Not all relocations from a .eh_frame that point to an executable
section should be ignored. In particular, the relocation finding the
personality function should not.

This is a reduction from trying to bootstrap a static lld on linux.

llvm-svn: 276329

llvm-svn: 275803

llvm-svn: 274429

llvm-svn: 270532

Previously, mergeable section's constructors did more than just
setting member variables; it split section contents into small
pieces. It is not always computationally cheap task because if
the section is a mergeable string section, it needs to scan the
entire section to split them by NUL characters.

If a section would be thrown away by GC, that cost ended up
being a waste of time. It is going to be larger problem if the
section is compressed -- the whole time to uncompress it and
split it up is going to be a waste.

Luckily, we can defer section splitting after GC. We just have
to remember which offsets are in use during GC and apply that later.
This patch implements it.

Differential Revision: http://reviews.llvm.org/D20516

llvm-svn: 270455

This patch adds Size member to SectionPiece so that getRangeAndSize
can just return a SectionPiece instead of a std::pair<SectionPiece *, uint_t>.
Also renamed the function.

llvm-svn: 270346

We were using std::pair to represents pieces of splittable section
contents. It hurt readability because "first" and "second" are not
meaningful. This patch give them names.

One more thing is that piecewise liveness information is stored to
the second element of the pair as a special value of output section
offset. It was confusing, so I defiend a new bit, "Live", in the
new struct.

llvm-svn: 270340

We have to add sections to the work list, not just mark them live.

llvm-svn: 268628

We were previously using an output offset of -1 for both GC'd and tail
merged pieces. We need to distinguish these two cases in order to filter
GC'd symbols from the symbol table -- we were previously asserting when we
asked for the VA of a symbol pointing into a dead piece, which would end
up asking the tail merging string table for an offset even though we hadn't
initialized it properly.

This patch fixes the bug by using an offset of -1 to exclusively mean GC'd
pieces, using 0 for tail merges, and distinguishing the tail merge case from
an offset of 0 by asking the output section whether it is tail merge.

Differential Revision: http://reviews.llvm.org/D19953

llvm-svn: 268604

llvm-svn: 268286

Patch implements one of suggestions from Rafael Ávila de Espíndola,
to fix segfault after section that contains personality being
garbage collected.

Suggestion was just to keep alive all non executable sections
referenced by .eh_frame.

This fixes PR27529.

Differential revision: http://reviews.llvm.org/D19656

llvm-svn: 268228

This patch implements a new design for the symbol table that stores
SymbolBodies within a memory region of the Symbol object. Symbols are mutated
by constructing SymbolBodies in place over existing SymbolBodies, rather
than by mutating pointers. As mentioned in the initial proposal [1], this
memory layout helps reduce the cache miss rate by improving memory locality.

Performance numbers:

           old(s) new(s)
Without debug info:
chrome      7.178  6.432 (-11.5%)
LLVMgold.so 0.505  0.502 (-0.5%)
clang       0.954  0.827 (-15.4%)
llvm-as     0.052  0.045 (-15.5%)
With debug info:
scylla      5.695  5.613 (-1.5%)
clang      14.396 14.143 (-1.8%)

Performance counter results show that the fewer required indirections is
indeed the cause of the improved performance. For example, when linking
chrome, stalled cycles decreases from 14,556,444,002 to 12,959,238,310, and
instructions per cycle increases from 0.78 to 0.83. We are also executing
many fewer instructions (15,516,401,933 down to 15,002,434,310), probably
because we spend less time allocating SymbolBodies.

The new mechanism by which symbols are added to the symbol table is by calling
add* functions on the SymbolTable.

In this patch, I handle local symbols by storing them inside "unparented"
SymbolBodies. This is suboptimal, but if we do want to try to avoid allocating
these SymbolBodies, we can probably do that separately.

I also removed a few members from the SymbolBody class that were only being
used to pass information from the input file to the symbol table.

This patch implements the new design for the ELF linker only. I intend to
prepare a similar patch for the COFF linker.

[1] http://lists.llvm.org/pipermail/llvm-dev/2016-April/098832.html

Differential Revision: http://reviews.llvm.org/D19752

llvm-svn: 268178

Differential Revision: http://reviews.llvm.org/D19490

llvm-svn: 267637

We were only doing it for .so and --export-dynamic, but those are not
the only ways a symbol ends up in the dynamic symbol table.

Problem diagnostic and earlier patch version by Peter Collingbourne.

llvm-svn: 267568

The fix is to handle local symbols referring to SHF_MERGE sections.

Original message:

GC entries of SHF_MERGE sections.

It is a fairly direct extension of the gc algorithm. For merge sections
instead of remembering just a live bit, we remember which offsets
were used.

This reduces the .rodata sections in chromium from 9648861 to 9477472
bytes.

llvm-svn: 267233

    This reverts commit r267164.

    Revert "Trying to fix the windows build."

    This reverts commit r267168.

Debugging a bootstrap problem.

llvm-svn: 267194

These are properties of a symbol name, rather than a particular instance
of a symbol in an object file. We can simplify the code by collecting these
properties in Symbol.

The MustBeInDynSym flag has been renamed ExportDynamic, as its semantics
have been changed to be the same as those of --dynamic-list and
--export-dynamic-symbol, which do not cause hidden symbols to be exported.

Differential Revision: http://reviews.llvm.org/D19400

llvm-svn: 267183

It is a fairly direct extension of the gc algorithm. For merge sections
instead of remembering just a live bit, we remember which offsets were
used.

