[Buildroot] [PATCH v2 02/17] arch/arm: Cortex-M3 provides only Thumb-2
Yann E. MORIN
yann.morin.1998 at free.fr
Fri Mar 18 22:34:56 UTC 2016
Thomas, All,
On 2016-03-18 22:08 +0100, Thomas Petazzoni spake thusly:
> The Cortex-M cores only support Thumb-2, not Thumb. In fact, Thumb-2
> is a superset of Thumb, and we could have a single option for both in
> Buildroot, since -mthumb on ARMv4/v5 means original Thumb, while
> -mthumb on ARMv7 means Thumb 2. However, for clarity, it makes sense
> to have two separate options. But in this case, Cortex-M3 should not
> advertise that it supports Thumb, as in fact selecting Thumb would
> generate Thumb-2 code.
So, if a package has some assembly code written in Thumb not Thimb2, it
should do sometinh like:
ifeq ($(BR2_ARM_CPU_HAS_THUMB)$(BR2_ARM_CPU_HAS_THUMB2),y)
FOO_OPTS += --enable-thumb
endif
whereas now it would only need to do:
ifeq ($(BR2_ARM_CPU_HAS_THUMB)$(BR2_ARM_CPU_HAS_THUMB2),y)
FOO_OPTS += --enable-thumb
endif
Right?
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Regards,
Yann E. MORIN.
> ---
> arch/Config.in.arm | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/Config.in.arm b/arch/Config.in.arm
> index 33f763a..cd1ec33 100644
> --- a/arch/Config.in.arm
> +++ b/arch/Config.in.arm
> @@ -172,7 +172,6 @@ config BR2_cortex_a17
> select BR2_ARCH_HAS_MMU_OPTIONAL
> config BR2_cortex_m3
> bool "cortex-M3"
> - select BR2_ARM_CPU_HAS_THUMB
> select BR2_ARM_CPU_HAS_THUMB2
> select BR2_ARM_CPU_ARMV7M
> config BR2_fa526
> --
> 2.6.4
>
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