[GTALUG] cortex-m instruction set

[Lennart Sorensen]

On Tue, Jan 11, 2022 at 09:37:45PM -0500, Trevor Woerner via talk wrote:
> i couldn't answer Hugh's question at this evening's meeting off the top of
> my head, but wikipedia to the rescue:
> https://en.wikipedia.org/wiki/ARM_Cortex-M#Instruction_sets
> 
> "All Cortex-M cores implement a common subset of instructions that consists
> of most Thumb-1, some Thumb-2, including a 32-bit result multiply."
> 
> I was much more involved with cortex-m SoCs in the earlier days but wasn't
> 100% sure of the instruction sets of the latest members of the family but,
> according to wikipedia, all cortex-m's use some variant of the thumb
> instruction set.

Yes the Cortex-M lines have none of the standard arm instruction set.
Thunmb2 seems very good though, and as far as I understand it, the armhf
architecture runs almost entirely thumb2 code for the 32 bit Cortex-A
chips.  64 bit arm (aarch64) appears to be essentially the 32 bit arm
instructions, although conditional execution feature seems to be almost
entirely gone.  It was a neat feature but probably was getting in the way.

-- 
Len Sorensen