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How to check if Neon instructions are used?

Former Member
Former Member

I am running code in ADStudio using Fixed Virtual Platforms simulator, so no hardware board is connected. 

I am trying to profile a sub-routine, so I count cycles for a peace of code:

int64_t prev, curr, delta;
asm volatile("isb;mrs %0, pmccntr_el0" : "=r"(prev));

// function body

asm volatile("isb;mrs %0, pmccntr_el0" : "=r"(curr));
delta = curr - prev;

My compiler settings are --target=aarch64-arm-none-eabi -march=armv8-a -mcpu=cortex-a53. 

I wanted to check if compiler uses NEON instructions: 

#ifdef __aarch64__
printf("--- THIS IS ARCH64 \n");
#endif

#ifdef __ARM_NEON__
printf("--- THIS IS NEON \n");
#endif

But it seems that it is not using neon.

1) Is my define __ARM_NEON__ wrong? 

2) What is the default -gfpu? 

3) How do I force neon with -gfpu?

4) When I set -gfpu=none my cycle count is THE SAME as default one. I find this rather strange, shouldn't the math heavy code be much slower? Is there an explanation?

Thanks.

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