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//===- FunctionImport.cpp - ThinLTO Summary-based Function Import ---------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file implements Function import based on summaries.
#include "llvm/Transforms/IPO/FunctionImport.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/IR/AutoUpgrade.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalObject.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ModuleSummaryIndex.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/Linker/IRMover.h"
#include "llvm/Object/ModuleSymbolTable.h"
#include "llvm/Object/SymbolicFile.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/IPO/Internalize.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/FunctionImportUtils.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <cassert>
#include <memory>
#include <set>
#include <string>
#include <system_error>
#include <tuple>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "function-import"
STATISTIC(NumImportedFunctions, "Number of functions imported");
STATISTIC(NumImportedModules, "Number of modules imported from");
STATISTIC(NumDeadSymbols, "Number of dead stripped symbols in index");
STATISTIC(NumLiveSymbols, "Number of live symbols in index");
/// Limit on instruction count of imported functions.
static cl::opt<unsigned> ImportInstrLimit(
"import-instr-limit", cl::init(100), cl::Hidden, cl::value_desc("N"),
cl::desc("Only import functions with less than N instructions"));
static cl::opt<float>
ImportInstrFactor("import-instr-evolution-factor", cl::init(0.7),
cl::Hidden, cl::value_desc("x"),
cl::desc("As we import functions, multiply the "
"`import-instr-limit` threshold by this factor "
"before processing newly imported functions"));
static cl::opt<float> ImportHotInstrFactor(
"import-hot-evolution-factor", cl::init(1.0), cl::Hidden,
cl::desc("As we import functions called from hot callsite, multiply the "
"`import-instr-limit` threshold by this factor "
"before processing newly imported functions"));
static cl::opt<float> ImportHotMultiplier(
"import-hot-multiplier", cl::init(10.0), cl::Hidden, cl::value_desc("x"),
cl::desc("Multiply the `import-instr-limit` threshold for hot callsites"));
static cl::opt<float> ImportCriticalMultiplier(
"import-critical-multiplier", cl::init(100.0), cl::Hidden,
"Multiply the `import-instr-limit` threshold for critical callsites"));
// FIXME: This multiplier was not really tuned up.
static cl::opt<float> ImportColdMultiplier(
"import-cold-multiplier", cl::init(0), cl::Hidden, cl::value_desc("N"),
cl::desc("Multiply the `import-instr-limit` threshold for cold callsites"));
static cl::opt<bool> PrintImports("print-imports", cl::init(false), cl::Hidden,
cl::desc("Print imported functions"));
static cl::opt<bool> ComputeDead("compute-dead", cl::init(true), cl::Hidden,
cl::desc("Compute dead symbols"));
static cl::opt<bool> EnableImportMetadata(
"enable-import-metadata", cl::init(
#if !defined(NDEBUG)
true /*Enabled with asserts.*/
cl::Hidden, cl::desc("Enable import metadata like 'thinlto_src_module'"));
/// Summary file to use for function importing when using -function-import from
/// the command line.
static cl::opt<std::string>
cl::desc("The summary file to use for function importing."));
/// Used when testing importing from distributed indexes via opt
// -function-import.
static cl::opt<bool>
cl::desc("Import all external functions in index."));
// Load lazily a module from \p FileName in \p Context.
static std::unique_ptr<Module> loadFile(const std::string &FileName,
LLVMContext &Context) {
SMDiagnostic Err;
DEBUG(dbgs() << "Loading '" << FileName << "'\n");
// Metadata isn't loaded until functions are imported, to minimize
// the memory overhead.
std::unique_ptr<Module> Result =
getLazyIRFileModule(FileName, Err, Context,
/* ShouldLazyLoadMetadata = */ true);
if (!Result) {
Err.print("function-import", errs());
return Result;
/// Given a list of possible callee implementation for a call site, select one
/// that fits the \p Threshold.
/// FIXME: select "best" instead of first that fits. But what is "best"?
/// - The smallest: more likely to be inlined.
/// - The one with the least outgoing edges (already well optimized).
