[PATCH] D16896: [CMake] Improve the clang order-file generation workflow

[Chris Bieneman via cfe-commits]

beanz created this revision.
beanz added a reviewer: bogner.
beanz added a subscriber: cfe-commits.

With this change generating clang order files using dtrace uses the following workflow:

# Configure LLVM & Clang using any options on a system with dtrace
cmake <whatever options you want>

# Builds clang and runs the perf-training data to generate the order file
ninja generate-order-file

# Re-link clang with the new order file
ninja clang

This patch works by setting a default path to the order file (which can be overridden by the user). If the order file doesn't exist during configuration CMake will create an empty one.

CMake then ties up the dependencies between the clang link job and the order file, and generate-order-file overwrites CLANG_ORDER_FILE with the new order file.

http://reviews.llvm.org/D16896

Files:
  CMakeLists.txt
  tools/driver/CMakeLists.txt
  utils/perf-training/CMakeLists.txt

Index: utils/perf-training/CMakeLists.txt
===================================================================
--- utils/perf-training/CMakeLists.txt
+++ utils/perf-training/CMakeLists.txt
@@ -55,9 +55,8 @@
     COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py clean ${CMAKE_CURRENT_BINARY_DIR} dtrace
     COMMENT "Clearing old dtrace data")
 
-
   add_custom_target(generate-order-file
-    COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py gen-order-file --binary $<TARGET_FILE:clang> --output ${CMAKE_CURRENT_BINARY_DIR}/clang.order ${CMAKE_CURRENT_BINARY_DIR}
+    COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/perf-helper.py gen-order-file --binary $<TARGET_FILE:clang> --output ${CLANG_ORDER_FILE} ${CMAKE_CURRENT_BINARY_DIR}
     COMMENT "Generating order file"
     DEPENDS generate-dtrace-logs)
 endif()
Index: tools/driver/CMakeLists.txt
===================================================================
--- tools/driver/CMakeLists.txt
+++ tools/driver/CMakeLists.txt
@@ -87,8 +87,10 @@
   set(TOOL_INFO_BUILD_VERSION)
 endif()
 
-if(CLANG_ORDER_FILE)
+# The MSVC linker doesn't respect the order_file option
+if(NOT MSVC)
   target_link_libraries(clang "-Wl,-order_file,${CLANG_ORDER_FILE}")
+  set_target_properties(clang PROPERTIES LINK_DEPENDS ${CLANG_ORDER_FILE})
 endif()
 
 if(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)
Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -586,9 +586,19 @@
   add_subdirectory(docs)
 endif()
 
-set(CLANG_ORDER_FILE "" CACHE FILEPATH
+# this line is needed as a cleanup to ensure that any CMakeCaches with the old
+# default value get updated to the new default.
+if(CLANG_ORDER_FILE STREQUAL "")
+  unset(CLANG_ORDER_FILE CACHE)
+endif()
+
+set(CLANG_ORDER_FILE ${CMAKE_CURRENT_BINARY_DIR}/clang.order CACHE FILEPATH
   "Order file to use when compiling clang in order to improve startup time.")
 
+if(NOT EXISTS ${CLANG_ORDER_FILE})
+  execute_process(COMMAND ${CMAKE_COMMAND} -E touch ${CLANG_ORDER_FILE})
+endif()
+
 if (CLANG_BUILT_STANDALONE OR CMAKE_VERSION VERSION_EQUAL 3 OR
     CMAKE_VERSION VERSION_GREATER 3)
   # Generate a list of CMake library targets so that other CMake projects can


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