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Diffstat (limited to 'llvm/lib/Transforms/Utils/FunctionImportUtils.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Utils/FunctionImportUtils.cpp | 313 |
1 files changed, 313 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp new file mode 100644 index 000000000000..76b4635ad501 --- /dev/null +++ b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp @@ -0,0 +1,313 @@ +//===- lib/Transforms/Utils/FunctionImportUtils.cpp - Importing utilities -===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements the FunctionImportGlobalProcessing class, used +// to perform the necessary global value handling for function importing. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Utils/FunctionImportUtils.h" +#include "llvm/IR/InstIterator.h" +using namespace llvm; + +/// Checks if we should import SGV as a definition, otherwise import as a +/// declaration. +bool FunctionImportGlobalProcessing::doImportAsDefinition( + const GlobalValue *SGV, SetVector<GlobalValue *> *GlobalsToImport) { + + // Only import the globals requested for importing. + if (!GlobalsToImport->count(const_cast<GlobalValue *>(SGV))) + return false; + + assert(!isa<GlobalAlias>(SGV) && + "Unexpected global alias in the import list."); + + // Otherwise yes. + return true; +} + +bool FunctionImportGlobalProcessing::doImportAsDefinition( + const GlobalValue *SGV) { + if (!isPerformingImport()) + return false; + return FunctionImportGlobalProcessing::doImportAsDefinition(SGV, + GlobalsToImport); +} + +bool FunctionImportGlobalProcessing::shouldPromoteLocalToGlobal( + const GlobalValue *SGV) { + assert(SGV->hasLocalLinkage()); + // Both the imported references and the original local variable must + // be promoted. + if (!isPerformingImport() && !isModuleExporting()) + return false; + + if (isPerformingImport()) { + assert((!GlobalsToImport->count(const_cast<GlobalValue *>(SGV)) || + !isNonRenamableLocal(*SGV)) && + "Attempting to promote non-renamable local"); + // We don't know for sure yet if we are importing this value (as either + // a reference or a def), since we are simply walking all values in the + // module. But by necessity if we end up importing it and it is local, + // it must be promoted, so unconditionally promote all values in the + // importing module. + return true; + } + + // When exporting, consult the index. We can have more than one local + // with the same GUID, in the case of same-named locals in different but + // same-named source files that were compiled in their respective directories + // (so the source file name and resulting GUID is the same). Find the one + // in this module. + auto Summary = ImportIndex.findSummaryInModule( + SGV->getGUID(), SGV->getParent()->getModuleIdentifier()); + assert(Summary && "Missing summary for global value when exporting"); + auto Linkage = Summary->linkage(); + if (!GlobalValue::isLocalLinkage(Linkage)) { + assert(!isNonRenamableLocal(*SGV) && + "Attempting to promote non-renamable local"); + return true; + } + + return false; +} + +#ifndef NDEBUG +bool FunctionImportGlobalProcessing::isNonRenamableLocal( + const GlobalValue &GV) const { + if (!GV.hasLocalLinkage()) + return false; + // This needs to stay in sync with the logic in buildModuleSummaryIndex. + if (GV.hasSection()) + return true; + if (Used.count(const_cast<GlobalValue *>(&GV))) + return true; + return false; +} +#endif + +std::string FunctionImportGlobalProcessing::getName(const GlobalValue *SGV, + bool DoPromote) { + // For locals that must be promoted to global scope, ensure that + // the promoted name uniquely identifies the copy in the original module, + // using the ID assigned during combined index creation. When importing, + // we rename all locals (not just those that are promoted) in order to + // avoid naming conflicts between locals imported from different modules. + if (SGV->hasLocalLinkage() && (DoPromote || isPerformingImport())) + return ModuleSummaryIndex::getGlobalNameForLocal( + SGV->getName(), + ImportIndex.getModuleHash(SGV->getParent()->getModuleIdentifier())); + return