Cortex-R with -fno-omit-frame-pointer option and conflict on register R7

Asked by jdobry on 2018-04-14

Hi,

I want to use -fno-omit-frame-pointer option for debugging purpose.
But there is problem. I am using register R7 too in inline asm. When I try compile this code it fail with "error: r7 cannot be used in asm here".
But it is strange. Register R7 could be used as frame pointer, but on Cortex-M0 platform, not on my Cortex-R. Frame pointer = FP = R11 on my platform .
See http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042f/IHI0042F_aapcs.pdf
Why compiler didn't allow me to use R7?

Jiri

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GNU Arm Embedded Toolchain Edit question
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Last query:
2018-04-14
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2018-04-30
jdobry (jdobry) said : #1

OK I see reason. GCC in Thumb mode use R7 as frame pointer anytime.
Now it is clear.
I have only one question. Where is it documented?

Launchpad Janitor (janitor) said : #2

This question was expired because it remained in the 'Open' state without activity for the last 15 days.