Commit Graph

239 Commits

Author SHA1 Message Date
Eugene Leviant 19e238746b [ThinLTO] Recommit of import global variables
This wasreverted in r326638 due to link problems and fixed
afterwards

llvm-svn: 327254
2018-03-12 10:30:50 +00:00
Eric Christopher 3caa0fd050 Revert "[ThinLTO] Keep available_externally symbols live"
This reverts commit r327041 and the followup attempts at fixing the testcase as they're still failing.

llvm-svn: 327094
2018-03-09 01:25:18 +00:00
Vlad Tsyrklevich 7b66ef1036 [ThinLTO] Keep available_externally symbols live
Summary:
This change fixes PR36483. The bug was originally introduced by a change
that marked non-prevailing symbols dead. This broke LowerTypeTests
handling of available_externally functions, which are non-prevailing.
LowerTypeTests uses liveness information to avoid emitting thunks for
unused functions.

Marking available_externally functions dead is incorrect, the functions
are used though the function definitions are not. This change keeps them
live, and lets the EliminateAvailableExternally/GlobalDCE passes remove
them later instead.

I've also enabled EliminateAvailableExternally for all optimization
levels, I believe it being disabled for O1 was an oversight.

Reviewers: pcc, tejohnson

Reviewed By: tejohnson

Subscribers: grimar, mehdi_amini, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D43690

llvm-svn: 327041
2018-03-08 18:48:03 +00:00
Chandler Carruth a4619d9944 [ThinLTO] Revert r325320: Import global variables
This caused some links to fail with ThinLTO due to missing symbols as
well as causing some binaries to have failures at runtime. We're working
with the author to get a test case, but want to get the tree green
again.

Further, it appears to introduce a data race. While the test usage of
threads was disabled in r325361 & r325362, that isn't an acceptable fix.
I've reverted both of these as well. This code needs to be thread safe.
Test cases for this are already on the original commit thread.

llvm-svn: 326638
2018-03-02 23:40:08 +00:00
Charles Saternos b040fcc693 [ThinLTO] Add GraphTraits for FunctionSummaries
Add GraphTraits definitions to the FunctionSummary and ModuleSummaryIndex classes. These GraphTraits will be used to construct find SCC's in ThinLTO analysis passes.

Third attempt - moved function from lambda to static function due to build failures.

llvm-svn: 325506
2018-02-19 15:14:50 +00:00
Simon Pilgrim 0efed32577 Revert: [llvm] r325448 - [ThinLTO] Add GraphTraits for FunctionSummaries
Add GraphTraits definitions to the FunctionSummary and ModuleSummaryIndex classes. These GraphTraits will be used to construct find SCC's in ThinLTO analysis passes.

Second attempt, since last patch caused stage2 build to fail (now using function_ref rather than std::function).

Reverted due to buildbot failures

llvm-svn: 325454
2018-02-18 00:01:36 +00:00
Charles Saternos 35878ee7a4 [ThinLTO] Add GraphTraits for FunctionSummaries
Add GraphTraits definitions to the FunctionSummary and ModuleSummaryIndex classes. These GraphTraits will be used to construct find SCC's in ThinLTO analysis passes.

Second attempt, since last patch caused stage2 build to fail (now using function_ref rather than std::function).

llvm-svn: 325448
2018-02-17 21:39:24 +00:00
Eugene Leviant 7331a0bf1c [ThinLTO] Import global variables
Differential revision: https://reviews.llvm.org/D43077

llvm-svn: 325320
2018-02-16 08:11:04 +00:00
Volodymyr Sapsai 2ad768bb13 Revert "[ThinLTO] Add GraphTraits for FunctionSummaries"
It caused assertion failure
Assertion failed: (!DD.IsLambda && !MergeDD.IsLambda && "faked up lambda definition?"), function MergeDefinitionData, file /Users/buildslave/jenkins/workspace/clang-stage1-configure-RA/llvm/tools/clang/lib/Serialization/ASTReaderDecl.cpp, line 1675.

on the second stage build bots.

llvm-svn: 324932
2018-02-12 20:43:31 +00:00
Charles Saternos d3e7d19f59 [ThinLTO] Add GraphTraits for FunctionSummaries
Add GraphTraits definitions to the FunctionSummary and ModuleSummaryIndex classes. These GraphTraits will be used to construct find SCC's in ThinLTO analysis passes.

llvm-svn: 324854
2018-02-11 22:06:20 +00:00
Steven Wu 33ba93c2b5 [ThinLTO] Teach ThinLTO about auto hide symbols
Summary:
For symbols that has linkonce_odr linkage and unnamed_addr, it can be
auto hide by linker to avoid weak external symbols. Teach ThinLTO to
perform auto hide so it can safely promote linkonce_odr to weak symbols
without breaking this nice property.

Reviewers: tejohnson, mehdi_amini

Reviewed By: tejohnson

Subscribers: inglorion, eraman, rnk, pcc, llvm-commits

Differential Revision: https://reviews.llvm.org/D43130

llvm-svn: 324757
2018-02-09 18:34:08 +00:00
Teresa Johnson 5a95c47730 [ThinLTO] Convert dead alias to declarations
Summary:
This complements the fixes in r323633 and r324075 which drop the
definitions of dead functions and variables, respectively.

Fixes PR36208.

