Function arm_recip_q31

bsp/efm32/Libraries/CMSIS/Include/arm_math.h:496–542

   */

  __STATIC_INLINE uint32_t arm_recip_q31(
  q31_t in,
  q31_t * dst,
  q31_t * pRecipTable)
  {

    uint32_t out, tempVal;
    uint32_t index, i;
    uint32_t signBits;

    if(in > 0)
    {
      signBits = __CLZ(in) - 1;
    }
    else
    {
      signBits = __CLZ(-in) - 1;
    }

    /* Convert input sample to 1.31 format */
    in = in << signBits;

    /* calculation of index for initial approximated Val */
    index = (uint32_t) (in >> 24u);
    index = (index & INDEX_MASK);

    /* 1.31 with exp 1 */
    out = pRecipTable[index];

    /* calculation of reciprocal value */
    /* running approximation for two iterations */
    for (i = 0u; i < 2u; i++)
    {
      tempVal = (q31_t) (((q63_t) in * out) >> 31u);
      tempVal = 0x7FFFFFFF - tempVal;
      /*      1.31 with exp 1 */
      //out = (q31_t) (((q63_t) out * tempVal) >> 30u);
      out = (q31_t) clip_q63_to_q31(((q63_t) out * tempVal) >> 30u);
    }

    /* write output */
    *dst = out;

    /* return num of signbits of out = 1/in value */
    return (signBits + 1u);

  }

  /**
   * @brief Function to Calculates 1/in(reciprocal) value of Q15 Data type.