[RUNTIME][IR] Allow non-nullable ObjectRef, introduce Optional<T>.

apps/android_camera/app/src/main/jni/Application.mk

@@ -31,7 +31,7 @@ include $(config)
 APP_ABI ?= all
 APP_STL := c++_shared
 
-APP_CPPFLAGS += -DDMLC_LOG_STACK_TRACE=0 -DTVM4J_ANDROID=1 -std=c++11 -Oz -frtti
+APP_CPPFLAGS += -DDMLC_LOG_STACK_TRACE=0 -DTVM4J_ANDROID=1 -std=c++14 -Oz -frtti
 ifeq ($(USE_OPENCL), 1)
     APP_CPPFLAGS += -DTVM_OPENCL_RUNTIME=1
 endif

apps/android_deploy/app/src/main/jni/Application.mk

@@ -27,7 +27,7 @@ include $(config)
 
 APP_STL := c++_static
 
-APP_CPPFLAGS += -DDMLC_LOG_STACK_TRACE=0 -DTVM4J_ANDROID=1 -std=c++11 -Oz -frtti
-ifeq ($(USE_OPENCL), 1)                                                                                                                                             
+APP_CPPFLAGS += -DDMLC_LOG_STACK_TRACE=0 -DTVM4J_ANDROID=1 -std=c++14 -Oz -frtti
+ifeq ($(USE_OPENCL), 1)
 	APP_CPPFLAGS += -DTVM_OPENCL_RUNTIME=1
 endif

apps/android_rpc/app/src/main/jni/Application.mk

@@ -31,7 +31,7 @@ include $(config)
 APP_ABI ?= armeabi-v7a arm64-v8a x86 x86_64 mips
 APP_STL := c++_shared
 
-APP_CPPFLAGS += -DDMLC_LOG_STACK_TRACE=0 -DTVM4J_ANDROID=1 -std=c++11 -Oz -frtti
+APP_CPPFLAGS += -DDMLC_LOG_STACK_TRACE=0 -DTVM4J_ANDROID=1 -std=c++14 -Oz -frtti
 ifeq ($(USE_OPENCL), 1)
     APP_CPPFLAGS += -DTVM_OPENCL_RUNTIME=1
 endif

apps/cpp_rpc/Makefile

@@ -28,7 +28,7 @@ else
 LINK_PTHREAD=
 endif
 
-PKG_CFLAGS = -std=c++11 -O2 -fPIC -Wall\
+PKG_CFLAGS = -std=c++14 -O2 -fPIC -Wall\
 	-I${TVM_ROOT}/include\
 	-I${DMLC_CORE}/include\
 	-I${TVM_ROOT}/3rdparty/dlpack/include

apps/dso_plugin_module/Makefile

@@ -16,7 +16,7 @@
 # under the License.
 
 TVM_ROOT=$(shell cd ../..; pwd)
-PKG_CFLAGS = -std=c++11 -O2 -fPIC\
+PKG_CFLAGS = -std=c++14 -O2 -fPIC\
 	-I${TVM_ROOT}/include\
 	-I${TVM_ROOT}/3rdparty/dmlc-core/include\
 	-I${TVM_ROOT}/3rdparty/dlpack/include

apps/extension/Makefile

@@ -17,7 +17,7 @@
 
 # Minimum Makefile for the extension package
 TVM_ROOT=$(shell cd ../..; pwd)
-PKG_CFLAGS = -std=c++11 -O2 -fPIC\
+PKG_CFLAGS = -std=c++14 -O2 -fPIC\
 	-I${TVM_ROOT}/include\
 	-I${TVM_ROOT}/3rdparty/dmlc-core/include\
 	-I${TVM_ROOT}/3rdparty/dlpack/include

apps/howto_deploy/Makefile

@@ -19,7 +19,7 @@
 TVM_ROOT=$(shell cd ../..; pwd)
 DMLC_CORE=${TVM_ROOT}/3rdparty/dmlc-core
 
