Our implementation draws heavily from LLD-ELF's, which in turn delegates
its string deduplication to llvm-mc's StringTableBuilder. The messiness of
this diff is largely due to the fact that we've previously assumed that
all InputSections get concatenated together to form the output. This is
no longer true with CStringInputSections, which split their contents into
StringPieces. StringPieces are much more lightweight than InputSections,
which is important as we create a lot of them. They may also overlap in
the output, which makes it possible for strings to be tail-merged. In
fact, the initial version of this diff implemented tail merging, but
I've dropped it for reasons I'll explain later.
**Alignment Issues**
Mergeable cstring literals are found under the `__TEXT,__cstring`
section. In contrast to ELF, which puts strings that need different
alignments into different sections, clang's Mach-O backend puts them all
in one section. Strings that need to be aligned have the `.p2align`
directive emitted before them, which simply translates into zero padding
in the object file.
I *think* ld64 extracts the desired per-string alignment from this data
by preserving each string's offset from the last section-aligned
address. I'm not entirely certain since it doesn't seem consistent about
doing this; but perhaps this can be chalked up to cases where ld64 has
to deduplicate strings with different offset/alignment combos -- it
seems to pick one of their alignments to preserve. This doesn't seem
correct in general; we can in fact can induce ld64 to produce a crashing
binary just by linking in an additional object file that only contains
cstrings and no code. See PR50563 for details.
Moreover, this scheme seems rather inefficient: since unaligned and
aligned strings are all put in the same section, which has a single
alignment value, it doesn't seem possible to tell whether a given string
doesn't have any alignment requirements. Preserving offset+alignments
for strings that don't need it is wasteful.
In practice, the crashes seen so far seem to stem from x86_64 SIMD
operations on cstrings. X86_64 requires SIMD accesses to be
16-byte-aligned. So for now, I'm thinking of just aligning all strings
to 16 bytes on x86_64. This is indeed wasteful, but implementation-wise
it's simpler than preserving per-string alignment+offsets. It also
avoids the aforementioned crash after deduplication of
differently-aligned strings. Finally, the overhead is not huge: using
16-byte alignment (vs no alignment) is only a 0.5% size overhead when
linking chromium_framework.
With these alignment requirements, it doesn't make sense to attempt tail
merging -- most strings will not be eligible since their overlaps aren't
likely to start at a 16-byte boundary. Tail-merging (with alignment) for
chromium_framework only improves size by 0.3%.
It's worth noting that LLD-ELF only does tail merging at `-O2`. By
default (at `-O1`), it just deduplicates w/o tail merging. @thakis has
also mentioned that they saw it regress compressed size in some cases
and therefore turned it off. `ld64` does not seem to do tail merging at
all.
**Performance Numbers**
CString deduplication reduces chromium_framework from 250MB to 242MB, or
about a 3.2% reduction.
Numbers for linking chromium_framework on my 3.2 GHz 16-Core Intel Xeon W:
N Min Max Median Avg Stddev
x 20 3.91 4.03 3.935 3.95 0.034641016
+ 20 3.99 4.14 4.015 4.0365 0.0492336
Difference at 95.0% confidence
0.0865 +/- 0.027245
2.18987% +/- 0.689746%
(Student's t, pooled s = 0.0425673)
As expected, cstring merging incurs some non-trivial overhead.
When passing `--no-literal-merge`, it seems that performance is the
same, i.e. the refactoring in this diff didn't cost us.
N Min Max Median Avg Stddev
x 20 3.91 4.03 3.935 3.95 0.034641016
+ 20 3.89 4.02 3.935 3.9435 0.043197831
No difference proven at 95.0% confidence
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D102964
When a library "host"'s reexports change their installName with
`$ld$os10.11$install_name$host`, we used to write a load command for "host" but
write the version numbers of the reexport instead of "host". This fixes that.
I first thought that the rule is to take the version numbers from the library
that originally had that install name (implemented in D103819), but that's not
what ld64 seems to be doing: It takes the version number from the first dylib
with that install name it loads, and it loads the reexporting library before
the reexports. We already did most of that, we just added reexports before the
reexporter. After this change, we add the reexporter before the reexports.
