intrinsics.hpp

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#ifndef CAROTENE_INTRINSICS_HPP
#define CAROTENE_INTRINSICS_HPP

#include <carotene/definitions.hpp>

#include <arm_neon.h>

namespace CAROTENE_NS { namespace internal {

/////////////// Custom NEON intrinsics ///////////////////

// calculate reciprocal value

inline float32x4_t vrecpq_f32(float32x4_t val)
{
    float32x4_t reciprocal = vrecpeq_f32(val);
    reciprocal = vmulq_f32(vrecpsq_f32(val, reciprocal), reciprocal);
    reciprocal = vmulq_f32(vrecpsq_f32(val, reciprocal), reciprocal);
    return reciprocal;
}

inline float32x2_t vrecp_f32(float32x2_t val)
{
    float32x2_t reciprocal = vrecpe_f32(val);
    reciprocal = vmul_f32(vrecps_f32(val, reciprocal), reciprocal);
    reciprocal = vmul_f32(vrecps_f32(val, reciprocal), reciprocal);
    return reciprocal;
}

// caclulate sqrt value

inline float32x4_t vrsqrtq_f32(float32x4_t val)
{
    float32x4_t e = vrsqrteq_f32(val);
    e = vmulq_f32(vrsqrtsq_f32(vmulq_f32(e, e), val), e);
    e = vmulq_f32(vrsqrtsq_f32(vmulq_f32(e, e), val), e);
    return e;
}

inline float32x2_t vrsqrt_f32(float32x2_t val)
{
    float32x2_t e = vrsqrte_f32(val);
    e = vmul_f32(vrsqrts_f32(vmul_f32(e, e), val), e);
    e = vmul_f32(vrsqrts_f32(vmul_f32(e, e), val), e);
    return e;
}

inline float32x4_t vsqrtq_f32(float32x4_t val)
{
    return vrecpq_f32(vrsqrtq_f32(val));
}

inline float32x2_t vsqrt_f32(float32x2_t val)
{
    return vrecp_f32(vrsqrt_f32(val));
}

// table lookup with the table in a 128-bit register

inline uint8x8_t vqtbl1_u8 (uint8x16_t a, uint8x8_t b)
{
#ifdef __aarch64__
    // AArch64 supports this natively
    return ::vqtbl1_u8(a, b);
#else
    union { uint8x16_t v; uint8x8x2_t w; } u = { a };
    return vtbl2_u8(u.w, b);
#endif
}

} }

#endif