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
Nico Weber