Change debug optimization level back to -O1

src/CMakeLists.txt

@@ -489,7 +489,7 @@ else()
 	endif()
 
 	set(CMAKE_CXX_FLAGS_RELEASE "-DNDEBUG ${RELEASE_WARNING_FLAGS} ${WARNING_FLAGS} ${OTHER_FLAGS} -O3 -ffast-math -Wall -fomit-frame-pointer -pipe -funroll-loops")
-	set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -Wall ${WARNING_FLAGS} ${OTHER_FLAGS}")
+	set(CMAKE_CXX_FLAGS_DEBUG "-g -O1 -Wall ${WARNING_FLAGS} ${OTHER_FLAGS}")
 
 	if(USE_GPROF)
 		set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -pg")