diff -up cmake-3.5.2/Modules/Compiler/GNU.cmake.than cmake-3.5.2/Modules/Compiler/GNU.cmake
--- cmake-3.5.2/Modules/Compiler/GNU.cmake.than	2016-06-02 13:42:38.186383915 +0200
+++ cmake-3.5.2/Modules/Compiler/GNU.cmake	2016-06-02 14:00:26.256271135 +0200
@@ -48,7 +48,7 @@ macro(__compiler_gnu lang)
   set(CMAKE_${lang}_FLAGS_INIT "")
   set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
   set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
+  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O2 -DNDEBUG")
   set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
diff -up cmake-3.5.2/Modules/Platform/GNU.cmake.than cmake-3.5.2/Modules/Platform/GNU.cmake