void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
// Check the summaries to see if the symbol gets resolved to a known local
// definition.
if (GV.hasName()) {
ValueInfo VI = ImportIndex.getValueInfo(GV.getGUID());
if (VI) {
// Need to check all summaries are local in case of hash collisions.
bool IsLocal = VI.getSummaryList().size() &&
llvm::all_of(VI.getSummaryList(),
[](const std::unique_ptr<GlobalValueSummary> &Summary) {
return Summary->isDSOLocal();
});
if (IsLocal)
GV.setDSOLocal(true);
}
}
bool DoPromote = false;
if (GV.hasLocalLinkage() &&
((DoPromote = shouldPromoteLocalToGlobal(&GV)) || isPerformingImport())) {
// 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);
} 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_or_null<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 LTOCodeGenerator::
applyRestriction(GlobalValue &GV,
ArrayRef<StringRef> Libcalls,
std::vector<const char*> &MustPreserveList,
SmallPtrSetImpl<GlobalValue*> &AsmUsed,
Mangler &Mangler) {
// There are no restrictions to apply to declarations.
if (GV.isDeclaration())
return;
// There is nothing more restrictive than private linkage.
if (GV.hasPrivateLinkage())
return;
SmallString<64> Buffer;
TargetMach->getNameWithPrefix(Buffer, &GV, Mangler);
if (MustPreserveSymbols.count(Buffer))
MustPreserveList.push_back(GV.getName().data());
if (AsmUndefinedRefs.count(Buffer))
AsmUsed.insert(&GV);
// Conservatively append user-supplied runtime library functions to
// llvm.compiler.used. These could be internalized and deleted by
// optimizations like -globalopt, causing problems when later optimizations
// add new library calls (e.g., llvm.memset => memset and printf => puts).
// Leave it to the linker to remove any dead code (e.g. with -dead_strip).
if (isa<Function>(GV) &&
std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
AsmUsed.insert(&GV);
// Record the linkage type of non-local symbols so they can be restored prior
// to module splitting.
if (ShouldRestoreGlobalsLinkage && !GV.hasAvailableExternallyLinkage() &&
!GV.hasLocalLinkage() && GV.hasName())
ExternalSymbols.insert(std::make_pair(GV.getName(), GV.getLinkage()));
}
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()) {
FunctionSummary *FS = dyn_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-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 internalizeImmutableGVs.
//
// 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());
if (GVS && GVS->isReadOnly())
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);
}
}