Commit Graph

41 Commits

Author SHA1 Message Date
Teresa Johnson 04c9a2d63d [ThinLTO] Refactor ODR resolution and internalization (NFC)
Move the now index-based ODR resolution and internalization routines out
of ThinLTOCodeGenerator.cpp and into either LTO.cpp (index-based
analysis) or FunctionImport.cpp (index-driven optimizations).
This is to enable usage by other linkers.

llvm-svn: 270698
2016-05-25 14:03:11 +00:00
Teresa Johnson 4ae5ce7e8e [ThinLTO] Handle empty exports list for module.
We might have an empty exports list for a module and shouldn't assert
when checking if a symbol is exported.

llvm-svn: 270600
2016-05-24 19:12:48 +00:00
Teresa Johnson 141149ff48 [ThinLTO] Fix bot failures by avoiding threaded map modifications
Ensure multiple threads won't have to modify map, probable cause of
bot failures from r270584 such as:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/13095

llvm-svn: 270595
2016-05-24 18:44:01 +00:00
Teresa Johnson 4d2613f276 [ThinLTO] Change ODR resolution and internalization to be index-based
Summary:
This patch changes the ODR resolution and internalization to be based on
updates to the Index, which are consumed by the backend portion of the
transformations.

It will be followed by an NFC change to move these out of libLTO's
ThinLTOCodeGenerator so that it can be used by other linkers
(gold and lld) and by ThinLTO distributed backends.

The global summary-based portions use callbacks so that the client can
determine the prevailing copy and other information in a client-specific
way. Eventually, with the API being developed in D20268, these may be
modified to use information such as symbol resolutions, supplied by the
clients to the API.

Reviewers: joker-eph

Subscribers: joker.eph, pcc, llvm-commits

Differential Revision: http://reviews.llvm.org/D20290

llvm-svn: 270584
2016-05-24 17:24:25 +00:00
Teresa Johnson df6edc5277 [ThinLTO] Refactor module loader handling into new LTO file (NFC)
Moved the ModuleLoader and supporting helper loadModuleFromBuffer out of
ThinLTOCodeGenerator and into new LTO.h/LTO.cpp files. This is in
preparation for a patch that will utilize these in the gold-plugin.

Note that there are some other pending patches (D20268 and D20290) that
also plan to refactor common interfaces and functionality into this same
pair of new files.

llvm-svn: 270509
2016-05-23 22:54:06 +00:00
Mehdi Amini 819e9cdfb4 ThinLTO: sort inputs and schedule by decreasing size
This is a compile time optimization: keeping a large file to process
at the end hurts parallelism.
The heurisitic used right now is the input buffer size, however we
may want to consider the number of functions to import or the
different number of files to load for importing as well.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 269684
2016-05-16 19:33:07 +00:00
Mehdi Amini 001bb41556 ThinLTO caching: reload cached file with mmap and drop heap-allocated memory buffer
This is reducing pressure on the OS memory system, and is NFC
when not using a cache.
I measure a 10x memory consumption reduction when linking opt
with full debug info.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 269682
2016-05-16 19:11:59 +00:00
Mehdi Amini af52f28d9d ThinLTOCodeGenerator: fix race condition found using TSAN
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 269588
2016-05-15 05:49:47 +00:00
Mehdi Amini b02139d66f ThinLTOCodeGenerator: handle cases where temporary files can't be renamed
For instance when they're on different filesystem.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 269544
2016-05-14 05:16:35 +00:00
Mehdi Amini 2a16a5fae5 ThinLTOCodeGenerator: handle std::error_code instead of silently dropping it.
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 269541
2016-05-14 04:58:38 +00:00
Teresa Johnson 8570fe47ef [ThinLTO] Add option to emit imports files for distributed backends
Summary:
Add support for emission of plaintext lists of the imported files for
each distributed backend compilation. Used for distributed build file
staging.

