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

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