/// - One from a module already being imported from in order to reduce the
/// number of source modules parsed/linked.
/// - One that has PGO data attached.
/// - [insert you fancy metric here]
static const GlobalValueSummary *
selectCallee(const ModuleSummaryIndex &Index,
ArrayRef<std::unique_ptr<GlobalValueSummary>> CalleeSummaryList,
unsigned Threshold, StringRef CallerModulePath) {
auto It = llvm::find_if(
[&](const std::unique_ptr<GlobalValueSummary> &SummaryPtr) {
auto *GVSummary = SummaryPtr.get();
// For SamplePGO, in computeImportForFunction the OriginalId
// may have been used to locate the callee summary list (See
// comment there).
// The mapping from OriginalId to GUID may return a GUID
// that corresponds to a static variable. Filter it out here.
// This can happen when
// 1) There is a call to a library function which is not defined
// in the index.
// 2) There is a static variable with the OriginalGUID identical
// to the GUID of the library function in 1);
// When this happens, the logic for SamplePGO kicks in and
// the static variable in 2) will be found, which needs to be
// filtered out.
if (GVSummary->getSummaryKind() == GlobalValueSummary::GlobalVarKind)
return false;
if (GlobalValue::isInterposableLinkage(GVSummary->linkage()))
// There is no point in importing these, we can't inline them
return false;
auto *Summary = cast<FunctionSummary>(GVSummary->getBaseObject());
// If this is a local function, make sure we import the copy
// in the caller's module. The only time a local function can
// share an entry in the index is if there is a local with the same name
// in another module that had the same source file name (in a different
// directory), where each was compiled in their own directory so there
// was not distinguishing path.
// However, do the import from another module if there is only one
// entry in the list - in that case this must be a reference due
// to indirect call profile data, since a function pointer can point to
// a local in another module.
if (GlobalValue::isLocalLinkage(Summary->linkage()) &&
CalleeSummaryList.size() > 1 &&
Summary->modulePath() != CallerModulePath)
return false;
if (Summary->instCount() > Threshold)
return false;
if (Summary->notEligibleToImport())
return false;
return true;
if (It == CalleeSummaryList.end())
return nullptr;
return cast<GlobalValueSummary>(It->get());
namespace {
using EdgeInfo = std::tuple<const FunctionSummary *, unsigned /* Threshold */,
} // anonymous namespace
static ValueInfo
updateValueInfoForIndirectCalls(const ModuleSummaryIndex &Index, ValueInfo VI) {
if (!VI.getSummaryList().empty())
return VI;
// For SamplePGO, the indirect call targets for local functions will
// have its original name annotated in profile. We try to find the
// corresponding PGOFuncName as the GUID.
// FIXME: Consider updating the edges in the graph after building
// it, rather than needing to perform this mapping on each walk.
auto GUID = Index.getGUIDFromOriginalID(VI.getGUID());
if (GUID == 0)
return nullptr;
return Index.getValueInfo(GUID);
/// Compute the list of functions to import for a given caller. Mark these
/// imported functions and the symbols they reference in their source module as
/// exported from their source module.
static void computeImportForFunction(
const FunctionSummary &Summary, const ModuleSummaryIndex &Index,
const unsigned Threshold, const GVSummaryMapTy &DefinedGVSummaries,
SmallVectorImpl<EdgeInfo> &Worklist,
FunctionImporter::ImportMapTy &ImportList,
StringMap<FunctionImporter::ExportSetTy> *ExportLists = nullptr) {
for (auto &Edge : Summary.calls()) {
ValueInfo VI = Edge.first;
DEBUG(dbgs() << " edge -> " << VI.getGUID() << " Threshold:" << Threshold
<< "\n");
VI = updateValueInfoForIndirectCalls(Index, VI);
if (!VI)
if (DefinedGVSummaries.count(VI.getGUID())) {
DEBUG(dbgs() << "ignored! Target already in destination module.\n");
auto GetBonusMultiplier = [](CalleeInfo::HotnessType Hotness) -> float {
if (Hotness == CalleeInfo::HotnessType::Hot)
return ImportHotMultiplier;
if (Hotness == CalleeInfo::HotnessType::Cold)
return ImportColdMultiplier;
if (Hotness == CalleeInfo::HotnessType::Critical)
return ImportCriticalMultiplier;
return 1.0;
const auto NewThreshold =
Threshold * GetBonusMultiplier(Edge.second.Hotness);
auto *CalleeSummary = selectCallee(Index, VI.getSummaryList(), NewThreshold,
if (!CalleeSummary) {
DEBUG(dbgs() << "ignored! No qualifying callee with summary found.\n");
// "Resolve" the summary
const auto *ResolvedCalleeSummary = cast<FunctionSummary>(CalleeSummary->getBaseObject());
assert(ResolvedCalleeSummary->instCount() <= NewThreshold &&
"selectCallee() didn't honor the threshold");
auto GetAdjustedThreshold = [](unsigned Threshold, bool IsHotCallsite) {
// Adjust the threshold for next level of imported functions.