Reviewers: grimar, rafael

Subscribers: mehdi_amini, llvm-commits, inglorion

Differential Revision: https://reviews.llvm.org/D42856

llvm-svn: 324242
2018-02-05 15:44:27 +00:00
George Rimar 0410afd1a3 [ThinLTO] - Add comment. NFC.
Was requested during review of D42798.

llvm-svn: 324095
2018-02-02 15:06:09 +00:00
Peter Collingbourne 7873669be5 LTO: Drop comdats when converting definitions to declarations.
Differential Revision: https://reviews.llvm.org/D42715

llvm-svn: 323844
2018-01-31 02:51:03 +00:00
George Rimar eaf5172ca6 [ThinLTO] - Stop internalizing and drop non-prevailing symbols.
Implementation marks non-prevailing symbols as not live in the summary.
Then them are dropped in backends.

Fixes https://bugs.llvm.org/show_bug.cgi?id=35938

Differential revision: https://reviews.llvm.org/D42107

llvm-svn: 323633
2018-01-29 08:03:30 +00:00
Easwaran Raman c73cec84c9 Re-land "[ThinLTO] Add call edges' relative block frequency to per-module summary."
It was reverted after buildbot regressions.

Original commit message:

This allows relative block frequency of call edges to be passed
to the thinlink stage where it will be used to compute synthetic
entry counts of functions.

llvm-svn: 323460
2018-01-25 19:27:17 +00:00
Eugene Leviant 28d8a49f42 [ThinLTO] Re-commit of dot dumper after test fix
llvm-svn: 323116
2018-01-22 13:35:40 +00:00
Eugene Leviant 72b9bdb71a Temporarily revert r323062 to investigate buildbot failures
llvm-svn: 323065
2018-01-21 10:22:19 +00:00
Eugene Leviant 453c976a63 [ThinLTO] Implement summary visualizer
Differential revision: https://reviews.llvm.org/D41297

llvm-svn: 323062
2018-01-21 07:27:32 +00:00
Eugene Leviant c95b49603e [ThinLTO] Remove unused code
This is a re-commit of r320464, after patch for gold plugin
was landed.

llvm-svn: 320968
2017-12-18 10:53:45 +00:00
Teresa Johnson 69b2de8466 Fix NDEBUG build problem in r320895
Fix incorrect placement of #endif causing NDEBUG build failures.

llvm-svn: 320897
2017-12-16 00:29:31 +00:00
Teresa Johnson 81bbf74265 [ThinLTO] Enable importing of aliases as copy of aliasee
Summary:
This implements a missing feature to allow importing of aliases, which
was previously disabled because alias cannot be available_externally.
We instead import an alias as a copy of its aliasee.

Some additional work was required in the IndexBitcodeWriter for the
distributed build case, to ensure that the aliasee has a value id
in the distributed index file (i.e. even when it is not being
imported directly).

This is a performance win in codes that have many aliases, e.g. C++
applications that have many constructor and destructor aliases.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D40747

llvm-svn: 320895
2017-12-16 00:18:12 +00:00
Eugene Leviant d53f3da772 Revert r320464 as it breaks gold plugin tests
llvm-svn: 320467
2017-12-12 10:12:46 +00:00
Eugene Leviant 3695183395 [ThinLTO] Remove unused code from thinLTOInternalizeModule
Differential revision: https://reviews.llvm.org/D40970

llvm-svn: 320464
2017-12-12 09:12:32 +00:00
Eugene Zelenko e9ea08a097 [Transforms] Fix some Clang-tidy modernize and Include What You Use warnings; other minor fixes (NFC).
llvm-svn: 315383
2017-10-10 22:49:55 +00:00
Dehao Chen ea523ddb1b Revert the change that accidentally went in r314806.
llvm-svn: 314807
2017-10-03 15:50:42 +00:00
Dehao Chen f464627f28 Update getMergedLocation to check the instruction type and merge properly.
Summary: If the merged instruction is call instruction, we need to set the scope to the closes common scope between 2 locations, otherwise it will cause trouble when the call is getting inlined.

Reviewers: dblaikie, aprantl

Reviewed By: dblaikie, aprantl

Subscribers: llvm-commits, sanjoy

Differential Revision: https://reviews.llvm.org/D37877

llvm-svn: 314694
2017-10-02 18:13:14 +00:00
Teresa Johnson f625118ec7 [ThinLTO] Fix dead stripping analysis for SamplePGO
Summary:
The fix for dead stripping analysis in the case of SamplePGO indirect
calls to local functions (r313151) introduced the possibility of an
infinite loop.

Make sure we check for the value being already live after we update it
for SamplePGO indirect call handling.

Reviewers: danielcdh

Subscribers: mehdi_amini, inglorion, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D38086

llvm-svn: 313766
2017-09-20 17:09:47 +00:00
Peter Collingbourne cfbd089237 Reland r313157, "ThinLTO: Correctly follow aliasee references when dead stripping." which was reverted in r313222.
This reland includes a fix for the LowerTypeTests pass so that it
looks past aliases when determining which type identifiers are live.

Differential Revision: https://reviews.llvm.org/D37842

llvm-svn: 313229
2017-09-14 05:02:59 +00:00
Hans Wennborg ae050afeb9 Revert r313157 "ThinLTO: Correctly follow aliasee references when dead stripping."
This broke Chromium's CFI build; see crbug.com/765004.

> We were previously handling aliases during dead stripping by adding
> the aliased global's "original name" GUID to the worklist. This will
> lead to incorrect behaviour if the global has local linkage because
> the original name GUID will not correspond to the global's GUID in
> the summary.
>
> Because an alias is just another name for the global that it
> references, there is no need to mark the referenced global as used,
> or to follow references from any other copies of the global. So all
> we need to do is to follow references from the aliasee's summary
> instead of the alias.
>
> Differential Revision: https://reviews.llvm.org/D37789

llvm-svn: 313222
2017-09-14 00:40:14 +00:00
Peter Collingbourne d067c8ed59 ThinLTO: Correctly follow aliasee references when dead stripping.
We were previously handling aliases during dead stripping by adding
the aliased global's "original name" GUID to the worklist. This will
lead to incorrect behaviour if the global has local linkage because
the original name GUID will not correspond to the global's GUID in
the summary.

