[Buildroot] [PATCH] arch/arm: add support for thumb(1) mode
thomas.petazzoni at free-electrons.com
Wed Jul 17 15:58:38 UTC 2013
Dear Gustavo Zacarias,
On Wed, 17 Jul 2013 12:39:15 -0300, Gustavo Zacarias wrote:
> +config BR2_ARM_INSTRUCTIONS_THUMB
> + bool "Thumb"
> + depends on BR2_ARM_CPU_HAS_THUMB
> + help
> + This option instructions the compiler to generate Thumb
> + instructions, which allows to mix 16 bits instructions and
> + 32 bits instructions. This generally provides a much smaller
> + compiled binary size.
I think this is misleading: Thumb doesn't allow to mix 16 bits and 32
bits instructions like Thumb2 does. IIRC, with Thumb, a particular
function needs to be either completely Thumb (16 bits) or completely
ARM (32 bits), and there is the thumb-interworking mechanism between
Which leads me to this question: is adding Thumb support as simple as
what you're adding? Aren't there some additional thumb-interworking
complexities to handle?
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
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