Heap profiling with ETW shows that LLD performs 4,053,721 heap
allocations over its lifetime, and ~800,000 of them come from
assocEquals. These vectors are created just to do a comparison, so fuse
the comparison into the loop and avoid the allocation.
ICF is overall a small portion of the time spent linking, and I did not
measure overall throughput improvements from this change above the noise
threshold. However, these show up in the heap profiler, and the work is
done, so we might as well land it if the code is clear enough.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D79297
Sections with the SHF_LINK_ORDER flag must be ordered in the same relative
order as the Sections they have a link to. When using a linker script an
arbitrary expression may be used for the virtual address of the
OutputSection. In some cases the virtual address does not monotonically
increase as the OutputSection index increases, so if we base the ordering
of the SHF_LINK_ORDER sections on the index then we can get the order
wrong. We fix this by moving SHF_LINK_ORDER resolution till after we have
created OutputSection virtual addresses.
Differential Revision: https://reviews.llvm.org/D79286
This particular overload allocates memory, and we do this for every
S_[GL]PROC32_ID record. Instead, hardcode the offset of the typeindex
that we are looking for in the LF_[MEM]FUNC_ID record. We already
assumed that looking up the item index already found a record of this
kind.
Otherwise an ArgumentParser is constructed for every directive section,
and that involves copying the entire table of options into a vector.
There is no need for this, just have one option table.
Summary:
Lld test ELF/linkerscript/thunk-gen-mips.s was accidentally disabled due
to the use of wrong FileCheck directives. As a result the test seems to
have bitrotted as it fails to pass if fixing the directive. To ease
updates to the test in case of change of the __start address the checks
have been changed to use numeric variables to express all the addresses
based on the __start address.
Reviewed By: atanasyan
Differential Revision: https://reviews.llvm.org/D79270
This generalizes the main Windows command line tokenizer to be able to
produce StringRef substrings as well as freshly copied C strings. The
implementation is still shared with the normal tokenizer, which is
important, because we have unit tests for that.
.drective sections can be very long. They can potentially list up to
every symbol in the object file by name. It is worth avoiding these
string copies.
This saves a lot of memory when linking chrome.dll with PGO
instrumentation:
BEFORE AFTER % IMP
peak memory: 6657.76MB 4983.54MB -25%
real: 4m30.875s 2m26.250s -46%
The time improvement may not be real, my machine was noisy while running
this, but that the peak memory usage improvement should be real.
This change may also help apps that heavily use dllexport annotations,
because those also use linker directives in object files. Apps that do
not use many directives are unlikely to be affected.
Reviewed By: thakis
Differential Revision: https://reviews.llvm.org/D79262
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
This change add support for defined wasm globals in the .s format,
the MC layer, and wasm-ld
Currently there is no support custom initialization and all wasm
globals are initialized to zero.
Fixes: PR45742
Differential Revision: https://reviews.llvm.org/D79137
Lld test ELF/linkerscript/input-archive.s fails when path contain a @
because is not accepted in unquoted token in linker scripts which leads
to the path being broken in 2 around the @. This commit quotes the path
used in the linker script created by this and similar testcases allowing
the test to pass even in the presence of an @ sign in the path.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D79103
The current implementation assumes that R_PPC64_TOC16_HA is always followed
by R_PPC64_TOC16_LO_DS. This can break with R_PPC64_TOC16_LO:
// Load the address of the TOC entry, instead of the value stored at that address
addis 3, 2, .LC0@tloc@ha # R_PPC64_TOC16_HA
addi 3, 3, .LC0@tloc@l # R_PPC64_TOC16_LO
blr
which is used by boringssl's util/fipstools/delocate/delocate.go
https://github.com/google/boringssl/blob/master/crypto/fipsmodule/FIPS.md has some documentation.
In short, this tool converts an assembly file to avoid any potential relocations.
The distance to an input .toc is not a constant after linking, so it cannot use an `addis;ld` pair.
Instead, it jumps to a stub which loads the TOC entry address with `addis;addi`.
This patch checks the presence of R_PPC64_TOC16_LO and suppresses
toc-indirect to toc-relative relaxation if R_PPC64_TOC16_LO is seen.