Addresses https://bugs.llvm.org/show_bug.cgi?id=49800#c11 part 1.
(ld64 seems to add reexports after processing _all_ files on the command line,
while we add them right after the reexporter. For the common case of reexport +
$ld$ symbol changing back to the exporter name, this doesn't make a difference,
but you can construct a case where it does. I expect this to not make a
difference in practice though.)
Differential Revision: https://reviews.llvm.org/D103821
Also adds support for live_support sections, no_dead_strip sections,
.no_dead_strip symbols.
Chromium Framework 345MB unstripped -> 250MB stripped
(vs 290MB unstripped -> 236M stripped with ld64).
Doing dead stripping is a bit faster than not, because so much less
data needs to be processed:
% ministat lld_*
x lld_nostrip.txt
+ lld_strip.txt
N Min Max Median Avg Stddev
x 10 3.929414 4.07692 4.0269079 4.0089678 0.044214794
+ 10 3.8129408 3.9025559 3.8670411 3.8642573 0.024779651
Difference at 95.0% confidence
-0.144711 +/- 0.0336749
-3.60967% +/- 0.839989%
(Student's t, pooled s = 0.0358398)
This interacts with many parts of the linker. I tried to add test coverage
for all added `isLive()` checks, so that some test will fail if any of them
is removed. I checked that the test expectations for the most part match
ld64's behavior (except for live-support-iterations.s, see the comment
in the test). Interacts with:
- debug info
- export tries
- import opcodes
- flags like -exported_symbol(s_list)
- -U / dynamic_lookup
- mod_init_funcs, mod_term_funcs
- weak symbol handling
- unwind info
- stubs
- map files
- -sectcreate
- undefined, dylib, common, defined (both absolute and normal) symbols
It's possible it interacts with more features I didn't think of,
of course.
I also did some manual testing:
- check-llvm check-clang check-lld work with lld with this patch
as host linker and -dead_strip enabled
- Chromium still starts
- Chromium's base_unittests still pass, including unwind tests
Implemenation-wise, this is InputSection-based, so it'll work for
object files with .subsections_via_symbols (which includes all
object files generated by clang). I first based this on the COFF
implementation, but later realized that things are more similar to ELF.
I think it'd be good to refactor MarkLive.cpp to look more like the ELF
part at some point, but I'd like to get a working state checked in first.
Mechanical parts:
- Rename canOmitFromOutput to wasCoalesced (no behavior change)
since it really is for weak coalesced symbols
- Add noDeadStrip to Defined, corresponding to N_NO_DEAD_STRIP
(`.no_dead_strip` in asm)
Fixes PR49276.
Differential Revision: https://reviews.llvm.org/D103324
We used to not print dylibs referenced by other dylibs in `-t` mode. This
affected reexports, and with `-flat_namespace` also just dylibs loaded by
dylibs. Now we print them.
Fixes PR49514.
Differential Revision: https://reviews.llvm.org/D103428
In all of these cases, the functions could simply return a nullptr instead of {}.
There is no case where Optional<nullptr> has a special meaning.
Differential Revision: https://reviews.llvm.org/D103489
This omits load commands for unreferenced dylibs if:
- the dylib was loaded implicitly,
- it is marked MH_DEAD_STRIPPABLE_DYLIB
- or -dead_strip_dylibs is passed
This matches ld64.
Currently, the "is dylib referenced" state is computed before dead code
stripping and is not updated after dead code stripping. This too matches ld64.
We should do better here.
With this, clang-format linked with lld (like with ld64) no longer has
libobjc.A.dylib in `otool -L` output. (It was implicitly loaded as a reexport
of CoreFoundation.framework, but it's not needed.)
Differential Revision: https://reviews.llvm.org/D103430
lld/MachO/Driver.cpp and lld/MachO/SyntheticSections.cpp include
llvm/Config/config.h which doesn't exist when building standalone lld.
