kconfig: Change how optimization level is set

This patch does several things, most notably it changes the semantics
of CONFIG_DEBUG. CONFIG_DEBUG continues to behave as a vaguely defined
"debug mode" that enables printf's, -Og, etc. but now the user may
choose to be in "debug mode" while using a different optimization
level than -Og.

Tp support this a new config is defined to enable -Og;
CONFIG_DEBUG_OPTIMIZATIONS.

Additionally CONFIG_SIZE_OPTIMIZATIONS is introduced to allow the user
to explicitly request optimizing for size instead of relying on
defaulting to it.

The three config's {NO,SIZE,DEBUG}_OPTIMIZATIONS are now organized in
a Kconfig choice to ensure that at most one can be enabled at a time.

Finally, selected users of CONFIG_DEBUG have been ported to use one of
the optimizations configs when it was clear from usage that the
intention was to behave differently when using a different
optimization level and not when in "debug mode".

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>

CMakeLists.txt

@@ -82,15 +82,18 @@ endif()
 #
 # Finally, the user can use Kconfig to add compiler options that will
 # come after these options and override them
-set_ifndef(OPTIMIZE_FOR_SIZE_FLAG     "-Os")
-set_ifndef(OPTIMIZE_FOR_DEBUG_FLAG    "-Og")
 set_ifndef(OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG "-O0")
+set_ifndef(OPTIMIZE_FOR_DEBUG_FLAG            "-Og")
+set_ifndef(OPTIMIZE_FOR_SIZE_FLAG             "-Os")
+
 if(CONFIG_NO_OPTIMIZATIONS)
-	set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
-elseif(CONFIG_DEBUG)
+  set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
+elseif(CONFIG_DEBUG_OPTIMIZATIONS)
   set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_DEBUG_FLAG})
-else()
+elseif(CONFIG_SIZE_OPTIMIZATIONS)
   set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_SIZE_FLAG}) # Default
+else()
+  assert(0 "Unreachable code. Expected optimization level to have been chosen. See misc/Kconfig.")
 endif()
 
 zephyr_compile_options(

include/linker/kobject-text.ld

@@ -1,5 +1,5 @@
 #ifndef KOBJECT_TEXT_AREA
-#if defined(CONFIG_DEBUG) || defined(CONFIG_STACK_CANARIES)
+#if ! defined(CONFIG_SIZE_OPTIMIZATIONS) || defined(CONFIG_STACK_CANARIES)
 #define KOBJECT_TEXT_AREA	256
 #else
 #define KOBJECT_TEXT_AREA	128

misc/Kconfig

@@ -136,14 +136,35 @@ config NATIVE_APPLICATION
 	  Build as a native application that can run on the host and using
 	  resources and libraries provided by the host.
 
-config NO_OPTIMIZATIONS
-	bool "Lower compiler optimziations to -O0"
-	default n
+choice
+	prompt "Optimization level"
+	default NO_OPTIMIZATIONS    if COVERAGE
+	default DEBUG_OPTIMIZATIONS if DEBUG
+	default SIZE_OPTIMIZATIONS
 	help
-	  When selected, compiler optimizations will be set to -O0 independently of
-	  other options.
-	  Note that this flag shall only control the compiler optimization level, and
-	  that no extra debug code shall be conditionally compiled based on it.
+	  Note that these flags shall only control the compiler
+	  optimization level, and that no extra debug code shall be
+	  conditionally compiled based on them.
+
+config SIZE_OPTIMIZATIONS
+	bool "Optimize for size"
+	help
+	  Compiler optimizations will be set to -Os independently of other
+	  options.
+
+config DEBUG_OPTIMIZATIONS
+	bool "Optimize debugging experience"
+	help
+	  Compiler optimizations will be set to -Og independently of other
+	  options.
+
+config NO_OPTIMIZATIONS
+	bool "Optimize nothing"
+	help
+	  Compiler optimizations will be set to -O0 independently of other
+	  options.
+
+endchoice
 
 config COMPILER_OPT
 	string

tests/Kconfig

@@ -27,7 +27,6 @@ config TEST_EXTRA_STACKSIZE
 config COVERAGE
 	bool "Create coverage data"
 	depends on NATIVE_APPLICATION
-	select NO_OPTIMIZATIONS
 	default n
 	help
 	  This option will build your application with the -coverage option