Reland 994cea3f0a2d0caf4d66321ad5a06ab330144d89 after bolt tests no
longer rely on -pie --unresolved-symbols=ignore-all with no input DSO
generating PLT entries.
---
Commit f10441ad003236ef3b9e5415a571d2be0c0ce5ce , while dropping a
special case for isUndefWeak and --no-dynamic-linking, made
--export-dynamic ineffective when -pie is used without any input DSO.
This change restores --export-dynamic and unifies -pie and -pie
--no-dynamic-linker when there is no input DSO.
* -pie with no input DSO suppresses undefined symbols in .dynsym.
Previously this only appied to -pie --no-dynamic-linker.
* As a side effect, -pie with no input DSO suppresses PLT.
LLVM has started to emit AArch64 build attributes sections called
.ARM.attributes. LLD does not yet have support for these so they are
accumulating in the ELF output. As the first part of that support
discard all the .ARM.attributes sections. This can be built upon by the
full implementation in LLD.
The build attributes specification only defines build attributes for
relocatable objects. The intention for LLD is that files of type ET_EXEC
and ET_SHARED will not have a build attributes in the output. A
relocatable link with -r will need a merged build attributes, but until
the merge is implemented it is better to discard.
Reland #120514 after 2f6e3df08a8b7cd29273980e47310cf09c6fdbd8 fixed
iteration order issue and libstdc++/libc++ differences.
---
Both options instruct the linker to optimize section layout with the
following goals:
* `--bp-compression-sort=[data|function|both]`: Improve Lempel-Ziv
compression by grouping similar sections together, resulting in a
smaller compressed app size.
* `--bp-startup-sort=function --irpgo-profile=<file>`: Utilize a
temporal profile file to reduce page faults during program startup.
The linker determines the section order by considering three groups:
* Function sections ordered according to the temporal profile
(`--irpgo-profile=`), prioritizing early-accessed and frequently
accessed functions.
* Function sections. Sections containing similar functions are placed
together, maximizing compression opportunities.
* Data sections. Similar data sections are placed together.
Within each group, the sections are ordered using the Balanced
Partitioning algorithm.
The linker constructs a bipartite graph with two sets of vertices:
sections and utility vertices.
* For profile-guided function sections:
+ The number of utility vertices is determined by the symbol order
within the profile file.
+ If `--bp-compression-sort-startup-functions` is specified, extra
utility vertices are allocated to prioritize nearby function similarity.
* For sections ordered for compression: Utility vertices are determined
by analyzing k-mers of the section content and relocations.
The call graph profile is disabled during this optimization.
When `--symbol-ordering-file=` is specified, sections described in that
file are placed earlier.
Co-authored-by: Pengying Xu <xpy66swsry@gmail.com>
The ELF/bp-section-orderer.s test is failing on some buildbots due to
what seems like non-determinism issues, see comments on the original PR
and #125450
Reverting to green the build.
This reverts commit 0154dce8d39d2688b09f4e073fe601099a399365 and
follow-up commits 046dd4b28b9c1a75a96cf63465021ffa9fe1a979 and
c92f20416e6dbbde9790067b80e75ef1ef5d0fa4.
Add new ELF linker options for profile-guided section ordering
optimizations:
- `--irpgo-profile=<file>`: Read IRPGO profile data for use with startup
and compression optimizations
- `--bp-startup-sort={none,function}`: Order sections based on profile
data to improve star tup time
- `--bp-compression-sort={none,function,data,both}`: Order sections
using balanced partitioning to improve compressed size
- `--bp-compression-sort-startup-functions`: Additionally optimize
startup functions for compression
- `--verbose-bp-section-orderer`: Print statistics about balanced
partitioning section ordering
Thanks to the @ellishg, @thevinster, and their team's work.
---------
Co-authored-by: Fangrui Song <i@maskray.me>
Commit f10441ad003236ef3b9e5415a571d2be0c0ce5ce dropped a special case
for isUndefWeak and --no-dynamic-linking but also made --export-dynamic
ineffective for static PIE.
This change restores the --export-dynamic behavior and entirely drops
special handling of --no-dynamic-linker:
* -pie with no input DSO, similar to --no-dynamic-linker, suppresses
undefined symbols in .dynsym
The new behaviors resemble GNU ld more.
