https://maskray.me/blog/2022-01-16-archives-and-start-lib
For every definition in an extracted archive member, we intern the symbol twice,
once for the archive index entry, once for the .o symbol table after extraction.
This is inefficient.
Symbols in a --start-lib ObjFile/BitcodeFile are only interned once because the
result is cached in symbols[i].
Just handle an archive using the --start-lib code path. We can therefore remove
ArchiveFile and LazyArchive. For many projects, archive member extraction ratio
is high and it is a net performance win. Linking a Release build of clang is
1.01x as fast.
Note: --start-lib scans symbols in the same order that llvm-ar adds them to the
index, so in the common case the semantics should be identical. If the archive
symbol table was created in a different order, or is incomplete, this strategy
may have different semantics. Such cases are considered user error.
The `is neither ET_REL nor LLVM bitcode` error is changed to a warning.
Previously an archive may have such members without a diagnostic. Using a
warning prevents breakage.
* For some tests, the diagnostics get improved where we did not consider
the archive member name: `b.a:` => `b.a(b.o):`.
* `no-obj.s`: the link is now allowed, matching GNU ld
* `archive-no-index.s`: the `is neither ET_REL nor LLVM bitcode` diagnostic is
demoted to a warning.
* `incompatible.s`: even when an archive is unextracted, we may report an
"incompatible with" error.
---
I recently decreased sizeof(SymbolUnion) by 8 and decreased memory usage quite a
bit, so retaining `symbols` for un-extracted archive members should not cause a
memory usage problem.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D119074
These global TLS symbols are shared across all shared libraries and
therefor should not be assumed to be local to the current module.
Also add new error in the linker when TLS relocations are used against
undefined symbols. TLS relocations are offsets into the current modules
tls data segment, and don't make sense for undefined symbols which are
modeled as global imports.
Fixes: https://github.com/emscripten-core/emscripten/issues/13398
Differential Revision: https://reviews.llvm.org/D119630
By unsetting this property, we are now able to internalize more symbols
during LTO. I compared the output of `-save-temps` for both LLD and
ld64, and we now match ld64's behavior as far as `lto-internalize.ll` is
concerned.
(Thanks @smeenai for working on an initial version of this diff!)
Fixes https://github.com/llvm/llvm-project/issues/50574.
Reviewed By: #lld-macho, thakis
Differential Revision: https://reviews.llvm.org/D119372
Makes lld-link work in a non-MSVC shell by autodetecting MSVC toolchain. Also
adds support for /winsysroot and a few other switches.
All this is done by refactoring to share code with clang-cl's existing support
for the same.
Differential Revision: https://reviews.llvm.org/D118070
... to use hyphens instead of underscores, making it consistent with
our other substitutions like %no-arg-lld and %lld-watchos.
Reviewed By: keith
Differential Revision: https://reviews.llvm.org/D119513
We have a mix of substituted lld (`%lld`) and hard-coded lld (`ld64.lld`) commands.
When testing with different versions of LLD, this would require going into every place
where lld is hard-coded and changing that. If we centralize it, this'll only require us
to modify it in only one place and will make it easy to run the same test suite. Plus,
this will make it be consistent with how we write other tests.
Reviewed By: #lld-macho, int3, oontvoo
Differential Revision: https://reviews.llvm.org/D119394
https://maskray.me/blog/2022-02-06-all-about-common-symbols#no-define-common
In GNU ld, -dc only affects -r links and causes COMMON symbols to be allocated.
--no-define-common is defined to make COMMON symbols undefined for -shared.
AIUI --no-define-common is a workaround around glibc 2.1 time and not really useful.
gold confuses --define-common with -d/FORCE_COMMON_ALLOCATION and implements
--define-common with -d semantics. Its --no-define-common is incompatible with
GNU ld.
In ld.lld, b2a23cf3c0 fixed the default -r
behavior for COMMON symbols but ported the incompatible gold
--[no-]define-common. To the best of my knowledge, no project uses -dp
--[no-]define-common. So just remove these options.
-d/-dc are used by the following projects:
* grub grub-core/genmod.sh.in uses -Wl,-r,-d (https://lists.gnu.org/archive/html/grub-devel/2022-02/msg00088.html)
* FreeBSD crunchgen uses -Wl,-dc (https://reviews.freebsd.org/D34215)
A no-op implementation works for them. Only when a program inspects relocatable
output by itself and does not recognize COMMON symbols, there may be a problem.
This is an extremely unlikely case.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D119108
This fixes the issue raised in https://reviews.llvm.org/D108850#3303452
Before C++17, the function object is evaluated in a unspecified order. In the following example: https://godbolt.org/z/8ao4vdsr7 the function object is either evaluated before or after the arguments, depending on the compiler. With MSVC and /std:c++14 the function object is evaluated after the arguments; with clang and gcc, it is evaluated before. With C++17, the function object is guaranteed to be evaluated before the arguments, see: https://riptutorial.com/cplusplus/example/19369/evaluation-order-of-function-arguments
In our case, the issue was that the `args` conversion to `ArrayRef` was evaluated before the lambda call `link`, which internally was calling `parseFlavor()`, which in turned modified `args`. We ended with an `ArrayRef` argument that reflected the previous contents of `args`.