Because an alias is just another name for the global that it
references, there is no need to mark the referenced global as used,
or to follow references from any other copies of the global. So all
we need to do is to follow references from the aliasee's summary
instead of the alias.

Differential Revision: https://reviews.llvm.org/D37789

llvm-svn: 313157
2017-09-13 17:09:20 +00:00
Teresa Johnson 1958083d35 [ThinLTO] For SamplePGO, need to handle ICP targets consistently in thin link
Summary:
SamplePGO indirect call profiles record the target as the original GUID
for statics. The importer had special handling to map to the normal GUID
in that case. The dead global analysis needs the same treatment or
inconsistencies arise, resulting in linker unsats due to some dead
symbols being exported and kept, leaving in references to other dead
symbols that are removed.

This can happen when a SamplePGO profile collected by one binary is used
for a different binary, so the indirect call profiles may not accurately
reflect live targets.

Reviewers: danielcdh

Subscribers: mehdi_amini, inglorion, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D37783

llvm-svn: 313151
2017-09-13 15:16:38 +00:00
Benjamin Kramer 154411e0e7 [FunctionImport] Avoid unused variable warnings in Release builds
Just skip the entire block in NDEBUG. No functionality change intended.

llvm-svn: 312031
2017-08-29 20:24:39 +00:00
Teresa Johnson 2df7fc7991 [ThinLTO] Clean up stale alias import handling
Summary:
Remove some code that was no longer needed. The first FIXME is
stale since we long ago started using the index to drive importing,
rather than doing force importing based on linkage type. And
now with r309278, we no longer import any aliases.

Reviewers: dblaikie

Subscribers: inglorion, llvm-commits

Differential Revision: https://reviews.llvm.org/D37266

llvm-svn: 312019
2017-08-29 18:15:34 +00:00
Teresa Johnson 73305f82e9 [ThinLTO] Fix ThinLTO crash
Summary:
Follow up to fix in r311023, which fixed the case where the combined
index is written to disk. The same samplePGO logic exists for the
in-memory index when computing imports, so we need to filter out
GlobalVariable summaries there too.

Reviewers: davidxl

Subscribers: inglorion, llvm-commits

Differential Revision: https://reviews.llvm.org/D36919

llvm-svn: 311254
2017-08-19 18:04:25 +00:00
Xinliang David Li 24524f314c Fix typo /NFC
llvm-svn: 310737
2017-08-11 17:49:20 +00:00
Dehao Chen 8260d66556 Increase the ImportHotMultiplier to 10.0
Summary: The original 3.0 hot mupltiplier is too small, and would prevent hot callsites from being inline. This patch increases the hot multilier to 10.0

Reviewers: davidxl, tejohnson

Reviewed By: tejohnson

Subscribers: llvm-commits, sanjoy

Differential Revision: https://reviews.llvm.org/D35969

llvm-svn: 309344
2017-07-28 01:02:34 +00:00
Davide Italiano 82c7d3768d [FunctionImport] Prefer isa<> to dyn_cast<> as the value is not used.
This change makes GCC7 happy again.

llvm-svn: 309305
2017-07-27 18:38:09 +00:00
David Blaikie 2f0cc477ab ThinLTO: Don't import aliases of any kind (even linkonce_odr)
Summary:
Until a more advanced version of importing can be implemented for
aliases (one that imports an alias as an available_externally definition
of the aliasee), skip the narrow subset of cases that was possible but
came at a cost: aliases of linkonce_odr functions could be imported
because the linkonce_odr function could be safely duplicated from the
source module. This came/comes at the cost of not being able to 'home'
imported linkonce functions (they had to be emitted linkonce_odr in all
the destination modules (even if they weren't used by an alias) rather
than as available_externally - causing extra object size).

Tangentially, this also was the only reason ThinLTO would emit multiple
CUs in to the resulting DWARF - which happens to be a problem for
Fission (there's a fix for this in GDB but not released yet, etc).
(actually it's not the only reason - but I'm sending a patch to fix the
other reason shortly)

There's no reason to believe this particularly narrow alias importing
was especially/meaningfully important, only that it was /possible/ to
implement in this way. When a more general solution is done, it should
still satisfy the DWARF concerns above, since the import will still be
available_externally, and thus not create extra CUs.

Since now all aliases are treated the same, I removed/simplified some
test cases since they were testing corner cases where there are no
longer any corners.

Reviewers: tejohnson, mehdi_amini

Differential Revision: https://reviews.llvm.org/D35875

llvm-svn: 309278
2017-07-27 15:09:06 +00:00
Teresa Johnson f9dc3deaa6 Revert "Restore with fix "[ThinLTO] Ensure we always select the same function copy to import""
This reverts commit r308114 (and follow on fixes to test).

There is a linking failure in a ThinLTO bot:
http://green.lab.llvm.org/green/job/clang-stage2-configure-Rthinlto_build/3663/

(and undefined reference). It seems like it must be a second order
effect of the heuristic change I made, and may take some time to try
to reproduce locally and track down. Therefore, reverting for now.

llvm-svn: 308206
2017-07-17 19:25:38 +00:00
Teresa Johnson a7660b0127 Restore with fix "[ThinLTO] Ensure we always select the same function copy to import"
This restores r308078/r308079 with a fix for bot non-determinisim (make
sure we run llvm-lto in single threaded mode so the debug output doesn't get
interleaved).

llvm-svn: 308114
2017-07-15 22:58:06 +00:00
Chandler Carruth d78a38ed2e Revert r308078 (and subsequent tweak in r308079) which introduces a test
that appears to exhibit non-determinism and is flaking on the bots
pretty consistently.

r308078: [ThinLTO] Ensure we always select the same function copy to import
r308079: Require asserts in new test that uses debug flag
llvm-svn: 308095
2017-07-15 13:50:26 +00:00
Teresa Johnson 82b4fb1afe [ThinLTO] Ensure we always select the same function copy to import
Summary:
Check if the first eligible callee is under the instruction threshold.
Checking this on the first eligible callee ensures that we don't end
up selecting different callees to import when we invoke this routine
with different thresholds due to reaching the callee via paths that
are shallower or hotter (when there are multiple copies, i.e. with
weak or linkonce linkage). We don't want to leave the decision of which
copy to import up to the backend.

