib, that path is dropped entirely. (rdar://problem/6438270).
+ If the last -syslibroot is "/", all of them are ignored entirely.
(rdar://problem/5829579).
At least, that's my best interpretation of what ld64 does in buildSearchPaths.
llvm-svn: 212706
Jez Ng