// The threshold is different for hot callsites because we can then
// inline chains of hot calls.
if (IsHotCallsite)
return Threshold * ImportHotInstrFactor;
return Threshold * ImportInstrFactor;
bool IsHotCallsite = Edge.second.Hotness == CalleeInfo::HotnessType::Hot;
const auto AdjThreshold = GetAdjustedThreshold(Threshold, IsHotCallsite);
auto ExportModulePath = ResolvedCalleeSummary->modulePath();
auto &ProcessedThreshold = ImportList[ExportModulePath][VI.getGUID()];
/// Since the traversal of the call graph is DFS, we can revisit a function
/// a second time with a higher threshold. In this case, it is added back to
/// the worklist with the new threshold.
if (ProcessedThreshold && ProcessedThreshold >= AdjThreshold) {
DEBUG(dbgs() << "ignored! Target was already seen with Threshold "
<< ProcessedThreshold << "\n");
bool PreviouslyImported = ProcessedThreshold != 0;
// Mark this function as imported in this module, with the current Threshold
ProcessedThreshold = AdjThreshold;
// Make exports in the source module.
if (ExportLists) {
auto &ExportList = (*ExportLists)[ExportModulePath];
if (!PreviouslyImported) {
// This is the first time this function was exported from its source
// module, so mark all functions and globals it references as exported
// to the outside if they are defined in the same source module.
// For efficiency, we unconditionally add all the referenced GUIDs
// to the ExportList for this module, and will prune out any not
// defined in the module later in a single pass.
for (auto &Edge : ResolvedCalleeSummary->calls()) {
auto CalleeGUID = Edge.first.getGUID();
for (auto &Ref : ResolvedCalleeSummary->refs()) {
auto GUID = Ref.getGUID();
// Insert the newly imported function to the worklist.
Worklist.emplace_back(ResolvedCalleeSummary, AdjThreshold, VI.getGUID());
/// Given the list of globals defined in a module, compute the list of imports
/// as well as the list of "exports", i.e. the list of symbols referenced from
/// another module (that may require promotion).
static void ComputeImportForModule(
const GVSummaryMapTy &DefinedGVSummaries, const ModuleSummaryIndex &Index,
FunctionImporter::ImportMapTy &ImportList,
StringMap<FunctionImporter::ExportSetTy> *ExportLists = nullptr) {
// Worklist contains the list of function imported in this module, for which
// we will analyse the callees and may import further down the callgraph.
SmallVector<EdgeInfo, 128> Worklist;
// Populate the worklist with the import for the functions in the current
// module
for (auto &GVSummary : DefinedGVSummaries) {
if (!Index.isGlobalValueLive(GVSummary.second)) {
DEBUG(dbgs() << "Ignores Dead GUID: " << GVSummary.first << "\n");
auto *FuncSummary =
if (!FuncSummary)
// Skip import for global variables
DEBUG(dbgs() << "Initialize import for " << GVSummary.first << "\n");
computeImportForFunction(*FuncSummary, Index, ImportInstrLimit,
DefinedGVSummaries, Worklist, ImportList,
// Process the newly imported functions and add callees to the worklist.
while (!Worklist.empty()) {
auto FuncInfo = Worklist.pop_back_val();
auto *Summary = std::get<0>(FuncInfo);
auto Threshold = std::get<1>(FuncInfo);
auto GUID = std::get<2>(FuncInfo);
// Check if we later added this summary with a higher threshold.