Add coverage for `-flavor` which we didn't have before.
Differential Revision: https://reviews.llvm.org/D119278
This makes it easier to pinpoint the source of the problem.
TODO: Have more relocation error messages make use of this
functionality.
Reviewed By: #lld-macho, oontvoo
Differential Revision: https://reviews.llvm.org/D118798
to decrease sizeof(SymbolUnion) from 72 to 64 on ELF64 platforms.
Use a dummy `Undefined` to prevent null pointer dereference (though unused)
`*rel.sym` in InputSectionBase::relocateAlloc.
The relocation order may shuffle a bit, but otherwise there is no behavior
difference.
Adds `-pagezero_size`. `-pagezero_size` commonly used for kernel development.
`-pagezero_size` changes the `__PAGEZERO` size, removing that segment if it is set to zero.
One of the four flags from {D118570}
Now with error messages and tests.
Differential Revision: https://reviews.llvm.org/D118724
For -no-pie/-pie, when `__real_foo` is interposable in a shared object, `foo` is
exported. This rule does not match GNU ld and is unneeded because:
* the exported `foo` does not interpose `__real_foo` at run-time
* the similar `__wrap_foo` <-> `foo` relation does not have the rule
A STV_PROTECTED shared definition does not set exportDynamic of a defined
symbol. This is on the basis that a protected definition cannot be preempted so
the export is unnecessary. However, the condition is imperfect because we don't
know whether the shared object was built with a symbolic option. Since dropping
the condition simplifies code and matches GNU ld, let's do it.
There's a couple of motivations here:
* LLD 12 (which I was originally testing with) was adding an undefined
symbol to the symbol table if you attempted to wrap an unreferenced
lazy symbol, which would later break `--no-allow-shlib-undefined`. LLD
on main actually produces a weak undefined symbol, so this doesn't
break anyway, but it's cleaner to not have the weak undefined symbol
as well. The new behavior also matches bfd and gold.
* PROVIDE in a linker script referencing a wrapped symbol would think
that an otherwise-unreferenced lazy symbol which was wrapped was
actually referenced, and therefore proceed with the definition, which
goes against expectations. The new behavior also matches bfd and gold.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D118756
-fprofile-use=/-fprofile-sample-use= compiles may produce REL-format
.rel.llvm.call-graph-profile even if the prevailing format is RELA on AArch64.
Add R_AARCH64_NONE to getImplicitAddend to fix this linker error:
```
ld.lld: error: internal linker error: cannot read addend for relocation R_AARCH64_NONE
PLEASE submit a bug report to https://crbug.com and run tools/clang/scripts/process_crashreports.py (only works inside Google) which will upload a report and include the crash backtrace.
```
In the case your framework bundles contain relocatable objects, and your
objects include LC_LINKER_OPTIONs for the framework, previously they
would not be deduplicated like they would have if they were static
archives. This was also the case if you passed `-framework` for the
framework as well.
Reviewed By: #lld-macho, thakis, oontvoo
Differential Revision: https://reviews.llvm.org/D114841
This diff adds support for ADRP+ADD optimization for AArch64 described in
d2ca58c54b
i.e. under appropriate constraints
ADRP x0, symbol
ADD x0, x0, :lo12: symbol
can be turned into
NOP
ADR x0, symbol
Test plan: make check-all
Differential revision: https://reviews.llvm.org/D117614
See the updated insert-before.test for the effects: many synthetic
sections are SHF_ALLOC|SHF_WRITE. If they are discarded, we don't want
to propagate their flags to subsequent output section descriptions.
`getFirstInputSection(sec) == nullptr` can technically be merged into
`isDiscardable` but I'd like to postpone that as not sharing code may give more
refactoring opportunity.
Depends on D118529.
Reviewed By: peter.smith, bluca
Differential Revision: https://reviews.llvm.org/D118530
adjustSectionsBeforeSorting updates some output section attributes
(alignment/flags) and removes discardable empty sections. When it is called,
INSERT commands have not been processed. Therefore the flags propagation rule
may not affect output sections defined in an INSERT command properly.
Fix this by moving processInsertCommands before adjustSectionsBeforeSorting.
adjustSectionsBeforeSorting is somewhat misnamed. The order between it and
sortInputSections does not matter. With the pass shuffle, the name of
adjustSectionsBeforeSorting becomes wrong. Therefore rename it. The new
name is not set into stone. The function mixes several tasks and the
code may be refactored in a way that we may give them more meaningful
names.
With this patch, I think the behavior of attribute propagation becomes more
reasonable. In particular, in the absence of non-INSERT SECTIONS,
inserting a section after a SHF_ALLOC one will give us a SHF_ALLOC section,
not a non-SHF_ALLOC one (see linkerscript/insert-after.test).