-PKG_CFLAGS = -std=c++11 -O2 -fPIC\
+PKG_CFLAGS = -std=c++14 -O2 -fPIC\
 	-I${TVM_ROOT}/include\
 	-I${DMLC_CORE}/include\
 	-I${TVM_ROOT}/3rdparty/dlpack/include\

apps/howto_deploy/tvm_runtime_pack.cc

@@ -24,7 +24,7 @@
  *   include in your project.
  *
  *  - Copy this file into your project which depends on tvm runtime.
- *  - Compile with -std=c++11
+ *  - Compile with -std=c++14
  *  - Add the following include path
  *     - /path/to/tvm/include/
  *     - /path/to/tvm/3rdparty/dmlc-core/include/

apps/rocm_rpc/Makefile

@@ -21,7 +21,7 @@ ROCM_PATH=/opt/rocm
 TVM_ROOT=$(shell cd ../..; pwd)
 DMLC_CORE=${TVM_ROOT}/3rdparty/dmlc-core
 
-PKG_CFLAGS = -std=c++11 -O2 -fPIC\
+PKG_CFLAGS = -std=c++14 -O2 -fPIC\
 	-I${TVM_ROOT}/include\
 	-I${DMLC_CORE}/include\
 	-I${TVM_ROOT}/3rdparty/dlpack/include\

apps/tf_tvmdsoop/CMakeLists.txt

@@ -17,7 +17,7 @@
 cmake_minimum_required(VERSION 3.2)
 project(tf_tvmdsoop C CXX)
 
-set(TFTVM_COMPILE_FLAGS -std=c++11)
+set(TFTVM_COMPILE_FLAGS -std=c++14)
 set(BUILD_TVMDSOOP_ONLY ON)
 set(CMAKE_CURRENT_SOURCE_DIR ${TVM_ROOT})
 set(CMAKE_CURRENT_BINARY_DIR ${TVM_ROOT}/build)

golang/Makefile

@@ -25,7 +25,7 @@ NATIVE_SRC = tvm_runtime_pack.cc
 GOPATH=$(CURDIR)/gopath
 GOPATHDIR=${GOPATH}/src/${TARGET}/
 CGO_CPPFLAGS="-I. -I${TVM_BASE}/ -I${TVM_BASE}/3rdparty/dmlc-core/include -I${TVM_BASE}/include -I${TVM_BASE}/3rdparty/dlpack/include/"
-CGO_CXXFLAGS="-std=c++11"
+CGO_CXXFLAGS="-std=c++14"
 CGO_CFLAGS="-I${TVM_BASE}"
 CGO_LDFLAGS="-ldl -lm"
 

include/tvm/ir/attrs.h

@@ -85,6 +85,8 @@ namespace tvm {
  */
 template<typename TObjectRef>
 inline TObjectRef NullValue() {
+  static_assert(TObjectRef::_type_is_nullable,
+                "Can only get NullValue for nullable types");
   return TObjectRef(ObjectPtr<Object>(nullptr));
 }
 

include/tvm/ir/expr.h

@@ -317,6 +317,47 @@ class FloatImm : public PrimExpr {
   TVM_DEFINE_OBJECT_REF_METHODS(FloatImm, PrimExpr, FloatImmNode);
 };
 
