The MIPS GOT section has a number of local entries based on the number of pages
needed for output sections referenced by GOT page relocations. The number is
recorded in the DT_MIPS_LOCAL_GOTNO dynamic section tag. However, the dynamic tag
is added before assignAddresses has been called, meaning that any section size used
to calculate the value will not include size modifications caused by, for example,
linker scripts and thunks.
This change moves the calculation of DT_MIPS_LOCAL_GOTNO until writeTo, by which
time the output section sizes have been finalized.
Reviewers: ruiu, rafael
Differential Revision: https://reviews.llvm.org/D39493
llvm-svn: 318828
No difference in practice other than having sh_entsize in the output.
This should simplify the patch for handling SHF_MERGE in -r.
Based on a patch by George Rimar.
llvm-svn: 318306
microMIPS symbols including microMIPS PLT records created for regular
symbols needs to be marked by STO_MIPS_MICROMIPS flag in a symbol table.
Additionally microMIPS entries in a dynamic symbol table should have
configured less-significant bit. That allows to escape teaching a
dynamic linker about microMIPS symbols.
llvm-svn: 318097
We have a lot of "if (MIPS)" conditions in lld because the MIPS' ABI
is different at various places than other arch's ABIs at where it
don't have to be different, but we at least want to reduce MIPS-ness
from the regular classes.
llvm-svn: 317525
Now that DefinedRegular is the only remaining derived class of
Defined, we can merge the two classes.
Differential Revision: https://reviews.llvm.org/D39667
llvm-svn: 317448
Common symbols are now represented with a DefinedRegular that points
to a BssSection, even during symbol resolution.
Differential Revision: https://reviews.llvm.org/D39666
llvm-svn: 317447
Now that we have only SymbolBody as the symbol class. So, "SymbolBody"
is a bit strange name now. This is a mechanical change generated by
perl -i -pe s/SymbolBody/Symbol/g $(git grep -l SymbolBody lld/ELF lld/COFF)
nd clang-format-diff.
Differential Revision: https://reviews.llvm.org/D39459
llvm-svn: 317370
SymbolBody and Symbol were separated classes due to a historical reason.
Symbol used to be a pointer to a SymbolBody, and the relationship
between Symbol and SymbolBody was n:1.
r2681780 changed that. Since that patch, SymbolBody and Symbol are
allocated next to each other to improve memory locality, and they have
1:1 relationship now. So, the separation of Symbol and SymbolBody no
longer makes sense.
This patch merges them into one class. In order to avoid updating too
many places, I chose SymbolBody as a unified name. I'll rename it Symbol
in a follow-up patch.
Differential Revision: https://reviews.llvm.org/D39406
llvm-svn: 317006
DSO is short for dynamic shared object, so the function name was a
little confusing because it sounded like it didn't work when we were
a creating statically-linked executable or something.
What we mean by "DSO" here is the current output file that we are
creating. Thus the new name. Alternatively, we could call it the current
ELF module, but "module" is a overloaded word, so I avoided that.
llvm-svn: 316809
The Android relocation packing format is a more compact
format for dynamic relocations in executables and DSOs
that is based on delta encoding and SLEBs. An overview
of the format can be found in the Android source code:
https://android.googlesource.com/platform/bionic/+/refs/heads/master/tools/relocation_packer/src/delta_encoder.h
This patch implements relocation packing using that format.
This implementation uses a more intelligent algorithm for compressing
relative relocations than Android's own relocation packer. As a
result it can generally create smaller relocation sections than
that packer. If I link Chromium for Android targeting ARM32 I get a
.rel.dyn of size 174693 bytes, as compared to 371832 bytes with gold
and the Android packer.
Differential Revision: https://reviews.llvm.org/D39152
llvm-svn: 316775
When an OutputSection is larger than the branch range for a Target we
need to place thunks such that they are always in range of their caller,
and sufficiently spaced to maximise the number of callers that can use
the thunk. We use the simple heuristic of placing the
ThunkSection at intervals corresponding to a target specific branch range.
If the OutputSection is small we put the thunks at the end of the executable
sections.
Differential Revision: https://reviews.llvm.org/D34689
llvm-svn: 316751
Previously, EhFrameSection pushes data to EhFrameHdr by calling addFde
function. By making EhFrameHdr pull data from EhFrameSection, we can
eliminate a member from EhFrameHdr.
llvm-svn: 316730
When LLD do ICF for 2 identical sections it leaves 2 duplicate entries in .eh_frame
pointing to the same address. After that it fixes .eh_frame_header's header,
so that it says it contains single FDE, though section itself contains 2
(it contains garbage data at tail).