Reviewers: mehdi_amini

Subscribers: inglorion, fhahn, llvm-commits

Differential Revision: https://reviews.llvm.org/D35436

llvm-svn: 308078
2017-07-15 04:53:05 +00:00
Dehao Chen 64c46574b0 Increase the import-threshold for crtical functions.
Summary: For interative sample-pgo, if a hot call site is inlined in the profiling binary, we should inline it in before profile annotation in the backend. Before that, the compile phase first collects all GUIDs that needs to be imported and creates virtual "hot" call edge in the summary. However, "hot" is not good enough to guarantee the callsites get inlined. This patch introduces "critical" call edge, and assign much higher importing threshold for those edges.

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: sanjoy, mehdi_amini, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D35096

llvm-svn: 307439
2017-07-07 21:01:00 +00:00
Davide Italiano f4891d29f8 [lib/LTO] Add a comment to explain where we set the linkage in the summary.
Pointed out by Teresa!

llvm-svn: 307305
2017-07-06 20:04:20 +00:00
Davide Italiano 6a5fbe52fa [LTO] Fix the interaction between linker redefined symbols and ThinLTO
This is the same as r304719 but for ThinLTO.
The substantial difference is that in this case we don't have
whole visibility, just the summary.
In the LTO case, when we got the resolution for the input file we
could just see if the linker told us whether a symbol was linker
redefined (using --wrap or --defsym) and switch the linkage directly
for the GV.

Here, we have the summary. So, we record that the linkage changed
from <whatever it was> to $weakany to prevent IPOs across this symbol
boundaries and actually just switch the linkage at FunctionImport time.

This patch should also fixes the lld bits (as all the scaffolding for
communicating if a symbol is linker redefined should be there & should
be the same), but I'll make sure to add some tests there as well.

Fixes PR33192.

Differential Revision:  https://reviews.llvm.org/D35064

llvm-svn: 307303
2017-07-06 19:58:26 +00:00
Evgeniy Stepanov 56584bbf16 (NFC) Track global summary liveness in GVFlags.
Replace GVFlags::LiveRoot with GVFlags::Live and use that instead of
all the DeadSymbols sets. This is refactoring in order to make
liveness information available in the RegularLTO pipeline.

llvm-svn: 304466
2017-06-01 20:30:06 +00:00
Adrian Prantl 660437975b Revert "ThinLTO: Verify bitcode before lauching the ThinLTOCodeGenerator."
This reverts commit r303438 while deliberating buildbot breakage.

llvm-svn: 303467
2017-05-19 23:32:21 +00:00
Adrian Prantl f9ab9bfc39 ThinLTO: Verify bitcode before lauching the ThinLTOCodeGenerator.
rdar://problem/31233625

Differential Revision: https://reviews.llvm.org/D33151

llvm-svn: 303438
2017-05-19 17:55:02 +00:00
Peter Collingbourne c3d677f9d9 FunctionImport: Simplify function llvm::thinLTOInternalizeModule. NFCI.
llvm-svn: 302595
2017-05-09 22:43:31 +00:00
Peter Collingbourne 9667b91b13 Re-apply r302108, "IR: Use pointers instead of GUIDs to represent edges in the module summary. NFCI."
with a fix for the clang backend.

llvm-svn: 302176
2017-05-04 18:03:25 +00:00
Eric Liu f6039f255e Revert "IR: Use pointers instead of GUIDs to represent edges in the module summary. NFCI."
This reverts commit r302108. This causes crash in clang bootstrap with LTO.

Contacted the auther in the original commit.

llvm-svn: 302140
2017-05-04 11:49:39 +00:00
Peter Collingbourne 5f85a9deda IR: Use pointers instead of GUIDs to represent edges in the module summary. NFCI.
When profiling a no-op incremental link of Chromium I found that the functions
computeImportForFunction and computeDeadSymbols were consuming roughly 10% of
the profile. The goal of this change is to improve the performance of those
functions by changing the map lookups that they were previously doing into
pointer dereferences.

This is achieved by changing the ValueInfo data structure to be a pointer to
an element of the global value map owned by ModuleSummaryIndex, and changing
reference lists in the GlobalValueSummary to hold ValueInfos instead of GUIDs.
This means that a ValueInfo will take a client directly to the summary list
for a given GUID.

