Re: question about linker

On 11/12/2024 18:22, Michael S wrote:

On Wed, 11 Dec 2024 16:15:25 +0100
David Brown <david.brown@hesbynett.no> wrote:
 

>
Suffice it to say that as far as code generation is concerned, the
Cortex-A devices on the RPi's are completely different from the
Cortex-M devices in microcontrollers.  It's like comparing the 80286
with the Z80A.
>

 With exception of RPi1, saying so would be an exaggeration.
RPi2 through 5 are technically capable to run Thumb2-encoded user level
routines.

I did not know that the 64-bit Cortex-A devices could run 32-bit Thumb2-encoded instructions.  That does reduce the difference somewhat.
Compilers targeting 64-bit ARM would generate 64-bit (AArch64) instructions, which are of course significantly different.  But perhaps a compiler targeting 32-bit Cortex-A devices might be able to generate Thumb2 instructions.
However, you would not expect binary compatibility between code generated for a 32-bit Cortex-M device and a Cortex-A platform, even if it supports Thumb2 instructions - you have major differences in the ABI, memory layouts, and core features beyond the basic registers.

May be, mutual incompatibility with MCUs would become true again in the
next generation of RPi. But more likely it would not happen until RPi7.