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Re: ARM arch: unknown asm insn "mrc" in v5T_semantics()


I'm targetting an ARM7 TDMI processor, and gcc 3.3.2 complains about this inline asm instruction from function arm_stub.h:v5T_semantics().


    asm volatile ("mrc  p15,0,%0,c0,c0,0\n"
		  : "=r" (id) : /* no inputs */);


What's up with this insn, I can't find it in the reference. And what should I correct to make it work?


Which reference? It is covered in the ARM Architectural Reference Manual.
The instruction reads the CPU ID register and is valid for all ARM cpus.

My bad, I only looked in the thumb ref card. So that's an ARM instruction... I'm compiling with -mthumb. I left away all the thumb-interwork flags, since I don't need to integrate any ARM code libs. Could that be a problem?


Otherwise, I would probably have to switch to ARM mode before the mrc. I'm gonna try that.

Heiko


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