diff --git a/makefile b/makefile
index 72210ab9..b4bafe2e 100644
--- a/makefile
+++ b/makefile
@@ -1313,10 +1313,10 @@ ifneq ($(DEBUG),)
   LTO =
 else
   ifneq (,$(findstring clang,$(COMPILER_NAME))$(findstring LLVM,$(COMPILER_NAME)))
-    CFLAGS_O = -O2 -fno-strict-overflow
+    CFLAGS_O = -O3 -fno-strict-overflow
     GCC_OPTIMIZERS_CMD = ${GCC} --help 2>&1
   else
-    CFLAGS_O := -O2
+    CFLAGS_O := -O3
   endif
   LDFLAGS_O = 
   GCC_MAJOR_VERSION = $(firstword $(subst  ., ,$(GCC_VERSION)))
@@ -1356,7 +1356,7 @@ else
   ifneq (,$(LTO))
     ifneq (,$(findstring -flto,$(GCC_OPTIMIZERS)))
       CFLAGS_O += -flto
-      ifneq (,$(and $(findstring gcc,$(COMPILER_NAME)),$(findstring -fwhole-program,$(GCC_OPTIMIZERS))))
+      ifneq (,$(and $(or $(findstring gcc,$(COMPILER_NAME)),$(findstring GCC,$(COMPILER_NAME))),$(findstring -fwhole-program,$(GCC_OPTIMIZERS))))
         CFLAGS_O += -fwhole-program
       endif
       LTO_FEATURE = , with Link Time Optimization,