Added StrictVTablePointers linking requirement

[Prazek]

Summary

Generates code like this
!llvm.module.flags = !{!0, !1}

!0 = !{i32 1, !"StrictVTablePointers", i32 1}
!1 = !{i32 3, !"StrictVTablePointersRequirement", !2}
!2 = !{!"StrictVTablePointers", i32 1}

[rsmith]

Functionally LGTM, but please add a test case. Is there any precedent for how to spell these module flags (StrictVTablePointers / strict_vtable_pointers / strict.vtable.pointers)?

[Prazek]

I see that CGObjCMac.cpp names it like this:

"Objective-C Garbage Collection"

[rsmith]

LGTM

lib/CodeGen/CodeGenModule.cpp

if (CodeGenOpts.DwarfVersion) {
     // We can change from Warning to Latest if such mode is supported.
     getModule().addModuleFlag(llvm::Module::Warning, "Dwarf Version",
                               CodeGenOpts.DwarfVersion);
   }
   if (CodeGenOpts.EmitCodeView) {
     // 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
     // (and warn about it, too).
     getModule().addModuleFlag(llvm::Module::Warning, "Debug Info Version",
                               llvm::DEBUG_METADATA_VERSION);
 
   // We need to record the widths of enums and wchar_t, so that we can generate

test/CodeGenCXX/strict-vtable-pointers.cpp

 // RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -fstrict-vtable-pointers -disable-llvm-optzns -O2 -emit-llvm -o %t.ll
 // RUN: FileCheck --check-prefix=CHECK-CTORS %s < %t.ll
 // RUN: FileCheck --check-prefix=CHECK-NEW %s < %t.ll
 // RUN: FileCheck --check-prefix=CHECK-DTORS %s < %t.ll
+// RUN: FileCheck --check-prefix=CHECK-LINK-REQ %s < %t.ll
 
 typedef __typeof__(sizeof(0)) size_t;
 void *operator new(size_t, void*) throw();
 
 struct NotTrivialDtor {
   ~NotTrivialDtor();
 };
 

 
 // CHECK-DTORS-LABEL: define linkonce_odr void @_ZN12DynamicBase1D2Ev
 // CHECK-DTORS: call i8* @llvm.invariant.group.barrier(
 // CHECK-DTORS-LABEL: }
 
 // CHECK-DTORS-LABEL: define linkonce_odr void @_ZN14DynamicDerivedD2Ev
 // CHECK-DTORS-NOT: call i8* @llvm.invariant.group.barrier(
 // CHECK-DTORS-LABEL: }
+
+
+// CHECK-LINK-REQ: !llvm.module.flags = !{![[FIRST:.*]], ![[SEC:.*]]{{.*}}}
+
+// CHECK-LINK-REQ: ![[FIRST]] = !{i32 1, !"StrictVTablePointers", i32 1}
+// CHECK-LINK-REQ: ![[SEC]] = !{i32 3, !"StrictVTablePointersRequirement", ![[META:.*]]}
+// CHECK-LINK-REQ: ![[META]] = !{!"StrictVTablePointers", i32 1}
+