To do this, change the representation of lazy loaded functions.
The previous representation cannot differentiate between a function whose body
has been removed and one whose body hasn't been read from the .bc file. That
means that in order to drop a function, the entire body had to be read.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220580 91177308-0d34-0410-b5e6-96231b3b80d8
The plugin API doesn't have the notion of linkonce, only weak. It is up to the
plugin to figure out if a symbol used only for the symbol table can be dropped.
In particular, it has to avoid dropping a linkonce_odr selected by gold if there
is also a weak_odr.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219188 91177308-0d34-0410-b5e6-96231b3b80d8
The call to copyAttributesFrom will copy the visibility, which might assert
if it were to produce something invalid like "internal hidden". We avoid it
by first creating the replacement with the original linkage and then setting
it to internal affter the call to copyAttributesFrom.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219184 91177308-0d34-0410-b5e6-96231b3b80d8
When creating an internal function replacement for use in an alias we were
not remapping the argument uses in the instructions to point to the new
arguments.
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This format is simply a regular object file with the bitcode stored in a
section named ".llvmbc", plus any number of other (non-allocated) sections.
One immediate use case for this is to accommodate compilation processes
which expect the object file to contain metadata in non-allocated sections,
such as the ".go_export" section used by some Go compilers [1], although I
imagine that in the future we could consider compiling parts of the module
(such as large non-inlinable functions) directly into the object file to
improve LTO efficiency.
[1] http://golang.org/doc/install/gccgo#Imports
Differential Revision: http://reviews.llvm.org/D4371
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With this a DataLayoutPass can be reused for multiple modules.
Once we have doInitialization/doFinalization, it doesn't seem necessary to pass
a Module to the constructor.
Overall this change seems in line with the idea of making DataLayout a required
part of Module. With it the only way of having a DataLayout used is to add it
to the Module.
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This is the plugin version of pr20882.
This handles the case of every common symbol being in the IR. We will need some
support from gold to handle the case where some symbols are in ELF and some in
the IR.
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I took a guess at the changes to the gold plugin, because that doesn't
seem to build by default for me. Not sure what dependencies I might be
missing for that.
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This forces callers to use std::move when calling it. It is somewhat odd to have
code with std::move that doesn't always move, but it is also odd to have code
without std::move that sometimes moves.
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By taking a reference we can do the ownership transfer in one place instead of
expecting every caller to do it.
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Take a StringRef instead of a "const char *".
Take a "std::error_code &" instead of a "std::string &" for error.
A create static method would be even better, but this patch is already a bit too
big.
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There are two parts to this. First, the plugin needs to tell gold the comdat by
setting comdat_key.
What gets things a bit more complicated is that gold only seems
symbols. In particular, if A is an alias to B, it only sees the symbols
A and B. It can then ask us to keep symbol A but drop symbol B. What
we have to do instead is to create an internal version of B and make A
an alias to that.
At some point some of this logic should be moved to lib/Linker so that
we don't map a Constant to an internal version just to have lib/Linker
map that again to the destination module.
The reason for implementing this in tools/gold for now is simplicity.
With it in place it should be possible to update clang to use comdats
for constructors and destructors on ELF without breaking the LTO
bootstrap. Once that is done I intend to come back and improve the
interface lib/Linker exposes.
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There is a fundamental difference between how the gold API and lib/LTO view
the LTO process.
The gold API talks about a particular symbol in a particular file. The lib/LTO
API talks about a symbol in the merged module.
The merged module is then defined in terms of the IR semantics. In particular,
a linkonce_odr GV is only copied if it is used, since it is valid to drop
unused linkonce_odr GVs.
In the testcase in pr19901 both properties collide. What happens is that gold
asks us to keep a particular linkonce_odr symbol, but the IR linker doesn't
copy it to the merged module and we never have a chance to ask lib/LTO to keep
it.
This patch fixes it by having a more direct implementation of the gold API. If
it asks us to keep a symbol, we change the linkage so it is not linkonce. If it
says we can drop a symbol, we do so. All of this before we even send the module
to lib/Linker.
Since now we don't have to produce LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN,
during symbol resolution we can use a temporary LLVMContext and do lazy
module loading. This allows us to keep the minimum possible amount of
allocated memory around. This should also allow as much parallelism as
we want, since there is no shared context.
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On at least my machine, ar does not register an all symbols read hook (which
previously triggered target initialization), but it does register a claim
files hook, which depends on the targets being initialized.
Differential Revision: http://reviews.llvm.org/D4372
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This fixes a regression that made clang -flto -Wl,--plugin-opt=-mattr=+aes not
pass the "+aes" option to the LTOCodeGenerator attributes.
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Back in r128440 tools/LTO started exporting the disassembler interface. It
was never clear why, but whatever the reason I am pretty sure it doesn't hold
for tools/gold.
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This fixes the processing of --plugin-opt=-jump-table-type=arity.
Nice properties:
* We call InitTargetOptionsFromCodeGenFlags once.
* We call parseCodeGenDebugOptions once.
* It works :-)
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The tools/lto API is not the best choice for implementing a gold plugin. Among
other issues:
* It is an stable ABI. Old errors stay and we have to be really careful
before adding new features.
* It has to support two fairly different linkers: gold and ld64.
* We end up with a plugin that depends on a shared lib, something quiet
unusual in LLVM land.
* It hides LLVM. For some features in the gold plugin it would be really
nice to be able to just get a Module or a GlobalValue.
This change is intended to be a very direct translation from the C API. It
will just enable other fixes and cleanups.
Tested with a LTO bootstrap on linux.
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dynamic-no-pic is just another output type. If gnu ld gets support for MachO,
it should also add something like LDPO_DYN_NO_PIC to the plugin interface.
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This is a minimal change to remove the header. I will remove the occurrences
of "using std::error_code" in a followup patch.
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This compiles with no changes to clang/lld/lldb with MSVC and includes
overloads to various functions which are used by those projects and llvm
which have OwningPtr's as parameters. This should allow out of tree
projects some time to move. There are also no changes to libs/Target,
which should help out of tree targets have time to move, if necessary.
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