This matches ld.bfd and ld.gold behavior. The change is simple enough
and avoid trouble to consumers (they don't have to change their Makefiles).
Side note: found while trying to build FreeBSD base system with lld.
llvm-svn: 251408
.eh_frame sections need to be preserved if they refer to live sections.
So the liveness relation is reverse for eh_frame sections. For now,
we simply preserve all .eh_frame sections. Thanks Rafael for pointing
this out. .jcr are kept for the same reason.
llvm-svn: 251068
Section garbage collection is a feature to remove unused sections
from outputs. Unused sections are sections that cannot be reachable
from known GC-root symbols or sections. Naturally the feature is
implemented as a mark-sweep garbage collector.
In this patch, I added Live bit to InputSectionBase. If and only
if Live bit is on, the section will be written to the output.
Starting from GC-root symbols or sections, a new function, markLive(),
visits all reachable sections and sets their Live bits. Writer then
ignores sections whose Live bit is off, so that such sections are
excluded from the output.
This change has small negative impact on performance if you use
the feature because making sections means more work. The time to
link Clang changes from 0.356s to 0.386s, or +8%.
It reduces Clang size from 57,764,984 bytes to 55,296,600 bytes.
That is 4.3% reduction.
http://reviews.llvm.org/D13950
llvm-svn: 251043
This patch implements --hash-style command line switch.
* By default, or with "sysv" or "both" parameters, the linker generates
a standard ELF hash section.
* With "gnu" or "both", it produces a GNU-style hash section.
That section requires the symbols in the dynamic symbol table section, which
are referenced in the GNU hash section, to be placed after not hashed ones and
to be sorted to correspond the order of hash buckets in the GNU Hash section.
The division function, as well as estimations for the section's parameters,
are just the first rough attempt and the subjects for further adjustments.
Differential Revision: http://reviews.llvm.org/D13815
llvm-svn: 251000
The section header table index of the entry that is associated with the section name string table.
Differential Revision: http://reviews.llvm.org/D13904
llvm-svn: 250836
Target has supportsLazyRelocations() method which can switch lazy relocations on/off (currently all targets are OFF except x64 which is ON). So no any other targets are affected now.
Differential Revision: http://reviews.llvm.org/D13856?id=37726
llvm-svn: 250808
The option now just sets NOW bit in DT_FLAGS_1 but some loaders
seem to require also BIND_NOW bit to be set in DT_FLAGS. This is,
also, what ld.bfd and gold do.
Differential Revision: http://reviews.llvm.org/D13883
llvm-svn: 250799
The two names are similar enough that they might lead to confusion.
The output of readobj clarifies but I missed it when I originally
committed this. Found while linking FreeBSD userland with lld.
llvm-svn: 250739
The reason of collecting all undefines in vector is that during reading files we already need to have Symtab created. Or like was done in that patch - to put undefines from scripts somewhere to delay Symtab.addUndefinedOpt() call.
Differential Revision: http://reviews.llvm.org/D13870
llvm-svn: 250711
Instead of specifically creating .plt entries for weak undef symbols, mirror
the logic in r250584, and use canBePreempted to determine is a REL24 relocation
needs a .plt entry. This might cause relocateOne to be called for a weak undef
symbol, with a REL24 relocation, but ignore this as a special case (this will
cause SA == 0, which won't happen under any other circumstance).
llvm-svn: 250597
There is sometimes no need to generate relocation via PLT.
Example - when symbol is not undefined and we are not creating shared library. Then we can create relative relocation instead of referencing and creating PLT records.
Differential Revision: http://reviews.llvm.org/D13835
llvm-svn: 250584
When we have a R_PPC64_ADDR64 for a weak undef symbol, which thus resolves to
0, and we're creating a shared library, we need to make sure that it stays 0
(because code that conditionally calls the weak function tests for this).
Unfortunately, we were creating a R_PPC64_RELATIVE for these relocation
targets, making the address of the undefined weak symbol equal to the base
address of the shared library (which is non-zero). In general, we should not be
creating RelativeReloc relocs for undef weak symbols.
llvm-svn: 250558
R_PPC64_TOC does not have an associated symbol, but does have a non-zero VA
that target-specific code must compute using some non-trivial rule. We
handled this as a special case in PPC64TargetInfo::relocateOne, where
we knew to write this special address, but that did not work when creating shared
libraries. The special TOC address needs to be the subject of a
R_PPC64_RELATIVE relocation, and so we also need to know how to encode this
special address in the addend of that relocation.
Thus, some target-specific logic is necessary when creating R_PPC64_RELATIVE as
well. To solve this problem, we teach getLocalRelTarget to handle R_PPC64_TOC
as a special case. This allows us to remove the special case in
PPC64TargetInfo::relocateOne (simplifying code there), and naturally allows the
existing logic to do the right thing when creating associated R_PPC64_RELATIVE
relocations for shared libraries.
llvm-svn: 250555
If a section name is valid as a C identifier (which is rare because of
the leading '.'), linkers are expected to define __start_<secname> and
__stop_<secname> symbols. They are at beginning and end of the section,
respectively. This is not requested by the ELF standard, but GNU ld and
gold provide this feature.
llvm-svn: 250432
Unfortunately, the check was not as dead as I had thought, and adjusting the
starting VA again exposed the problem. We end up trying to relocate the bl
(using a 24-bit relative offset) to a symbol address of zero, and in general,
that does not fit.
Thus, reverting for now, and adding a test case.
llvm-svn: 250423
After some additional post-commit (post-revert) discussion and research, this
reverts, in part, r250205, so the ABI-recommended starting address can be used
on PPC64 (as is done by other linkers).
Also, this addresses the FIXME in ELF/Writer.cpp by making VAStart a
target-dependent property.
llvm-svn: 250378
If an argument for --entry is a number, that's not a symbol name but
an absolute address. If that's the case, the address is directly set
to ELF header's e_entry.
llvm-svn: 250334
Previously, we used input section names as output section names.
That resulted that we created lots of sections for comdat
or -f{function,data}-section sections.
This patch reduces the number of sections by dropping suffix from
all section names which start with ".text.", ".rodata.", ".data."
or ".bss.". GNU linker does this using the internal linker script,
but for LLD I chose to do that directly.
Interestingly, this makes the linker faster. Time to link Clang
is this.
Before:
real 0m0.537s
user 0m0.433s
sys 0m0.104s
After:
real 0m0.390s
user 0m0.268s
sys 0m0.120s
It make sense because previously we created 57659 sections now only 27.
llvm-svn: 250315
- Make the `MipsTargetInfo` template class with `ELFType` argument. Use
the argument to select an appropriate relocation type and read/write
routines.
- Add template function `add32` to add-and-write relocation value in
both big and little endian cases. Keep the `add32le` to reduce code
changes.
Differential Revision: http://reviews.llvm.org/D13723
llvm-svn: 250297
Michael J. Spencer