As a result excessive entries in .eh_frame and excessive dummy data in .eh_frame_header
emited to output. Patch fixes that. This is PR34518.
Differential revision: https://reviews.llvm.org/D38998
llvm-svn: 316648
Summary:
The COFF linker and the ELF linker have long had similar but separate
Error.h and Error.cpp files to implement error handling. This change
introduces new error handling code in Common/ErrorHandler.h, changes the
COFF and ELF linkers to use it, and removes the old, separate
implementations.
Reviewers: ruiu
Reviewed By: ruiu
Subscribers: smeenai, jyknight, emaste, sdardis, nemanjai, nhaehnle, mgorny, javed.absar, kbarton, fedor.sergeev, llvm-commits
Differential Revision: https://reviews.llvm.org/D39259
llvm-svn: 316624
By assuming that mergeable input sections are smaller than 4 GiB,
lld's memory usage when linking clang with debug info drops from
2.788 GiB to 2.019 GiB (measured by valgrind, and that does not include
memory space for mmap'ed files). I think that's a reasonable assumption
given such a large RAM savings, so this patch.
According to valgrind, gold needs 3.54 GiB of RAM to do the same thing.
NB: This patch does not introduce a limitation on the size of
output sections. You can still create sections larger than 4 GiB.
llvm-svn: 316280
The original patch was reported to break a libcxx bot. Unfortunately I
could not reproduce the issue and the bot log is not available anymore.
This patch changes the handling of shared symbols. I will watch the
bot and see it breaks.
Original message:
--------------------------------------------------------------
Handle shared and lazy symbol in the gnu hash construction.
We were not considering those symbols undefined and they could end up
in the end of the dynamic symbol table.
--------------------------------------------------------------
llvm-svn: 316051
The original patch was reported to break a libcxx bot. Unfortunately
I could not reproduce the issue and the bot log is not available anymore.
This patch changes the handling of just lazy symbols. I will watch the
bot and see it breaks.
Original message:
--------------------------------------------------------------
Handle shared and lazy symbol in the gnu hash construction.
We were not considering those symbols undefined and they could end up
in the end of the dynamic symbol table.
--------------------------------------------------------------
llvm-svn: 316004
Summary:
This will allow using the functionality from other linkers. It is also
a prerequisite for sharing the error logging code.
Reviewers: ruiu
Reviewed By: ruiu
Subscribers: emaste, mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D38822
llvm-svn: 315725
It doesn't make sense to link from an alloc section to a non alloc
one as we were doing.
This matches the behavior of both gold and bfd.
llvm-svn: 315584
"Commands" was ambiguous because in the linker script, everything is
a command. We used to handle only SECTIONS commands, and at the time,
it might make sense to call them the commands, but it is no longer
the case. We handle not only SECTIONS but also MEMORY, PHDRS, VERSION,
etc., and they are all commands.
llvm-svn: 315409
The condition whether a section is alive or not by default
is becoming increasingly complex, so the decision of garbage
collection is spreading over InputSection.h and MarkLive.cpp,
which is not a good state.
This moves the code to MarkLive.cpp, to keep the file the central
place to make decisions about garbage collection.
llvm-svn: 315384
When parsing linker scripts, LLD previously started with a '.' value of 0,
regardless of the internal default image base for the target, and regardless of
switches such as --image-base. It seems reasonable to use a different image base
value when using linker scripts and --image-base is specified, since otherwise the
switch has no effect. This change does this, as well as removing unnecessary
initialisation of Dot where it is not used.
The default image base should not be used when processing linker
scripts, because this will change the behaviour for existing linker script users,
and potentially result in invalid output being produced, as a subsequent assignment
to Dot could move the location counter backwards. Instead, we maintain the existing
behaviour of starting from 0 if --image-base is not specified.
Reviewers: ruiu
Differential Revision: https://reviews.llvm.org/D38360
llvm-svn: 315293
LLD produces broken .dynamic section when --no-rosegment and at least
one of following options is present:
1) -z rodynamic is given.
2) MIPS target.
That happens because code that writes .dynamic assumes target buffer
is zero-filled, what can be not true after LLD fills it with trap
instructions. With one of two options above, .dynamic becomes
SHF_ALLOC section, so can be affected.
Differential revision: https://reviews.llvm.org/D38580
llvm-svn: 315054
We produce broken output currently.
Code that writes .dynsym assumes output buffer is zero-filled,
though that is not always true. When --no-rosegment is given,
buffer can be filled with trap instructions. Patch fixes the issue.
It is relative with PR34705.
