[IR][Debug] Add dump and print for debugging (NFC)

- Add two utility functions for debugging. With this change,
  developers could use

  `print op->dump()` or 'print op->print()`

  inside a debugger (lldb or gdb). Object op could be either
  of type Object or ObjectRef.

  Note that the existing tvm::Dump(ref) does not work on
  objects of type tvm::Object. Sometimes lldb cannot locate
  this Dump function inside a visitor context.

Signed-off-by: Wei Pan <weip@nvidia.com>

include/tvm/runtime/object.h

@@ -239,6 +239,9 @@ class Object {
     return *this;
   }
 
+  void dump() const;
+  std::string print() const;
+
  protected:
   // The fields of the base object cell.
   /*! \brief Type index(tag) that indicates the type of the object. */
@@ -567,6 +570,9 @@ class ObjectRef {
   /*! \brief type indicate the container type. */
   using ContainerType = Object;
 
+  void dump() const;
+  std::string print() const;
+
  protected:
   /*! \brief Internal pointer that backs the reference. */
   ObjectPtr<Object> data_;

src/runtime/object.cc

@@ -32,6 +32,10 @@
 #include "runtime_base.h"
 
 namespace tvm {
+
+// Forward declaration.
+std::string PrettyPrint(const tvm::runtime::ObjectRef& node);
+
 namespace runtime {
 
 /*! \brief Type information */
@@ -203,6 +207,22 @@ uint32_t Object::TypeKey2Index(const std::string& key) {
   return TypeContext::Global()->TypeKey2Index(key);
 }
 
+void Object::dump() const {
+  std::cerr << print();
+}
+
+std::string Object::print() const {
+  auto ref = GetRef<ObjectRef>(this);
+  return std::move(tvm::PrettyPrint(ref));
+}
+
+void ObjectRef::dump() const {
+  std::cerr << print();
+}
+
+std::string ObjectRef::print() const {
+  return std::move(tvm::PrettyPrint(*this));
+}
 
 TVM_REGISTER_GLOBAL("runtime.ObjectHash")
 .set_body_typed([](ObjectRef obj) {