[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
diff --git a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
index 104fb19..b62db61 100644
--- a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -234,16 +234,16 @@
// Convert the PreservedSymbols map from "Name" based to "GUID" based.
static DenseSet<GlobalValue::GUID>
-computeGUIDPreservedSymbols(const StringSet<> &PreservedSymbols,
- const Triple &TheTriple) {
- DenseSet<GlobalValue::GUID> GUIDPreservedSymbols(PreservedSymbols.size());
- for (auto &Entry : PreservedSymbols) {
+convertSymbolNamesToGUID(const StringSet<> &NamedSymbols,
+ const Triple &TheTriple) {
+ DenseSet<GlobalValue::GUID> GUIDSymbols(NamedSymbols.size());
+ for (auto &Entry : NamedSymbols) {
StringRef Name = Entry.first();
if (TheTriple.isOSBinFormatMachO() && Name.size() > 0 && Name[0] == '_')
Name = Name.drop_front();
- GUIDPreservedSymbols.insert(GlobalValue::getGUID(Name));
+ GUIDSymbols.insert(GlobalValue::getGUID(Name));
}
- return GUIDPreservedSymbols;
+ return GUIDSymbols;
}
std::unique_ptr<MemoryBuffer> codegenModule(Module &TheModule,
@@ -554,10 +554,7 @@
}
void ThinLTOCodeGenerator::crossReferenceSymbol(StringRef Name) {
- // FIXME: At the moment, we don't take advantage of this extra information,
- // we're conservatively considering cross-references as preserved.
- // CrossReferencedSymbols.insert(Name);
- PreservedSymbols.insert(Name);
+ CrossReferencedSymbols.insert(Name);
}
// TargetMachine factory
@@ -620,7 +617,7 @@
Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
// Convert the preserved symbols set from string to GUID
- auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
+ auto GUIDPreservedSymbols = convertSymbolNamesToGUID(
PreservedSymbols, Triple(TheModule.getTargetTriple()));
// Compute "dead" symbols, we don't want to import/export these!
@@ -641,11 +638,13 @@
// Promote the exported values in the index, so that they are promoted
// in the module.
- auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
+ auto isExported = [&](StringRef ModuleIdentifier,
+ GlobalValue::GUID GUID) -> SummaryResolution {
const auto &ExportList = ExportLists.find(ModuleIdentifier);
- return (ExportList != ExportLists.end() &&
- ExportList->second.count(GUID)) ||
- GUIDPreservedSymbols.count(GUID);
+ if ((ExportList != ExportLists.end() && ExportList->second.count(GUID)) ||
+ GUIDPreservedSymbols.count(GUID))
+ return Exported;
+ return Internal;
};
thinLTOInternalizeAndPromoteInIndex(Index, isExported);
@@ -665,7 +664,7 @@
Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
// Convert the preserved symbols set from string to GUID
- auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
+ auto GUIDPreservedSymbols = convertSymbolNamesToGUID(
PreservedSymbols, Triple(TheModule.getTargetTriple()));
// Compute "dead" symbols, we don't want to import/export these!
@@ -739,7 +738,7 @@
// Convert the preserved symbols set from string to GUID
auto GUIDPreservedSymbols =
- computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
+ convertSymbolNamesToGUID(PreservedSymbols, TMBuilder.TheTriple);
// Collect for each module the list of function it defines (GUID -> Summary).
StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
@@ -761,11 +760,13 @@
return;
// Internalization
- auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
+ auto isExported = [&](StringRef ModuleIdentifier,
+ GlobalValue::GUID GUID) -> SummaryResolution {
const auto &ExportList = ExportLists.find(ModuleIdentifier);
- return (ExportList != ExportLists.end() &&
- ExportList->second.count(GUID)) ||
- GUIDPreservedSymbols.count(GUID);
+ if ((ExportList != ExportLists.end() && ExportList->second.count(GUID)) ||
+ GUIDPreservedSymbols.count(GUID))
+ return Exported;
+ return Internal;
};
thinLTOInternalizeAndPromoteInIndex(Index, isExported);
thinLTOInternalizeModule(TheModule,
@@ -894,7 +895,9 @@
// Convert the preserved symbols set from string to GUID, this is needed for
// computing the caching hash and the internalization.
auto GUIDPreservedSymbols =
- computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
+ convertSymbolNamesToGUID(PreservedSymbols, TMBuilder.TheTriple);
+ auto GUIDCrossRefSymbols =
+ convertSymbolNamesToGUID(CrossReferencedSymbols, TMBuilder.TheTriple);
// Compute "dead" symbols, we don't want to import/export these!
auto DeadSymbols = computeDeadSymbols(*Index, GUIDPreservedSymbols);
@@ -916,11 +919,16 @@
// impacts the caching.
resolveWeakForLinkerInIndex(*Index, ResolvedODR);
- auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
+ auto isExported = [&](StringRef ModuleIdentifier,
+ GlobalValue::GUID GUID) -> SummaryResolution {
+ if (GUIDPreservedSymbols.count(GUID))
+ return Exported;
+ if (GUIDCrossRefSymbols.count(GUID))
+ return Hidden;
const auto &ExportList = ExportLists.find(ModuleIdentifier);
- return (ExportList != ExportLists.end() &&
- ExportList->second.count(GUID)) ||
- GUIDPreservedSymbols.count(GUID);
+ if (ExportList != ExportLists.end() && ExportList->second.count(GUID))
+ return Hidden;
+ return Internal;
};
// Use global summary-based analysis to identify symbols that can be