[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
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 98567fb..0e70571 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -423,6 +423,14 @@
"Multiple prevailing defs are not allowed");
GlobalRes.Prevailing = true;
GlobalRes.IRName = Sym.getIRName();
+ } else if (!GlobalRes.Prevailing && GlobalRes.IRName.empty()) {
+ // Sometimes it can be two copies of symbol in a module and prevailing
+ // symbol can have no IR name. That might happen if symbol is defined in
+ // module level inline asm block. In case we have multiple modules with
+ // the same symbol we want to use IR name of the prevailing symbol.
+ // Otherwise, if we haven't seen a prevailing symbol, set the name so that
+ // we can later use it to check if there is any prevailing copy in IR.
+ GlobalRes.IRName = Sym.getIRName();
}
// Set the partition to external if we know it is re-defined by the linker
@@ -747,12 +755,31 @@
Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
// Compute "dead" symbols, we don't want to import/export these!
DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
- for (auto &Res : GlobalResolutions)
+ DenseMap<GlobalValue::GUID, PrevailingType> GUIDPrevailingResolutions;
+ for (auto &Res : GlobalResolutions) {
+ // Normally resolution have IR name of symbol. We can do nothing here
+ // otherwise. See comments in GlobalResolution struct for more details.
+ if (Res.second.IRName.empty())
+ continue;
+
+ GlobalValue::GUID GUID = GlobalValue::getGUID(
+ GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
+
if (Res.second.VisibleOutsideSummary && Res.second.Prevailing)
GUIDPreservedSymbols.insert(GlobalValue::getGUID(
GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
- computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
+ GUIDPrevailingResolutions[GUID] =
+ Res.second.Prevailing ? PrevailingType::Yes : PrevailingType::No;
+ }
+
+ auto isPrevailing = [&](GlobalValue::GUID G) {
+ auto It = GUIDPrevailingResolutions.find(G);
+ if (It == GUIDPrevailingResolutions.end())
+ return PrevailingType::Unknown;
+ return It->second;
+ };
+ computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols, isPrevailing);
if (auto E = runRegularLTO(AddStream))
return E;
@@ -800,7 +827,7 @@
if (!Conf.CodeGenOnly) {
for (const auto &R : GlobalResolutions) {
- if (!R.second.Prevailing)
+ if (!R.second.isPrevailingIRSymbol())
continue;
if (R.second.Partition != 0 &&
R.second.Partition != GlobalResolution::External)
@@ -1114,7 +1141,7 @@
// If the symbol does not have external references or it is not prevailing,
// then not need to mark it as exported from a ThinLTO partition.
if (Res.second.Partition != GlobalResolution::External ||
- !Res.second.Prevailing)
+ !Res.second.isPrevailingIRSymbol())
continue;
auto GUID = GlobalValue::getGUID(
GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 0705326..1898d4b 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -399,6 +399,17 @@
return Error::success();
}
+static void dropDeadSymbols(Module &Mod, const GVSummaryMapTy &DefinedGlobals,
+ const ModuleSummaryIndex &Index) {
+ for (auto &GV : Mod) {
+ auto It = DefinedGlobals.find(GV.getGUID());
+ if (It == DefinedGlobals.end())
+ continue;
+ if (!Index.isGlobalValueLive(It->second))
+ convertToDeclaration(GV);
+ }
+}
+
Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
Module &Mod, const ModuleSummaryIndex &CombinedIndex,
const FunctionImporter::ImportMapTy &ImportList,
@@ -420,6 +431,8 @@
renameModuleForThinLTO(Mod, CombinedIndex);
+ dropDeadSymbols(Mod, DefinedGlobals, CombinedIndex);
+
thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals);
if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
diff --git a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
index b5ac5a7..b2e34c5 100644
--- a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -621,6 +621,18 @@
thinLTOInternalizeAndPromoteInIndex(Index, isExported);
}
+static void computeDeadSymbolsInIndex(
+ ModuleSummaryIndex &Index,
+ const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
+ // We have no symbols resolution available. And can't do any better now in the
+ // case where the prevailing symbol is in a native object. It can be refined
+ // with linker information in the future.
+ auto isPrevailing = [&](GlobalValue::GUID G) {
+ return PrevailingType::Unknown;
+ };
+ computeDeadSymbols(Index, GUIDPreservedSymbols, isPrevailing);
+}
+
/**
* Perform promotion and renaming of exported internal functions.
* Index is updated to reflect linkage changes from weak resolution.
@@ -639,7 +651,7 @@
PreservedSymbols, Triple(TheModule.getTargetTriple()));
// Compute "dead" symbols, we don't want to import/export these!
- computeDeadSymbols(Index, GUIDPreservedSymbols);
+ computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
@@ -678,7 +690,7 @@
PreservedSymbols, Triple(TheModule.getTargetTriple()));
// Compute "dead" symbols, we don't want to import/export these!
- computeDeadSymbols(Index, GUIDPreservedSymbols);
+ computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
@@ -755,7 +767,7 @@
Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
// Compute "dead" symbols, we don't want to import/export these!
- computeDeadSymbols(Index, GUIDPreservedSymbols);
+ computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
// Generate import/export list
StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
@@ -901,7 +913,7 @@
computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
// Compute "dead" symbols, we don't want to import/export these!
- computeDeadSymbols(*Index, GUIDPreservedSymbols);
+ computeDeadSymbolsInIndex(*Index, GUIDPreservedSymbols);
// Collect the import/export lists for all modules from the call-graph in the
// combined index.