Added llvm.module flag for strict vtable pointers

It is dangerous to do LTO on code with strict-vtable-pointers, because
one module has invariant.group.barriers, and the other one not.

In the future I want to just strip all invariant.group metadata from
vptrs loads/stores and get rid of invariant.group.barrier calls.

http://reviews.llvm.org/D12580

llvm-svn: 247724

clang/lib/CodeGen/CodeGenModule.cpp

@@ -398,6 +398,22 @@ void CodeGenModule::Release() {
     // Indicate that we want CodeView in the metadata.
     getModule().addModuleFlag(llvm::Module::Warning, "CodeView", 1);
   }
+  if (CodeGenOpts.OptimizationLevel > 0 && CodeGenOpts.StrictVTablePointers) {
+    // We don't support LTO with 2 with different StrictVTablePointers
+    // FIXME: we could support it by stripping all the information introduced
+    // by StrictVTablePointers.
+
+    getModule().addModuleFlag(llvm::Module::Error, "StrictVTablePointers",1);
+
+    llvm::Metadata *Ops[2] = {
+              llvm::MDString::get(VMContext, "StrictVTablePointers"),
+              llvm::ConstantAsMetadata::get(llvm::ConstantInt::get(
+                  llvm::Type::getInt32Ty(VMContext), 1))};
+
+    getModule().addModuleFlag(llvm::Module::Require,
+                              "StrictVTablePointersRequirement",
+                              llvm::MDNode::get(VMContext, Ops));
+  }
   if (DebugInfo)
     // We support a single version in the linked module. The LLVM
     // parser will drop debug info with a different version number