Makefile: adding config variable for Os/O2/O3 compilation

Conflicts:

	init/Kconfig

Makefile

@@ -566,9 +566,13 @@ all: vmlinux
 
 ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
 KBUILD_CFLAGS	+= -Os
-else
+endif
+ifdef CONFIG_CC_OPTIMIZE_DEFAULT
 KBUILD_CFLAGS	+= -O2
 endif
+ifdef CONFIG_CC_OPTIMIZE_ALOT
+KBUILD_CFLAGS	+= -O3
+endif
 
 include $(srctree)/arch/$(SRCARCH)/Makefile
 

init/Kconfig

@@ -947,13 +947,20 @@ source "usr/Kconfig"
 
 endif
 
+choice
+  prompt "Optimization level"
+  default CC_OPTIMIZE_DEFAULT
+
 config CC_OPTIMIZE_FOR_SIZE
-	bool "Optimize for size"
-	help
-	  Enabling this option will pass "-Os" instead of "-O2" to gcc
-	  resulting in a smaller kernel.
+	bool "Use -Os"
 
-	  If unsure, say Y.
+config CC_OPTIMIZE_DEFAULT
+	bool "Use -O2"
+
+config CC_OPTIMIZE_ALOT
+	bool "Use -O3"
+
+endchoice
 
 config SYSCTL
 	bool