Merge topic 'ipo-policy-CMP0069'

dfa8263f Implement interprocedural optimization for GNU compilers
1588a577 Add policy CMP0069 to enforce INTERPROCEDURAL_OPTIMIZATION
a7575700 Refactoring: s,GetFeatureAsBool,IsIPOEnabled,
e05835c3 CheckIPOSupported: Visual Studio and Xcode generators do not support IPO

Acked-by: Kitware Robot <kwrobot@kitware.com>
Reviewed-by: Brad King <brad.king@kitware.com>
Reviewed-by: Nils Gladitz <nilsgladitz@gmail.com>
Merge-request: !568

7 files changed, 78 insertions, 4 deletions

diff --git a/Modules/CheckIPOSupported.cmake b/Modules/CheckIPOSupported.cmake
index 6f7bc82..31c1bd3 100644
--- a/Modules/CheckIPOSupported.cmake
+++ b/Modules/CheckIPOSupported.cmake
@@ -28,6 +28,9 @@ property.
     Specify languages whose compilers to check.
     Languages ``C`` and ``CXX`` are supported.
 
+It makes no sense to use this module when :policy:`CMP0069` is set to ``OLD`` so
+module will return error in this case. See policy :policy:`CMP0069` for details.
+
 Examples
 ^^^^^^^^
 
@@ -125,7 +128,17 @@ macro(_ipo_run_language_check language)
 endmacro()
 
 function(check_ipo_supported)
-  # TODO: IPO policy
+  cmake_policy(GET CMP0069 x)
+
+  string(COMPARE EQUAL "${x}" "" not_set)
+  if(not_set)
+    message(FATAL_ERROR "Policy CMP0069 is not set")
+  endif()
+
+  string(COMPARE EQUAL "${x}" "OLD" is_old)
+  if(is_old)
+    message(FATAL_ERROR "Policy CMP0069 set to OLD")
+  endif()
 
   set(optional)
   set(one RESULT OUTPUT)
@@ -203,7 +216,12 @@ function(check_ipo_supported)
   endif()
 
   if(NOT _CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER)
-    _ipo_not_supported("compiler doesn't support IPO")
+    _ipo_not_supported("Compiler doesn't support IPO")
+    return()
+  endif()
+
+  if(CMAKE_GENERATOR MATCHES "^(Visual Studio |Xcode$)")
+    _ipo_not_supported("CMake doesn't support IPO for current generator")
     return()
   endif()
 
diff --git a/Modules/CheckIPOSupported/CMakeLists-C.txt.in b/Modules/CheckIPOSupported/CMakeLists-C.txt.in
index d20f31f..5a3b8ee 100644
--- a/Modules/CheckIPOSupported/CMakeLists-C.txt.in
+++ b/Modules/CheckIPOSupported/CMakeLists-C.txt.in
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION "@CMAKE_VERSION@")
 project("@TRY_COMPILE_PROJECT_NAME@" LANGUAGES C)
 
-# TODO: IPO policy
+cmake_policy(SET CMP0069 NEW)
 
 add_library(foo foo.c)
 add_executable(boo main.c)
diff --git a/Modules/CheckIPOSupported/CMakeLists-CXX.txt.in b/Modules/CheckIPOSupported/CMakeLists-CXX.txt.in
index 4b55c70..30993fa 100644
--- a/Modules/CheckIPOSupported/CMakeLists-CXX.txt.in
+++ b/Modules/CheckIPOSupported/CMakeLists-CXX.txt.in
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION "@CMAKE_VERSION@")
 project("@TRY_COMPILE_PROJECT_NAME@" LANGUAGES CXX)
 
-# TODO: IPO policy
+cmake_policy(SET CMP0069 NEW)
 
