[Buildroot] [PATCH] arch/arm: add support for thumb(1) mode

Gustavo Zacarias gustavo at zacarias.com.ar
Wed Jul 17 16:03:56 UTC 2013


On 07/17/2013 12:58 PM, Thomas Petazzoni wrote:

> 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
> the two.
> 
> 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?

http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042e/IHI0042E_aapcs.pdf
Section 5.6 is of interest, once OABI (APCS) was dropped interworking
isn't that hard since it's mandatory for AAPCS.
Regards.




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