Imported functions and variable get the visibility from the module supplying the
definition. However, non-imported definitions do not get the visibility from
(ELF) the most constraining visibility among all modules (Mach-O) the visibility
of the prevailing definition.
This patch
* adds visibility bits to GlobalValueSummary::GVFlags
* computes the result visibility and propagates it to all definitions
Protected/hidden can imply dso_local which can enable some optimizations (this
is stronger than GVFlags::DSOLocal because the implied dso_local can be
leveraged for ELF -shared while default visibility dso_local has to be cleared
for ELF -shared).
Note: we don't have summaries for declarations, so for ELF if a declaration has
the most constraining visibility, the result visibility may not be that one.
Differential Revision: https://reviews.llvm.org/D92900
This matches LLD and fixes https://sourceware.org/bugzilla/show_bug.cgi?id=26262#c1
.o is a bad choice for save-temps output because it is easy to override the bitcode file (*.o)
```
# Use bfd for the example, -fuse-ld=gold is similar.
clang -flto -c a.c # generate bitcode file a.o
clang -fuse-ld=bfd -flto a.o -o a -Wl,-plugin-opt=save-temps # override a.o
# The user repeats the command but get surprised, because a.o is now a combined module.
clang -fuse-ld=bfd -flto a.o -o a -Wl,-plugin-opt=save-temps
```
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D84132
Summary:
That unless the user requested an output object (--lto-obj-path), the an
unused empty combined module is not emitted.
This changed is helpful for some target (ex. RISCV-V) which encoded the
ABI info in IR module flags (target-abi). Empty unused module has no ABI
info so the linker would get the linking error during merging
incompatible ABIs.
Reviewers: tejohnson, espindola, MaskRay
Subscribers: emaste, inglorion, arichardson, hiraditya, simoncook, MaskRay, steven_wu, dexonsmith, PkmX, dang, lenary, s.egerton, luismarques, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78988
Follow-up for D74433
What the function returns are almost standard BFD names, except that "ELF" is
in uppercase instead of lowercase.
This patch changes "ELF" to "elf" and changes ARM/AArch64 to use their BFD names.
MIPS and PPC64 have endianness differences as well, but this patch does not intend to address them.
Advantages:
* llvm-objdump: the "file format " line matches GNU objdump on ARM/AArch64 objects
* "file format " line can be extracted and fed into llvm-objcopy -O literally.
(https://github.com/ClangBuiltLinux/linux/issues/779 has such a use case)
Affected tools: llvm-readobj, llvm-objdump, llvm-dwarfdump, MCJIT (internal implementation detail, not exposed)
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D76046
Summary:
We hit undefined references building with ThinLTO when one source file
contained explicit instantiations of a template method (weak_odr) but
there were also implicit instantiations in another file (linkonce_odr),
and the latter was the prevailing copy. In this case the symbol was
marked hidden when the prevailing linkonce_odr copy was promoted to
weak_odr. It led to unsats when the resulting shared library was linked
with other code that contained a reference (expecting to be resolved due
to the explicit instantiation).
Add a CanAutoHide flag to the GV summary to allow the thin link to
identify when all copies are eligible for auto-hiding (because they were
all originally linkonce_odr global unnamed addr), and only do the
auto-hide in that case.
Most of the changes here are due to plumbing the new flag through the
bitcode and llvm assembly, and resulting test changes. I augmented the
existing auto-hide test to check for this situation.
Reviewers: pcc
Subscribers: mehdi_amini, inglorion, eraman, dexonsmith, arphaman, dang, llvm-commits, steven_wu, wmi
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59709
llvm-svn: 360466
Summary:
GNU nm (and other nm implementations, such as "go tool nm") prints an explicit "no symbols" message when an object file has no symbols. Currently llvm-nm just doesn't print anything. Adding an explicit "no symbols" message will allow llvm-nm to be used in place of nm: some scripts and build processes use `nm <file> | grep "no symbols"` as a test to see if a file has no symbols. It will also be more familiar to anyone used to nm.
