Add isConstant argument to MDBuilder::createTBAAStructTagNode

[apilipenko]

Summary

According to the TBAA description struct-path tag node can have an optional IsConstant field. Add corresponding argument to MDBuilder::createTBAAStructTagNode.

[hfinkel]

lib/IR/MDBuilder.cpp

174

Please only add the extra parameter if it is true. Let's not increase the memory footprint of the metadata for the common case.

[hfinkel]

LGTM.

include/llvm/IR/MDBuilder.h

public:
   /// \brief Return metadata for a TBAA scalar type node with the
   /// given name, an offset and a parent in the TBAA type DAG.
   MDNode *createTBAAScalarTypeNode(StringRef Name, MDNode *Parent,
                                    uint64_t Offset = 0);
 
   /// \brief Return metadata for a TBAA tag node with the given
   /// base type, access type and offset relative to the base type.
   MDNode *createTBAAStructTagNode(MDNode *BaseType, MDNode *AccessType,
-                                  uint64_t Offset);
+                                  uint64_t Offset, bool IsConstant = false);
 };
 
 } // end namespace llvm
 
 #endif

lib/IR/MDBuilder.cpp

MDNode *MDBuilder::createTBAAScalarTypeNode(StringRef Name, MDNode *Parent,
   ConstantInt *Off = ConstantInt::get(Type::getInt64Ty(Context), Offset);
   Metadata *Ops[3] = {createString(Name), Parent, createConstant(Off)};
   return MDNode::get(Context, Ops);
 }
 
 /// \brief Return metadata for a TBAA tag node with the given
 /// base type, access type and offset relative to the base type.
 MDNode *MDBuilder::createTBAAStructTagNode(MDNode *BaseType, MDNode *AccessType,
-                                           uint64_t Offset) {
+                                           uint64_t Offset, bool IsConstant) {
   Type *Int64 = Type::getInt64Ty(Context);
+  if (IsConstant) {
+    Metadata *Ops[4] = {BaseType, AccessType,
+                        createConstant(ConstantInt::get(Int64, Offset)),
+                        createConstant(ConstantInt::get(Int64, 1))};
+    return MDNode::get(Context, Ops);
+  } else {
     Metadata *Ops[3] = {BaseType, AccessType,
                         createConstant(ConstantInt::get(Int64, Offset))};
     return MDNode::get(Context, Ops);
   }
+}