kconfig: add a compiler speed optimization (e8413d18) · Commits · Wenxi XU / zephyr

Zephyr currently allows users to choose a compiler optimization between -O0, -Og and -Os, the default being the latter as it offers a good compromise between speed and flash usage. In cases the speed matters and/or the flash usage doesn't, optimizing for speed with -O2 is another alternative. For example in case of a simple application doing cryptographic signature validation with mbedtls, the flash size increase by about 15% compared to -Os, while it provides a 15% speed boost for a RSA signature and 30% speed boost for a ECC signature. This patches therefore adds a new option CONFIG_SPEED_OPTIMIZATIONS corresponding to the -O2 flag, but keep the default set to CONFIG_SIZE_OPTIMIZATIONS. Signed-off-by:

Aurelien Jarno <aurelien@aurel32.net>

CMakeLists.txt

+3 −0

Original line number	Diff line number	Diff line
		@@ -91,11 +91,14 @@ endif()
		set_ifndef(OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG "-O0")
		set_ifndef(OPTIMIZE_FOR_DEBUG_FLAG "-Og")
		set_ifndef(OPTIMIZE_FOR_SIZE_FLAG "-Os")
		set_ifndef(OPTIMIZE_FOR_SPEED_FLAG "-O2")

		if(CONFIG_NO_OPTIMIZATIONS)
		set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_NO_OPTIMIZATIONS_FLAG})
		elseif(CONFIG_DEBUG_OPTIMIZATIONS)
		set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_DEBUG_FLAG})
		elseif(CONFIG_SPEED_OPTIMIZATIONS)
		set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_SPEED_FLAG})
		elseif(CONFIG_SIZE_OPTIMIZATIONS)
		set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_SIZE_FLAG}) # Default
		else()

misc/Kconfig

+6 −0

Original line number	Diff line number	Diff line
		@@ -152,6 +152,12 @@ config SIZE_OPTIMIZATIONS
		Compiler optimizations will be set to -Os independently of other
		options.

		config SPEED_OPTIMIZATIONS
		bool "Optimize for speed"
		help
		Compiler optimizations will be set to -O2 independently of other
		options.

		config DEBUG_OPTIMIZATIONS
		bool "Optimize debugging experience"
		help

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