Invoked with new gold-plugin thinlto-emit-imports-files option, which is
only valid with thinlto-index-only (i.e. for distributed builds), or
from llvm-lto with new -thinlto-action=emitimports value.

Depends on D19556.

Reviewers: joker.eph

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D19636

llvm-svn: 269067
2016-05-10 15:54:09 +00:00
Teresa Johnson 84174c3771 Restore "[ThinLTO] Emit individual index files for distributed backends"
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
2016-05-10 13:48:23 +00:00
Vitaly Buka 1df2338bb6 Revert "[ThinLTO] Emit individual index files for distributed backends"
MemorySanitizer: use-of-uninitialized-value in lib/Bitcode/Writer/BitcodeWriter.cpp:364:70
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/12544/steps/check-llvm%20msan/logs/stdio

This reverts commit 0c4a898ea550699d1b2f4fe3767251c8f9a48d52.

llvm-svn: 268660
2016-05-05 18:31:00 +00:00
Teresa Johnson 9254ebe3c0 [ThinLTO] Emit individual index files for distributed backends
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
2016-05-05 13:44:56 +00:00
Mehdi Amini 4b300e0ac2 ThinLTOCodeGenerator: remove useless temporary file that was emitted.
This was a remaining of a previous scheme where some IPOs were taking
place before we enter this code. This is not relevant anymore.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 268605
2016-05-05 05:14:16 +00:00
Sjoerd Meijer 41beee6575 Clean up to avoid compiler warnings for casting away const qualifiers.
Differential Revision: http://reviews.llvm.org/D19598

llvm-svn: 267753
2016-04-27 18:35:02 +00:00
Mehdi Amini aa309b1a81 ThinLTOCodeGenerator: preserve linkonce when in "MustPreserved" set
If the linker specifically requested for a linkonce to be preserved,
we need to make sure we won't drop it even if all the uses in the
current module disappear.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267543
2016-04-26 10:35:01 +00:00
Teresa Johnson c851d216e2 [ThinLTO] Introduce typedef for commonly-used map type (NFC)
Add a typedef for the std::map<GlobalValue::GUID, GlobalValueSummary *>
map that is passed around to identify summaries for values defined in a
particular module. This shortens up declarations in a variety of places.

llvm-svn: 267471
2016-04-25 21:09:51 +00:00
Teresa Johnson 28e457bccd [ThinLTO] Remove GlobalValueInfo class from index
Summary:
Remove the GlobalValueInfo and change the ModuleSummaryIndex to directly
reference summary objects. The info structure was there to support lazy
parsing of the combined index summary objects, which is no longer
needed and not supported.

Reviewers: joker.eph

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19462

llvm-svn: 267344
2016-04-24 14:57:11 +00:00
Mehdi Amini 059464fe36 Add an internalization step to the ThinLTOCodeGenerator
Keeping as much as possible internal/private is
known to help the optimizer. Let's try to benefit from
this in ThinLTO.
Note: this is early work, but is enough to build clang (and
all the LLVM tools). I still need to write some lit-tests...

Differential Revision: http://reviews.llvm.org/D19103

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 267317
2016-04-24 03:18:01 +00:00
Teresa Johnson 6fb3f19959 [ThinLTO] Remove unused/incomplete lazy summary reading support (NFC)
This removes the interfaces added (and not yet complete) to support
lazy reading of summaries. This support is not expected to be needed
since we are moving to a model where the full index is only being
traversed in the thin link step, instead of the back ends.

(The second part of this that I plan to do next is remove the
GlobalValueInfo from the ModuleSummaryIndex - it was mostly needed to
support lazy parsing of summaries. The index can instead reference the
summary structures directly.)

llvm-svn: 267097
2016-04-22 01:52:00 +00:00
Mehdi Amini f95f77adf6 ThinLTO: add module caching handling.
Differential Revision: http://reviews.llvm.org/D18494

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266959
2016-04-21 05:54:23 +00:00
Mehdi Amini a71a5a6289 ThinLTO: Resolve linkonce_odr aliases just like functions
This help to streamline the process of handling importing since
we don't need to special case alias everywhere: just like
linkonce_odr function, make sure at least one alias is emitted
by turning it weak.