// If so, skip this entry.
auto ExportModulePath = Summary->modulePath();
auto &LatestProcessedThreshold = ImportList[ExportModulePath][GUID];
if (LatestProcessedThreshold > Threshold)
computeImportForFunction(*Summary, Index, Threshold, DefinedGVSummaries,
Worklist, ImportList, ExportLists);
/// Compute all the import and export for every module using the Index.
void llvm::ComputeCrossModuleImport(
const ModuleSummaryIndex &Index,
const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
StringMap<FunctionImporter::ImportMapTy> &ImportLists,
StringMap<FunctionImporter::ExportSetTy> &ExportLists) {
// For each module that has function defined, compute the import/export lists.
for (auto &DefinedGVSummaries : ModuleToDefinedGVSummaries) {
auto &ImportList = ImportLists[DefinedGVSummaries.first()];
DEBUG(dbgs() << "Computing import for Module '"
<< DefinedGVSummaries.first() << "'\n");
ComputeImportForModule(DefinedGVSummaries.second, Index, ImportList,
// When computing imports we added all GUIDs referenced by anything
// imported from the module to its ExportList. Now we prune each ExportList
// of any not defined in that module. This is more efficient than checking
// while computing imports because some of the summary lists may be long
// due to linkonce (comdat) copies.
for (auto &ELI : ExportLists) {
const auto &DefinedGVSummaries =
for (auto EI = ELI.second.begin(); EI != ELI.second.end();) {
if (!DefinedGVSummaries.count(*EI))
EI = ELI.second.erase(EI);
#ifndef NDEBUG
DEBUG(dbgs() << "Import/Export lists for " << ImportLists.size()
<< " modules:\n");
for (auto &ModuleImports : ImportLists) {
auto ModName = ModuleImports.first();
auto &Exports = ExportLists[ModName];
DEBUG(dbgs() << "* Module " << ModName << " exports " << Exports.size()
<< " functions. Imports from " << ModuleImports.second.size()
<< " modules.\n");
for (auto &Src : ModuleImports.second) {
auto SrcModName = Src.first();
DEBUG(dbgs() << " - " << Src.second.size() << " functions imported from "
<< SrcModName << "\n");
#ifndef NDEBUG
static void dumpImportListForModule(StringRef ModulePath,
FunctionImporter::ImportMapTy &ImportList) {
DEBUG(dbgs() << "* Module " << ModulePath << " imports from "
<< ImportList.size() << " modules.\n");
for (auto &Src : ImportList) {
auto SrcModName = Src.first();
DEBUG(dbgs() << " - " << Src.second.size() << " functions imported from "
<< SrcModName << "\n");
/// Compute all the imports for the given module in the Index.
void llvm::ComputeCrossModuleImportForModule(
StringRef ModulePath, const ModuleSummaryIndex &Index,
FunctionImporter::ImportMapTy &ImportList) {
// Collect the list of functions this module defines.
// GUID -> Summary
GVSummaryMapTy FunctionSummaryMap;
Index.collectDefinedFunctionsForModule(ModulePath, FunctionSummaryMap);
// Compute the import list for this module.
DEBUG(dbgs() << "Computing import for Module '" << ModulePath << "'\n");
ComputeImportForModule(FunctionSummaryMap, Index, ImportList);
#ifndef NDEBUG
dumpImportListForModule(ModulePath, ImportList);
// Mark all external summaries in Index for import into the given module.
