--- gmic-1.7.9/CMakeLists.txt
+++ gmic-1.7.9/CMakeLists.txt
@@ -190,9 +190,9 @@
     "Choose the type of build, options are: Debug Release RelWithDebInfo."
     FORCE)
 endif(NOT CMAKE_BUILD_TYPE)
-SET(CMAKE_CXX_FLAGS_DEBUG " -O0 -g -ansi -pedantic -Dcimg_verbosity=3 ${COMPILE_FLAGS}")
-SET(CMAKE_CXX_FLAGS_RELEASE " -O3 -mtune=generic ${COMPILE_FLAGS}")
-SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO " -O3 -g -mtune=generic ${COMPILE_FLAGS}")
+SET(CMAKE_CXX_FLAGS_DEBUG " -ansi -pedantic -Dcimg_verbosity=3 ${COMPILE_FLAGS}")
+SET(CMAKE_CXX_FLAGS_RELEASE " ${COMPILE_FLAGS}")
+SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO " ${COMPILE_FLAGS}")
 
 
 # source files