[MLIR] Use more threads when building mlir+llvm (#4147)

* Use optimal processor count for parallel build.

* Add missing dependency.

cmake/external_mlir.cmake

@@ -44,7 +44,7 @@ set(NGRAPH_LIT_TEST_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR}/test/mlir)
 # we will fetch and build it from the source if cmake is not configured to use
 # the prebuilt mlir
 if (NOT NGRAPH_USE_PREBUILT_MLIR)
-	configure_file(${CMAKE_SOURCE_DIR}/cmake/mlir_fetch.cmake.in ${MLIR_PROJECT_ROOT}/CMakeLists.txt)
+    configure_file(${CMAKE_SOURCE_DIR}/cmake/mlir_fetch.cmake.in ${MLIR_PROJECT_ROOT}/CMakeLists.txt @ONLY)
     execute_process(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
                     WORKING_DIRECTORY "${MLIR_PROJECT_ROOT}")
 

cmake/mlir_fetch.cmake.in

@@ -23,35 +23,43 @@ project(mlir-fetch NONE)
 ExternalProject_Add(
     ext_mlir_llvm
     PREFIX mlir_llvm
-    GIT_REPOSITORY ${MLIR_LLVM_REPO_URL}
-    GIT_TAG ${MLIR_LLVM_COMMIT_ID}
+    GIT_REPOSITORY @MLIR_LLVM_REPO_URL@
+    GIT_TAG @MLIR_LLVM_COMMIT_ID@
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
     INSTALL_COMMAND ""
     UPDATE_COMMAND ""
-    SOURCE_DIR ${MLIR_LLVM_ROOT}
+    SOURCE_DIR @MLIR_LLVM_ROOT@
     DOWNLOAD_NO_PROGRESS TRUE
     EXCLUDE_FROM_ALL TRUE
     )
 
+set(MLIR_DEPENDS ext_mlir_llvm)
+
+include(ProcessorCount)
+ProcessorCount(N)
+if(N EQUAL 0)
+    set(N 8)
+endif()
+
 ExternalProject_Add(
     ext_mlir
     PREFIX mlir
     DEPENDS ${MLIR_DEPENDS}
-    GIT_REPOSITORY ${MLIR_REPO_URL}
-    GIT_TAG ${MLIR_COMMIT_ID}
+    GIT_REPOSITORY @MLIR_REPO_URL@
+    GIT_TAG @MLIR_COMMIT_ID@
     CONFIGURE_COMMAND ""
-    CMAKE_GENERATOR ${CMAKE_GENERATOR}
-    CMAKE_GENERATOR_PLATFORM ${CMAKE_GENERATOR_PLATFORM}
-    CMAKE_GENERATOR_TOOLSET ${CMAKE_GENERATOR_TOOLSET}
+    CMAKE_GENERATOR "@CMAKE_GENERATOR@"
+    CMAKE_GENERATOR_PLATFORM @CMAKE_GENERATOR_PLATFORM@
+    CMAKE_GENERATOR_TOOLSET @CMAKE_GENERATOR_TOOLSET@
 
-    BUILD_COMMAND ${CMAKE_COMMAND} ../llvm -DLLVM_BUILD_EXAMPLES=ON -DLLVM_TARGETS_TO_BUILD=host -DLLVM_ENABLE_RTTI=ON -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-    COMMAND ${CMAKE_COMMAND} --build . --target check-mlir -- -j8 
+    BUILD_COMMAND @CMAKE_COMMAND@ ../llvm -DLLVM_BUILD_EXAMPLES=ON -DLLVM_TARGETS_TO_BUILD=host -DLLVM_ENABLE_RTTI=ON -DCMAKE_BUILD_TYPE=@CMAKE_BUILD_TYPE@
+    COMMAND @CMAKE_COMMAND@ --build . --target check-mlir -- -j${N}
     INSTALL_COMMAND ""
     UPDATE_COMMAND ""
-    SOURCE_DIR ${MLIR_SOURCE_DIR}
-    BINARY_DIR ${MLIR_BUILD_DIR}
-    STAMP_DIR "${MLIR_PROJECT_ROOT}/mlir/stamp"
+    SOURCE_DIR @MLIR_SOURCE_DIR@
+    BINARY_DIR @MLIR_BUILD_DIR@
+    STAMP_DIR "@MLIR_PROJECT_ROOT@/mlir/stamp"
     DOWNLOAD_NO_PROGRESS TRUE
     EXCLUDE_FROM_ALL TRUE
     )