// Used for distributed builds using a distributed index.
void llvm::ComputeCrossModuleImportForModuleFromIndex(
StringRef ModulePath, const ModuleSummaryIndex &Index,
FunctionImporter::ImportMapTy &ImportList) {
for (auto &GlobalList : Index) {
// Ignore entries for undefined references.
if (GlobalList.second.SummaryList.empty())
auto GUID = GlobalList.first;
assert(GlobalList.second.SummaryList.size() == 1 &&
"Expected individual combined index to have one summary per GUID");
auto &Summary = GlobalList.second.SummaryList[0];
// Skip the summaries for the importing module. These are included to
// e.g. record required linkage changes.
if (Summary->modulePath() == ModulePath)
// Doesn't matter what value we plug in to the map, just needs an entry
// to provoke importing by thinBackend.
ImportList[Summary->modulePath()][GUID] = 1;
#ifndef NDEBUG
dumpImportListForModule(ModulePath, ImportList);
void llvm::computeDeadSymbols(
ModuleSummaryIndex &Index,
const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
if (!ComputeDead)
if (GUIDPreservedSymbols.empty())
// Don't do anything when nothing is live, this is friendly with tests.
unsigned LiveSymbols = 0;
SmallVector<ValueInfo, 128> Worklist;
Worklist.reserve(GUIDPreservedSymbols.size() * 2);
for (auto GUID : GUIDPreservedSymbols) {
ValueInfo VI = Index.getValueInfo(GUID);
if (!VI)
for (auto &S : VI.getSummaryList())
// Add values flagged in the index as live roots to the worklist.
for (const auto &Entry : Index)
for (auto &S : Entry.second.SummaryList)
if (S->isLive()) {
DEBUG(dbgs() << "Live root: " << Entry.first << "\n");
// Make value live and add it to the worklist if it was not live before.
// FIXME: we should only make the prevailing copy live here
auto visit = [&](ValueInfo VI) {
// FIXME: If we knew which edges were created for indirect call profiles,
// we could skip them here. Any that are live should be reached via
// other edges, e.g. reference edges. Otherwise, using a profile collected
// on a slightly different binary might provoke preserving, importing
// and ultimately promoting calls to functions not linked into this
// binary, which increases the binary size unnecessarily. Note that
// if this code changes, the importer needs to change so that edges
// to functions marked dead are skipped.
VI = updateValueInfoForIndirectCalls(Index, VI);
if (!VI)
for (auto &S : VI.getSummaryList())
if (S->isLive())
for (auto &S : VI.getSummaryList())
while (!Worklist.empty()) {
auto VI = Worklist.pop_back_val();
for (auto &Summary : VI.getSummaryList()) {
GlobalValueSummary *Base = Summary->getBaseObject();
for (auto Ref : Base->refs())
if (auto *FS = dyn_cast<FunctionSummary>(Base))
for (auto Call : FS->calls())
unsigned DeadSymbols = Index.size() - LiveSymbols;
DEBUG(dbgs() << LiveSymbols << " symbols Live, and " << DeadSymbols
<< " symbols Dead \n");
NumDeadSymbols += DeadSymbols;
NumLiveSymbols += LiveSymbols;
/// Compute the set of summaries needed for a ThinLTO backend compilation of
/// \p ModulePath.
void llvm::gatherImportedSummariesForModule(
StringRef ModulePath,
const StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
const FunctionImporter::ImportMapTy &ImportList,
std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex) {
// Include all summaries from the importing module.
ModuleToSummariesForIndex[ModulePath] =
// Include summaries for imports.
for (auto &ILI : ImportList) {
auto &SummariesForIndex = ModuleToSummariesForIndex[ILI.first()];
const auto &DefinedGVSummaries =
for (auto &GI : ILI.second) {
const auto &DS = DefinedGVSummaries.find(GI.first);
assert(DS != DefinedGVSummaries.end() &&
"Expected a defined summary for imported global value");
SummariesForIndex[GI.first] = DS->second;
/// Emit the files \p ModulePath will import from into \p OutputFilename.
llvm::EmitImportsFiles(StringRef ModulePath, StringRef OutputFilename,
const FunctionImporter::ImportMapTy &ModuleImports) {
std::error_code EC;
raw_fd_ostream ImportsOS(OutputFilename, EC, sys::fs::OpenFlags::F_None);
if (EC)
return EC;
for (auto &ILI : ModuleImports)
ImportsOS << ILI.first() << "\n";
return std::error_code();
/// Fixup WeakForLinker linkages in \p TheModule based on summary analysis.
