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  /*                                                                      *
   * SKP_Silk_sum_sqr_shift.c                                           *
   *                                                                      *
   * compute number of bits to right shift the sum of squares of a vector *
   * of int16s to make it fit in an int32                                 *
   *                                                                      *
   * Copyright 2006-2008 (c), Skype Limited                               *
   *                                                                      */
  #include "SKP_Silk_SigProc_FIX.h"
  #if (EMBEDDED_ARM<5) 
  /* Compute number of bits to right shift the sum of squares of a vector */
  /* of int16s to make it fit in an int32                                 */
  void SKP_Silk_sum_sqr_shift(
      SKP_int32            *energy,            /* O    Energy of x, after shifting to the right            */
      SKP_int              *shift,             /* O    Number of bits right shift applied to energy        */
      const SKP_int16      *x,                 /* I    Input vector                                        */
      SKP_int              len                 /* I    Length of input vector                              */
  )
  {
      SKP_int   i, shft;
      SKP_int32 in32, nrg_tmp, nrg;
  
      if( (SKP_int32)( (SKP_int_ptr_size)x & 2 ) != 0 ) {
          /* Input is not 4-byte aligned */
          nrg = SKP_SMULBB( x[ 0 ], x[ 0 ] );
          i = 1;
      } else {
          nrg = 0;
          i   = 0;
      }
      shft = 0;
      len--;
      while( i < len ) {
          /* Load two values at once */
          in32 = *( (SKP_int32 *)&x[ i ] );
          nrg = SKP_SMLABB_ovflw( nrg, in32, in32 );
          nrg = SKP_SMLATT_ovflw( nrg, in32, in32 );
          i += 2;
          if( nrg < 0 ) {
              /* Scale down */
              nrg = (SKP_int32)SKP_RSHIFT_uint( (SKP_uint32)nrg, 2 );
              shft = 2;
              break;
          }
      }
      for( ; i < len; i += 2 ) {
          /* Load two values at once */
          in32 = *( (SKP_int32 *)&x[ i ] );
          nrg_tmp = SKP_SMULBB( in32, in32 );
          nrg_tmp = SKP_SMLATT_ovflw( nrg_tmp, in32, in32 );
          nrg = (SKP_int32)SKP_ADD_RSHIFT_uint( nrg, (SKP_uint32)nrg_tmp, shft );
          if( nrg < 0 ) {
              /* Scale down */
              nrg = (SKP_int32)SKP_RSHIFT_uint( (SKP_uint32)nrg, 2 );
              shft += 2;
          }
      }
      if( i == len ) {
          /* One sample left to process */
          nrg_tmp = SKP_SMULBB( x[ i ], x[ i ] );
          nrg = (SKP_int32)SKP_ADD_RSHIFT_uint( nrg, nrg_tmp, shft );
      }
  
      /* Make sure to have at least one extra leading zero (two leading zeros in total) */
      if( nrg & 0xC0000000 ) {
          nrg = SKP_RSHIFT_uint( (SKP_uint32)nrg, 2 );
          shft += 2;
      }
  
      /* Output arguments */
      *shift  = shft;
      *energy = nrg;
  }
  
  #endif
  