That said, the format implemented here is slightly different, in that it doesn't print the tool name in the message (which IMHO is not useful to include).
Demo:
```
$ for nm in nm bin/llvm-nm ; do echo "nm implementation: $nm"; $nm /tmp/foo{1,2}.o; echo; done
nm implementation: nm
/tmp/foo1.o:
nm: /tmp/foo1.o: no symbols
/tmp/foo2.o:
0000000000000000 T foo2
nm implementation: bin/llvm-nm
/tmp/foo1.o:
no symbols
/tmp/foo2.o:
0000000000000000 T foo2
```
Reviewers: MaskRay
Reviewed By: MaskRay
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D52810
llvm-svn: 343742
Summary:
In the individual index files emitted for distributed ThinLTO backends,
the module path ids are not contiguous. Assign slots to module paths in
order to handle this better and also to get contiguous numbering in the
summary assembly.
Reviewers: davidxl, dexonsmith
Subscribers: mehdi_amini, inglorion, eraman, llvm-commits, steven_wu
Differential Revision: https://reviews.llvm.org/D48698
llvm-svn: 336148
Summary:
A recent fix to drop dead symbols (r323633) did not work for ThinLTO
distributed backends because we lose the WithGlobalValueDeadStripping
set on the index during the thin link. This patch adds a new flags
record to the bitcode format for the index, and serializes this flag
for the combined index (it would always be 0 for the per-module index
generated by the compile step, so no need to serialize the new flags
record there until/unless we add another flag that applies to the
per-module indexes).
Generally this flag should always be set for the distributed backends,
which are necessarily performed after the thin link. However, if we were
to simply set this flag on the index applied to the distributed backends
(invoked via clang), we would lose the ability to disable dead stripping
via -compute-dead=false for debugging purposes.
Reviewers: grimar, pcc
Subscribers: mehdi_amini, inglorion, eraman, llvm-commits
Differential Revision: https://reviews.llvm.org/D42799
llvm-svn: 324444
Summary:
1. Use stream 0 only for combined module. Previously if combined module was not
processes ThinLTO used the stream for own output. However small changes in input,
could trigger combined module and shuffle outputs making life of llvm::LTO harder.
2. Always process combined module and write output to stream 0. Processing empty
combined module is cheap and allows llvm::LTO users to avoid implementing processing
which is already done in llvm::LTO.
Subscribers: mehdi_amini, inglorion, eraman, hiraditya
Differential Revision: https://reviews.llvm.org/D41267
llvm-svn: 320905
Add a top-level STRTAB block containing a string table blob, and start storing
strings for module codes FUNCTION, GLOBALVAR, ALIAS, IFUNC and COMDAT in
the string table.
This change allows us to share names between globals and comdats as well
as between modules, and improves the efficiency of loading bitcode files by
no longer using a bit encoding for symbol names. Once we start writing the
irsymtab to the bitcode file we will also be able to share strings between
it and the module.
On my machine, link time for Chromium for Linux with ThinLTO decreases by
about 7% for no-op incremental builds or about 1% for full builds. Total
bitcode file size decreases by about 3%.
As discussed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2017-April/111732.html
Differential Revision: https://reviews.llvm.org/D31838
llvm-svn: 300464
These tests are missing a target triple and the -m elf_x86_64 gold option,
which makes them fail on non-x86 targets.
Differential revision: https://reviews.llvm.org/D28285
Reviewers: tejohnson
llvm-svn: 290965
Also, udpate the ~60 failing tests in the tree which did
not contain a valid datalayout.
This fixes PR31123. lld will be updated in a following patch,
immediately after this is committed.
Differential Revision: https://reviews.llvm.org/D27082
llvm-svn: 289719
Summary:
The gold-plugin changes added along with the new LTO API in r278338 had
the effect of removing the management of the PluginInputFile that
ensured the files weren't released back to gold until the backend
threads were complete. Add back the old file handling.