Differential Revision: http://reviews.llvm.org/D19308

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266958
2016-04-21 05:47:17 +00:00
Teresa Johnson 07c7e25718 Enable ODR uniquing of DITypes in more places
Summary:
This is a follow-on to apply Duncan's new DIType ODR uniquing from
r266549 and r266713 in more places.

Enable enableDebugTypeODRUniquing() for ThinLTO backends invoked via
libLTO, similar to the way r266549 enabled this for ThinLTO backend
threads launched from gold-plugin.

Also enable enableDebugTypeODRUniquing in opt, similar to the way
r266549 enabled this for llvm-link (on by default, can be disabled with
new -disable-debug-info-type-map option), since we may perform ThinLTO
importing from opt.

Reviewers: dexonsmith, joker.eph

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D19263

llvm-svn: 266746
2016-04-19 15:48:30 +00:00
Mehdi Amini 1aafabf752 ThinLTO: Move the ODR resolution to be based purely on the summary.
This is a requirement for the cache handling in D18494

Differential Revision: http://reviews.llvm.org/D18908

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266519
2016-04-16 07:02:16 +00:00
Mehdi Amini 8dcc8080ce ThinLTO: linkonce compile-time optimization, do not bother when there is only one input file
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266281
2016-04-14 08:46:22 +00:00
Teresa Johnson 2d5487cf44 [ThinLTO] Move summary computation from BitcodeWriter to new pass
Summary:
This is the first step in also serializing the index out to LLVM
assembly.

The per-module summary written to bitcode is moved out of the bitcode
writer and to a new analysis pass (ModuleSummaryIndexWrapperPass).
The pass itself uses a new builder class to compute index, and the
builder class is used directly in places where we don't have a pass
manager (e.g. llvm-as).

Because we are computing summaries outside of the bitcode writer, we no
longer can use value ids created by the bitcode writer's
ValueEnumerator. This required changing the reference graph edge type
to use a new ValueInfo class holding a union between a GUID (combined
index) and Value* (permodule index). The Value* are converted to the
appropriate value ID during bitcode writing.

Also, this enables removal of the BitWriter library's dependence on the
Analysis library that was previously required for the summary computation.

Reviewers: joker.eph

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D18763

llvm-svn: 265941
2016-04-11 13:58:45 +00:00
Teresa Johnson 3c35e0999b Clean up calls to WriteBitcodeToFile (NFC)
Remove a default parameter value being passed unnecessarily, which
also reduces the changes required when this parameter is changed in
D18763.

Document the remaining non-default bool value passed for another
parameter.

llvm-svn: 265348
2016-04-04 21:19:31 +00:00
Mehdi Amini 024a79f780 Revert "ThinLTO: add module caching handling."
This reverts commit r265214, unintentionally commited.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265216
2016-04-02 05:08:18 +00:00
Mehdi Amini 2cd609482d ThinLTO: add module caching handling.
Reviewers: tejohnson

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D18494

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265214
2016-04-02 05:07:08 +00:00
Hans Wennborg fa6e414eef Fix -Wpedantic warning about extra semi-colon
llvm-svn: 265204
2016-04-02 01:03:41 +00:00
Mehdi Amini 5a2e5d324e ThinLTO: special handling for LinkOnce functions
These function can be dropped by the compiler if they are no longer
referenced in the current module. However there is a change that
another module is still referencing them because of the import.

Multiple solutions can be used:

- Always import LinkOnce when a caller is imported. This ensure that
  every module with a call to a LinkOnce has the definition and will
  be able to emit it if it emits the call.
- Turn the LinkOnce into Weak, so that it is always emitted.
- Turn all LinkOnce into available_externally and come back after all
  modules are codegen'ed to emit only one copy of the linkonce, when
  there is still a reference to it.

