This change includes a fix for https://code.google.com/p/chromium/issues/detail?id=499508#c3,
which required updating the visibility for symbols with eliminated definitions.
--Original Commit Message--
Add new EliminateAvailableExternally module pass, which is performed in
O2 compiles just before GlobalDCE, unless we are preparing for LTO.
This pass eliminates available externally globals (turning them into
declarations), regardless of whether they are dead/unreferenced, since
we are guaranteed to have a copy available elsewhere at link time.
This enables additional opportunities for GlobalDCE.
If we are preparing for LTO (e.g. a -flto -c compile), the pass is not
included as we want to preserve available externally functions for possible
link time inlining. The FE indicates whether we are doing an -flto compile
via the new PrepareForLTO flag on the PassManagerBuilder.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241466 91177308-0d34-0410-b5e6-96231b3b80d8
We don't have a good way to detect most situations where
DS offsets are usable on SI, so add an option to force using
them even if unsafe for debugging performance problems.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241462 91177308-0d34-0410-b5e6-96231b3b80d8
Originally added in r139314.
Back then it didn't actually get the address, it got whatever value the
relocation used: address or offset.
The values in different object formats are:
* MachO: Always an offset.
* COFF: Always an address, but when talking about the virtual address of
sections it says: "for simplicity, compilers should set this to zero".
* ELF: An offset for .o files and and address for .so files. In the case of the
.so, the relocation in not linked to any section (sh_info is 0). We can't
really compute an offset.
Some API mappings would be:
* Use getAddress for everything. It would be quite cumbersome. To compute the
address elf has to follow sh_info, which can be corrupted and therefore the
method has to return an ErrorOr. The address of the section is also the same
for every relocation in a section, so we shouldn't have to check the error
and fetch the value for every relocation.
* Use a getValue and make it up to the user to know what it is getting.
* Use a getOffset and:
* Assert for dynamic ELF objects. That is a very peculiar case and it is
probably fair to ask any tool that wants to support it to use ELF.h. The
only tool we have that reads those (llvm-readobj) already does that. The
only other use case I can think of is a dynamic linker.
* Check that COFF .obj files have sections with zero virtual address spaces. If
it turns out that some assembler/compiler produces these, we can change
COFFObjectFile::getRelocationOffset to subtract it. Given COFF format,
this can be done without the need for ErrorOr.
The getRelocationAddress method was never implemented for COFF. It also
had exactly one use in a very peculiar case: a shortcut for adding the
section value to a pcrel reloc on MachO.
Given that, I don't expect that there is any use out there of the C API. If
that is not the case, let me know and I will add it back with the implementation
inlined and do a proper deprecation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241450 91177308-0d34-0410-b5e6-96231b3b80d8
The code in AArch64A57FPLoadBalancing::scavengeRegister() to handle dead defs
was not correctly handling aliased registers. E.g. if the dead def was of D2,
then S2 was not being marked as unavailable, so it could potentially be used
across a live-range in which it would be clobbered.
Patch by Geoff Berry <gberry@codeaurora.org>!
Phabricator: http://reviews.llvm.org/D10900
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241449 91177308-0d34-0410-b5e6-96231b3b80d8
When talking about the virtual address of sections the coff spec says:
... for simplicity, compilers should set this to zero. Otherwise, it is an
arbitrary value that is subtracted from offsets during relocation.
We don't currently subtract it, so check that it is zero.
If some producer does create such files, we can change getRelocationOffset
instead.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241447 91177308-0d34-0410-b5e6-96231b3b80d8
From the linker's perspective, an available_externally global is equivalent
to an external declaration (per isDeclarationForLinker()), so it is incorrect
to consider it to be a weak definition.
Also clean up some logic in the dead argument elimination pass and clarify
its comments to better explain how its behavior depends on linkage,
introduce GlobalValue::isStrongDefinitionForLinker() and start using
it throughout the optimizers and backend.
Differential Revision: http://reviews.llvm.org/D10941
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241413 91177308-0d34-0410-b5e6-96231b3b80d8
There is some functional change here because it changes target code from
atoi(3) to StringRef::getAsInteger which has error checking. For valid
constraints there should be no difference.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241411 91177308-0d34-0410-b5e6-96231b3b80d8
Followup to D10433 and D10589 that fixes i8/i16 uint2fp vector conversions by zero extending to i32 and using the sint2fp path (unless the target does actually support uint2fp).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241394 91177308-0d34-0410-b5e6-96231b3b80d8
Although this does cut the number of traces recomputed by ~10% for the
test case mentioned in http://reviews.llvm.org/D10460, it doesn't
make a dent in the overall performance. That example needs to be more
selective when invalidating traces.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241393 91177308-0d34-0410-b5e6-96231b3b80d8
This is needed for COFF linkers to distinguish between weak external aliases
and regular symbols with LLVM weak linkage, which are represented as strong
symbols in COFF.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241389 91177308-0d34-0410-b5e6-96231b3b80d8
Requested by Eugene Rozenfeld of the LLILC team, this feature allows JIT
clients to skip relocations for selected external symbols by returning ~0ULL
from their symbol resolver. If this value is returned for a given symbol,
RuntimeDyld will skip all relocations for that symbol. The client will be
responsible for applying the skipped relocations manually before the code
is executed.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241383 91177308-0d34-0410-b5e6-96231b3b80d8
SHT_NOBITS sections do not have content in an object file. Now the yaml2obj
tool does not accept `Content` field for such sections, and the obj2yaml
tool does not attempt to read the section content from a file.
Restore r241350 and r241352.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241377 91177308-0d34-0410-b5e6-96231b3b80d8