void llvm::thinLTOResolveWeakForLinkerModule(
Module &TheModule, const GVSummaryMapTy &DefinedGlobals) {
auto ConvertToDeclaration = [](GlobalValue &GV) {
DEBUG(dbgs() << "Converting to a declaration: `" << GV.getName() << "\n");
if (Function *F = dyn_cast<Function>(&GV)) {
} else if (GlobalVariable *V = dyn_cast<GlobalVariable>(&GV)) {
} else
// For now we don't resolve or drop aliases. Once we do we'll
// need to add support here for creating either a function or
// variable declaration, and return the new GlobalValue* for
// the caller to use.
llvm_unreachable("Expected function or variable");
auto updateLinkage = [&](GlobalValue &GV) {
// See if the global summary analysis computed a new resolved linkage.
const auto &GS = DefinedGlobals.find(GV.getGUID());
if (GS == DefinedGlobals.end())
auto NewLinkage = GS->second->linkage();
if (NewLinkage == GV.getLinkage())
// Switch the linkage to weakany if asked for, e.g. we do this for
// linker redefined symbols (via --wrap or --defsym).
// We record that the visibility should be changed here in `addThinLTO`
// as we need access to the resolution vectors for each input file in
// order to find which symbols have been redefined.
// We may consider reorganizing this code and moving the linkage recording
// somewhere else, e.g. in thinLTOResolveWeakForLinkerInIndex.
if (NewLinkage == GlobalValue::WeakAnyLinkage) {
if (!GlobalValue::isWeakForLinker(GV.getLinkage()))
// Check for a non-prevailing def that has interposable linkage
// (e.g. non-odr weak or linkonce). In that case we can't simply
// convert to available_externally, since it would lose the
// interposable property and possibly get inlined. Simply drop
// the definition in that case.
if (GlobalValue::isAvailableExternallyLinkage(NewLinkage) &&
else {
DEBUG(dbgs() << "ODR fixing up linkage for `" << GV.getName() << "` from "
<< GV.getLinkage() << " to " << NewLinkage << "\n");
// Remove declarations from comdats, including available_externally
// as this is a declaration for the linker, and will be dropped eventually.
// It is illegal for comdats to contain declarations.
auto *GO = dyn_cast_or_null<GlobalObject>(&GV);
if (GO && GO->isDeclarationForLinker() && GO->hasComdat())
// Process functions and global now
for (auto &GV : TheModule)
for (auto &GV : TheModule.globals())
for (auto &GV : TheModule.aliases())
/// Run internalization on \p TheModule based on symmary analysis.
void llvm::thinLTOInternalizeModule(Module &TheModule,
const GVSummaryMapTy &DefinedGlobals) {
// Declare a callback for the internalize pass that will ask for every
// candidate GlobalValue if it can be internalized or not.
auto MustPreserveGV = [&](const GlobalValue &GV) -> bool {
// Lookup the linkage recorded in the summaries during global analysis.
auto GS = DefinedGlobals.find(GV.getGUID());
if (GS == DefinedGlobals.end()) {
// Must have been promoted (possibly conservatively). Find original
// name so that we can access the correct summary and see if it can
// be internalized again.
// FIXME: Eventually we should control promotion instead of promoting
// and internalizing again.
StringRef OrigName =
std::string OrigId = GlobalValue::getGlobalIdentifier(
OrigName, GlobalValue::InternalLinkage,
GS = DefinedGlobals.find(GlobalValue::getGUID(OrigId));
if (GS == DefinedGlobals.end()) {
// Also check the original non-promoted non-globalized name. In some
// cases a preempted weak value is linked in as a local copy because
// it is referenced by an alias (IRLinker::linkGlobalValueProto).
// In that case, since it was originally not a local value, it was
// recorded in the index using the original name.
// FIXME: This may not be needed once PR27866 is fixed.