Commit 3733ed6f1c6b0eef1e13e175ac81ad309fc0b080 introduced isExported to
cache includeInDynsym. If we don't unnecessarily set isExported for
undefined symbols, exportDynamic/includeInDynsym can be replaced with
isExported.
Similar to the change to MarkLive.cpp when isExported was introduced.
includeInDynsym might return true even when isExported is false for
statically linked executables.
Commit 2a26292388fcab0c857c91b2d08074c33abd37e8 made `isExported`
accurate except a few linker-synthesized symbols in finalizeSections.
We can collect these linker-synthesized symbols into a vector
and avoid recomputation for other symbols.
This is reland of 1a4d6de1b532149b10522eae5dabce39e5f7c687 after
`isExported` has been made accurate by f10441ad003236ef3b9e5415a571d2be0c0ce5ce
`includeInDynsym` has a special case for isUndefWeak and
--no-dynamic-linker, which can be removed if we simplify disallow
dynamic symbols for static-pie.
The partition feature reports errors only when a symbol `isExported`.
We need to link in a DSO to trigger the mips error.
This reverts commit 048f35037779763963c4b4478a0884e828ea9538.
This reverts commit f7bbc40b0736cc417f57cd039b098b504cf6a71f.
Related to #95949. A developer with no prior lld contribution and very
little AMD contribution sneaked in these application-specific section
order rules we discourage.
Commit 2a26292388fcab0c857c91b2d08074c33abd37e8 made `isExported`
accurate except a few linker-synthesized symbols in finalizeSections.
We can collect these linker-synthesized symbols into a vector
and avoid recomputation for other symbols.
LTO compilation might define symbols not in the symbol table (e.g.
__emutls_v.x in test/ELF/lto/wrap-unreferenced-before-codegen.test).
These symbols have a false `isExported` until
`demoteSymbolsAndComputeIsPreemptible`. This is usually benign as we do
not reference `isExported` that early.
Ensure that `isExported` is correct early. This helps remove a redundant
`isExported` computation in `demoteSymbolsAndComputeIsPreemptible`.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change the Fatal to
ErrAlways (not-recoverable) as subsequent code assumes SHF_LINK_ORDER
sh_link is correct.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change a few Fatal to
recoverable Err.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change a few Fatal to
recoverable Err.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1. Change a few Fatal to
recoverable Err.
These diagnostics are mostly reported by a thread during writeSections.
In LLD_IN_TEST=2 mode, when a thread calls Fatal, there will be no
output even if the process exits with code 1.
.note.GNU-stack with the SHF_EXECINSTR flag requires an executable
stack. This is exceedingly rare. We report an error to force
the user to explicitly request an executable stack.
Close#121234
Pull Request: https://github.com/llvm/llvm-project/pull/124068
Depends on #120010
Support `R_AARCH64_AUTH_TLSDESC_ADR_PAGE21`, `R_AARCH64_AUTH_TLSDESC_LD64_LO12`
and `R_AARCH64_AUTH_TLSDESC_LD64_LO12` static relocations and
`R_AARCH64_AUTH_TLSDESC` dynamic relocation. IE/LE optimization is not
currently supported for AUTH TLSDESC.
According to the binutils spec:
https://sourceware.org/binutils/docs/ld/Input-Section-Basics.html
You should be able to specify all files in an archive using this syntax
`archivename:` , however, lld currently will only accept `archivename:*`
to match all files within an archive.
This patch will, only when necessary, create a copy of the file
specification and add an implicit wildcard `*` to the end. It also
updates the filename-spec linkerscript test to check for this behavior.
---------
Co-authored-by: Peter Smith <peter.smith@arm.com>
Port https://reviews.llvm.org/D117354 from the MachO port.
If both --symbol-ordering-file and call graph profile are present, the
--symbol-ordering-file takes precedence, but the call graph profile is
still used for symbols that don't appear in the order file.
In addition, call graph profile described sections are now ordered
before other sections.
cg_profile in object is from CGProfilePass and it is often inaccurate.
While call-graph-ordering-file is provided by user. It is weird to
aggregate them together especially when call-graph-ordering-file is
accurate enough.
`InputSectionBase::relsOrRelas` make at most one array-ref non-empty. One-off counter (as debugging log) shows the number of empty member containers is 2 or 3 in a real build.