This patch replaces llvm/Config/config.h include with llvm/Config/llvm-config.h
just like it is in lld/ELF/Driver.cpp and HAVE_LIBXAR with LLVM_HAVE_LIXAR and
moves LLVM_HAVE_LIBXAR from config.h to llvm-config.h
Also it adds LLVM_HAVE_LIBXAR to LLVMConfig.cmake and links liblldMachO2.so
with XAR_LIB if LLVM_HAVE_LIBXAR is set.
Differential Revision: https://reviews.llvm.org/D102084
That way, it's done only once instead of every time shouldExportSymbol() is
called.
Possibly a bit faster:
% ministat at_main at_symtodo
x at_main
+ at_symtodo
N Min Max Median Avg Stddev
x 30 3.9732189 4.114846 4.024621 4.0304692 0.037022865
+ 30 3.93766 4.0510042 3.9973931 3.991469 0.028472565
Difference at 95.0% confidence
-0.0390002 +/- 0.0170714
-0.967635% +/- 0.423559%
(Student's t, pooled s = 0.0330256)
In other runs with n=30 it makes no perf difference, so maybe it's just noise.
But being able to quickly and conveniently answer "is this symbol exported?"
is useful for fixing PR50373 and for implementing -dead_strip, so this seems
like a good change regardless.
No behavior change.
Differential Revision: https://reviews.llvm.org/D102661
Has the effect that `__mh_execute_header` stays in the symbol table of
outputs even after running `strip` on the output. I don't know if that's
important for anything -- my motivation for the patch is just is to make
the output more similar to ld64.
(Corresponds to symbolTableInAndNeverStrip in ld64.)
Differential Revision: https://reviews.llvm.org/D102619
Extend the range of calls beyond an architecture's limited branch range by first calling a thunk, which loads the far address into a scratch register (x16 on ARM64) and branches through it.
Other ports (COFF, ELF) use multiple passes with successively-refined guesses regarding the expansion of text-space imposed by thunk-space overhead. This MachO algorithm places thunks during MergedOutputSection::finalize() in a single pass using exact thunk-space overheads. Thunks are kept in a separate vector to avoid the overhead of inserting into the `inputs` vector of `MergedOutputSection`.
FIXME:
* arm64-stubs.s test is broken
* add thunk tests
* Handle thunks to DylibSymbol in MergedOutputSection::finalize()
Differential Revision: https://reviews.llvm.org/D100818
We had a hardcoded check and a stale TODO, written back when we only had
support for one architecture.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D102154
In particular, we should apply the `-undefined` behavior to all
such symbols, include those that are specified via the command line
(i.e. `-e`, `-u`, and `-exported_symbol`). ld64 supports this too.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D102143
This would cause us to pull in symbols (and code) that should
be unused.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D102137
Symbols explicitly exported via command-line options `--exported_symbol SYM` and `--exported_symbols_list FILE` must be defined. Before this fix, lazy symbols defined in archives would be left to languish. We now force them to be included in the linked output.
Differential Revision: https://reviews.llvm.org/D102100
We need to account for path rerooting when generating the response
file. We could either reroot the paths before generating the file, or pass
through the original filenames and change just the syslibroot. I've opted for
the latter, in order that the reproduction run more closely mirrors the
original.
We must also be careful *not* to make an absolute path relative if it is
shadowed by a rerooted path. See repro6.tar in reroot-path.s for
details.
I've moved the call to `createResponseFile()` after the initialization of
`config->systemLibraryRoots`, since it now needs to know what those roots are.
Reviewed By: #lld-macho, oontvoo
Differential Revision: https://reviews.llvm.org/D101224
ld64 automatically renames many sections depending on output type and assorted flags. Here, we implement the most common configs. We can add more obscure flags and behaviors as needed.
Depends on D101393
Differential Revision: https://reviews.llvm.org/D101395
@thakis pointed out that `mach_header` and `mach_header_64`
actually have the same set of (used) fields, with the 64-bit version
having extra padding. So we can access the fields we need using the
single `mach_header` type instead of using templates to switch between
the two.
