DRA829J: warning: call to function without interrupt attribute could clobber interruptee's VFP registers; consider using the `interrupt_save_fp` attribute to prevent this behavior [-Wextra]

Ralph Neumann

Part Number: DRA829J

Hello,

I use the ti-cgt-armllvm_2.1.0.LTS compiler and get the following warning: call to function without interrupt attribute could clobber interruptee's VFP registers; consider using the `interrupt_save_fp` attribute to prevent this behavior [-Wextra]. but the interrupt_save_fp attribute is not documented anywhere. where can i find the documentation for this attribute?

Regards
Ralph

over 1 year ago

0 Stanley Liu over 1 year ago

TI__Guru 50045 points

Could you check the below thread for details?

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1019277/am6442-clang-warning-call-to-function-without-interrupt-attribute-could-clobber-interruptee-s-vfp-registers

Regards,
Stanley

0 Ralph Neumann over 1 year ago in reply to Stanley Liu

Prodigy 165 points

Hi Stanley,

If an ISR on a R5F core use floating point, do i have to save/restore the FPU Registers by myself (I do not use an OS)?
Which FPU Registers have to be saved/restored?
This will not be solved by the attribute 'interrupt_save_fp'?

Regards
Ralph

0 George Mock over 1 year ago in reply to Ralph Neumann

TI__Guru**** 241485 points

Please see the documentation of the interrupt function attribute from the tiarmclang online manual. Note how it states: FPU Registers are Not Automatically Preserved by Interrupt Functions.

Internal discussion about the attribute interrupt_save_fp is still ongoing. At this point it seems likely that the compiler will get changed to not emit this diagnostic ...

Ralph Neumann said:
call to function without interrupt attribute could clobber interruptee's VFP registers; consider using the `interrupt_save_fp` attribute to prevent this behavior [-Wextra]

... and interrupt_save_fp will continue to not be documented, and thus should not be used. I'll get back to you on that.

Thanks and regards,

-George

+1 George Mock over 1 year ago in reply to George Mock

TI__Guru**** 241485 points

I filed EXT_EP-11126 to have the compiler changed to no longer issue that diagnostic. You are welcome to follow it with that link. Until then, the documentation about how FPU registers are not preserved continues to be the best information on this issue.

Thanks and regards,

-George

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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DRA829J: warning: call to function without interrupt attribute could clobber interruptee's VFP registers; consider using the `interrupt_save_fp` attribute to prevent this behavior [-Wextra]