On 2014-03-05 02:36, [email protected] wrote:
> From: Jon Ringle <[email protected]>
>
> Signed-off-by: Jon Ringle <[email protected]>
> ---
> Makefile | 2 ++
> init/Kconfig | 19 ++++++++++++++++---
> 2 files changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 78209ee..e7f0b3c 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -581,6 +581,8 @@ all: vmlinux
>
> ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
> KBUILD_CFLAGS += -Os $(call cc-disable-warning,maybe-uninitialized,)
> +else ifdef CONFIG_CC_OPTIMIZE_FOR_SPEED
> +KBUILD_CFLAGS += -O3
> else
> KBUILD_CFLAGS += -O2
> endif
> diff --git a/init/Kconfig b/init/Kconfig
> index 009a797..17d4c62 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1233,13 +1233,26 @@ source "usr/Kconfig"
>
> endif
>
> +choice
> + prompt "Optimize"
> +
> +config CC_OPTIMIZE_NORMAL
> + bool "Optimize Normal (-O2)"
> + help
> + Enabling this option will pass "-O2" to gcc
> config CC_OPTIMIZE_FOR_SIZE
> - bool "Optimize for size"
> + bool "Optimize for size (-Os)"
> help
> - Enabling this option will pass "-Os" instead of "-O2" to gcc
> + Enabling this option will pass "-Os" to gcc
> resulting in a smaller kernel.
>
> - If unsure, say N.
> +config CC_OPTIMIZE_FOR_SPEED
> + bool "Optimze for speed (-O3)"
> + help
> + Enabling this option will pass "-O3" to gcc
> + resulting in a larger kernel (but possibly faster)
> +
> +endchoice
>
> config SYSCTL
> bool
>
I would suggest putting a warning in the Kconfig text that this might
make things break in new and unusual ways (and possibly making it depend
on EXPERT). All of the cases of -O3 breaking userspace software that I
have seen involve really edgy and complex (and often potentially
ambiguous) code, and while the core kernel doesn't have much of this,
there are a number drivers that do (The Synopsis DWC USB OTG driver
immediately comes to mind, as well as a number of drivers from staging).
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