I also spotted a potential issue where hasObjCSection tries to parse a
file w/o checking if it does indeed match the target arch... As such,
I've added a quick magic number check to ensure we don't access invalid
memory during `findCommand()`.
Addresses PR50180.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D101724
This just parses the `-arch armv7` and emits the right header flags.
The rest will be slowly fleshed out in upcoming diffs.
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D101557
Modern versions of macOS (>= 10.7) and in general all modern Mach-O
target archs want PIEs by default. ld64 defaults to PIE for iOS >= 4.3,
as well as for all versions of watchOS and simulators. Basically all the
platforms LLD is likely to target want PIE. So instead of cluttering LLD's
code with legacy version checks, I think it's simpler to just default to
PIE for everything.
Note that `-no_pie` still works, so users can still opt out of it.
Reviewed By: #lld-macho, thakis, MaskRay
Differential Revision: https://reviews.llvm.org/D101513
Add option to limit (or remove limits) on the number of errors printed before exiting. This option exists in the other lld ports: COFF & ELF.
Differential Revision: https://reviews.llvm.org/D101274
This load command records a range spanning from the end of the load
commands to the end of the `__TEXT` segment. Presumably the kernel will encrypt
all this data.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D100973
This diff adds initial support for the legacy LC_VERSION_MIN_* load commands.
Test plan: make check-lld-macho
Differential revision: https://reviews.llvm.org/D100523
This diff creates an empty XAR file and copies it into
`__LLVM,__bundle`. Follow-up work will actually populate the contents of
that XAR.
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D100650
From what I can tell, it's pretty similar to arm64. The two main differences
are:
1. No 64-bit relocations
2. Stub code writes to 32-bit registers instead of 64-bit
Plus of course the various on-disk structures like `segment_command` are using
the 32-bit instead of the 64-bit variants.
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D99822
From what I can tell, it's pretty similar to arm64. The two main differences
are:
1. No 64-bit relocations
2. Stub code writes to 32-bit registers instead of 64-bit
Plus of course the various on-disk structures like `segment_command` are using
the 32-bit instead of the 64-bit variants.
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D99822
Swift builds seem to use it. All it requires is emitting the
corresponding paths as STABS.
Fixes llvm.org/PR49385.
Reviewed By: clayborg
Differential Revision: https://reviews.llvm.org/D100076
The test is loosely based off LLD-ELF's `thinlto.ll`. However, I
found that test questionable because the the -save_temps behavior it
checks for is identical regardless of whether we are running in single-
or multi-threaded mode. I tried writing a test based on `--time-trace`
but couldn't get it to run deterministically... so I've opted to just
skip checking that behavior for now.
Reviewed By: #lld-macho, gkm
Differential Revision: https://reviews.llvm.org/D99356
If either `time-trace-granularity` or `time-trace-file` is specified, then don't make users specify `-time-trace`.
It seems silly that I have to type all three options, eg, `-time-trace -time-trace-file=- -time-trace-granularity=...`.
Differential Revision: https://reviews.llvm.org/D100011
- use "empty()" instead of "size()"
- refactor the re-export code so it doesn't create a new vector every time.
Differential Revision: https://reviews.llvm.org/D100019
We bikeshedded about it here: https://reviews.llvm.org/D98837#inline-931557
I initially suggested SubsectionMapping, but I thought the discussion
landed on doing `std::vector<SubsectionEntry>`. @alexshap went and did
both, but on hindsight I regret adding 3 more characters to an already
long name, and I think SubsectionEntry is descriptive enough...
This diff also renames `subsectionMap` to `subsecMap` for consistency
with other variable names in the codebase.
TextAPI/ELF has moved out into InterfaceStubs, so theres no longer a
need to seperate out TextAPI between formats.
Reviewed By: ributzka, int3, #lld-macho
Differential Revision: https://reviews.llvm.org/D99811
The main challenge was handling the different on-disk structures (e.g.
`mach_header` vs `mach_header_64`). I tried to strike a balance between
sprinkling `target->wordSize == 8` checks everywhere (branchy = slow, and ugly)
and templatizing everything (causes code bloat, also ugly). I think I struck a
decent balance by judicious use of type erasure.
