From 1681091991ebdc58dff1329d4dcd2c2cf01eb1de Mon Sep 17 00:00:00 2001
From: Chris Bieneman <beanz@apple.com>
Date: Fri, 5 Feb 2016 01:22:03 +0000
Subject: [PATCH] [CMake] Improve the clang order-file generation workflow

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

cmake <whatever options you want>

ninja generate-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.

Reviewers: bogner

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D16896

llvm-svn: 259862
---
 clang/CMakeLists.txt                     | 12 +++++++++++-
 clang/tools/driver/CMakeLists.txt        |  6 +++++-
 clang/utils/perf-training/CMakeLists.txt |  3 +--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/clang/CMakeLists.txt b/clang/CMakeLists.txt
index 7ac3df4..d7a498d 100644
--- a/clang/CMakeLists.txt
+++ b/clang/CMakeLists.txt
@@ -586,9 +586,19 @@ if( CLANG_INCLUDE_DOCS )
   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
diff --git a/clang/tools/driver/CMakeLists.txt b/clang/tools/driver/CMakeLists.txt
index ffcfbb5..2971bf8 100644
--- a/clang/tools/driver/CMakeLists.txt
+++ b/clang/tools/driver/CMakeLists.txt
@@ -87,8 +87,12 @@ if (APPLE)
   set(TOOL_INFO_BUILD_VERSION)
 endif()
 
-if(CLANG_ORDER_FILE)
+check_cxx_compiler_flag("-Wl,-order_file,${CLANG_ORDER_FILE}"
+  LINKER_HAS_ORDER_FILE_FLAG)
+
+if(LINKER_HAS_ORDER_FILE_FLAG)
   target_link_libraries(clang "-Wl,-order_file,${CLANG_ORDER_FILE}")
+  set_target_properties(clang PROPERTIES LINK_DEPENDS ${CLANG_ORDER_FILE})
 endif()
 
 if(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)
diff --git a/clang/utils/perf-training/CMakeLists.txt b/clang/utils/perf-training/CMakeLists.txt
index 32f7c84..f8647a0 100644
--- a/clang/utils/perf-training/CMakeLists.txt
+++ b/clang/utils/perf-training/CMakeLists.txt
@@ -55,9 +55,8 @@ if(DTRACE)
     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()
-- 
2.7.4