GS = DefinedGlobals.find(GlobalValue::getGUID(OrigName));
assert(GS != DefinedGlobals.end());
return !GlobalValue::isLocalLinkage(GS->second->linkage());
// FIXME: See if we can just internalize directly here via linkage changes
// based on the index, rather than invoking internalizeModule.
internalizeModule(TheModule, MustPreserveGV);
/// Make alias a clone of its aliasee.
static Function *replaceAliasWithAliasee(Module *SrcModule, GlobalAlias *GA) {
Function *Fn = cast<Function>(GA->getBaseObject());
ValueToValueMapTy VMap;
Function *NewFn = CloneFunction(Fn, VMap);
// Clone should use the original alias's linkage and name, and we ensure
// all uses of alias instead use the new clone (casted if necessary).
GA->replaceAllUsesWith(ConstantExpr::getBitCast(NewFn, GA->getType()));
return NewFn;
// Automatically import functions in Module \p DestModule based on the summaries
// index.
Expected<bool> FunctionImporter::importFunctions(
Module &DestModule, const FunctionImporter::ImportMapTy &ImportList) {
DEBUG(dbgs() << "Starting import for Module "
<< DestModule.getModuleIdentifier() << "\n");
unsigned ImportedCount = 0;
IRMover Mover(DestModule);
// Do the actual import of functions now, one Module at a time
std::set<StringRef> ModuleNameOrderedList;
for (auto &FunctionsToImportPerModule : ImportList) {
for (auto &Name : ModuleNameOrderedList) {
// Get the module for the import
const auto &FunctionsToImportPerModule = ImportList.find(Name);
assert(FunctionsToImportPerModule != ImportList.end());
Expected<std::unique_ptr<Module>> SrcModuleOrErr = ModuleLoader(Name);
if (!SrcModuleOrErr)
return SrcModuleOrErr.takeError();
std::unique_ptr<Module> SrcModule = std::move(*SrcModuleOrErr);
assert(&DestModule.getContext() == &SrcModule->getContext() &&
"Context mismatch");
// If modules were created with lazy metadata loading, materialize it
// now, before linking it (otherwise this will be a noop).
if (Error Err = SrcModule->materializeMetadata())
return std::move(Err);
auto &ImportGUIDs = FunctionsToImportPerModule->second;
// Find the globals to import
SetVector<GlobalValue *> GlobalsToImport;
for (Function &F : *SrcModule) {
if (!F.hasName())
auto GUID = F.getGUID();
auto Import = ImportGUIDs.count(GUID);
DEBUG(dbgs() << (Import ? "Is" : "Not") << " importing function " << GUID
<< " " << F.getName() << " from "
<< SrcModule->getSourceFileName() << "\n");
if (Import) {
if (Error Err = F.materialize())
return std::move(Err);
if (EnableImportMetadata) {
// Add 'thinlto_src_module' metadata for statistics and debugging.
for (GlobalVariable &GV : SrcModule->globals()) {
if (!GV.hasName())
auto GUID = GV.getGUID();
auto Import = ImportGUIDs.count(GUID);
DEBUG(dbgs() << (Import ? "Is" : "Not") << " importing global " << GUID
<< " " << GV.getName() << " from "
<< SrcModule->getSourceFileName() << "\n");
if (Import) {
if (Error Err = GV.materialize())
return std::move(Err);
for (GlobalAlias &GA : SrcModule->aliases()) {
if (!GA.hasName())
auto GUID = GA.getGUID();
auto Import = ImportGUIDs.count(GUID);
DEBUG(dbgs() << (Import ? "Is" : "Not") << " importing alias " << GUID
<< " " << GA.getName() << " from "
<< SrcModule->getSourceFileName() << "\n");
if (Import) {
if (Error Err = GA.materialize())
return std::move(Err);
// Import alias as a copy of its aliasee.
GlobalObject *Base = GA.getBaseObject();
if (Error Err = Base->materialize())
return std::move(Err);
auto *Fn = replaceAliasWithAliasee(SrcModule.get(), &GA);
DEBUG(dbgs() << "Is importing aliasee fn " << Base->getGUID()
<< " " << Base->getName() << " from "
<< SrcModule->getSourceFileName() << "\n");
if (EnableImportMetadata) {
// Add 'thinlto_src_module' metadata for statistics and debugging.