Note that LLD-ELF has a similar architecture, though it seems to use more templating.
Linking chromium_framework takes about the same time before and after this
change:
N Min Max Median Avg Stddev
x 20 4.52 4.67 4.595 4.5945 0.044423204
+ 20 4.5 4.71 4.575 4.582 0.056344803
No difference proven at 95.0% confidence
Reviewed By: #lld-macho, oontvoo
Differential Revision: https://reviews.llvm.org/D99633
This diff addresses FIXME in SyntheticSections.cpp and removes
the dependency of emitEndFunStab on .subsections_via_symbols.
Test plan: make check-lld-macho
Differential revision: https://reviews.llvm.org/D99054
This diff is a preparation for fixing FunStabs (incorrect size calculation).
std::map<uint32_t, InputSection*> (SubsectionMap) is replaced with
a sorted vector + binary search. If .subsections_via_symbols is set
this vector will contain the list of subsections, otherwise,
the offsets will be used for calculating the symbols sizes.
Test plan: make check-all
Differential revision: https://reviews.llvm.org/D98837
Within `lld/macho/`, only `InputFiles.cpp` and `Symbols.h` require the `macho::` namespace qualifier to disambiguate references to `class Symbol`.
Add braces to outer `for` of a 5-level single-line `if`/`for` nest.
Differential Revision: https://reviews.llvm.org/D99555
Summary: We needed to use `Joined` instead of `Flag`. This wasn't caught
because the relevant test that was copied from LLD-ELF was still
invoking LLD-ELF instead of LLD-MachO...
Differential Revision: https://reviews.llvm.org/D99313
Pretty simple code-wise. Also threw in some refactoring:
* Put the functionStartSection under Writer instead of InStruct, since
it doesn't need to be accessed outside of Writer
* Adjusted the test to put all files under the temp dir instead of at
the top-level
* Added some CHECK-LABELs to make it clearer where the function starts
data is
Differential Revision: https://reviews.llvm.org/D99112
I added just enough to allow us to see a top-level breakdown of time taken. This
is the result of loading the time-trace output into `chrome:://tracing`:
ef5e8234f3/tracing.png
Reviewed By: oontvoo
Differential Revision: https://reviews.llvm.org/D99311
This reverts commit 4876ba5b2d.
Third-attemp relanding D98559, new change:
- explicitly cast enum to underlying type to avoid ambiguity (workaround to clang's bug).
This reverts commit 3c21166a94.
The build is broken (clang-8 host compiler):
lld/MachO/DriverUtils.cpp:271:8: error: use of overloaded operator '<<' is ambiguous (with operand types 'llvm::raw_fd_ostream' and 'lld::macho::DependencyTracker::DepOpCode')
os << opcode;
~~ ^ ~~~~~~
This reverts commit 9670d2e4af.
Second attemp to reland D98559. New changes:
- inline functions removed from cpp file.
- updated tests to use CHECK-DAG instead of CHECK-NEXT
- fixed ambiguous "<<" operator by switching `char` to uint8_t
This reverts commit 2554b95db5.
Relanding [lld-macho] Implement -dependency_info (D98559) with changes:
- inline functions removed from cpp file.
- updated tests to not check libSystem.tbd with other input files (because of possible indeterministic ordering)
This reverts commit c53a1322f3.
Test only passes depending on build dir having a lexicographically later name
than the source dir, and doesn't link on mac/win. See
https://reviews.llvm.org/D98559#2640265 onward.
Bug: https://bugs.llvm.org/show_bug.cgi?id=49278
The flag is not well documented, so this implementation is based on observed behaviour.
When specified, `-dependency_info <path>` produced a text file containing information pertaining to the current linkage, such as input files, output file, linker version, etc.
This file's layout is also not documented, but it seems to be a series of null ('\0') terminated strings in the form `<op code><path>`
`<op code>` could be:
`0x00` : linker version
`0x10` : input
`0x11` : files not found(??)
