r247724 - Added llvm.module flag for strict vtable pointers

[Piotr Padlewski via cfe-commits]

Author: prazek
Date: Tue Sep 15 16:46:50 2015
New Revision: 247724

URL: http://llvm.org/viewvc/llvm-project?rev=247724&view=rev
Log:
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

Modified:
    cfe/trunk/lib/CodeGen/CodeGenModule.cpp
    cfe/trunk/test/CodeGenCXX/strict-vtable-pointers.cpp

Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=247724&r1=247723&r2=247724&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Tue Sep 15 16:46:50 2015
@@ -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

Modified: cfe/trunk/test/CodeGenCXX/strict-vtable-pointers.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/strict-vtable-pointers.cpp?rev=247724&r1=247723&r2=247724&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/strict-vtable-pointers.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/strict-vtable-pointers.cpp Tue Sep 15 16:46:50 2015
@@ -2,6 +2,7 @@
 // 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();
@@ -191,3 +192,11 @@ struct DynamicFromStatic;
 // 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}
+