This approach is conservative and loses some relaxation opportunities but is easy to implement.
addis 3, 2, .LC0@toc@ha # no relaxation
addi 3, 3, .LC0@toc@l # no relaxation
li 9, 0
addis 4, 2, .LC0@toc@ha # can relax but suppressed
ld 4, .LC0@toc@l(4) # can relax but suppressed
Also note that interleaved R_PPC64_TOC16_HA and R_PPC64_TOC16_LO_DS is
possible and this patch accounts for that.
addis 3, 2, .LC1@toc@ha # can relax
addis 4, 2, .LC2@toc@ha # can relax
ld 3, .LC1@toc@l(3) # can relax
ld 4, .LC2@toc@l(4) # can relax
Reviewed By: #powerpc, sfertile
Differential Revision: https://reviews.llvm.org/D78431
gold has an option --print-symbol-counts= which prints:
// For each archive
archive $archive $members $fetched_members
// For each object file
symbols $object $defined_symbols $used_defined_symbols
In most cases, `$defined_symbols = $used_defined_symbols` unless weak
symbols are present. Strangely `$used_defined_symbols` includes symbols defined relative to --gc-sections discarded sections.
The `symbols` lines do not appear to be useful.
`archive` lines are useful: `$fetched_members=0` lines correspond to
unused archives. The information can be used to trim dependencies.
This patch implements --print-archive-stats= which prints the number of
members and the number of fetched members for each archive.
Reviewed By: grimar
Differential Revision: https://reviews.llvm.org/D78983
Currently, getVA() returns a virtual address with the assumption that
the ImageBase is zero. As I understand, this is what lld-ELF is doing.
However, under our current design, it seems like an awkward setup --
I'm finding that I have to add and subtract ImageBase in several places
to make things work out.
As such, I think it's simpler to have getVA() return a non-relative VA,
but I'm not sure if I'm missing something. Would love to hear more from
folks familiar with lld-ELF.
Differential Revision: https://reviews.llvm.org/D78168
Build the trie by performing a three-way radix quicksort: We start by
sorting the strings by their first characters, then sort the strings
with the same first characters by their second characters, and so on
recursively. Each time the prefixes diverge, we add a node to the trie.
Thanks to @ruiu for the idea.
I used llvm-mc's radix quicksort implementation as a starting point. The
trie offset fixpoint code was taken from
MachONormalizedFileBinaryWriter.cpp.
Differential Revision: https://reviews.llvm.org/D76977
--gdb-index currently crashes when reading a translation unit with
DWARF v5 .debug_loclists . Call stack:
```
SyntheticSections.cpp GdbIndexSection::create
SyntheticSections.cpp readAddressAreas
DWARFUnit.cpp DWARFUnit::tryExtractDIEsIfNeeded
DWARFListTable.cpp DWARFListTableHeader::extract
...
DWARFDataExtractor.cpp DWARFDataExtractor::getRelocatedValue
lld/ELF/DWARF.cpp LLDDwarfObj<ELFT>::find (sec.sec is nullptr)
...
```
This patch adds support for .debug_loclists to make `DWARFUnit::tryExtractDIEsIfNeeded` happy.
Building --gdb-index does not need .debug_loclists
Reviewed By: dblaikie, grimar
Differential Revision: https://reviews.llvm.org/D79061
Drops the behavior from rL217112.
Use the Gnu driver mode by default for all platforms when ld is
invoked. Other names for the program (such as link or ld64) continue
working as before.
Reviewed By: MaskRay, srhines, smeenai, ruiu
Differential Revision: https://reviews.llvm.org/D78837
Summary:
Use the Gnu driver mode by default for all platforms when ld is
invoked. Other names for the program (such as link or ld64) continue
working as before.
Reviewers: MaskRay, int3, srhines, smeenai, ruiu
Reviewed By: MaskRay, srhines, smeenai, ruiu
Subscribers: smeenai, srhines, nickdesaulniers, llvm-commits
Tags: #lld, #llvm
Differential Revision: https://reviews.llvm.org/D78837
This reverts commit 03ffe58605.
Full tile of reverted commit is:
[ELF][PPC64] Don't perform toc-indirect to toc-relative relaxation for
R_PPC64_TOC16_HA not followed by R_PPC64_TOC16_LO_DS
Breaks the multistage lld PowerPC buildbot.