Fixes PR29020.
Reviewers: mehdi_amini
Subscribers: mehdi_amini, llvm-commits, hjl.tools
Differential Revision: https://reviews.llvm.org/D23721
llvm-svn: 279356
This restores commit r278330, with fixes for a few bot failures:
- Fix a late change I had made to the save temps output file that I
missed due to existing files sitting on my disk
- Fix a bunch of Windows bot failures with "ambiguous call to overloaded
function" due to confusion between llvm::make_unique vs
std::make_unique (preface the new make_unique calls with "llvm::")
- Attempt to fix a modules bot failure by adding a missing include
to LTO/Config.h.
Original change:
Resolution-based LTO API.
Summary:
This introduces a resolution-based LTO API. The main advantage of this API over
existing APIs is that it allows the linker to supply a resolution for each
symbol in each object, rather than the combined object as a whole. This will
become increasingly important for use cases such as ThinLTO which require us
to process symbol resolutions in a more complicated way than just adjusting
linkage.
Patch by Peter Collingbourne.
Reviewers: rafael, tejohnson, mehdi_amini
Subscribers: lhames, tejohnson, mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D20268
llvm-svn: 278338
This reverts commit r278330.
I made a change to the save temps output that is causing issues with the
bots. Didn't realize this because I had older output files sitting on
disk in my test output directory.
llvm-svn: 278331
Summary:
This introduces a resolution-based LTO API. The main advantage of this API over
existing APIs is that it allows the linker to supply a resolution for each
symbol in each object, rather than the combined object as a whole. This will
become increasingly important for use cases such as ThinLTO which require us
to process symbol resolutions in a more complicated way than just adjusting
linkage.
Patch by Peter Collingbourne.
Reviewers: rafael, tejohnson, mehdi_amini
Subscribers: lhames, tejohnson, mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D20268
Address review comments
llvm-svn: 278330
While testing a follow-on change to enable index-based symbol resolution
and internalization in the distributed backends, I realized that a test
case change I made in r275247 was only required because we were not
analyzing symbols in the claimed files in thinlto-index-only mode.
In the fixed test case there should be no internalization because we are
linking in -shared mode, so f() is in fact exported, which is detected
properly when we analyze symbols in thinlto-index-only mode. Note that
this is not (yet) a correctness issue (because we are not yet performing
the index-based linkage optimizations in the distributed backends -
that's coming in a follow-on patch).
llvm-svn: 275277
Internalization was missing cases where we originally had a local symbol
that was promoted eagerly but not actually exported. This is because we
were only internalizing the set of global (non-local) symbols that were
PREVAILAING_DEF_IRONLY. Instead, collect the set of global symbols that
are referenced outside of a single IR file, and skip internalization for
those.
llvm-svn: 275247
This restores commit r268627:
Summary:
When launching ThinLTO backends in a distributed build (currently
supported in gold via the thinlto-index-only plugin option), emit
an individual index file for each backend process as described here:
http://lists.llvm.org/pipermail/llvm-dev/2016-April/098272.html
...
Differential Revision: http://reviews.llvm.org/D19556
Address msan failures by avoiding std::prev on map.end(), the
theory is that this is causing issues due to some known UB problems
in __tree.
llvm-svn: 269059
Summary:
When launching ThinLTO backends in a distributed build (currently
supported in gold via the thinlto-index-only plugin option), emit
an individual index file for each backend process as described here:
http://lists.llvm.org/pipermail/llvm-dev/2016-April/098272.html
The individual index file encodes the summary and module information
required for implementing the importing/exporting decisions made
for a given module in the thin link step.
This is in place of the current mechanism that uses the combined index
to make importing decisions in each back end independently. It is an
enabler for doing global summary based optimizations in the thin link
step (which will be recorded in the individual index files), and reduces
the size of the index that must be sent to each backend process, and
the amount of work to scan it in the backends.
