(NFC) Track global summary liveness in GVFlags.

Replace GVFlags::LiveRoot with GVFlags::Live and use that instead of
all the DeadSymbols sets. This is refactoring in order to make
liveness information available in the RegularLTO pipeline.

llvm-svn: 304466

1 files changed, 14 insertions, 4 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 9efc095..b8698c8 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -930,6 +930,17 @@ ThinBackend lto::createWriteIndexesThinBackend(std::string OldPrefix,
   };
 }
 
+static bool IsLiveByGUID(const ModuleSummaryIndex &Index,
+                         GlobalValue::GUID GUID) {
+  auto VI = Index.getValueInfo(GUID);
+  if (!VI)
+    return false;
+  for (auto &I : VI.getSummaryList())
+    if (Index.isGlobalValueLive(I.get()))
+      return true;
+  return false;
+}
+
 Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
                       bool HasRegularLTO) {
   if (ThinLTO.ModuleMap.empty())
@@ -973,11 +984,10 @@ Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
             GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
     }
 
-    auto DeadSymbols =
-        computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
+    computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
 
     ComputeCrossModuleImport(ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
-                             ImportLists, ExportLists, &DeadSymbols);
+                             ImportLists, ExportLists);
 
     std::set<GlobalValue::GUID> ExportedGUIDs;
     for (auto &Res : GlobalResolutions) {
@@ -992,7 +1002,7 @@ Error LTO::runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
       auto GUID = GlobalValue::getGUID(
           GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
       // Mark exported unless index-based analysis determined it to be dead.
-      if (!DeadSymbols.count(GUID))
+      if (IsLiveByGUID(ThinLTO.CombinedIndex, GUID))
         ExportedGUIDs.insert(GUID);
     }