[lld-macho][nfc] Run clang-format on lld/MachO/*.{h,cpp}

- fixed inconsistent indents and spaces
- prevent extraneous formatting changes in other patches

Differential Revision: https://reviews.llvm

[lld-macho][nfc] Run clang-format on lld/MachO/*.{h,cpp}

- fixed inconsistent indents and spaces
- prevent extraneous formatting changes in other patches

Differential Revision: https://reviews.llvm.org/D126262

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[lld/mac] Implement support for section$start and section$ end symbols

With this, libclang_rt.profile_osx.a can be linked, that is coverage
and PGO-instrumented builds should now work with lld.

sec

[lld/mac] Implement support for section$start and section$ end symbols

With this, libclang_rt.profile_osx.a can be linked, that is coverage
and PGO-instrumented builds should now work with lld.

section$start and section$end symbols can create non-existing sections.
They're also undefined symbols that are only magic if there isn't a
regular symbol with their name, which means the need to be handled
in treatUndefined() instead of just looping over all existing
sections and adding start and end symbols like the ELF port does.

To represent the actual symbols, this uses absolute symbols that
get their value updated once an output section is layed out.

segment$start and segment$end are still missing for now, but they produce a
nicer error message after this patch.

Main part of PR50760.

Differential Revision: https://reviews.llvm.org/D106629

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[lld/mac] Let OutputSegment store its start address

segment$start$/segment$end$ symbols allow creating segments without
sections, so getting the segment address off the first section
won't work ther

[lld/mac] Let OutputSegment store its start address

segment$start$/segment$end$ symbols allow creating segments without
sections, so getting the segment address off the first section
won't work there. Storing the address on the segment is arguably a
bit simpler too.

No behavior change, part of PR50760.

Differential Revision: https://reviews.llvm.org/D106665

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[lld-macho] Refactor segment/section creation, sorting, and merging

Summary:
There were a few issues with the previous setup:

1. The section sorting comparator used a declarative map of section nam

[lld-macho] Refactor segment/section creation, sorting, and merging

Summary:
There were a few issues with the previous setup:

1. The section sorting comparator used a declarative map of section names to
determine the correct order, but it turns out we need to match on more than
just names -- in particular, an upcoming diff will sort based on whether the
S_ZERO_FILL flag is set. This diff changes the sorter to a more imperative but
flexible form.

2. We were sorting OutputSections stored in a MapVector, which left the
MapVector in an inconsistent state -- the wrong keys map to the wrong values!
In practice, we weren't doing key lookups (only container iteration) after the
sort, so this was fine, but it was still a dubious state of affairs. This diff
copies the OutputSections to a vector before sorting them.

3. We were adding unneeded OutputSections to OutputSegments and then filtering
them out later, which meant that we had to remember whether an OutputSegment
was in a pre- or post-filtered state. This diff only adds the sections to the
segments if they are needed.

In addition to those major changes, two minor ones worth noting:

1. I renamed all OutputSection variable names to `osec`, to parallel `isec`.
Previously we were using some inconsistent combination of `osec`, `os`, and
`section`.

2. I added a check (and a test) for InputSections with names that clashed with
those of our synthetic OutputSections.

Reviewers: #lld-macho

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D81887

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[lld] Merge Mach-O input sections

Summary: Similar to other formats, input sections in the MachO
implementation are now grouped under output sections. This is primarily
a refactor, although there's

[lld] Merge Mach-O input sections

Summary: Similar to other formats, input sections in the MachO
implementation are now grouped under output sections. This is primarily
a refactor, although there's some new logic (like resolving the output
section's flags based on its inputs).

Differential Revision: https://reviews.llvm.org/D77893

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