ancient ARM cpus
tg at gmplib.org
Sun Nov 15 11:57:47 UTC 2015
nisse at lysator.liu.se (Niels Möller) writes:
Where and how do you set ARM_THUMB_MODE? If I understand these things
correctly, the right check is not whether or not gmp is compiled in
thumb mode, but whether or not it's going to run on a machine where
thumb code might call it. Which I guess needs a configure option, since
it is difficult for configure to guess correctly and automatically.
What's the corresponding gcc flag to avoid using bx in compiler
I don't recall the details here, but I think the following is true:
* The bx instruction is not available before v5, except v4t...
* Using "mov lr, pc" (or ldm including pc) will not work correctly in
ARM state for returning to thumb state.
If I haven't misundertstood things, our unconditional use of bx in
mpn/arm/*.asm is incorrect. Such code should live in mpn/arm/v5, or
else be conditionalised to use bx when available.
I don't know the following:
* Is bx always available in v5 (and later) or only when there is also
thumb support (which I think was optional before v7).
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