This patch implement the second option, with am optimization that
only *one* module will turn the LinkOnce into Weak, while the others
will turn it into available_externally, so that there is exactly one
copy emitted for the whole compilation.

http://reviews.llvm.org/D18346

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265190
2016-04-01 21:53:50 +00:00
Mehdi Amini 215d59e7b0 ThinLTO: move ObjCARCContractPass in the CodeGen pipeline
This is to be coherent with Full LTO.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265118
2016-04-01 08:22:59 +00:00
Mehdi Amini 43b657b5c7 Add a libLTO API to stop/restart ThinLTO between optimizations and CodeGen
This allows the linker to instruct ThinLTO to perform only the
optimization part or only the codegen part of the process.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 265113
2016-04-01 06:47:02 +00:00
Mehdi Amini 01e321306b ThinLTO: use the callgraph from the combined index to drive the FunctionImporter
Summary:
Now that the summary contains the full reference/call graph, we can
replace the existing function importer that loads and inspect the IR
to iteratively walk the call graph by a traversal based purely on the
summary information. Decouple the actual importing decision from any
IR manipulation.

Reviewers: tejohnson

Subscribers: llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D18343

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 264503
2016-03-26 05:40:34 +00:00
Teresa Johnson 26ab5772b0 [ThinLTO] Renaming of function index to module summary index (NFC)
(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
2016-03-15 00:04:37 +00:00
Teresa Johnson cec0cae313 Revert "[ThinLTO] Renaming of function index to module summary index (NFC)"
This reverts commit r263490. Missed a file.

llvm-svn: 263493
2016-03-14 21:18:10 +00:00
Teresa Johnson 892920b358 [ThinLTO] Renaming of function index to module summary index (NFC)
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
2016-03-14 21:05:56 +00:00
Teresa Johnson 76a1c1d0ba [ThinLTO] Support for reference graph in per-module and combined summary.
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
2016-03-11 18:52:24 +00:00
Mehdi Amini 09b4a8daa3 Add a flag to the LLVMContext to disable name for Value other than GlobalValue
Summary:
This is intended to be a performance flag, on the same level as clang
cc1 option "--disable-free". LLVM will never initialize it by default,
it will be up to the client creating the LLVMContext to request this
behavior. Clang will do it by default in Release build (just like
--disable-free).

"opt" and "llc" can opt-in using -disable-named-value command line
option.

When performing LTO on llvm-tblgen, the initial merging of IR peaks
at 92MB without this patch, and 86MB after this patch,setNameImpl()
drops from 6.5MB to 0.5MB.
The total link time goes from ~29.5s to ~27.8s.

Compared to a compile-time flag (like the IRBuilder one), it performs
very close. I profiled on SROA and obtain these results:

 420ms with IRBuilder that preserve name
 372ms with IRBuilder that strip name
 375ms with IRBuilder that preserve name, and a runtime flag to strip

Reviewers: chandlerc, dexonsmith, bogner

Subscribers: joker.eph, llvm-commits

Differential Revision: http://reviews.llvm.org/D17946

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 263086
2016-03-10 01:28:54 +00:00
Mehdi Amini 7c4a1a8d48 libLTO: add a ThinLTOCodeGenerator on the model of LTOCodeGenerator.
This is intended to provide a parallel (threaded) ThinLTO scheme
for linker plugin use through the libLTO C API.

The intent of this patch is to provide a first implementation as a
proof-of-concept and allows linker to start supporting ThinLTO by
definiing the libLTO C API. Some part of the libLTO API are left
unimplemented yet. Following patches will add support for these.

The current implementation can link all clang/llvm binaries.

Differential Revision: http://reviews.llvm.org/D17066

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 262977
2016-03-09 01:37:22 +00:00