SGV->getName(); +} + +GlobalValue::LinkageTypes +FunctionImportGlobalProcessing::getLinkage(const GlobalValue *SGV, + bool DoPromote) { + // Any local variable that is referenced by an exported function needs + // to be promoted to global scope. Since we don't currently know which + // functions reference which local variables/functions, we must treat + // all as potentially exported if this module is exporting anything. + if (isModuleExporting()) { + if (SGV->hasLocalLinkage() && DoPromote) + return GlobalValue::ExternalLinkage; + return SGV->getLinkage(); + } + + // Otherwise, if we aren't importing, no linkage change is needed. + if (!isPerformingImport()) + return SGV->getLinkage(); + + switch (SGV->getLinkage()) { + case GlobalValue::LinkOnceODRLinkage: + case GlobalValue::ExternalLinkage: + // External and linkonce definitions are converted to available_externally + // definitions upon import, so that they are available for inlining + // and/or optimization, but are turned into declarations later + // during the EliminateAvailableExternally pass. + if (doImportAsDefinition(SGV) && !isa<GlobalAlias>(SGV)) + return GlobalValue::AvailableExternallyLinkage; + // An imported external declaration stays external. + return SGV->getLinkage(); + + case GlobalValue::AvailableExternallyLinkage: + // An imported available_externally definition converts + // to external if imported as a declaration. + if (!doImportAsDefinition(SGV)) + return GlobalValue::ExternalLinkage; + // An imported available_externally declaration stays that way. + return SGV->getLinkage(); + + case GlobalValue::LinkOnceAnyLinkage: + case GlobalValue::WeakAnyLinkage: + // Can't import linkonce_any/weak_any definitions correctly, or we might + // change the program semantics, since the linker will pick the first + // linkonce_any/weak_any definition and importing would change the order + // they are seen by the linker. The module linking caller needs to enforce + // this. + assert(!doImportAsDefinition(SGV)); + // If imported as a declaration, it becomes external_weak. + return SGV->getLinkage(); + + case GlobalValue::WeakODRLinkage: + // For weak_odr linkage, there is a guarantee that all copies will be + // equivalent, so the issue described above for weak_any does not exist, + // and the definition can be imported. It can be treated similarly + // to an imported externally visible global value. + if (doImportAsDefinition(SGV) && !isa<GlobalAlias>(SGV)) + return GlobalValue::AvailableExternallyLinkage; + else + return GlobalValue::ExternalLinkage; + + case GlobalValue::AppendingLinkage: + // It would be incorrect to import an appending linkage variable, + // since it would cause global constructors/destructors to be + // executed multiple times. This should have already been handled + // by linkIfNeeded, and we will assert in shouldLinkFromSource + // if we try to import, so we simply return AppendingLinkage. + return GlobalValue::AppendingLinkage; + + case GlobalValue::InternalLinkage: + case GlobalValue::PrivateLinkage: + // If we are promoting the local to global scope, it is handled + // similarly to a normal externally visible global. + if (DoPromote) { + if (doImportAsDefinition(SGV) && !isa<GlobalAlias>(SGV)) + return GlobalValue::AvailableExternallyLinkage; + else + return GlobalValue::ExternalLinkage; + } + // A non-promoted imported local definition stays local. + // The ThinLTO pass will eventually force-import their definitions. + return SGV->getLinkage(); + + case GlobalValue::ExternalWeakLinkage: + // External weak doesn't apply to definitions, must be a declaration. + assert(!doImportAsDefinition(SGV)); + // Linkage stays external_weak. + return SGV->getLinkage(); + + case GlobalValue::CommonLinkage: + // Linkage stays common on definitions. + // The ThinLTO pass will eventually force-import their definitions. + return SGV->getLinkage(); + } + + llvm_unreachable("unknown linkage type"); +} + +void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) { + + ValueInfo VI; + if (GV.hasName()) { + VI = ImportIndex.getValueInfo(GV.getGUID()); + // Set