Adding arch option instead MCPU for no dsp and no fpu support

[deepikabhavnani]

Description

Cortex-M33 has optional floating point and DSP, the mcpu option by default enables optional features. To disable optional features we need to add +nodsp +nofp.

But nofp is supported after 8.x version of toolchain. Hence to get this we will have to use -march option instead of -mcpu

Pull request type

[X] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[cmonr]

@deepikabhavnani I thought it was mentioned in a different PR that +nofp was needed.

[deepikabhavnani]

@cmonr - Yes in #8449

We have few Cortex-M33 with optional floating point and DSP, the mcpu option by default enables optional features. To disable optional features we need to add +nodsp +nofp.

But in tools if we set core as cortex-M33 it is without optional features, to select particular feature we need to explicitly append F - Floating point.

In 8449, Cortex-M33F was added and Cortex-M33 was updated.

Cortex-M33 = cortex-m33+nodsp+nofp - But nofp is supported after 8.x version of toolchain. Hence to get this we will have to use -march option instead of -mcpu

Cortex-M33F= cortex-m33+nodsp - This enables floating point for 8449.

Hope this helps.

[gaborkertesz]

Musca-A GCC_ARM build is working as expected with this fix.

[adbridge]

@deepikabhavnani Could you clarify the description for this PR please.

No FPU option is valid, but supported only for 8.x releases, with 7.x release +nofp gives build errors.

This is not very clear especially to the casual observer.

[adbridge]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3622
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8729/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[gaborkertesz]

@adbridge @deepikabhavnani
The background of this change (revert of a previous commit) is that the nofp feature is added by GCC 8 (https://gcc.gnu.org) for Cortex-M33, but version 8 is not yet published as a binary by Arm, the latest is 7.3 (https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/downloads)

So we shouldn't use +nofp for Cortex-M33 until GCC 8 is released for M class processors and if it's released and its features used by mbed build, the corresponding compiler version should be enforced by the build system.

[mbed-ci]

Exporter Build : FAILURE

Build number : 3230
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8729/

[mbed-ci]

Test : FAILURE

Build number : 3406
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8729/3406

[deepikabhavnani]

@ARMmbed/mbed-os-maintainers - Failures does not look like related to PR, is it some CI issue ?

[0xc0170]

@ARMmbed/mbed-os-maintainers - Failures does not look like related to PR, is it some CI issue ?

That is correct, I'll add this to the new rollup PR to restart testing there

[0xc0170]

Note: This PR is now a part of a rollup PR (#8753).

In order to expedite remaining CI testing, this PR has been bundled into the above rollup PR.

No further work is needed here, as once that PR is merged, this PR will also be closed and marked as merged.

If any more commits are made in this PR, this PR will remain open and have to go through CI on its own.

[cmonr]

Please ignore. I derped.