This diff implements basic support for writing a symbol table.
Attributes are loosely supported for extern symbols and not at all for
other types.
Initial version by Kellie Medlin <kelliem@fb.com>
Originally committed in a3d95a50ee and reverted in fbae153ca5 due to
UBSAN erroring over unaligned writes. That has been fixed in the
current diff with the following changes:
```
diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp
--- a/lld/MachO/SyntheticSections.cpp
+++ b/lld/MachO/SyntheticSections.cpp
@@ -133,6 +133,9 @@ SymtabSection::SymtabSection(StringTableSection &stringTableSection)
: stringTableSection(stringTableSection) {
segname = segment_names::linkEdit;
name = section_names::symbolTable;
+ // TODO: When we introduce the SyntheticSections superclass, we should make
+ // all synthetic sections aligned to WordSize by default.
+ align = WordSize;
}
size_t SymtabSection::getSize() const {
diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -371,6 +371,7 @@ void Writer::assignAddresses(OutputSegment *seg) {
ArrayRef<InputSection *> sections = p.second;
for (InputSection *isec : sections) {
addr = alignTo(addr, isec->align);
+ // We must align the file offsets too to avoid misaligned writes of
+ // structs.
+ fileOff = alignTo(fileOff, isec->align);
isec->addr = addr;
addr += isec->getSize();
fileOff += isec->getFileSize();
@@ -396,6 +397,7 @@ void Writer::writeSections() {
uint64_t fileOff = seg->fileOff;
for (auto § : seg->getSections()) {
for (InputSection *isec : sect.second) {
+ fileOff = alignTo(fileOff, isec->align);
isec->writeTo(buf + fileOff);
fileOff += isec->getFileSize();
}
```
I don't think it's easy to write a test for alignment (that doesn't
involve brittly hard-coding file offsets), so there isn't one... but
UBSAN builds pass now.
Differential Revision: https://reviews.llvm.org/D79050
The current implementation assumes that R_PPC64_TOC16_HA is always followed
by R_PPC64_TOC16_LO_DS. This can break with:
// Load the address of the TOC entry, instead of the value stored at that address
addis 3, 2, .LC0@tloc@ha # R_PPC64_TOC16_HA
addi 3, 3, .LC0@tloc@l # R_PPC64_TOC16_LO
blr
which is used by boringssl's util/fipstools/delocate/delocate.go
https://github.com/google/boringssl/blob/master/crypto/fipsmodule/FIPS.md has some documentation.
In short, this tool converts an assembly file to avoid any potential relocations.
The distance to an input .toc is not a constant after linking, so the assembly cannot use an `addis;ld` pair.
Instead, delocate changes the code to jump to a stub (`addis;addi`) which loads the TOC entry address.
Reviewed By: sfertile
Differential Revision: https://reviews.llvm.org/D78431
This speeds up linking chrome.dll with PGO instrumentation by 13%
(154271ms -> 134033ms).
LLVM's Option library is very slow. In particular, it allocates at least
one large-ish heap object (Arg) for every argument. When PGO
instrumentation is enabled, all the __profd_* symbols are added to the
@llvm.used list, which compiles down to these /INCLUDE: directives. This
means we have O(#symbols) directives to parse in the section, so we end
up allocating an Arg for every function symbol in the object file. This
is unnecessary.
To address the issue and speed up the link, extend the fast path that we
already have for /EXPORT:, which has similar scaling issues.
I promise that I took a hard look at optimizing the Option library, but
its data structures are very general and would need a lot of cleanup. We
have accumulated lots of optional features (option groups, aliases,
multiple values) over the years, and these are now properties of every
parsed argument, when the vast majority of arguments do not use these
features.
Reviewed By: thakis
Differential Revision: https://reviews.llvm.org/D78845
This is primarily motivated by the desire to move from Python2 to
Python3. `PYTHON_EXECUTABLE` is ambiguous. This explicitly identifies
the python interpreter in use. Since the LLVM build seems to be able to
completed successfully with python3, use that across the build. The old
path aliases `PYTHON_EXECUTABLE` to be treated as Python3.
