[lld-macho] Fill out release notes for 12.x

[smeenai]

lld/docs/ReleaseNotes.rst

64

Nit: Mach-O (and I'd probably change it above as well)

[int3]

Mach-O

[int3]

lld/docs/ReleaseNotes.rst

64

Haha I wrote it here w/o the hyphen because of the title above :p but yeah changed both

[tschuett]

lld/docs/ReleaseNotes.rst

76

How about listing them instead? Are there plans beyond ARM64?

[int3]

lld/docs/ReleaseNotes.rst

76

yes, we'll likely want to support x86 and arm32 as well, since watchOS is 32-bit.

[tschuett]

But "Support for architectures other than x86_64" sounds like it is secret, which other ISAs you want to support.

[int3]

list architectures explicitly

[int3]

Fair enough :)

[smeenai]

LGTM

[int3]

Landed in https://github.com/llvm/llvm-project/commit/440b16a4fc04a4bb614a60c26f42ab2ec27049a4.

lld/docs/ReleaseNotes.rst

 
 * Handle the ``--demangle`` and ``--no-demangle`` options.
   (`D93950 <https://reviews.llvm.org/D93950>`_)
 
 
 MachO Improvements
 ------------------
 
-* Item 1.
+We've gotten the new implementation of LLD for MachO to the point where it is
+able to link large x86_64 programs, and we'd love to get some alpha testing on
+it. The new Darwin back-end can be invoked as follows:
+
+.. code-block::
+   clang -fuse-ld=lld.darwinnew /path/to/file.c
+
+To reach this point, we implemented numerous features, and it's easier to list
+the major features we *haven't* yet completed:
+
+* LTO support
+* Stack unwinding for exceptions
+* Support for architectures other than x86_64
+
+If you stumble upon an issue and it doesn't fall into one of these categories,
+please file a bug report!
+
 
 WebAssembly Improvements
 ------------------------