Differential revision: https://reviews.llvm.org/D38579
llvm-svn: 315053
When reporting a symbol conflict, LLD parses the debug info to report
source location information. Sections have not been decompressed at this
point, so if an object file contains zlib compressed debug info, LLD
ends up passing this compressed debug info to the DWARF parser, which
causes debug info parsing failures and can trigger assertions in the
parser (as the test case demonstrates).
Decompress debug sections when constructing the LLDDwarfObj to avoid
this issue. This doesn't handle GNU-style compressed debug info sections
(.zdebug_*), which at present are simply ignored by LLDDwarfObj; those
can be done in a follow-up.
Differential Revision: https://reviews.llvm.org/D38491
llvm-svn: 314866
The issue with std:🧵:hardware_concurrency is that it forwards
to libc and some implementations (like glibc) don't take thread
affinity into consideration.
With this change a llvm program that can execute in only 2 cores will
use 2 threads, even if the machine has 32 cores.
This makes benchmarking a lot easier, but should also help if someone
doesn't want to use all cores for compilation for example.
llvm-svn: 314810
New lld's files are spread under lib subdirectory, and it isn't easy
to find which files are actually maintained. This patch moves maintained
files to Common subdirectory.
Differential Revision: https://reviews.llvm.org/D37645
llvm-svn: 314719
Currently LLD calls the `isMicroMips` routine to determine type of PLT entries
needs to be generated: regular or microMIPS. This routine checks ELF
header flags in the `FirstObj` to retrieve type of linked object files.
So if the first file does not contain microMIPS code, LLD will generate
PLT entries with regular (non-microMIPS) code only.
Ideally, if a PLT entry is referenced by microMIPS code only this entry
should contain microMIPS code, if a PLT entry is referenced by regular
code this entry should contain regular code. In a "mixed" case the PLT
entry can be either microMIPS or regular, but each "cross-mode-call" has
additional cost.
It's rather difficult to implement this ideal solution. But we can
assume that if there is an input object file with microMIPS code, the
most part of the code is microMIPS too. So we need to deduce type of PLT
entries based on finally calculated ELF header flags and do not check
only the first input object file.
This change implements this.
- The `getMipsEFlags` renamed to the `calcMipsEFlags`. The function
called from the `LinkerDriver::link`. Result is stored in
the Configuration::MipsEFlags field.
- The `isMicroMips` and `isMipsR6` routines access the `MipsEFlags`
field to get and check calculated ELF flags.
- New types of PLT records created when necessary.
Differential revision: https://reviews.llvm.org/D37747
llvm-svn: 314675
String merging is one of the most time-consuming functions in lld.
This patch parallelize it to speed it up. On my 2-socket 20-core
40-threads Xeon E5-2680 @ 2.8 GHz machine, this patch shorten the
clang debug build link time from 7.11s to 5.16s. It's a 27%
improvement and actually pretty noticeable. In this test condition,
lld is now 4x faster than gold.
Differential Revision: https://reviews.llvm.org/D38266
llvm-svn: 314588
Convert all common symbols to regular symbols after scan.
This means that the downstream code does not to handle common symbols as a special case.
Differential Revision: https://reviews.llvm.org/D38137
llvm-svn: 314495
This is "Bug 34688 - lld much slower than bfd when linking the linux kernel"
Inside copyRelocations() we have O(N*M) algorithm, where N - amount of
relocations and M - amount of symbols in symbol table. It isincredibly slow
for linking linux kernel.
Patch creates local search tables to speedup.
With this fix link time goes for me from 12.95s to 0.55s what is almost 23x
faster. (used release LLD).
Differential revision: https://reviews.llvm.org/D38129
llvm-svn: 314282
Previously`InX::Got` and InX::MipsGot synthetic sections
were not removed if ElfSym::GlobalOffsetTable was defined.
ElfSym::GlobalOffsetTable is a symbol for _GLOBAL_OFFSET_TABLE_.
Patch moves ElfSym::GlobalOffsetTable check out from removeUnusedSyntheticSections.
Also note that there was no point to check ElfSym::GlobalOffsetTable for MIPS case
because InX::MipsGot::empty() always returns false for non-relocatable case, and in case
of relocatable output we do not create special symbols anyways.
Differential revision: https://reviews.llvm.org/D37623
llvm-svn: 314099
We used to sort and uniquify CU vectors, but looks like CU vectors in
.gdb_index sections created by gold are not guaranteed to be sorted.
llvm-svn: 314095
We used to use std::set to uniquify CU vector elements, but as we know,
std::set is pretty slow. Fortunately we didn't actually have to use a
std::set here. This patch replaces it with std::vector.