`0x40` : output
`<path>` : is the file path, except for the linker-version case.
(??) This part is a bit unclear. I think it means all the files the linker attempted to look at, but could not find.
Differential Revision: https://reviews.llvm.org/D98559
This fixes defects in D98223 [lld-macho] implement options -(un)exported_symbol(s_list):
* disallow export of hidden symbols
* verify that whitelisted literal names are defined in the symbol table
* reflect export-status overrides in `nlist` attribute of `N_EXT` or `N_PEXT`
Thanks to @thakis for raising these issues
Differential Revision: https://reviews.llvm.org/D98381
Previously, it was difficult to write code that handled both synthetic
and regular sections generically. We solve this problem by creating a
fake InputSection at the start of every SyntheticSection.
This refactor allows us to handle DSOHandle like a regular Defined
symbol (since Defined symbols must be attached to an InputSection), and
paves the way for supporting `__mh_*header` symbols. Additionally, it
simplifies our binding/rebase code.
I did have to extend Defined a little -- it now has a `linkerInternal`
flag, to indicate that `___dso_handle` should not be in the final symbol
table.
I've also added some additional testing for `___dso_handle`.
Reviewed By: #lld-macho, oontvoo
Differential Revision: https://reviews.llvm.org/D98545
Previously, SyntheticSections.cpp did not have a top-level `using namespace
llvm::MachO` because it caused a naming conflict: `llvm::MachO::Symbol` would
collide with `lld::macho::Symbol`.
`MachO::Symbol` represents the symbols defined in InterfaceFiles (TBDs). By
moving the inclusion of InterfaceFile.h into our .cpp files, we can avoid this
name collision in other files where we are only dealing with LLD's own symbols.
Along the way, I removed all unnecessary "MachO::" prefixes in our code.
Cons of this approach: If TextAPI/MachO/Symbol.h gets included via some other
header file in the future, we could run into this collision again.
Alternative 1: Have either TextAPI/MachO or BinaryFormat/MachO.h use a different
namespace. Most of the benefit of `using namespace llvm::MachO` comes from being
able to use things in BinaryFormat/MachO.h conveniently; if TextAPI was under a
different (and fully-qualified) namespace like `llvm::tapi` that would solve our
problems. Cons: lots of files across llvm-project will need to be updated, and
folks who own the TextAPI code need to agree to the name change.
Alternative 2: Rename our Symbol to something like `LldSymbol`. I think this is
ugly.
Personally I think alternative #1 is ideal, but I'm not sure the effort to do it is
worthwhile, this diff's halfway solution seems good enough to me. Thoughts?
Reviewed By: #lld-macho, oontvoo, MaskRay
Differential Revision: https://reviews.llvm.org/D98149
This is the minimal port from ELF. Any extension should easy from here
Test plan: ninja check-all-macho
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D98419
Pointer and reference induction variables of range-based for loops are often const, and code authors often lax about qualifying them.
Differential Revision: https://reviews.llvm.org/D98317
The flag doesn't (and shouldn't) have an effect in that case.
ld64 doesn't warn on this, but it seems like a good thing to do.
If it causes problems in practice for some reason, we can revert it.
Also add a dedicated test for install_name.
Differential Revision: https://reviews.llvm.org/D98259
lld doesn't read MH_DEAD_STRIPPABLE_DYLIB to strip dead dylibs yet,
but now it can produce dylibs with it set.
While here, also switch an existing test that looks only at the main Mach-O
header from --all-headers to --private-header.
Differential Revision: https://reviews.llvm.org/D98262
Top-level `using llvm::opt` has been present in `lld/MachO/Driver*.cpp` for some time, so remove lingering `opt::` prefixes.
Differential Revision: https://reviews.llvm.org/D98314
lld policy discourages `auto`. Replace it with a type name whenever reasonable. Retain `auto` to avoid ...
* redundancy, as for decls such as `auto *t = mumble_cast<TYPE *>` or similar that specifies the result type on the RHS
* verbosity, as for iterators
* gratuitous suffering, as for lambdas
Along the way, add `const` when appropriate.