 add_library(foo foo.cpp)
 add_executable(boo main.cpp)
diff --git a/Modules/Compiler/Clang.cmake b/Modules/Compiler/Clang.cmake
index 96263fc..6b99a08 100644
--- a/Modules/Compiler/Clang.cmake
+++ b/Modules/Compiler/Clang.cmake
@@ -27,5 +27,13 @@ else()
       set(CMAKE_${lang}_COMPILE_OPTIONS_TARGET "--target=")
       set(CMAKE_${lang}_COMPILE_OPTIONS_EXTERNAL_TOOLCHAIN "--gcc-toolchain=")
     endif()
+
+    set(_CMAKE_IPO_SUPPORTED_BY_CMAKE NO)
+    set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER NO)
+
+    unset(CMAKE_${lang}_COMPILE_OPTIONS_IPO)
+    unset(CMAKE_${lang}_ARCHIVE_CREATE_IPO)
+    unset(CMAKE_${lang}_ARCHIVE_APPEND_IPO)
+    unset(CMAKE_${lang}_ARCHIVE_FINISH_IPO)
   endmacro()
 endif()
diff --git a/Modules/Compiler/GNU.cmake b/Modules/Compiler/GNU.cmake
index b67002c..4b1c598 100644
--- a/Modules/Compiler/GNU.cmake
+++ b/Modules/Compiler/GNU.cmake
@@ -45,4 +45,43 @@ macro(__compiler_gnu lang)
   if(NOT APPLE OR NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4) # work around #4462
     set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
   endif()
+
+  set(_CMAKE_IPO_SUPPORTED_BY_CMAKE YES)
+  set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER NO)
+
+  # '-flto' introduced since GCC 4.5:
+  # * https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Option-Summary.html (no)
+  # * https://gcc.gnu.org/onlinedocs/gcc-4.5.4/gcc/Option-Summary.html (yes)
+  if(NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4.5)
+    set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER YES)
+    set(__lto_flags -flto)
+
+    if(NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4.7)
+      # '-ffat-lto-objects' introduced since GCC 4.7:
+      # * https://gcc.gnu.org/onlinedocs/gcc-4.6.4/gcc/Option-Summary.html (no)
+      # * https://gcc.gnu.org/onlinedocs/gcc-4.7.4/gcc/Option-Summary.html (yes)
+      list(APPEND __lto_flags -fno-fat-lto-objects)
+    endif()
+
+    set(CMAKE_${lang}_COMPILE_OPTIONS_IPO ${__lto_flags})
+
+    # Need to use version of 'ar'/'ranlib' with plugin support.
+    # Quote from [documentation][1]:
+    #
+    #   To create static libraries suitable for LTO,
+    #   use gcc-ar and gcc-ranlib instead of ar and ranlib
+    #
+    # [1]: https://gcc.gnu.org/onlinedocs/gcc-4.9.4/gcc/Optimize-Options.html
+    set(CMAKE_${lang}_ARCHIVE_CREATE_IPO
+      "${CMAKE_GCC_AR} cr <TARGET> <LINK_FLAGS> <OBJECTS>"
+    )
+
+    set(CMAKE_${lang}_ARCHIVE_APPEND_IPO
+      "${CMAKE_GCC_AR} r <TARGET> <LINK_FLAGS> <OBJECTS>"
+    )
+
+    set(CMAKE_${lang}_ARCHIVE_FINISH_IPO
+      "${CMAKE_GCC_RANLIB} <TARGET>"
+    )
+  endif()
 endmacro()
diff --git a/Modules/Compiler/QCC.cmake b/Modules/Compiler/QCC.cmake
index 2d7e881..695a138 100644
--- a/Modules/Compiler/QCC.cmake
+++ b/Modules/Compiler/QCC.cmake
@@ -12,4 +12,12 @@ macro(__compiler_qcc lang)
 
   set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-Wp,-isystem,")
   set(CMAKE_DEPFILE_FLAGS_${lang} "-Wc,-MD,<DEPFILE>,-MT,<OBJECT>,-MF,<DEPFILE>")
+
+  set(_CMAKE_IPO_SUPPORTED_BY_CMAKE NO)
+  set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER NO)
+
+  unset(CMAKE_${lang}_COMPILE_OPTIONS_IPO)
+  unset(CMAKE_${lang}_ARCHIVE_CREATE_IPO)
+  unset(CMAKE_${lang}_ARCHIVE_APPEND_IPO)
+  unset(CMAKE_${lang}_ARCHIVE_FINISH_IPO)
 endmacro()
diff --git a/Modules/Platform/Linux-Intel.cmake b/Modules/Platform/Linux-Intel.cmake
index 45dc36f..6e2978a 100644
--- a/Modules/Platform/Linux-Intel.cmake
+++ b/Modules/Platform/Linux-Intel.cmake
@@ -39,6 +39,7 @@ macro(__linux_compiler_intel lang)
       "${XIAR} cr <TARGET> <LINK_FLAGS> <OBJECTS> "
       "${XIAR} -s <TARGET> ")
     set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER YES)
+    set(_CMAKE_IPO_LEGACY_BEHAVIOR YES)
   else()
     set(_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER NO)
   endif()