Differential Revision: https://reviews.llvm.org/D32471

llvm-svn: 302108
2017-05-04 03:36:16 +00:00
Peter Collingbourne c15d60b772 Object: Remove ModuleSummaryIndexObjectFile class.
Differential Revision: https://reviews.llvm.org/D32195

llvm-svn: 301832
2017-05-01 20:42:32 +00:00
Davide Italiano 91239088a1 [FunctionImport] assert(false) -> llvm_unreachable(). NFCI.
llvm-svn: 300344
2017-04-14 17:22:02 +00:00
Dehao Chen 4a435e0896 SamplePGO ThinLTO ICP fix for local functions.
Summary:
In SamplePGO, if the profile is collected from non-LTO binary, and used to drive ThinLTO, the indirect call promotion may fail because ThinLTO adjusts local function names to avoid conflicts. There are two places of where the mismatch can happen:

1. thin-link prepends SourceFileName to front of FuncName to build the GUID (GlobalValue::getGlobalIdentifier). Unlike instrumentation FDO, SamplePGO does not use the PGOFuncName scheme and therefore the indirect call target profile data contains a hash of the OriginalName.
2. backend compiler promotes some local functions to global and appends .llvm.{$ModuleHash} to the end of the FuncName to derive PromotedFunctionName

This patch tries at the best effort to find the GUID from the original local function name (in profile), and use that in ICP promotion, and in SamplePGO matching that happens in the backend after importing/inlining:

1. in thin-link, it builds the map from OriginalName to GUID so that when thin-link reads in indirect call target profile (represented by OriginalName), it knows which GUID to import.
2. in backend compiler, if sample profile reader cannot find a profile match for PromotedFunctionName, it will try to find if there is a match for OriginalFunctionName.
3. in backend compiler, we build symbol table entry for OriginalFunctionName and pointer to the same symbol of PromotedFunctionName, so that ICP can find the correct target to promote.

Reviewers: mehdi_amini, tejohnson

Reviewed By: tejohnson

Subscribers: llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D30754

llvm-svn: 297757
2017-03-14 17:33:01 +00:00
Teresa Johnson d820447212 Perform symbol binding for .symver versioned symbols
Summary:
In a .symver assembler directive like:
.symver name, name2@@nodename
"name2@@nodename" should get the same symbol binding as "name".

While the ELF object writer is updating the symbol binding for .symver
aliases before emitting the object file, not doing so when the module
inline assembly is handled by the RecordStreamer is causing the wrong
behavior in *LTO mode.

E.g. when "name" is global, "name2@@nodename" must also be marked as
global. Otherwise, the symbol is skipped when iterating over the LTO
InputFile symbols (InputFile::Symbol::shouldSkip). So, for example,
when performing any *LTO via the gold-plugin, the versioned symbol
definition is not recorded by the plugin and passed back to the
linker. If the object was in an archive, and there were no other symbols
needed from that object, the object would not be included in the final
link and references to the versioned symbol are undefined.

The llvm-lto2 tests added will give an error about an unused symbol
resolution without the fix.

Reviewers: rafael, pcc

Reviewed By: pcc

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D30485

llvm-svn: 297332
2017-03-09 00:19:49 +00:00
Peter Collingbourne e6fd9ff96a IRMover: Merge flags LinkModuleInlineAsm and IsPerformingImport.
Currently these flags are always the inverse of each other, so there is
no need to keep them separate.

Differential Revision: https://reviews.llvm.org/D29471

llvm-svn: 294016
2017-02-03 17:01:14 +00:00
Peter Collingbourne 6d8f817f8b FunctionImport: Use IRMover directly.
The importer was previously using ModuleLinker in a sort of "IRMover mode". Use
IRMover directly instead in order to remove a level of indirection.

I will remove all importing support from ModuleLinker in a separate
change.

Differential Revision: https://reviews.llvm.org/D29468

llvm-svn: 294014
2017-02-03 16:56:27 +00:00
Mehdi Amini 1380edf4ef Revert "[ThinLTO] Add an auto-hide feature"
This reverts commit r293970.

After more discussion, this belongs to the linker side and
there is no added value to do it at this level.

llvm-svn: 293993
2017-02-03 07:41:43 +00:00
Mehdi Amini b0a8ff71e5 [ThinLTO] Add an auto-hide feature
When a symbol is not exported outside of the
DSO, it is can be hidden. Usually we try to internalize
as much as possible, but it is not always possible, for
instance a symbol can be referenced outside of the LTO
unit, or there can be cross-module reference in ThinLTO.

This is a recommit of r293912 after fixing build failures,
and a recommit of r293918 after fixing LLD tests.

Differential Revision: https://reviews.llvm.org/D28978

llvm-svn: 293970
2017-02-03 00:32:38 +00:00
Mehdi Amini 21c89dc920 Revert "[ThinLTO] Add an auto-hide feature"
This reverts commit r293918, one lld test does not pass.

llvm-svn: 293961
2017-02-02 23:20:36 +00:00
Peter Collingbourne 37e2459186 FunctionImport: Remove the -disable-force-link-odr flag and change importFunctions to never force link.
This removes some functionality that was only being used by tests.

Differential Revision: https://reviews.llvm.org/D29439

llvm-svn: 293919
2017-02-02 18:42:25 +00:00
Mehdi Amini 97624fb1ec [ThinLTO] Add an auto-hide feature
When a symbol is not exported outside of the
DSO, it is can be hidden. Usually we try to internalize
as much as possible, but it is not always possible, for
instance a symbol can be referenced outside of the LTO
unit, or there can be cross-module reference in ThinLTO.

This is a recommit of r293912 after fixing build failures.

Differential Revision: https://reviews.llvm.org/D28978

llvm-svn: 293918
2017-02-02 18:31:35 +00:00
Mehdi Amini 827600deaf Revert "[ThinLTO] Add an auto-hide feature"
This reverts r293912, bots are broken.

llvm-svn: 293914
2017-02-02 18:24:37 +00:00
Mehdi Amini dc5a7444f0 [ThinLTO] Add an auto-hide feature
When a symbol is not exported outside of the
DSO, it is can be hidden. Usually we try to internalize
as much as possible, but it is not always possible, for
instance a symbol can be referenced outside of the LTO
unit, or there can be cross-module reference in ThinLTO.