Fix the typo.
Depends on #114525
Support `R_AARCH64_AUTH_GOT_ADR_PREL_LO21` and `R_AARCH64_AUTH_GOT_LD_PREL19`
GOT-generating relocations. A corresponding `RE_AARCH64_AUTH_GOT_PC` member
of `RelExpr` is added, which is an AUTH-specific variant of `R_GOT_PC`.
Depends on #113811
Support `R_AARCH64_AUTH_ADR_GOT_PAGE`, `R_AARCH64_AUTH_GOT_LO12_NC` and
`R_AARCH64_AUTH_GOT_ADD_LO12_NC` GOT-generating relocations. For preemptible
symbols, dynamic relocation `R_AARCH64_AUTH_GLOB_DAT` is emitted. Otherwise,
we unconditionally emit `R_AARCH64_AUTH_RELATIVE` dynamic relocation since
pointers in signed GOT needs to be signed during dynamic link time.
Apologies for the large change, I looked for ways to break this up and
all of the ones I saw added real complexity. This change focuses on the
option's prefixed names and the array of prefixes. These are present in
every option and the dominant source of dynamic relocations for PIE or
PIC users of LLVM and Clang tooling. In some cases, 100s or 1000s of
them for the Clang driver which has a huge number of options.
This PR addresses this by building a string table and a prefixes table
that can be referenced with indices rather than pointers that require
dynamic relocations. This removes almost 7k dynmaic relocations from the
`clang` binary, roughly 8% of the remaining dynmaic relocations outside
of vtables. For busy-boxing use cases where many different option tables
are linked into the same binary, the savings add up a bit more.
The string table is a straightforward mechanism, but the prefixes
required some subtlety. They are encoded in a Pascal-string fashion with
a size followed by a sequence of offsets. This works relatively well for
the small realistic prefixes arrays in use.
Lots of code has to change in order to land this though: both all the
option library code has to be updated to use the string table and
prefixes table, and all the users of the options library have to be
updated to correctly instantiate the objects.
Some follow-up patches in the works to provide an abstraction for this
style of code, and to start using the same technique for some of the
other strings here now that the infrastructure is in place.
A linkonce_odr definition can be omitted in LTO compilation if
`canBeOmittedFromSymbolTable()` is true in all bitcode files.
Currently, we don't respect the `canBeOmittedFromSymbolTable()` bit from
symbols in a non-prevailing COMDAT, which could lead to incorrect
omission of a definition when merging a prevailing linkonce_odr and a
non-prevailing weak_odr, e.g. an implicit template instantiation and an
explicit template instantiation.
To fix#111341, allow the non-prevailing COMDAT code path to clear the
`ltoCanOmit` bit, so that `VisibleToRegularObj` could be false in
LTO.cpp. We could resolve either an Undefined or a Defined. For
simplicity, just use a Defined like the prevailing case (similar to how
we resolve symbols in ObjectFile COMDAT reviews.llvm.org/D120626).
Pull Request: https://github.com/llvm/llvm-project/pull/119332
Section merging can increase section alignment after potential spill
sections are created. Since this operation is never performed on spill
sections, they can keep their earlier, smaller, alignment, which
produces a misalignment if a spill occurs.
This change propagates alignment increases forward after merging.
Thumb short thunks use the B.w instruction. This instruction is not
present on Arm v6-m so we should prevent these targets from using
short-thunks. We want to permit Arm v8-m.base targets to continue using
short thunks as it does have the B.w instruction despite not
implementing all of Thumb 2.
Add a check to see if the Movt and Movw instructions are present before
enabling short thunks for Thumb. The v6-m architecture has
J1J2BranchEncoding, but it does not have Movt and Movw, whereas
v8-m.base has both.
The memory map and limited flash size of an Arm v6-m CPU makes a short
thunk very unlikely in practice, but it is worth getting it right just
in case.
isExported, intended to replace exportDynamic, is primarily set in two
locations, (a) after parseSymbolVersion and (b) during demoteSymbols.
In the future, we should try removing exportDynamic. Currently,
merging exportDynamic/isExported would cause
riscv-gp.s to fail:
* The first isExported computation considers the undefined symbol exported
* Defined as a linker-synthesized symbol
* isExported remains true, while it should be false