This reduces the .rodata sections in chromium from 9648861 to 9477472
bytes.

llvm-svn: 267164

It turns out that this will read data from the section to properly
handle Elf_Rel implicit addends.

Sorry for the noise.

Original messages:

Try to fix Windows lld build.

Move getRelocTarget to ObjectFile.
It doesn't use anything from the InputSection.

llvm-svn: 267163

llvm\tools\lld\ELF\MarkLive.cpp(49): error C2872: 'ObjectFile': ambiguous symbol
llvm\tools\lld\elf\InputFiles.h(100): note: could be 'lld::elf::ObjectFile'
llvm\include\llvm/Object/IRObjectFile.h(26): note: or       'llvm::object::ObjectFile'
llvm\tools\lld\ELF\MarkLive.cpp(133): note: see reference to function template instantiation
    'void forEachSuccessor<ELFT>(lld::elf::InputSection<ELFT> *,
                                 std::function<void (lld::elf::InputSectionBase<ELFT> *)>)'
    being compiled with
                [ ELFT=llvm::object::ELF32LE ]
llvm\tools\lld\ELF\MarkLive.cpp(136): note: see reference to function template instantiation
    'void lld::elf::markLive<llvm::object::ELF32LE>(lld::elf::SymbolTable<llvm::object::ELF32LE> *)
    being compiled

llvm-svn: 267161

It doesn't use anything from the InputSection.

llvm-svn: 267154

llvm-svn: 267147

llvm-svn: 267081

Originally, linker scripts were basically an alternative way to specify
options to the command line options. But as we add more features to hanlde
symbols and sections, many member functions needed to be templated.
Now most the members are templated. It is probably time to template the
entire class.

Previously, LinkerScript is an executor of the linker script as well as
a storage of linker script configurations. This is not suitable to template
the class because when we are reading linker script files, we don't know
the ELF type yet, so we can't instantiate ELF-templated classes.

In this patch, I defined a new class, ScriptConfiguration, to store
linker script configurations. ScriptParser writes parse results to it,
and LinkerScript uses them.

Differential Revision: http://reviews.llvm.org/D19302

llvm-svn: 266908

This makes it impossible to forget to call repl on the SymbolBody.

llvm-svn: 266432

We never need to iterate over the K,V pairs, so we can avoid copying the
key as MapVector does.

This is a small speedup on most benchmarks.

llvm-svn: 266364

The DenseMap doesn't store hash results. This means that when it is
resized it has to recompute them.

This patch is a small hack that wraps the StringRef in a struct that
remembers the hash value. That way we can be sure it is only hashed
once.

llvm-svn: 266357

Our symbol representation was redundant, and some times would get out of
sync. It had an Elf_Sym, but some fields were copied to SymbolBody.

Different parts of the code were checking the bits in SymbolBody and
others were checking Elf_Sym.

There are two general approaches to fix this:
* Copy the required information and don't store and Elf_Sym.
* Don't copy the information and always use the Elf_Smy.

The second way sounds tempting, but has a big problem: we would have to
template SymbolBody. I started doing it, but it requires templeting
*everything* and creates a bit chicken and egg problem at the driver
where we have to find ELFT before we can create an ArchiveFile for
example.

As much as possible I compared the test differences with what gold and
bfd produce to make sure they are still valid. In most cases we are just
adding hidden visibility to a local symbol, which is harmless.

In most tests this is a small speedup. The only slowdown was scylla
(1.006X). The largest speedup was clang with no --build-id, -O3 or
--gc-sections (i.e.: focus on the relocations): 1.019X.

llvm-svn: 265293

llvm-svn: 263510

pr26878 shows a case where locals have to be in the got.

llvm-svn: 263222

llvm-svn: 262159

This fixes the https://llvm.org/bugs/show_bug.cgi?id=22906 bug.

In GNU Binutils, a reference to start or stop is sufficient to 
prevent the section from being garbage collected.
Patch implements the same behavior for lld.

Differential revision: http://reviews.llvm.org/D17502

llvm-svn: 261840

"Discarded" section is a marker for discarded sections, and we do not
use the instance except for checking its identity. In that sense, it
is just another type of a "null" pointer for InputSectionBase. So,
it doesn't have to be a real instance of InputSectionBase class.

In this patch, we no longer instantiate Discarded section but instead
use -1 as a pointer value. This eliminates a global variable which
needed initialization at startup.

llvm-svn: 261761

When link-time garbage collection is in use (-gc-sections), it is 
often useful to mark sections that should not be eliminated. 
This is accomplished by surrounding an input section's wildcard 
entry with KEEP(). Patch implements that command.

Differential revision: http://reviews.llvm.org/D17242

llvm-svn: 261616

llvm-svn: 257527

llvm-svn: 256970

llvm-svn: 256845

There are 3 symbol types that a .bc can provide during lto: defined,
undefined, common.

Defined and undefined symbols have already been refactored. I was
working on common and noticed that absolute symbols would become an
oddity: They would be the only symbol type present in a .o but not in
a.bc.

Looking a bit more, other than the special section number they were only
used for special rules for computing values. In that way they are
similar to TLS, and we don't have a DefinedTLS.

This patch deletes it. With it we have a reasonable rule of the thumb
for having a symbol kind: It exists if it has special resolution
semantics.

llvm-svn: 256383

llvm-svn: 256379

This change eliminates a string comparison from the
garbage collector.

llvm-svn: 256378