+# Configure LTO
+# NOTE, cmake 3.0 has a INTERPROCEDURAL_OPTIMIZATION target
+# property for this (http://www.cmake.org/cmake/help/v3.0/prop_tgt/INTERPROCEDURAL_OPTIMIZATION.html)
+if(enable_lto) # User wants LTO. Try if we can do that
+ set(enable_lto OFF)
+ if(enable_compile_optimizations
+ AND CMAKE_COMPILER_IS_GNUCC
+ AND (NOT enable_model-checking))
+ # On windows, we need 4.8 or higher to enable lto because of http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50293
+ # We are experiencing assertion failures even with 4.8 on MinGW.
+ # Push the support forward: will see if 4.9 works when we test it.
+ #
+ # On Linux, we got the following with GCC 4.8.4 on Centos and Ubuntu
+ # lto1: internal compiler error: in output_die, at dwarf2out.c:8478
+ # Please submit a full bug report, with preprocessed source if appropriate.
+ # So instead, we push the support forward
+
+ if ( (CMAKE_C_COMPILER_VERSION VERSION_GREATER "4.8.5")
+ AND (LINKER_VERSION VERSION_GREATER "2.22"))
+ set(enable_lto ON)
+ endif()
+ endif()
+ if(enable_lto)
+ message(STATUS "LTO seems usable.")
+ else()
+ if(NOT enable_compile_optimizations)
+ message(STATUS "LTO disabled: Compile-time optimizations turned off.")
+ else()
+ if(enable_model-checking)
+ message(STATUS "LTO disabled when compiling with model-checking.")
+ else()
+ message(STATUS "LTO does not seem usable -- try updating your build chain.")
+ endif()
+ endif()
+ endif()
+else()
+ message(STATUS "LTO disabled on the command line.")
+endif()
+if(enable_lto) # User wants LTO, and it seems usable. Go for it
+ set(optCFLAGS "${optCFLAGS} -flto ")
+ # See https://gcc.gnu.org/wiki/LinkTimeOptimizationFAQ#ar.2C_nm_and_ranlib:
+ # "Since version 4.9 gcc produces slim object files that only contain
+ # the intermediate representation. In order to handle archives of
+ # these objects you have to use the gcc wrappers:
+ # gcc-ar, gcc-nm and gcc-ranlib."
+ if(${CMAKE_C_COMPILER_ID} STREQUAL "GNU"
+ AND CMAKE_C_COMPILER_VERSION VERSION_GREATER "4.8")
+ set (CMAKE_AR gcc-ar)
+ set (CMAKE_RANLIB gcc-ranlib)
+ endif()