synthetic function entry counts. + if (VI && ImportIndex.hasSyntheticEntryCounts()) { + if (Function *F = dyn_cast<Function>(&GV)) { + if (!F->isDeclaration()) { + for (auto &S : VI.getSummaryList()) { + auto *FS = cast<FunctionSummary>(S->getBaseObject()); + if (FS->modulePath() == M.getModuleIdentifier()) { + F->setEntryCount(Function::ProfileCount(FS->entryCount(), + Function::PCT_Synthetic)); + break; + } + } + } + } + } + // Check the summaries to see if the symbol gets resolved to a known local + // definition. + if (VI && VI.isDSOLocal()) { + GV.setDSOLocal(true); + if (GV.hasDLLImportStorageClass()) + GV.setDLLStorageClass(GlobalValue::DefaultStorageClass); + } + } + + // Mark read/write-only variables which can be imported with specific + // attribute. We can't internalize them now because IRMover will fail + // to link variable definitions to their external declarations during + // ThinLTO import. We'll internalize read-only variables later, after + // import is finished. See internalizeGVsAfterImport. + // + // If global value dead stripping is not enabled in summary then + // propagateConstants hasn't been run. We can't internalize GV + // in such case. + if (!GV.isDeclaration() && VI && ImportIndex.withGlobalValueDeadStripping()) { + const auto &SL = VI.getSummaryList(); + auto *GVS = SL.empty() ? nullptr : dyn_cast<GlobalVarSummary>(SL[0].get()); + // At this stage "maybe" is "definitely" + if (GVS && (GVS->maybeReadOnly() || GVS->maybeWriteOnly())) + cast<GlobalVariable>(&GV)->addAttribute("thinlto-internalize"); + } + + bool DoPromote = false; + if (GV.hasLocalLinkage() && + ((DoPromote = shouldPromoteLocalToGlobal(&GV)) || isPerformingImport())) { + // Save the original name string before we rename GV below. + auto Name = GV.getName().str(); + // Once we change the name or linkage it is difficult to determine + // again whether we should promote since shouldPromoteLocalToGlobal needs + // to locate the summary (based on GUID from name and linkage). Therefore, + // use DoPromote result saved above. + GV.setName(getName(&GV, DoPromote)); + GV.setLinkage(getLinkage(&GV, DoPromote)); + if (!GV.hasLocalLinkage()) + GV.setVisibility(GlobalValue::HiddenVisibility); + + // If we are renaming a COMDAT leader, ensure that we record the COMDAT + // for later renaming as well. This is required for COFF. + if (const auto *C = GV.getComdat()) + if (C->getName() == Name) + RenamedComdats.try_emplace(C, M.getOrInsertComdat(GV.getName())); + } else + GV.setLinkage(getLinkage(&GV, /* DoPromote */ false)); + + // Remove functions imported as available externally defs from comdats, + // 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<GlobalObject>(&GV); + if (GO && GO->isDeclarationForLinker() && GO->hasComdat()) { + // The IRMover should not have placed any imported declarations in + // a comdat, so the only declaration that should be in a comdat + // at this point would be a definition imported as available_externally. + assert(GO->hasAvailableExternallyLinkage() && + "Expected comdat on definition (possibly available external)"); + GO->setComdat(nullptr); + } +} + +void FunctionImportGlobalProcessing::processGlobalsForThinLTO() { + for (GlobalVariable &GV : M.globals()) + processGlobalForThinLTO(GV); + for (Function &SF : M) + processGlobalForThinLTO(SF); + for (GlobalAlias &GA : M.aliases()) + processGlobalForThinLTO(GA); + + // Replace any COMDATS that required renaming (because the COMDAT leader was + // promoted and renamed). + if (!RenamedComdats.empty()) + for (auto &GO : M.global_objects()) + if (auto *C = GO.getComdat()) { + auto Replacement = RenamedComdats.find(C); + if (Replacement != RenamedComdats.end()) + GO.setComdat(Replacement->second); + } +} + +bool FunctionImportGlobalProcessing::run() { + processGlobalsForThinLTO(); + return false; +} + +bool llvm::renameModuleForThinLTO(Module &M, const ModuleSummaryIndex &Index, + SetVector<GlobalValue *> *GlobalsToImport) { + FunctionImportGlobalProcessing ThinLTOProcessing(M, Index, GlobalsToImport); + return ThinLTOProcessing.run(); +} |