surge-math 0.1.30-alpha.0

surge synthesizer -- dsp math used in synthesis
Documentation 
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ix!();

// Snabba sin(x) substitut
// work in progress
#[inline] pub fn sine_float_nowrap(x: f32) -> f32 
{
   // http://www.devmaster.net/forums/showthread.php?t=5784
    let four_over_pi:         f32 = (4.0 / PI) as f32;
    let minus_four_over_pi_2: f32 = (-4.0 / (PI * PI)) as f32;

    let y: f32 = four_over_pi * x + minus_four_over_pi_2 * x * x.abs();

    // EXTRA_PRECISION
    //  const float Q = 0.775;
    let p: f32 = 0.225;

    // Q * y + P * y * abs(y)
    p * (y * y.abs() - y) + y 
}

#[inline] pub fn sine_ps_nowrap(x: __m128) -> __m128 
{
    unsafe {
        let four_over_pi: __m128 = _mm_set1_ps((4.0 / PI) as f32);
        let minus_four_over_pi_2: __m128 = _mm_set1_ps((-4.0 / (PI * PI)) as f32);

        // todo wrap x [0..1] ?

        // y = B * x + C * x * abs(x);
        let y: __m128 = _mm_add_ps(
            _mm_mul_ps(four_over_pi, x), 
            _mm_mul_ps(
                _mm_mul_ps(minus_four_over_pi_2, x), 
                _mm_and_ps(m128_mask_absval![], x)));

        // EXTRA_PRECISION
        //  const float Q = 0.775;
        let p: __m128 = _mm_set1_ps(0.2250);

        _mm_add_ps(
            _mm_mul_ps(
                _mm_sub_ps(
                    _mm_mul_ps(
                        _mm_and_ps(
                            m128_mask_absval![], 
                            y), 
                        y), 
                    y), 
                p), 
            y)
    }
}

/// sin(x*pi)
#[inline] pub fn sine_xpi_ps_sse2(mut x: __m128) -> __m128 
{
    unsafe {
        let four:    __m128  = _mm_set1_ps(4.0);
        let mask:    __m128i = _mm_set1_epi32(0x01ffffff);
        let offset:  __m128i = _mm_set1_epi32(0x01000000);

        // wrap x
        x = _mm_cvtepi32_ps(
            _mm_sub_epi32(
                _mm_and_si128(
                    _mm_add_epi32(
                        offset, 
                        _mm_cvttps_epi32(x)), 
                    mask), 
                offset));

        let y: __m128 = _mm_mul_ps(
            four, 
            _mm_sub_ps(
                x, 
                _mm_mul_ps(
                    x, 
                    _mm_and_ps(
                        m128_mask_absval![], 
                        x))));


        let p: __m128 = _mm_set1_ps(0.2250);

        _mm_add_ps(
            _mm_mul_ps(
                _mm_sub_ps(
                    _mm_mul_ps(
                        _mm_and_ps(
                            m128_mask_absval![], 
                            y), 
                        y), 
                    y), 
                p), 
            y)
    }
}

#[cfg(target_argh = "x86")]
pub fn sine(x: __m64) -> __m64 
{
    unsafe {

        let xabs: __m64 = _mm_xor_si64(
            x, 
            _mm_srai_pi16(x, 15));

        let mut y: __m64 = _mm_subs_pi16(
            _mm_srai_pi16(x, 1), 
            _mm_mulhi_pi16(x, xabs));

        y = _mm_slli_pi16(y, 2);
        y = _mm_adds_pi16(y, y);

        let q: __m64 = _mm_set1_pi16(0x6333);
        let p: __m64 = _mm_set1_pi16(0x1CCD);

        let yabs: __m64 = _mm_xor_si64(
            y, 
            _mm_srai_pi16(y, 15));

        let y1: __m64 = _mm_mulhi_pi16(q, y);

        let y2: __m64 = _mm_mulhi_pi16(
            p, 
            _mm_slli_pi16(
                _mm_mulhi_pi16(y, yabs), 
                1));

        y = _mm_add_pi16(y1, y2);
        _mm_adds_pi16(y, y)
    }
}

/// 16-bit sine
#[cfg(target_argh = "x86_64")]
pub fn sine(x: i32) -> i32 
{
   x = ((x + 0x8000) & 0xffff) - 0x8000;

   let y: i32 = ((x << 2) - ((abs(x >> 1) * (x >> 1)) >> 11));
   let q: i32 = (0.7750 * 65536.0);
   let p: i32 = (0.2250 * 32768.0);

   ((q * y) >> 16) + (((((y >> 2) * abs(y >> 2)) >> 11) * p) >> 15)
}