Rather than create entirely new ModuleSummaryIndex structures (and all
the included unique_ptrs) for each backend index file, a map is created
to record all of the GUID and summary pointers needed for a particular
index file. The IndexBitcodeWriter walks this map instead of the full
index (hiding the details of managing the appropriate summary iteration
in a new iterator subclass). This is more efficient than walking the
entire combined index and filtering out just the needed summaries during
each backend bitcode index write.
Depends on D19481.
Reviewers: joker.eph
Subscribers: llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D19556
llvm-svn: 268627
Summary:
With the removal of support for lazy parsing of combined index summary
records (e.g. r267344), we no longer need to include the summary record
bitcode offset in the VST entries for definitions. Change the combined
index format to be similar to the per-module index format in using value
ids to cross-reference from the summary record to the VST entry (rather
than the summary record bitcode offset to cross-reference in the other
direction).
The visible changes are:
1) Add the value id to the combined summary records
2) Remove the summary offset from the combined VST records, which has
the following effects:
- No longer need the VST_CODE_COMBINED_GVDEFENTRY record, as all
combined index VST entries now only contain the value id and
corresponding GUID.
- No longer have duplicate VST entries in the case where there are
multiple definitions of a symbol (e.g. weak/linkonce), as they all
have the same value id and GUID.
An implication of #2 above is that in order to hook up an alias to the
correct aliasee based on the value id of the aliasee recorded in the
combined index alias record, we need to scan the entries in the index
for that GUID to find the one from the same module (i.e. the case where
there are multiple entries for the aliasee). But the reader no longer
has to maintain a special map to hook up the alias/aliasee.
Reviewers: joker.eph
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D19481
llvm-svn: 267712
Summary:
Let keep llvm-as "dumb": it converts textual IR to bitcode. This
commit removes the dependency from llvm-as to libLLVMAnalysis.
We'll add back summary in llvm-as if we get to a textual
representation for it at some point. In the meantime, opt seems
like a better place for that.
Reviewers: tejohnson
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D19032
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266131
(Resubmitting after fixing missing file issue)
With the changes in r263275, there are now more than just functions in
the summary. Completed the renaming of data structures (started in
r263275) to reflect the wider scope. In particular, changed the
FunctionIndex* data structures to ModuleIndex*, and renamed related
variables and comments. Also renamed the files to reflect the changes.
A companion clang patch will immediately succeed this patch to reflect
this renaming.
llvm-svn: 263513
With the changes in r263275, there are now more than just functions in
the summary. Completed the renaming of data structures (started in
r263275) to reflect the wider scope. In particular, changed the
FunctionIndex* data structures to ModuleIndex*, and renamed related
variables and comments. Also renamed the files to reflect the changes.
A companion clang patch will immediately succeed this patch to reflect
this renaming.
llvm-svn: 263490
Summary:
This patch adds support for including a full reference graph including
call graph edges and other GV references in the summary.
The reference graph edges can be used to make importing decisions
without materializing any source modules, can be used in the plugin
to make file staging decisions for distributed build systems, and is
expected to have other uses.
The call graph edges are recorded in each function summary in the
bitcode via a list of <CalleeValueIds, StaticCount> tuples when no PGO
data exists, or <CalleeValueId, StaticCount, ProfileCount> pairs when
there is PGO, where the ValueId can be mapped to the function GUID via
the ValueSymbolTable. In the function index in memory, the call graph
edges reference the target via the CalleeGUID instead of the
CalleeValueId.
The reference graph edges are recorded in each summary record with a
list of referenced value IDs, which can be mapped to value GUID via the
ValueSymbolTable.
Addtionally, a new summary record type is added to record references
from global variable initializers. A number of bitcode records and data
structures have been renamed to reflect the newly expanded scope of the
summary beyond functions. More cleanup will follow.
Reviewers: joker.eph, davidxl
Subscribers: joker.eph, llvm-commits
Differential Revision: http://reviews.llvm.org/D17212
llvm-svn: 263275
Summary:
Launch ThinLTO backends (LTO and codegen pipelines with importing) in
parallel using a ThreadPool, after creating the combined index.
