Question

Who can explain: how to enable intrinsics in c code?

I would like to use special dsp instructions in armv5TE

Consider qadd instruction, it nicely works when i use assembler approach, like this:

inline int function_qadd(int a, int b) {
    __asm__ (
            "qadd %0, %1, %2" : "=r" (a) : "r" (a), "r" (b));
    return a;
}

But when i tried to use __qadd intrinsic instead of asm like this:

int add_result = __qadd(5,10);
LOGI("qadd='%d'", add_result);

i got error:

error: undefined reference to ‘__qadd’

What i am doing wrong, how to enable intrinsics in c code?

UPDATE:

I have ndk android-ndk-r8c (windows version), it have GCC 4.6 as default:

The GCC 4.6 compiler is still the default,

Besides i explicitly specify in android.mk

NDK_TOOLCHAIN_VERSION=4.6

My compiler flags is:

LOCAL_CFLAGS += -std=c99 -ffast-math -march=armv5te -mfpu=vfp -mfloat-abi=softfp 

Besides i check the asm code generated by gcc throught -S compiler flag, it generate qadd instruction:

qadd r3, r3, r2

Answer 1

The intrinsic function __qadd is not available for the GCC compiler. The link to the documentation you’ve provided is for the (non-free) armcc compiler.

Using the assembler approach is the only practical way to use the qadd instruction if you’re using GCC.