Note: a future diff will ...
* add more `const` qualifiers
* remove `opt::` when we are already `using llvm::opt`
Differential Revision: https://reviews.llvm.org/D98313
Implement command-line options to alter a dylib's exported-symbols list:
* `-exported_symbol*` options override the default export list. The export list is compiled according to the command-line option(s) only.
* `-unexported_symbol*` options hide otherwise public symbols.
* `-*exported_symbol PATTERN` options specify a single literal or glob pattern.
* `-*exported_symbols_list FILE` options specify a file containing a series of lines containing symbol literals or glob patterns. Whitespace and `#`-prefix comments are stripped.
Note: This is a simple implementation of the primary use case. ld64 has much more complexity surrounding interactions with other options, many of which are obscure and undocumented. We will start simple and complexity as necessary.
Differential Revision: https://reviews.llvm.org/D98223
Previously, lld/mac only ad-hoc codesigned executables on arm64.
Matches ld64 behavior. Part of PR49443. Fixes 14 of 17 failures when running
check-llvm with lld as host linker on an M1 MBP.
Differential Revision: https://reviews.llvm.org/D97994
Previously, we were loading re-exports without checking whether
they were compatible with our target. Prior to {D97209}, it meant that
we were defining dylib symbols that were invalid -- usually a silent
failure unless our binary actually used them. D97209 exposed this as an
explicit error.
Along the way, I've extended our TAPI compatibility check to cover the
platform as well, instead of just checking the arch. To this end, I've
replaced MachO::Architecture with MachO::Target in our Config struct.
Reviewed By: #lld-macho, oontvoo
Differential Revision: https://reviews.llvm.org/D97867
We previously defaulted to x86_64 and an unknown platform, which was fine when
we only supported one arch and did no platform checks, but that will no longer
be true going ahead. Therefore, we should require those flags to be specified
whenever the linker is invoked.
Note that LLD-ELF and ld64 both infer the arch from their input object files,
but the usefulness of that is questionable since clang will always specify these
flags, and most of the time `lld` will be invoked via clang.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D97799
The option-iterating loop should be reserved for options whose command-line
order is important. I think LLD-ELF follows a similar design.
Reviewed By: #lld-macho, smeenai
Differential Revision: https://reviews.llvm.org/D97797
This reverts diff D97610 (commit 0223ab035c) and adds a one-line fix to verify that a `MemoryBufferRef` has sufficient length before reading a 4-byte magic number.
Differential Revision: https://reviews.llvm.org/D97757
-flat_namespace makes lld emit binaries that use name lookup that's more in
line with other POSIX systems: Instead of looking up symbols as (dylib,name)
pairs by dyld, they're instead looked up just by name.
-flat_namespace has three effects:
1. MH_TWOLEVEL and MH_NNOUNDEFS are no longer set in the Mach-O header
2. All symbols use BIND_SPECIAL_DYLIB_FLAT_LOOKUP as ordinal
3. When a dylib is added to the link, its dependent dylibs are also added,
so that lld can verify that no undefined symbols remain at the end of
a link with -flat_namespace. These transitive dylibs are added for symbol
resolution, but they are not emitted in LC_LOAD_COMMANDs.
-undefined with -flat_namespace still isn't implemented. Before this change,
it was impossible to hit that combination because -flat_namespace caused a
diagnostic. Now that it no longer does, emit a dedicated temporary diagnostic
when both flags are used.
Differential Revision: https://reviews.llvm.org/D97641
Matches the ELF and COFF ports, which use ld.lld and lld-link, respectively.
While here, also move up `cleanupCallback` to match ELF / COFF.
Differential Revision: https://reviews.llvm.org/D97715
Bifurcate the `readFile()` API into ...
* `readRawFile()` which performs no checks, and
* `readLinkableFile()` which enforces minimum length of 20 bytes, same as ld64
There are no new tests because tweaks to existing tests are sufficient.