+/*!
+ * \brief Boolean constant.
+ *
+ *  This reference type is useful to add additional compile-time
+ *  type checks and helper functions for Integer equal comparisons.
+ */
+class Bool : public IntImm {
+ public:
+  explicit Bool(bool value)
+      : IntImm(DataType::Bool(), value) {
+  }
+  Bool operator!() const {
+    return Bool((*this)->value == 0);
+  }
+  operator bool() const {
+    return (*this)->value != 0;
+  }
+
+  TVM_DEFINE_NOTNULLABLE_OBJECT_REF_METHODS(Bool, IntImm, IntImmNode);
+};
+
+// Overload operators to make sure we have the most fine grained types.
+inline Bool operator||(const Bool& a, bool b) {
+  return Bool(a.operator bool() || b);
+}
+inline Bool operator||(bool a, const Bool& b) {
+  return Bool(a || b.operator bool());
+}
+inline Bool operator||(const Bool& a, const Bool& b) {
+  return Bool(a.operator bool() || b.operator bool());
+}
+inline Bool operator&&(const Bool& a, bool b) {
+  return Bool(a.operator bool() && b);
+}
+inline Bool operator&&(bool a, const Bool& b) {
+  return Bool(a && b.operator bool());
+}
+inline Bool operator&&(const Bool& a, const Bool& b) {
+  return Bool(a.operator bool() && b.operator bool());
+}
+
 /*!
  * \brief Container of constant int that adds more constructors.
  *
@@ -346,10 +387,10 @@ class Integer : public IntImm {
    * \tparam Enum The enum type.
    * \param value The enum value.
    */
-  template<typename ENum,
-           typename = typename std::enable_if<std::is_enum<ENum>::value>::type>
-  explicit Integer(ENum value) : Integer(static_cast<int>(value)) {
-    static_assert(std::is_same<int, typename std::underlying_type<ENum>::type>::value,
+  template<typename Enum,
+           typename = typename std::enable_if<std::is_enum<Enum>::value>::type>
+  explicit Integer(Enum value) : Integer(static_cast<int>(value)) {
+    static_assert(std::is_same<int, typename std::underlying_type<Enum>::type>::value,
                   "declare enum to be enum int to use visitor");
   }
   /*!
@@ -368,6 +409,24 @@ class Integer : public IntImm {
         << " Trying to reference a null Integer";
     return (*this)->value;
   }
+  // comparators
+  Bool operator==(int other) const {
+    if (data_ == nullptr) return Bool(false);
+    return Bool((*this)->value == other);
+  }
+  Bool operator!=(int other) const {
+    return !(*this == other);
+  }
+  template<typename Enum,
+           typename = typename std::enable_if<std::is_enum<Enum>::value>::type>
+  Bool operator==(Enum other) const {
+    return *this == static_cast<int>(other);
+  }
+  template<typename Enum,
+           typename = typename std::enable_if<std::is_enum<Enum>::value>::type>
+  Bool operator!=(Enum other) const {
+    return *this != static_cast<int>(other);
+  }
 };
 
 /*! \brief range over one dimension */

include/tvm/ir/function.h

@@ -26,6 +26,7 @@
 
 #include <tvm/ir/expr.h>
 #include <tvm/ir/attrs.h>
+#include <tvm/runtime/container.h>
 #include <type_traits>
 #include <string>
 
@@ -90,25 +91,31 @@ class BaseFuncNode : public RelayExprNode {
    * \code
    *
    *  void GetAttrExample(const BaseFunc& f) {
-   *    Integer value = f->GetAttr<Integer>("AttrKey", 0);
+   *    auto value = f->GetAttr<Integer>("AttrKey", 0);
    *  }
    *
    * \endcode
    */
   template<typename TObjectRef>
-  TObjectRef GetAttr(const std::string& attr_key,
-                     TObjectRef default_value = NullValue<TObjectRef>()) const {
+  Optional<TObjectRef> GetAttr(
+      const std::string& attr_key,
+      Optional<TObjectRef> default_value = Optional<TObjectRef>(nullptr)) const {
     static_assert(std::is_base_of<ObjectRef, TObjectRef>::value,
                   "Can only call GetAttr with ObjectRef types.");
     if (!attrs.defined()) return default_value;
     auto it = attrs->dict.find(attr_key);
     if (it != attrs->dict.end()) {
-      return Downcast<TObjectRef>((*it).second);
+      return Downcast<Optional<TObjectRef>>((*it).second);
     } else {
       return default_value;
     }
   }
-
+  // variant that uses TObjectRef to enable implicit conversion to default value.
+  template<typename TObjectRef>
+  Optional<TObjectRef> GetAttr(
+      const std::string& attr_key, TObjectRef default_value) const {
+    return GetAttr<TObjectRef>(attr_key, Optional<TObjectRef>(default_value));
+  }
   /*!
    * \brief Check whether the function has an non-zero integer attr.
    *
@@ -129,7 +136,7 @@ class BaseFuncNode : public RelayExprNode {
    * \endcode
    */
   bool HasNonzeroAttr(const std::string& attr_key) const {
-    return GetAttr<Integer>(attr_key, 0)->value != 0;
+    return GetAttr<Integer>(attr_key, 0) != 0;
   }
 
   static constexpr const char* _type_key = "BaseFunc";

include/tvm/node/node.h

@@ -63,7 +63,6 @@ using runtime::make_object;
 using runtime::PackedFunc;
 using runtime::TVMArgs;
 using runtime::TVMRetValue;
-using runtime::String;
 
 }  // namespace tvm
 #endif  // TVM_NODE_NODE_H_