Reviewed By: peter.smith, bluca
Differential Revision: https://reviews.llvm.org/D118529
The deduplication requires a DenseMap of the same size of the local part of
.strtab . I optimized it in e205445434 but it is
still quite slow.
For Release build of clang, deduplication makes .strtab 1.1% smaller and makes the link 3% slower.
For chrome, deduplication makes .strtab 0.1% smaller and makes the link 6% slower.
I suggest that we only perform the optimization with -O2 (default is -O1).
Not deduplicating local symbol names will simplify parallel symbol table write.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D118577
This is a ld64 option equivalent to `-sectcreate seg sect /dev/null`
that's useful for creating sections like the RESTRICT section.
Differential Revision: https://reviews.llvm.org/D117749
Previously functions that aren't included in the symtab were also
excluded from the function starts. Symbols missing from function starts
degrades the debugger experience in the case you don't have debug info
for them.
Differential Revision: https://reviews.llvm.org/D114275
* `RelocationBaseSection::addReloc` increases `numRelativeRelocs`, which
duplicates the work done by RelocationSection<ELFT>::writeTo.
* --pack-dyn-relocs=android has inappropropriate DT_RELACOUNT.
AndroidPackedRelocationSection does not necessarily place relative relocations
in the front and DT_RELACOUNT might cause semantics error (though our
implementation doesn't and Android bionic doesn't use DT_RELACOUNT anyway.)
Move `llvm::partition` to a new function `partitionRels` and compute
`numRelativeRelocs` there. Now `RelocationBaseSection::addReloc` is trivial and
can be moved to the header to enable inlining.
The rest of DynamicReloc and `-z combreloc` handling is moved to the
non-template `RelocationBaseSection::computeRels` to decrease code size. My
x86-64 lld executable is 44+KiB smaller.
While here, rename `sort` to `combreloc`.
When processing dependent libraries, if there's a directory of the same
name as the library being searched for, either in the current directory
or earlier in the search order, LLD will try to open it and report an
error. This is because LLD uses file existence check. To address this
issue we reverse the order, searching the library by basename first
and only considering search paths later, and current directory last.
Differential Revision: https://reviews.llvm.org/D118498
Close#52781: for LTO, the inline asm diagnostic uses `<inline asm>` as the file
name (lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp) and it is unclear which
module has the issue.
With this patch, we will see the module name (say `asm.o`) before `<inline asm>` with ThinLTO.
```
% clang -flto=thin -c asm.c && myld.lld asm.o -e f
ld.lld: error: asm.o <inline asm>:1:2: invalid instruction mnemonic 'invalid'
invalid
^~~~~~~
```
For regular LTO, unfortunately the original module name is lost and we only get
ld-temp.o.
Reviewed By: #lld-macho, ychen, Jez Ng
Differential Revision: https://reviews.llvm.org/D118434
In older versions of llvm (e.g. llvm 13), symbols were not individually
flagged as TLS. In this case, the indent was to implicitly mark any
symbols defined in TLS segments as TLS. However, we were not performing
this implicit conversion if the segment was explicitly marked as TLS
As it happens, llvm 13 was branched between the addition of the segment
flag and the addition of the symbol flag. See:
- segment flag added: https://reviews.llvm.org/D102202
- symbol flag added: https://reviews.llvm.org/D109426
Testing this is tricky because the assembler will imply the TLS status
of the symbol based on the segment its declared in, so we are forced to
use a yaml file here.
Fixes: https://github.com/emscripten-core/emscripten/issues/15891
Differential Revision: https://reviews.llvm.org/D118414
In start-end.s there is a lit check line `# SEG: _main` to begin the
check at the start of the function main where `_main` is the Darwin name
mangling for C main. Because the text file that FileCheck is getting as
input has the path of the compiler build in it from llvm-mc and
llvm-objdump, and because of the lack of a trailing colon in this check
line we end up inadvertently matching against the line of text with the
compiler path in it in the case where said path contains "_main" some
place. This can be very likely if the compiler branch has "main" or
"_main" in it.
To fix this I include the training : since that will match on the
function label and not the path line.
Notation: dst is `t->getThunkTargetSym()->getVA()`
On AArch64, when `src-0x8000000-r_addend <= dst < src-0x8000000`, the condition
`target->inBranchRange(rel.type, src, rel.sym->getVA(rel.addend))` may
incorrectly consider a thunk reusable.
`rel.addend = -getPCBias(rel.type)` resets the addend to 0 for AArch64/PPC
and the zero addend is used by `rel.sym->getVA(rel.addend)` to check
out-of-range relocations.
See the test for a case this computation is wrong:
`error: a.o:(.text_high+0x4): relocation R_AARCH64_JUMP26 out of range: -134217732 is not in [-134217728, 134217727]`
I have seen a real world case with r_addend=19960.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D117734
D54759 introduced aarch64-combined-dynrel.s and
aarch64-combined-dynrel-ifunc.s . Unfortunately the requires line
at the top was AArch64 instead of aarch64 which means they were never
run. Update the tests to use aarch64 and fix to match current lld output.
Differential Revision: https://reviews.llvm.org/D117896
Fangrui Song