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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216215 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211804 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211325 91177308-0d34-0410-b5e6-96231b3b80d8
This fixes the processing of --plugin-opt=-jump-table-type=arity.
Nice properties:
* We call InitTargetOptionsFromCodeGenFlags once.
* We call parseCodeGenDebugOptions once.
* It works :-)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211322 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211305 91177308-0d34-0410-b5e6-96231b3b80d8
This is a minimal change to remove the header. I will remove the occurrences
of "using std::error_code" in a followup patch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210803 91177308-0d34-0410-b5e6-96231b3b80d8
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203083 91177308-0d34-0410-b5e6-96231b3b80d8
The cmake build didn't support EXPORTED_SYMBOL_FILE. Instead, it had a
Windows-only implementation in tools/lto/CMakeLists.txt, a linux-only
implementation in tools/gold/CMakeLists.txt, and a darwin-only implementation
in tools/clang/tools/libclang/CMakeLists.txt.
This attempts to consolidate these one-offs into a single place. Clients can now
just set LLVM_EXPORTED_SYMBOL_FILE and things (hopefully) Just Work, like in
the make build.
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This file hasn't been updated in years. Remove old information and point to
the current documentation at GoldPlugin.rst.
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There are two ways one could implement hiding of linkonce_odr symbols in LTO:
* LLVM tells the linker which symbols can be hidden if not used from native
files.
* The linker tells LLVM which symbols are not used from other object files,
but will be put in the dso symbol table if present.
GOLD's API is the second option. It was implemented almost 1:1 in llvm by
passing the list down to internalize.
LLVM already had partial support for the first option. It is also very similar
to how ld64 handles hiding these symbols when *not* doing LTO.
This patch then
* removes the APIs for the DSO list.
* marks LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN all linkonce_odr unnamed_addr
global values and other linkonce_odr whose address is not used.
* makes the gold plugin responsible for handling the API mismatch.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193800 91177308-0d34-0410-b5e6-96231b3b80d8
Generalize the API so we can distinguish symbols that are needed just for a DSO
symbol table from those that are used from some native .o.
The symbols that are only wanted for the dso symbol table can be dropped if
llvm can prove every other dso has a copy (linkonce_odr) and the address is not
important (unnamed_addr).
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This makes it possible to add timers to the code generator and still use them
with -plugin-opt=emit-llvm.
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In order to appease people (in Apple) who accuse me for committing "huge change" (?) without proper review.
Thank Eric for fixing a compile-warning.
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1. Add some helper classes for partitions. They are designed in a
way such that the top-level LTO driver will not see much difference
with or without partitioning.
2. Introduce work-dir. Now all intermediate files generated during
LTO phases will be saved under work-dir. User can specify the workdir
via -lto-workdir=/path/to/dir. By default the work-dir will be
erased before linker exit. To keep the workdir, do -lto-keep, or -lto-keep=1.
TODO: Erase the workdir, if the linker exit prematurely.
We are currently not able to remove directory on signal. The support
routines simply ignore directory.
3. Add one new API lto_codegen_get_files_need_remove().
Linker and LTO plugin will communicate via this API about which files
(including directories) need to removed before linker exit.
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The main observation is that we never need both the filesize and the map size.
When mapping a slice of a file, it doesn't make sense to request a null
terminator and that would be the only case where the filesize would be used.
There are other cleanups that should be done in this area:
* A client should not have to pass the size (even an explicit -1) to say if
it wants a null terminator or not, so we should probably swap the argument
order.
* The default should be to not require a null terminator. Very few clients
require this, but many end up asking for it just because it is the default.
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The gold plugin was passing the desired map size as the file size. This was
working for two reasons:
* Recent version of gold provide the get_view callback, so this code was not
used.
* In older versions, getOpenFile was called, but the file size is never used
if we don't require null terminated buffers and map size defaults to the
file size.
Thanks to Eli Bendersky for noticing this.
I will try to make this api a bit less error prone.
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