Reland r313157, "ThinLTO: Correctly follow aliasee references when dead stripping." which was reverted in r313222.

This reland includes a fix for the LowerTypeTests pass so that it
looks past aliases when determining which type identifiers are live.

Differential Revision: https://reviews.llvm.org/D37842

llvm-svn: 313229

2 files changed, 10 insertions, 17 deletions

diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index da763b18d4d..9f20cbc6fed 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -324,10 +324,8 @@ static void ComputeImportForModule(
       DEBUG(dbgs() << "Ignores Dead GUID: " << GVSummary.first << "\n");
       continue;
     }
-    auto *Summary = GVSummary.second;
-    if (auto *AS = dyn_cast<AliasSummary>(Summary))
-      Summary = &AS->getAliasee();
-    auto *FuncSummary = dyn_cast<FunctionSummary>(Summary);
+    auto *FuncSummary =
+        dyn_cast<FunctionSummary>(GVSummary.second->getBaseObject());
     if (!FuncSummary)
       // Skip import for global variables
       continue;
@@ -488,17 +486,12 @@ void llvm::computeDeadSymbols(
   while (!Worklist.empty()) {
     auto VI = Worklist.pop_back_val();
     for (auto &Summary : VI.getSummaryList()) {
-      for (auto Ref : Summary->refs())
+      GlobalValueSummary *Base = Summary->getBaseObject();
+      for (auto Ref : Base->refs())
         visit(Ref);
-      if (auto *FS = dyn_cast<FunctionSummary>(Summary.get()))
+      if (auto *FS = dyn_cast<FunctionSummary>(Base))
         for (auto Call : FS->calls())
           visit(Call.first);
-      if (auto *AS = dyn_cast<AliasSummary>(Summary.get())) {
-        auto AliaseeGUID = AS->getAliasee().getOriginalName();
-        ValueInfo AliaseeVI = Index.getValueInfo(AliaseeGUID);
-        if (AliaseeVI)
-          visit(AliaseeVI);
-      }
     }
   }
   Index.setWithGlobalValueDeadStripping();
diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index 49cc14c5b59..027f426649c 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -1703,12 +1703,12 @@ bool LowerTypeTestsModule::lower() {
 
     for (auto &P : *ExportSummary) {
       for (auto &S : P.second.SummaryList) {
-        auto *FS = dyn_cast<FunctionSummary>(S.get());
-        if (!FS || !ExportSummary->isGlobalValueLive(FS))
+        if (!ExportSummary->isGlobalValueLive(S.get()))
           continue;
-        for (GlobalValue::GUID G : FS->type_tests())
-          for (Metadata *MD : MetadataByGUID[G])
-            AddTypeIdUse(MD).IsExported = true;
+        if (auto *FS = dyn_cast<FunctionSummary>(S->getBaseObject()))
+          for (GlobalValue::GUID G : FS->type_tests())
+            for (Metadata *MD : MetadataByGUID[G])
+              AddTypeIdUse(MD).IsExported = true;
       }
     }
   }