GNU tools generate mapping symbols "$d" for .ARM.exidx sections. The
symbols are added to the symbol table much earlier than the merging
takes place, and after that, they become dangling. Before the patch,
LLD output those symbols as SHN_ABS with the value of 0. The patch
removes such symbols from the symbol table.
Differential Revision: https://reviews.llvm.org/D78820
Summary:
Add logic for emitting the correct set of load commands and segments
when `-dylib` is passed.
I haven't gotten to implementing a real export trie yet, so we can only
emit a single symbol, but it's enough to replace the YAML test files
introduced in D76252.
Differential Revision: https://reviews.llvm.org/D76908
This diff implements basic support for writing a symbol table.
- Attributes are loosely supported for extern symbols and not at all for
other types
Immediate future work will involve implementing section merging.
Initial version by Kellie Medlin <kelliem@fb.com>
Differential Revision: https://reviews.llvm.org/D76742
Previously, the special segments `__PAGEZERO` and `__LINKEDIT` were
implemented as special LoadCommands. This diff implements them using
special sections instead which have an `isHidden()` attribute. We do not
emit section headers for hidden sections, but we use their addresses and
file offsets to determine that of their containing segments. In addition
to allowing us to share more segment-related code, this refactor is also
important for the next step of emitting dylibs:
1) dylibs don't have segments like __PAGEZERO, so we need an easy way of
omitting them w/o messing up segment indices
2) Unlike the kernel, which is happy to run an executable with
out-of-order segments, dyld requires dylibs to have their segment
load commands arranged in increasing address order. The refactor
makes it easier to implement sorting of sections and segments.
Differential Revision: https://reviews.llvm.org/D76839
Summary: The switch --plugin-opt=emit-asm can be used with the gold linker to dump the final assembly code generated by LTO in a user-friendly way. Unfortunately it doesn't work with lld. I'm hooking it up with lld. With that switch, lld emits assembly code into the output file (specified by -o) and if there are multiple input files, each of their assembly code will be emitted into a separate file named by suffixing the output file name with a unique number, respectively. The linking then stops after generating those assembly files.
Reviewers: espindola, wenlei, tejohnson, MaskRay, grimar
Reviewed By: tejohnson, MaskRay, grimar
Subscribers: pcc, emaste, inglorion, arichardson, hiraditya, MaskRay, steven_wu, dexonsmith, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77231
These stub new function were not being added to the symbol table
which in turn meant that we were crashing when trying to output
relocations against them.
Differential Revision: https://reviews.llvm.org/D78779
When discarding local symbols with --discard-all or --discard-locals,
the ones which are used in relocations should be preserved. LLD used
the simplest approach and just ignored those switches when -r or
--emit-relocs was specified.
The patch implements handling the --discard-* switches for the cases
when relocations are kept by identifying used local symbols and allowing
removing only unused ones. This makes the behavior of LLD compatible
with GNU linkers.
Differential Revision: https://reviews.llvm.org/D77807
Fixed error detected by msan. The size field of the .ARM.exidx synthetic
section needs to be initialized to at least estimation level before
calling assignAddresses as that will use the size field.
This was previously reverted in 1ca16fc4f5.
Differential Revision: https://reviews.llvm.org/D78422
This reverts commit f969c2aa65.
There are some msan buildbot failures sanitzer-x86_64-linux-fast that
I need to investigate.
Differential Revision: https://reviews.llvm.org/D78422
The contents of the .ARM.exidx section must be ordered by SHF_LINK_ORDER
rules. We don't need to know the precise address for this order, but we
do need to know the relative order of sections. We have been using the
sectionIndex for this purpose, this works when the OutputSection order
has a monotonically increasing virtual address, but it is possible to
write a linker script with non-monotonically increasing virtual address.
For these cases we need to evaluate the base address of the OutputSection
so that we can order the .ARM.exidx sections properly.
This change moves the finalisation of .ARM.exidx till after the first
call to AssignAddresses. This permits us to sort on virtual address which
is linker script safe. It also permits a fix for part of pr44824 where
we generate .ARM.exidx section for the vector table when that table is so
far away it is out of range of the .ARM.exidx section. This fix will come
in a follow up patch.
Differential Revision: https://reviews.llvm.org/D78422
Fangrui Song