With this patch, lld's -gdb-index overhead when linking a clang debug
build is now about 1 second (8.65 seconds without -gdb-index vs 9.60
seconds with -gdb-index). Since gold takes more than 6 seconds to create
a .gdb_index for the same output, our number isn't that bad.
llvm-svn: 314094
Previously, we had two levels of hash table lookup. The first hash
lookup uses CachedHashStringRefs as keys and returns offsets in string
table. Then, we did the second hash table lookup to obtain GdbSymbol
pointers. But we can directly map strings to GDbSymbols.
One test file is updated in this patch because we no longer have a '\0'
byte at the start of the string pool, which was automatically inserted
by StringTableBuilder.
This patch speeds up Clang debug build (with -gdb-index) link time by
0.3 seconds.
llvm-svn: 314092
This change alone speeds up linking of Clang debug build with -gdb-index
by 1.2 seconds, from 12.5 seconds to 11.3 seconds. (Without -gdb-index,
lld takes 8.5 seconds to link the same input files.)
llvm-svn: 314090
This patch rewrites a part of GdbIndexSection to address the following
issues in the previous implementation:
- Previously, some struct declarations were in GdbIndex.h while they
were not used in GdbIndex.cpp. Such structs are moved to
SyntheticSection.h.
- The actual implementation were split into GdbIndexSection and GdbHash
section, but that separation didn't make much sense. They are now
unified as GdbIndexSection.
In addition to the above changes, this patch splits functions, rename
variables and remove redundant functions/variables to generally improve
code quality.
llvm-svn: 314084
Its a PR34648 which was a segfault that happened because
we stored pointers to elements in DenseMap.
When DenseMap grows such pointers are invalidated.
Solution implemented is to keep elements by pointer
and not by value.
Differential revision: https://reviews.llvm.org/D38034
llvm-svn: 313741
EhSectionPiece used to have a pointer to a section, but that pointer was
mostly redundant because we almost always know what the section is without
using that pointer. This patch removes the pointer from the struct.
This patch also use uint32_t/int32_t instead of size_t to represent
offsets that are hardly be larger than 4 GiB. At the moment, I think it is
OK even if we cannot handle .eh_frame sections larger than 4 GiB.
Differential Revision: https://reviews.llvm.org/D38012
llvm-svn: 313697
CieRecord is a struct containing a CIE and FDEs, but oftentimes the
struct itself is named `Cie` which caused some confusion. This patch
renames them `CieRecords` or `Rec`.
llvm-svn: 313681
This patch removes lot of static Instances arrays from different input file
classes and introduces global arrays for access instead. Similar to arrays we
have for InputSections/OutputSectionCommands.
It allows to iterate over input files in a non-templated code.
Differential revision: https://reviews.llvm.org/D35987
llvm-svn: 313619
EhSectionPiece inherited from SectionPiece, but we did not actually use
EhSectionPiece objects as SectionPiece ojbects. They were handled as
distinct types. So it didn't make much sense to use inheritance.
llvm-svn: 313587
"Repl" member is guranteed to have a non-null pointer. If an input
section is not merged by ICF, "Repl" points to "this". Otherwise, it
points to some other section. It must not be NULL.
llvm-svn: 313556
to separate commons based on file name patterns. The following linker script
construct does not work because commons are allocated before section placement
is done and the only synthesized BssSection that holds all commons has no file
associated with it:
SECTIONS { .common_0 : { *file0.o(COMMON) }}
This patch changes the allocation of commons to create a section per common
symbol and let the section logic do the layout.
Differential revision: https://reviews.llvm.org/D37489
llvm-svn: 312796
The default padding for an executable segment is the target trap
instruction which for x86_64 is 0xCC. However, the .eh_frame section
requires the padding to be zero. The code that writes the .eh_frame
section assumes that its segment is zero initialized and does not
explicitly write the zero padding. This does not work when the .eh_frame
section is in the executable segment (for example when using
-no-rosegment).
This patch changes the .eh_frame writing code to explicitly write the
zero padding.
Differential Revision: https://reviews.llvm.org/D37462
llvm-svn: 312706
Previously it was called twice for .comment synthetic section.
That created 2 pieces of data, which was deduplicated anyways,
but was not clean.
llvm-svn: 312327
GdbIndexSection doesn't need lazy finalization because when an instance
of the class is created, we already know all debug info sections.
We can initialize the instnace in the ctor.
llvm-svn: 310931
Liveness is usually a notion of input sections, but this patch adds
"liveness" bit to common symbols because they don't belong to any
input section.
This patch is based on https://reviews.llvm.org/D36520
Differential Revision: https://reviews.llvm.org/D36546
llvm-svn: 310617
Rui Ueyama