Merge topic 'ipo-clang'

7d057b27 Clang IPO (LTO) support

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !717

2 files changed, 73 insertions, 6 deletions

diff --git a/Modules/Compiler/Clang-FindBinUtils.cmake b/Modules/Compiler/Clang-FindBinUtils.cmake
new file mode 100644
index 0000000..c81e77a
--- /dev/null
+++ b/Modules/Compiler/Clang-FindBinUtils.cmake
@@ -0,0 +1,25 @@
+if(NOT DEFINED _CMAKE_PROCESSING_LANGUAGE OR _CMAKE_PROCESSING_LANGUAGE STREQUAL "")
+  message(FATAL_ERROR "Internal error: _CMAKE_PROCESSING_LANGUAGE is not set")
+endif()
+
+# Try to find tools in the same directory as Clang itself
+get_filename_component(__clang_hint_1 "${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER}" REALPATH)
+get_filename_component(__clang_hint_1 "${__clang_hint_1}" DIRECTORY)
+
+get_filename_component(__clang_hint_2 "${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER}" DIRECTORY)
+
+set(__clang_hints ${__clang_hint_1} ${__clang_hint_2})
+
+# http://manpages.ubuntu.com/manpages/precise/en/man1/llvm-ar.1.html
+find_program(CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_AR NAMES
+    "${_CMAKE_TOOLCHAIN_PREFIX}llvm-ar"
+    HINTS ${__clang_hints}
+    DOC "LLVM archiver"
+)
+
+# http://manpages.ubuntu.com/manpages/precise/en/man1/llvm-ranlib.1.html
+find_program(CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_RANLIB NAMES
+    "${_CMAKE_TOOLCHAIN_PREFIX}llvm-ranlib"
+    HINTS ${__clang_hints}
+    DOC "Generate index for LLVM archive"
+)
diff --git a/Modules/Compiler/Clang.cmake b/Modules/Compiler/Clang.cmake
index 6b99a08..8c2f87d 100644
--- a/Modules/Compiler/Clang.cmake
+++ b/Modules/Compiler/Clang.cmake
@@ -28,12 +28,54 @@ else()
       set(CMAKE_${lang}_COMPILE_OPTIONS_EXTERNAL_TOOLCHAIN "--gcc-toolchain=")
     endif()
 
-    set(_CMAKE_IPO_SUPPORTED_BY_CMAKE NO)
-    set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER NO)
+    set(_CMAKE_IPO_SUPPORTED_BY_CMAKE YES)
+    set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER YES)
 
-    unset(CMAKE_${lang}_COMPILE_OPTIONS_IPO)
-    unset(CMAKE_${lang}_ARCHIVE_CREATE_IPO)
-    unset(CMAKE_${lang}_ARCHIVE_APPEND_IPO)
-    unset(CMAKE_${lang}_ARCHIVE_FINISH_IPO)
+    string(COMPARE EQUAL "${CMAKE_${lang}_COMPILER_ID}" "AppleClang" __is_apple_clang)
+
+    # '-flto=thin' available since Clang 3.9 and Xcode 8
+    # * http://clang.llvm.org/docs/ThinLTO.html#clang-llvm
+    # * https://trac.macports.org/wiki/XcodeVersionInfo
+    set(_CMAKE_LTO_THIN TRUE)
+    if(__is_apple_clang)
+      if(CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 8.0)
+        set(_CMAKE_LTO_THIN FALSE)
+      endif()
+    else()
+      if(CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 3.9)
+        set(_CMAKE_LTO_THIN FALSE)
+      endif()
+    endif()
+
+    if(_CMAKE_LTO_THIN)
+      set(CMAKE_${lang}_COMPILE_OPTIONS_IPO "-flto=thin")
+    else()
+      set(CMAKE_${lang}_COMPILE_OPTIONS_IPO "-flto")
+    endif()
+
+    if(ANDROID)
+      # https://github.com/android-ndk/ndk/issues/242
+      set(CMAKE_${lang}_LINK_OPTIONS_IPO "-fuse-ld=gold")
+    endif()
+
+    if(ANDROID OR __is_apple_clang)
+      set(__ar "${CMAKE_AR}")
+      set(__ranlib "${CMAKE_RANLIB}")
+    else()
+      set(__ar "${CMAKE_${lang}_COMPILER_AR}")
+      set(__ranlib "${CMAKE_${lang}_COMPILER_RANLIB}")
+    endif()
+
+    set(CMAKE_${lang}_ARCHIVE_CREATE_IPO
+      "${__ar} cr <TARGET> <LINK_FLAGS> <OBJECTS>"
+    )
+
+    set(CMAKE_${lang}_ARCHIVE_APPEND_IPO
+      "${__ar} r <TARGET> <LINK_FLAGS> <OBJECTS>"
+    )
+
+    set(CMAKE_${lang}_ARCHIVE_FINISH_IPO
+      "${__ranlib} <TARGET>"
+    )
   endmacro()
 endif()