[MLIR] Use prebuilt MLIR when specified with -DNGRAPH_USE_PREBUILT_MLIR (#4017)

* - update external_mlir_prebuilt.cmake to support pre built MLIR

* fix typo

* - unify prebuilt and external pull, build "mlir" cmake logic
- throw cmake error if MLIR_LLVM_PREBUILT_PATH is not specified when -DNGRAPH_USE_PREBUILT_MLIR=True

CMakeLists.txt

@@ -158,6 +158,7 @@ message(STATUS "NGRAPH_FORWARD_CMAKE_ARGS ${NGRAPH_FORWARD_CMAKE_ARGS}")
 # Prevent Eigen from using any LGPL3 code
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DEIGEN_MPL2_ONLY -DTBB_USE_THREADING_TOOLS")
 
+ngraph_var(NGRAPH_USE_PREBUILT_MLIR DEFAULT "FALSE")
 ngraph_var(NGRAPH_USE_PREBUILT_LLVM DEFAULT "FALSE")
 
 option(NGRAPH_UNIT_TEST_ENABLE "Control the building of unit tests" TRUE)
@@ -257,6 +258,7 @@ NORMALIZE_BOOL(NGRAPH_CODE_COVERAGE_ENABLE)
 NORMALIZE_BOOL(NGRAPH_LIB_VERSIONING_ENABLE)
 NORMALIZE_BOOL(NGRAPH_PYTHON_BUILD_ENABLE)
 NORMALIZE_BOOL(NGRAPH_USE_PREBUILT_LLVM)
+NORMALIZE_BOOL(NGRAPH_USE_PREBUILT_MLIR)
 NORMALIZE_BOOL(NGRAPH_PLAIDML_ENABLE)
 NORMALIZE_BOOL(NGRAPH_JSON_ENABLE)
 
@@ -288,6 +290,7 @@ message(STATUS "NGRAPH_CODE_COVERAGE_ENABLE:          ${NGRAPH_CODE_COVERAGE_ENA
 message(STATUS "NGRAPH_LIB_VERSIONING_ENABLE:         ${NGRAPH_LIB_VERSIONING_ENABLE}")
 message(STATUS "NGRAPH_PYTHON_BUILD_ENABLE:           ${NGRAPH_PYTHON_BUILD_ENABLE}")
 message(STATUS "NGRAPH_USE_PREBUILT_LLVM:             ${NGRAPH_USE_PREBUILT_LLVM}")
+message(STATUS "NGRAPH_USE_PREBUILT_MLIR:             ${NGRAPH_USE_PREBUILT_MLIR}")
 message(STATUS "NGRAPH_PLAIDML_ENABLE:                ${NGRAPH_PLAIDML_ENABLE}")
 message(STATUS "NGRAPH_DISTRIBUTED_ENABLE:            ${NGRAPH_DISTRIBUTED_ENABLE}")
 message(STATUS "NGRAPH_JSON_ENABLE:                   ${NGRAPH_JSON_ENABLE}")
@@ -494,6 +497,11 @@ add_custom_target(fix-mode
     -P ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules/fix_mode.cmake
 )
 
+if (NGRAPH_USE_PREBUILT_MLIR)
+	if (NOT DEFINED MLIR_LLVM_PREBUILT_PATH)
+	    message(FATAL_ERROR "MLIR_LLVM_PREBUILT_PATH not specified")
+    endif()
+endif()
 #-----------------------------------------------------------------------------------------------
 # enable or disable output from NGRAPH_DEBUG statements
 #-----------------------------------------------------------------------------------------------

cmake/external_mlir.cmake

@@ -24,7 +24,13 @@ set(MLIR_LLVM_COMMIT_ID 75990950)
 set(MLIR_COMMIT_ID 5e64e536)
 
 # MLIR environment variables. Some of them are used by LIT tool.
-set(MLIR_PROJECT_ROOT ${CMAKE_CURRENT_BINARY_DIR}/mlir_project)
+
+if (NGRAPH_USE_PREBUILT_MLIR)
+    set(MLIR_PROJECT_ROOT ${MLIR_LLVM_PREBUILT_PATH}/mlir_project)
+else()
+    set(MLIR_PROJECT_ROOT ${CMAKE_CURRENT_BINARY_DIR}/mlir_project)
+endif()
+
 set(MLIR_LLVM_ROOT ${MLIR_PROJECT_ROOT}/llvm-projects)
 set(MLIR_SOURCE_DIR ${MLIR_LLVM_ROOT}/llvm/projects/mlir)
 set(MLIR_BUILD_DIR ${MLIR_LLVM_ROOT}/build)
@@ -35,17 +41,21 @@ set(NGRAPH_LIT_TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/test/mlir)
 # MLIR has to be pre-built before ngraph build starts
 # this will clone and build MLIR during cmake config instead
 
-configure_file(${CMAKE_SOURCE_DIR}/cmake/mlir_fetch.cmake.in ${MLIR_PROJECT_ROOT}/CMakeLists.txt)
-execute_process(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
-                WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
+# we will fetch and build it from the source if cmake is not configured to use 
+# the prebuilt mlir
+if (NOT NGRAPH_USE_PREBUILT_MLIR)
+	configure_file(${CMAKE_SOURCE_DIR}/cmake/mlir_fetch.cmake.in ${MLIR_PROJECT_ROOT}/CMakeLists.txt)
+	execute_process(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
+			WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
 
-# clone and build llvm
-execute_process(COMMAND "${CMAKE_COMMAND}" --build . --target ext_mlir_llvm
-                WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
+	# clone and build llvm
+	execute_process(COMMAND "${CMAKE_COMMAND}" --build . --target ext_mlir_llvm
+			WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
 
-# clone and build mlir
-execute_process(COMMAND "${CMAKE_COMMAND}" --build . --target ext_mlir
-                WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
+	# clone and build mlir
+	execute_process(COMMAND "${CMAKE_COMMAND}" --build . --target ext_mlir
+			WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
+endif()
 
 # Enable modules for LLVM.
 set(LLVM_DIR "${MLIR_BUILD_DIR}/lib/cmake/llvm"