Differential Revision: https://reviews.llvm.org/D97610
Dynamic lookup symbols are symbols that work like dynamic symbols
in ELF: They're not bound to a dylib like normal Mach-O twolevel lookup
symbols, but they live in a global pool and dyld resolves them against
exported symbols from all loaded dylibs.
This adds support for dynamical lookup symbols to lld/mac. They are
represented as DylibSymbols with file set to nullptr.
This also uses this support to implement the -U flag, which makes
a specific symbol that's undefined at the end of the link a
dynamic lookup symbol.
For -U, it'd be sufficient to just to a pass over remaining undefined symbols
at the end of the link and to replace them with dynamic lookup symbols then.
But I'd like to use this code to implement flat_namespace too, and that will
require real support for resolving dynamic lookup symbols in SymbolTable. So
this patch adds this now already.
While writing tests for this, I noticed that we didn't set N_WEAK_DEF in the
symbol table for DylibSymbols, so this fixes that too.
Differential Revision: https://reviews.llvm.org/D97521
See discussion on https://reviews.llvm.org/D93263
-flat_namespace isn't implemented yet, and neither is -undefined dynamic,
so this makes -undefined pretty pointless in lld/MachO for now. But once
we implement -flat_namespace (which we need to do anyways to get check-llvm
to pass with lld as host linker), the code's already there.
Follow-up to https://reviews.llvm.org/D93263#2491865
Differential Revision: https://reviews.llvm.org/D96963
Differential Revision: https://reviews.llvm.org/D95913
Usage: -bundle_loader <executable>
This option specifies the executable that will load the build output file being linked.
When building a bundle, users can use the --bundle_loader to specify an executable
that contains symbols referenced, but not implemented in the bundle.
Since we emit diagnostics for undefineds in Writer::scanRelocations()
and symbols referenced by -u flags aren't referenced by any relocations,
this needs some manual code (similar to the entry point).
Differential Revision: https://reviews.llvm.org/D94371
This is an initial base commit for ARM64 target arch support. I don't represent that it complete or bug-free, but wish to put it out for review now that some basic things like branch target & load/store address relocs are working.
I can add more tests to this base commit, or add them in follow-up commits.
It is not entirely clear whether I use the "ARM64" (Apple) or "AArch64" (non-Apple) naming convention. Guidance is appreciated.
Differential Revision: https://reviews.llvm.org/D88629
This extends {D92539} to work even when we are loading archive
members via `-force_load`. I uncovered this issue while trying to
force-load archives containing bitcode -- we were segfaulting.
In addition to fixing the `-force_load` case, this diff also addresses
the behavior of `-ObjC` when LTO bitcode is involved -- we need to
force-load those archive members if they contain ObjC categories.
Reviewed By: #lld-macho, smeenai
Differential Revision: https://reviews.llvm.org/D95265
This makes our error messages more informative. But the bigger motivation is for
LTO symbol resolution, which will be in an upcoming diff. The changes in this
one are largely mechanical.
Reviewed By: #lld-macho, smeenai
Differential Revision: https://reviews.llvm.org/D94316
Add per-reloc-type attribute bits and migrate code from per-target file into target independent code, driven by reloc attributes.
Many cleanups
Differential Revision: https://reviews.llvm.org/D95121
Run the ObjCARCContractPass during LTO. The legacy LTO backend (under
LTO/ThinLTOCodeGenerator.cpp) already does this; this diff just adds that
behavior to the new LTO backend. Without that pass, the objc.clang.arc.use
intrinsic will get passed to the instruction selector, which doesn't know how to
handle it.
In order to test both the new and old pass managers, I've also added support for
the `--[no-]lto-legacy-pass-manager` flags.
P.S. Not sure if the ordering of the pass within the pipeline matters...
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D94547
We didn't have support for parsing DriverKit in our `-platform`
flag, so add that too. Also remove a bunch of unnecessary namespace
prefixes.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D93741
It's an extension to ld64, but all the other ports have it, and
someone asked for it in PR43721.
While here, change the COFF help text to match the other ports.
Differential Revision: https://reviews.llvm.org/D93491
Jez Ng
