1 files changed, 23 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 769027ef8d1..b7a3777fe45 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -382,6 +382,7 @@ void InstrProfStats::reportDiagnostics(DiagnosticsEngine &Diags,
 
 void CodeGenModule::Release() {
   EmitDeferred();
+  EmitVTablesOpportunistically();
   applyGlobalValReplacements();
   applyReplacements();
   checkAliases();
@@ -1386,6 +1387,24 @@ void CodeGenModule::EmitDeferred() {
   }
 }
 
+void CodeGenModule::EmitVTablesOpportunistically() {
+  // Try to emit external vtables as available_externally if they have emitted
+  // all inlined virtual functions.  It runs after EmitDeferred() and therefore
+  // is not allowed to create new references to things that need to be emitted
+  // lazily. Note that it also uses fact that we eagerly emitting RTTI.
+
+  assert(OpportunisticVTables.empty() || shouldOpportunisticallyEmitVTables() &&
+           "Only emit opportunistic vtables with optimizations");
+
+  for (const CXXRecordDecl *RD : OpportunisticVTables) {
+    assert(getVTables().isVTableExternal(RD) &&
+           "This queue should only contain external vtables");
+    if (getCXXABI().canSpeculativelyEmitVTable(RD))
+      VTables.GenerateClassData(RD);
+  }
+  OpportunisticVTables.clear();
+}
+
 void CodeGenModule::EmitGlobalAnnotations() {
   if (Annotations.empty())
     return;
@@ -1906,6 +1925,10 @@ bool CodeGenModule::shouldEmitFunction(GlobalDecl GD) {
   return !isTriviallyRecursive(F);
 }
 
+bool CodeGenModule::shouldOpportunisticallyEmitVTables() {
+  return CodeGenOpts.OptimizationLevel > 0;
+}
+
 void CodeGenModule::EmitGlobalDefinition(GlobalDecl GD, llvm::GlobalValue *GV) {
   const auto *D = cast<ValueDecl>(GD.getDecl());