The number of threads is controlled by the existing -jobs gold plugin
option, or the hardware concurrency if not specified.
The old behavior of exiting after creating the combined index can be
invoked via a new thinlto-index-only plugin option.
This commit involves just the ThinLTO-specific pieces of D15390, the NFC
and other restructuring pieces were committed independently:
r262677: Add hardware_concurrency interface to llvm::thread (NFC)
r262719: Change split code gen to use ThreadPool
r262721: Refactor gold-plugin codegen to prepare for ThinLTO threads (NFC)
Reviewers: pcc, joker.eph, rafael
Subscribers: rafael, davidxl, llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D15390
llvm-svn: 262724
This restores commit r260408, along with a fix for a bot failure.
The bot failure was caused by dereferencing a unique_ptr in the same
call instruction parameter list where it was passed via std::move.
Apparently due to luck this was not exposed when I built the compiler
with clang, only with gcc.
llvm-svn: 260442
Summary:
This patch uses the lower 64-bits of the MD5 hash of a function name as
a GUID in the function index, instead of storing function names. Any
local functions are first given a global name by prepending the original
source file name. This is the same naming scheme and GUID used by PGO in
the indexed profile format.
This change has a couple of benefits. The primary benefit is size
reduction in the combined index file, for example 483.xalancbmk's
combined index file was reduced by around 70%. It should also result in
memory savings for the index file in memory, as the in-memory map is
also indexed by the hash instead of the string.
Second, this enables integration with indirect call promotion, since the
indirect call profile targets are recorded using the same global naming
convention and hash. This will enable the function importer to easily
locate function summaries for indirect call profile targets to enable
their import and subsequent promotion.
The original source file name is recorded in the bitcode in a new
module-level record for use in the ThinLTO backend pipeline.
Reviewers: davidxl, joker.eph
Subscribers: llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D17028
llvm-svn: 260408
Summary:
Several fixes to the handling of bitcode files without function summary
sections so that they are skipped during ThinLTO processing in llvm-lto
and the gold plugin when appropriate instead of aborting.
1 Don't assert when trying to add a FunctionInfo that doesn't have
a summary attached.
2 Skip FunctionInfo structures that don't have attached function summary
sections when trying to create the combined function summary.
3 In both llvm-lto and gold-plugin, check whether a bitcode file has
a function summary section before trying to parse the index, and skip
the bitcode file if it does not.
4 Fix hasFunctionSummaryInMemBuffer in BitcodeReader, which had a bug
where we returned to early while looking for the summary section.
Also added llvm-lto and gold-plugin based tests for cases where we
don't have function summaries in the bitcode file. I verified that
either the first couple fixes described above are enough to avoid the
crashes, or fixes 1,3,4. But have combined them all here for added
robustness.
Reviewers: joker.eph
Subscribers: llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D14903
llvm-svn: 253796
Summary:
Adds support for automatically detecting and printing strings
represented by Array abbrev operands, analogous to the string dumping
performed for Blob abbrev operands.
Enhanced the ThinLTO combined index test to check for the appropriate
module and function strings.
Reviewers: dexonsmith, joker.eph, davidxl
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13553
llvm-svn: 249695
Summary:
The bitcode format is described in this document:
https://drive.google.com/file/d/0B036uwnWM6RWdnBLakxmeDdOeXc/view
For more info on ThinLTO see:
https://sites.google.com/site/llvmthinlto
The first customer is ThinLTO, however the data structures are designed
and named more generally based on prior feedback. There are a few
comments regarding how certain interfaces are used by ThinLTO, and the
options added here to gold currently have ThinLTO-specific names as the
behavior they provoke is currently ThinLTO-specific.
This patch includes support for generating per-module function indexes,
the combined index file via the gold plugin, and several tests
(more are included with the associated clang patch D11908).
Reviewers: dexonsmith, davidxl, joker.eph
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13107
llvm-svn: 249270
