Cortex-M33: Add RTX5 context switcher files

[deepikabhavnani]

RTX5 context switcher files from RTX5 added to mbed-os code, Required to support ARMv8-Mainline architecture.

[0xc0170]

RTX5 context switcher files from RTX5 added to mbed-os code, Required to support ARMv8-Mainline architecture.

What version does it include (or only develop for now) ? Just wondering if we are taking this as separate patch as it is, or we should update (we already experienced some issues/improvements that are in the cmsis rtos released version but not in our codebase)

[deepikabhavnani]

@0xc0170 - I am not sure what is the process to add cmsis releases into our codebase. This files I am adding are part of cortex-m23/m33 support. Files related to cortex-m23 are already pushed in and tool changes were done for both m-23/m-33.

[0xc0170]

cc @bulislaw @c1728p9

[bulislaw]

@deepikabhavnani when is that needed for? I want to update CMSIS just after 5.6 is out.

[deepikabhavnani]

@bulislaw - Files are for cortex mainline processors, at present we do not hardware to test. But adding them separately because

1. IAR specific files are missing in CMSIS
2. Pre-processing macro changes (as aligned to other assembly files)

You can review these after updating CMSIS, or just pick up this change along with update. I am fine with anything.

[bulislaw]

@deepikabhavnani should we contribute it to CMSIS then?

[deepikabhavnani]

@bulislaw - I have PR ARM-software/CMSIS_5#226 to add IAR baseline specific files to CMSIS, once it is approved I can add mainline as well.

It is not approved because Non-Secure and Secure code is duplicated in assembly files. Best solution is to have pre-processor defines (which are not supported in CMSIS). Conditional statements used in GCC/ARM assembly are not available in IAR assembly.

[bulislaw]

Ok, if the form we have it in this PR is correct I'm guessing we can merge it and in the future overwrite it with whats going to get committed to CMSIS. Please don't forget to update docs with additions/modifications to CMSIS/RTX:
https://github.com/ARMmbed/Handbook/blob/5.5/docs/advanced/cmsis-rtos.md

[0xc0170]

@deepikabhavnani Can you update the md file ? We can then trigger CI

[deepikabhavnani]

@bulislaw @0xc0170 update the md file, please review.

[0xc0170]

/morph test

[mbed-bot]

Result: SUCCESS

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/morph test

Output

mbed Build Number: 1438

All builds and test passed!