Differential Revision: https://reviews.llvm.org/D28978

llvm-svn: 293912
2017-02-02 18:13:46 +00:00
Teresa Johnson 4566c6db87 [ThinLTO] Drop non-prevailing non-ODR weak to declarations
Summary:
Allow non-ODR weak/linkonce non-prevailing copies to be marked
as available_externally in the index. Add support for dropping these to
declarations in the backend.

Reviewers: mehdi_amini, pcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28806

llvm-svn: 292656
2017-01-20 21:54:58 +00:00
Teresa Johnson 83aaf358fd [ThinLTO] Import static functions from the same module as caller
Summary:
We can sometimes end up with multiple copies of a local function that
have the same GUID in the index. This happens when there are local
functions with the same name that are in different source files with the
same name (but in different directories), and they were compiled in
their own directory so had the same path at compile time.

In this case make sure we import the copy in the caller's module. While
it isn't a correctness problem (the renamed reference which is based on the
module IR hash will be unique since the module must have had an
externally visible function that was imported), importing the wrong copy
will result in lost performance opportunity since it won't be referenced
and inlined.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28440

llvm-svn: 291841
2017-01-12 22:04:45 +00:00
Teresa Johnson 6c475a7595 ThinLTO: add early "dead-stripping" on the Index
Summary:
Using the linker-supplied list of "preserved" symbols, we can compute
the list of "dead" symbols, i.e. the one that are not reachable from
a "preserved" symbol transitively on the reference graph.
Right now we are using this information to mark these functions as
non-eligible for import.

The impact is two folds:
- Reduction of compile time: we don't import these functions anywhere
  or import the function these symbols are calling.
- The limited number of import/export leads to better internalization.

Patch originally by Mehdi Amini.

Reviewers: mehdi_amini, pcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23488

llvm-svn: 291177
2017-01-05 21:34:18 +00:00
Teresa Johnson 519465b993 [ThinLTO] Subsume all importing checks into a single flag
Summary:
This adds a new summary flag NotEligibleToImport that subsumes
several existing flags (NoRename, HasInlineAsmMaybeReferencingInternal
and IsNotViableToInline). It also subsumes the checking of references
on the summary that was being done during the thin link by
eligibleForImport() for each candidate. It is much more efficient to
do that checking once during the per-module summary build and record
it in the summary.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28169

llvm-svn: 291108
2017-01-05 14:32:16 +00:00
Mehdi Amini 19ef4fad91 Use lazy-loading of Metadata in MetadataLoader when importing is enabled (NFC)
Summary:
This is a relatively simple scheme: we use the index emitted in the
bitcode to avoid loading all the global metadata. Instead we load
the index with their position in the bitcode so that we can load each
of them individually. Materializing the global metadata block in this
condition only triggers loading the named metadata, and the ones
referenced from there (transitively). When materializing a function,
metadata from the global block are loaded lazily as they are
referenced.

Two main current limitations are:

1) Global values other than functions are not materialized on demand,
so we need to eagerly load METADATA_GLOBAL_DECL_ATTACHMENT records
(and their transitive dependencies).
2) When we load a single metadata, we don't recurse on the operands,
instead we use a placeholder or a temporary metadata. Unfortunately
tepmorary nodes are very expensive. This is why we don't have it
always enabled and only for importing.

These two limitations can be lifted in a subsequent improvement if
needed.

With this change, the total link time of opt with ThinLTO and Debug
Info enabled is going down from 282s to 224s (~20%).

Reviewers: pcc, tejohnson, dexonsmith

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28113

llvm-svn: 291027
2017-01-04 22:54:33 +00:00
Mehdi Amini 94f86ad4e0 Function-import: Disable IRVerifier on lazy-loaded modules: the ODR TypeUniquing generates invalid debug info.
llvm-svn: 290442
2016-12-23 19:19:44 +00:00
Mehdi Amini fc06b83ee7 Fix build after r290437 (missing include)
llvm-svn: 290438
2016-12-23 18:04:51 +00:00
Mehdi Amini 9a9077fdad FunctionImport: fix typo '#ifndef NDEBUG' instead of '#ifndef DEBUG'
llvm-svn: 290437
2016-12-23 17:59:24 +00:00
Mehdi Amini 96cdc49305 [ThinLTO] Verify lazy-loaded source module for function importing when assertions are enabled (NFC)
llvm-svn: 290416
2016-12-23 05:16:19 +00:00
Peter Collingbourne 598bd2a262 IPO: Remove the ModuleSummary argument to the FunctionImport pass. NFCI.
No existing client is passing a non-null value here. This will come back
in a slightly different form as part of the type identifier summary work.

Differential Revision: https://reviews.llvm.org/D28006

llvm-svn: 290222
2016-12-21 00:50:12 +00:00
Teresa Johnson edddca22c9 [ThinLTO] Thin link efficiency: More efficient export list computation
Summary:
Instead of checking whether a global referenced by a function being
imported is defined in the same module, speculatively always add the
referenced globals to the module's export list. After all imports are
computed, for each module prune any not in its defined set from its
export list.

For a huge C++ app with aggressive importing thresholds, even with
D27687 we spent a lot of time invoking modulePath() from
exportGlobalInModule (modulePath() was still the 2nd hottest routine in
profile). The reason is that with comdat/linkonce the summary lists for
each GUID can be long. For the app in question, for example, we were
invoking exportGlobalInModule almost 2 million times, and we traversed
an average of 63 entries in the summary list each time.

