Add support for out-of-tree building (#356)

Currently I haven't attempted to get the python bits working.
Instead the python bits are forcibly disabled.

CMakeLists.txt

@@ -1,26 +1,90 @@
-if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
-message(FATAL_ERROR
-  "This project is intended to be built as part of LLVM via "
-  "-DLLVM_EXTERNAL_PROJECTS=torch-mlir "
-  "-DLLVM_EXTERNAL_TORCH_MLIR_SOURCE_DIR=${CMAKE_CURRENT_SOURCE_DIR}")
+cmake_minimum_required(VERSION 3.12)
+
+if(POLICY CMP0068)
+  cmake_policy(SET CMP0068 NEW)
+  set(CMAKE_BUILD_WITH_INSTALL_NAME_DIR ON)
 endif()
 
+if(POLICY CMP0075)
+  cmake_policy(SET CMP0075 NEW)
+endif()
+
+if(POLICY CMP0077)
+  cmake_policy(SET CMP0077 NEW)
+endif()
+
+#-------------------------------------------------------------------------------
+# Project setup and globals
+#-------------------------------------------------------------------------------
+
+project(npcomp LANGUAGES CXX C)
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_CXX_STANDARD 14)
+
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+  # Out-of-tree build
+
+  #-------------------------------------------------------------------------------
+  # MLIR/LLVM Configuration
+  #-------------------------------------------------------------------------------
+
+  find_package(MLIR REQUIRED CONFIG)
+  message(STATUS "Using MLIRConfig.cmake in: ${MLIR_DIR}")
+  message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
+
+  set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/bin)
+  set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/lib)
+
+  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+  
+  # Define the default arguments to use with 'lit', and an option for the user to
+  # override.
+  set(LIT_ARGS_DEFAULT "-sv")
+  if (MSVC_IDE OR XCODE)
+    set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
+  endif()
+  set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
+
+  list(APPEND CMAKE_MODULE_PATH "${MLIR_CMAKE_DIR}")
+  list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
+  include(TableGen)
+  include(AddLLVM)
+  include(AddMLIR)
+  include(HandleLLVMOptions)
+
+  include(AddMLIRPython)
+  declare_mlir_python_sources(MLIRPythonSources)
+
+  # Don't try to compile the python extensions at the moment. We need
+  # to import lots of dependencies from AddMLIRPython to make this work.
+  set(MLIR_ENABLE_BINDINGS_PYTHON 0)
+
+  set(NPCOMP_BUILT_STANDALONE 1)
+  set(BACKEND_PACKAGE_STRING "LLVM ${LLVM_PACKAGE_VERSION}")
+else()
+  # In-tree build with LLVM_EXTERNAL_PROJECTS=torch-mlir
+  
   option(MLIR_ENABLE_BINDINGS_PYTHON "Enables MLIR Python Bindings" OFF)
   option(TORCH_MLIR_ENABLE_JIT_IR_IMPORTER "Enables JIT IR Importer" ON)
 
-set(TORCH_MLIR_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
-set(TORCH_MLIR_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
-message(STATUS "Building torch-mlir project at ${TORCH_MLIR_SOURCE_DIR} (into ${TORCH_MLIR_BINARY_DIR})")
-
   # TODO: Fix this upstream so that global include directories are not needed.
   set(MLIR_MAIN_SRC_DIR ${LLVM_MAIN_SRC_DIR}/../mlir)
   set(MLIR_INCLUDE_DIR ${LLVM_MAIN_SRC_DIR}/../mlir/include)
   set(MLIR_GENERATED_INCLUDE_DIR ${LLVM_BINARY_DIR}/tools/mlir/include)
+  set(MLIR_INCLUDE_DIRS "${MLIR_INCLUDE_DIR};${MLIR_GENERATED_INCLUDE_DIR}")
+  endif()
 
-# TODO: Needed for tablegen. Remove.
-include_directories(SYSTEM ${MLIR_INCLUDE_DIR})
-include_directories(SYSTEM ${MLIR_GENERATED_INCLUDE_DIR})
-include_directories(SYSTEM ${TORCH_MLIR_SOURCE_DIR}/include)
+set(TORCH_MLIR_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+set(TORCH_MLIR_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+message(STATUS "Building torch-mlir project at ${TORCH_MLIR_SOURCE_DIR} (into ${TORCH_MLIR_BINARY_DIR})")
+
+include_directories(${LLVM_INCLUDE_DIRS})
+include_directories(${MLIR_INCLUDE_DIRS})
+include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)
+include_directories(${CMAKE_CURRENT_BINARY_DIR}/include)
+# link_directories(${LLVM_BUILD_LIBRARY_DIR})
+# add_definitions(${LLVM_DEFINITIONS})
 
 function(torch_mlir_target_includes target)
   set(_dirs
@@ -69,7 +133,6 @@ add_subdirectory(tools)
 add_custom_target(check-torch-mlir-all)
 add_dependencies(check-torch-mlir-all
   check-torch-mlir
-  check-torch-mlir-python
   )
 
 if(MLIR_ENABLE_BINDINGS_PYTHON)
@@ -78,7 +141,12 @@ if(MLIR_ENABLE_BINDINGS_PYTHON)
   if(NOT TORCH_MLIR_PYTHON_PACKAGES_DIR)
     set(TORCH_MLIR_PYTHON_PACKAGES_DIR "${CMAKE_CURRENT_BINARY_DIR}/python_packages")
   endif()
+  add_dependencies(check-torch-mlir-all
+  check-torch-mlir-python
+  )
   add_subdirectory(python)
+else()
+  add_custom_target(TorchMLIRPythonModules)
 endif()
 
 add_subdirectory(test)