// Upgrade debug info after we're done materializing all the globals and we
// have loaded all the required metadata!
// Link in the specified functions.
if (renameModuleForThinLTO(*SrcModule, Index, &GlobalsToImport))
return true;
if (PrintImports) {
for (const auto *GV : GlobalsToImport)
dbgs() << DestModule.getSourceFileName() << ": Import " << GV->getName()
<< " from " << SrcModule->getSourceFileName() << "\n";
if (Mover.move(std::move(SrcModule), GlobalsToImport.getArrayRef(),
[](GlobalValue &, IRMover::ValueAdder) {},
report_fatal_error("Function Import: link error");
ImportedCount += GlobalsToImport.size();
NumImportedFunctions += ImportedCount;
DEBUG(dbgs() << "Imported " << ImportedCount << " functions for Module "
<< DestModule.getModuleIdentifier() << "\n");
return ImportedCount;
static bool doImportingForModule(Module &M) {
if (SummaryFile.empty())
report_fatal_error("error: -function-import requires -summary-file\n");
Expected<std::unique_ptr<ModuleSummaryIndex>> IndexPtrOrErr =
if (!IndexPtrOrErr) {
logAllUnhandledErrors(IndexPtrOrErr.takeError(), errs(),
"Error loading file '" + SummaryFile + "': ");
return false;
std::unique_ptr<ModuleSummaryIndex> Index = std::move(*IndexPtrOrErr);
// First step is collecting the import list.
FunctionImporter::ImportMapTy ImportList;
// If requested, simply import all functions in the index. This is used
// when testing distributed backend handling via the opt tool, when
// we have distributed indexes containing exactly the summaries to import.
if (ImportAllIndex)
ComputeCrossModuleImportForModuleFromIndex(M.getModuleIdentifier(), *Index,
ComputeCrossModuleImportForModule(M.getModuleIdentifier(), *Index,
// Conservatively mark all internal values as promoted. This interface is
// only used when doing importing via the function importing pass. The pass
// is only enabled when testing importing via the 'opt' tool, which does
// not do the ThinLink that would normally determine what values to promote.
for (auto &I : *Index) {
for (auto &S : I.second.SummaryList) {
if (GlobalValue::isLocalLinkage(S->linkage()))
// Next we need to promote to global scope and rename any local values that
// are potentially exported to other modules.
if (renameModuleForThinLTO(M, *Index, nullptr)) {
errs() << "Error renaming module\n";
return false;
// Perform the import now.
auto ModuleLoader = [&M](StringRef Identifier) {
return loadFile(Identifier, M.getContext());
FunctionImporter Importer(*Index, ModuleLoader);
Expected<bool> Result = Importer.importFunctions(M, ImportList);
// FIXME: Probably need to propagate Errors through the pass manager.
if (!Result) {
logAllUnhandledErrors(Result.takeError(), errs(),
"Error importing module: ");
return false;
return *Result;
namespace {
/// Pass that performs cross-module function import provided a summary file.
class FunctionImportLegacyPass : public ModulePass {
/// Pass identification, replacement for typeid
static char ID;
explicit FunctionImportLegacyPass() : ModulePass(ID) {}
/// Specify pass name for debug output
StringRef getPassName() const override { return "Function Importing"; }
bool runOnModule(Module &M) override {
if (skipModule(M))
return false;
return doImportingForModule(M);
} // end anonymous namespace
PreservedAnalyses FunctionImportPass::run(Module &M,
ModuleAnalysisManager &AM) {
if (!doImportingForModule(M))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
char FunctionImportLegacyPass::ID = 0;
INITIALIZE_PASS(FunctionImportLegacyPass, "function-import",
"Summary Based Function Import", false, false)
namespace llvm {
Pass *createFunctionImportPass() {
return new FunctionImportLegacyPass();
} // end namespace llvm