This patch reduced the thin link time for the app by about 10% (on top
of D27687) when using aggressive importing thresholds, and about 3.5% on
average with default importing thresholds.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27755

llvm-svn: 289918
2016-12-16 04:11:51 +00:00
Teresa Johnson 19f2aa7891 [ThinLTO] Thin link efficiency improvement: don't re-export globals (NFC)
Summary:
We were reinvoking exportGlobalInModule numerous times redundantly.
No need to re-export globals referenced by a global that was already
imported from its module. This resulted in a large speedup in the thin
link for a big application, particularly when importing aggressiveness
was cranked up.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27687

llvm-svn: 289896
2016-12-15 23:50:06 +00:00
Teresa Johnson eb0ac24172 [ThinLTO] Revert part of r289843 that belonged to another patch.
The code change for D27687 accidentally got committed along with the
main change in r289843. Revert it temporarily, so that I can recommit it
along with its test as intended.

llvm-svn: 289875
2016-12-15 21:39:42 +00:00
Teresa Johnson 0c3f57b133 [ThinLTO] Remove stale comment (NFC)
This should have been removed with r288446.

llvm-svn: 289871
2016-12-15 20:53:31 +00:00
Teresa Johnson 475b51a700 [ThinLTO] Thin link efficiency: skip candidate added later with higher threshold (NFC)
Summary:
Thin link efficiency improvement. After adding an importing candidate to
the worklist we might have later added it again with a higher threshold.
Skip it when popped from the worklist if we recorded a higher threshold
than the current worklist entry, it will get processed again at the
higher threshold when that entry is popped.

This required adding the summary's GUID to the worklist, so that it can
be used to query the recorded highest threshold for it when we pop from the
worklist.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27696

llvm-svn: 289867
2016-12-15 20:48:19 +00:00
Teresa Johnson 1b859a2306 [ThinLTO] Ensure callees get hot threshold when first seen on cold path
This is split out from D27696, since it turned out to be a bug fix and
not part of the NFC efficiency change.

Keep the same adjusted (possibly decayed) threshold in both the worklist
and the ImportList. Otherwise if we encountered it first along a cold
path, the callee would be added to the worklist with a lower decayed
threshold than when it is later encountered along a hot path. But the
logic uses the threshold recorded in the ImportList entry to check if
we should re-add it, and without this patch the threshold recorded there
is the same along both paths so we don't re-add it. Using the
same possibly decayed threshold in the ImportList ensures we re-add it
later with the higher non-decayed hot path threshold.

llvm-svn: 289843
2016-12-15 18:21:01 +00:00
Teresa Johnson a29bd6ffcc [ThinLTO] Remove useless code (NFC)
Should have been removed in r288446.

llvm-svn: 289466
2016-12-12 20:34:28 +00:00
Teresa Johnson 185b4ab6d4 [ThinLTO] Stop importing constant global vars as copies in the backend
Summary:
We were doing an optimization in the ThinLTO backends of importing
constant unnamed_addr globals unconditionally as a local copy (regardless
of whether the thin link decided to import them). This should be done in
the thin link instead, so that resulting exported references are marked
and promoted appropriately, but will need a summary enhancement to mark
these variables as constant unnamed_addr.

The function import logic during the thin link was trying to handle
this proactively, by conservatively marking all values referenced in
the initializer lists of exported global variables as also exported.
However, this only handled values referenced directly from the
initializer list of an exported global variable. If the value is itself
a constant unnamed_addr variable, we could end up exporting its
references as well. This caused multiple issues. The first is that the
transitively exported references weren't promoted. Secondly, some could
not be promoted/renamed (e.g. they had a section or other constraint).
recursively, instead of just adding the first level of initializer list
references to the ExportList directly.

Remove this optimization and the associated handling in the function
import backend. SPEC measurements indicate we weren't getting much
from it in any case.

Fixes PR31052.

Reviewers: mehdi_amini

Subscribers: krasin, llvm-commits

Differential Revision: https://reviews.llvm.org/D26880

llvm-svn: 288446
2016-12-02 01:02:30 +00:00
Peter Collingbourne 863cbfbeba Object: Extract a ModuleSymbolTable class from IRObjectFile.
This class represents a symbol table built from in-memory IR. It provides
access to GlobalValues and should only be used if such access is required
(e.g. in the LTO implementation). We will eventually change IRObjectFile
to read from a bitcode symbol table rather than using ModuleSymbolTable,
so it would not be able to expose the module.

Differential Revision: https://reviews.llvm.org/D27073

llvm-svn: 288319
2016-12-01 06:51:47 +00:00
Teresa Johnson 4fef68cb8d [ThinLTO] Only promote exported locals as marked in index
Summary:
We have always speculatively promoted all renamable local values
(except const non-address taken variables) for both the exporting
and importing module. We would then internalize them back based on
the ThinLink results if they weren't actually exported. This is
inefficient, and results in unnecessary renames. It also meant we
had to check the non-renamability of a value in the summary, which
was already checked during function importing analysis in the ThinLink.

Made renameModuleForThinLTO (which does the promotion/renaming) instead
use the index when exporting, to avoid unnecessary renames/promotions.
For importing modules, we can simply promoted all values as any local
we import by definition is exported and needs promotion.

This required changes to the method used by the FunctionImport pass
(only invoked from 'opt' for testing) and when invoked from llvm-link,
since neither does a ThinLink. We simply conservatively mark all locals
in the index as promoted, which preserves the current aggressive
promotion behavior.

I also needed to change an llvm-lto based test where we had previously
been aggressively promoting values that weren't importable (aliasees),
but now will not promote.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26467

llvm-svn: 286871
2016-11-14 19:21:41 +00:00
Teresa Johnson d5033a4576 [ThinLTO] Make inline assembly handling more efficient in summary
Summary:
The change in r285513 to prevent exporting of locals used in
inline asm added all locals in the llvm.used set to the reference
set of functions containing inline asm. Since these locals were marked
NoRename, this automatically prevented importing of the function.

