RFC: arch: arm: Remove aarch32 directory and split Cortex-M and Cortex-A/r code

[SgrrZhf]

This PR tries to do some cleaning work in the arch/arm/core directory and split some common code into Cortex-M and Cortex-A/R parts. This is a huge work, hope you can give your comments on this.

Below is the major changes:

1. It doesn't make sense to keep the aarch32 directory in the 'arch/arm/core' directory as the aarch64 has been moved out. This PR try to clean the 'aarch32' directory in 'arch/arm/core' and 'include/zephyr/arch/arm'.

2. There are too many differences between Cortex-M and Cortex-A/R, For easier to maintain, this PR try to split some common code in 'arch/arm/core'. They are:

   • arch/arm/core/swap.c
   • arch/arm/core/swap_helper.S
   • arch/arm/core/irq_manage.c
   • arch/arm/core/isr_wrapper.S

3. Move 'arch/arm/core/irq_relay.S to the cortex_m directory because it is only used by Cortex-M architecture.

There is a known issue about cleaning the 'aarch32' directory in the include/zephyr/arch/arm directory that boot/zephyr/arm_cleanup.c in the mcuboot module includes a header file resided in include/zephyr/arch/arm/aarch32 directory. It will lead to a build error.

https://github.com/zephyrproject-rtos/mcuboot/blob/74c4d1c52fd51d07904b27a7aa9b2303e896a4e3/boot/zephyr/arm_cleanup.c#L7C43-L7C52

[SgrrZhf]

@SgrrZhf could you rebase please? I think it clashed with 1fd3171, couple header removals

Done

[tejlmand]

this PR has broken armclang support.

When doing major rework, please remember to test with armclang, or ping someone who can carry out such test.

With armclang i'm now seeing errors like this:

CMake Error at /projects/github/ncs/zephyr/cmake/linker/armlink/target.cmake:74 (target_link_libraries):
  Error evaluating generator expression:                                                                                                                                                                                                      

    $<TARGET_OBJECTS:arch__arm__core__aarch32__cortex_m>                                                                                                                                                                                      

  Objects of target "arch__arm__core__aarch32__cortex_m" referenced but no                                                                                                                                                                    
  such target exists.                                                                                                                                                                                                                         
Call Stack (most recent call first):                                                                                                                                                                                                          
  /projects/github/ncs/zephyr/CMakeLists.txt:1427 (toolchain_ld_link_elf)        

[tejlmand]

@fabiobaltieri FYI

[fabiobaltieri]

When doing major rework, please remember to test with armclang, or ping someone who can carry out such test.

Is there any fundamental blocker from having an armclang run in CI? Sounds like the only sustainable option to me. We have a separate clang run already so unless there's some licensing issue I don't see why not.

[tejlmand]

We have a separate clang run already so unless there's some licensing issue I don't see why not.

we do have some licenses for armclang for develoment, but I guess no one has had the time to look into getting this up and running with CI.

Note also that we should checkup with arm that we are permitted to use those licenses in CI.

[tejlmand]

i'm curious why this PR, which touches so many files in 11 commits, only have a manifest label, and no build-system label or similar.

[tejlmand]

Fixed here: #62590

[fabiobaltieri]

i'm curious why this PR, which touches so many files in 11 commits, only have a manifest label, and no build-system label or similar.

I don't think it touches any files under "Build system" (https://github.com/zephyrproject-rtos/zephyr/blob/main/MAINTAINERS.yml#L334-L342), but regardless, the script that does the tagging does not apply more than 10 tags, this check kicked in: https://github.com/zephyrproject-rtos/zephyr/blob/main/scripts/set_assignees.py#L158

[fabiobaltieri]

When doing major rework, please remember to test with armclang, or ping someone who can carry out such test.

Note also that we should checkup with arm that we are permitted to use those licenses in CI.

This is not really a sustainable solution at the change volume that the project is dealing with. It also does not seem fair to block against a proprietary system that only few developer have access to.

If the tool is proprietary and we are not allowed to run in CI then regressions will have to be detected and fixed out band.