Unfortunately, this caused an explosion in the summary reference lists
in some cases. In my particular example, it happened for a large protocol
buffer generated C++ file, where many of the generated functions
contained an inline asm call. It was exacerbated when doing a ThinLTO
PGO instrumentation build, where the PGO instrumentation included
thousands of private __profd_* values that were added to llvm.used.

We really only need to include a single llvm.used local (NoRename) value
in the reference list of a function containing inline asm to block it
being imported. However, it seems cleaner to add a flag to the summary
that explicitly describes this situation, which is what this patch does.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26402

llvm-svn: 286840
2016-11-14 16:40:19 +00:00
Peter Collingbourne d9445c49ad Bitcode: Change module reader functions to return an llvm::Expected.
Differential Revision: https://reviews.llvm.org/D26562

llvm-svn: 286752
2016-11-13 07:00:17 +00:00
Peter Collingbourne 6de481a378 Bitcode: Change getModuleSummaryIndex() to return an llvm::Expected.
Differential Revision: https://reviews.llvm.org/D26539

llvm-svn: 286624
2016-11-11 19:50:39 +00:00
Peter Collingbourne 7f00d0a125 Bitcode: Change the materializer interface to return llvm::Error.
Differential Revision: https://reviews.llvm.org/D26439

llvm-svn: 286382
2016-11-09 17:49:19 +00:00
Teresa Johnson 58fbc916a0 [ThinLTO] Rename HasSection to NoRename (NFC)
Summary:
This is in preparation for a change to utilize this flag for symbols
referenced/defined in either inline or module level assembly.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26048

llvm-svn: 285376
2016-10-28 02:24:59 +00:00
Mehdi Amini 117296c0a0 Use StringRef in Pass/PassManager APIs (NFC)
llvm-svn: 283004
2016-10-01 02:56:57 +00:00
Piotr Padlewski d28694739c [thinlto] Don't decay threshold for hot callsites
Summary:
We don't want to decay hot callsites to import chains of hot
callsites. The same mechanism is used in LIPO.

Reviewers: tejohnson, eraman, mehdi_amini

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D24976

llvm-svn: 282833
2016-09-30 03:01:17 +00:00
Piotr Padlewski ba72b95f7b [thinlto] Add cold-callsite import heuristic
Summary:
Not tunned up heuristic, but with this small heuristic there is about
+0.10% improvement on SPEC 2006

Reviewers: tejohnson, mehdi_amini, eraman

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D24940

llvm-svn: 282733
2016-09-29 17:32:07 +00:00
Piotr Padlewski d9830eb79f [thinlto] Basic thinlto fdo heuristic
Summary:
This patch improves thinlto importer
by importing 3x larger functions that are called from hot block.

I compared performance with the trunk on spec, and there
were about 2% on povray and 3.33% on milc. These results seems
to be consistant and match the results Teresa got with her simple
heuristic. Some benchmarks got slower but I think they are just
noisy (mcf, xalancbmki, omnetpp)- running the benchmarks again with
more iterations to confirm. Geomean of all benchmarks including the noisy ones
were about +0.02%.

I see much better improvement on google branch with Easwaran patch
for pgo callsite inlining (the inliner actually inline those big functions)
Over all I see +0.5% improvement, and I get +8.65% on povray.
So I guess we will see much bigger change when Easwaran patch will land
(it depends on new pass manager), but it is still worth putting this to trunk
before it.

Implementation details changes:
- Removed CallsiteCount.
- ProfileCount got replaced by Hotness
- hot-import-multiplier is set to 3.0 for now,
didn't have time to tune it up, but I see that we get most of the interesting
functions with 3, so there is no much performance difference with higher, and
binary size doesn't grow as much as with 10.0.

Reviewers: eraman, mehdi_amini, tejohnson

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D24638

llvm-svn: 282437
2016-09-26 20:37:32 +00:00
Mehdi Amini 88c491ddec FunctionImport: missed one occurence of ImportListForModule to rename (NFC)
llvm-svn: 278778
2016-08-16 05:49:12 +00:00
Mehdi Amini 9b490f10e1 FunctionImport: rename ImportsForModule to ImportList for consistency (NFC)
llvm-svn: 278777
2016-08-16 05:47:12 +00:00
Mehdi Amini cdbcbf7477 [LTO] Simplify APIs and constify (NFC)
Summary:
Multiple APIs were taking a StringMap for the ImportLists containing
the entries for for all the modules while operating on a single entry
for the current module. Instead we can pass the desired ModuleImport
directly. Also some of the APIs were not const, I believe just to be
able to use operator[] on the StringMap.

Reviewers: tejohnson

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D23537

llvm-svn: 278776
2016-08-16 05:46:05 +00:00
Teresa Johnson 6107a4195d [ThinLTO] Remove functions resolved to available_externally from comdats
Summary:
thinLTOResolveWeakForLinkerModule needs to drop any preempted weak symbols
that were converted to available_externally from comdats, otherwise we
will get a verification failure (since available_externally is a
declaration for the linker, and no declarations can be in a comdat).

Reviewers: mehdi_amini

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D23015

llvm-svn: 278739
2016-08-15 21:00:04 +00:00
Piotr Padlewski 332b3b2210 Don't import variadic functions
Summary:
This patch adds IsVariadicFunction bit to summary in order
to not import variadic functions. Inliner doesn't inline
variadic functions because it is hard to reason about it.

This one small fix improves Importer by about 16%
(going from 86% to 100% of imported functions that are
inlined anywhere)
on some spec benchmarks like 'int' and others.

Reviewers: eraman, mehdi_amini, tejohnson

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D23339

llvm-svn: 278432
2016-08-11 22:13:57 +00:00