modified prescale calculation in hp20_fx_32_opt()

{

    Word32 i;

    Word32 a1_fx, a2_fx, b1_fx, b2_fx;

    Word32 diff_pos, diff_neg;

#ifndef ISSUE_1836_replace_overflow_libcom

    Flag Overflow = 0;

#endif

    Word16 prescale, prescaleOld, prescale_current_frame, diff;

    Word32 tmp_mem[4];

    prescale = L_norm_arr( signal_fx, lg );

    prescale_current_frame = sub( add( 1, HP20_FX_COEFF_SCALE ), prescale );

    prescaleOld = extract_l( mem_fx[4] );

#ifdef ISSUE_1836_replace_overflow_libcom

    diff_pos = norm_l( L_shl_sat( L_max( mem_fx[2], mem_fx[3] ), prescaleOld ) );

    diff_neg = norm_l( L_shl_sat( L_min( mem_fx[2], mem_fx[3] ), prescaleOld ) );

#else

    diff_pos = norm_l( L_shl_o( L_max( mem_fx[2], mem_fx[3] ), prescaleOld, &Overflow ) );

    diff_neg = norm_l( L_shl_o( L_min( mem_fx[2], mem_fx[3] ), prescaleOld, &Overflow ) );

#endif

    Copy32( mem_fx, tmp_mem, 4 );

    Scale_sig32( tmp_mem, 4, prescaleOld );

    diff = L_norm_arr( tmp_mem, 4 );

    prescale = s_min( prescale, diff );

    diff = L_min( diff_pos, diff_neg );

    prescale = sub( add( 1, HP20_FX_COEFF_SCALE ), prescale );

    IF( NE_16( diff, 0 ) )

    IF( EQ_16( prescale_current_frame, -29 ) ) // signal_fx buffer contains only zeros, so use the mem_fx scale_factor instead

    {

        prescale = s_min( prescale, diff );

        prescale_current_frame = prescale;

    }

    prescale = sub( add( 1, HP20_FX_COEFF_SCALE ), prescale );

    diff = sub( prescale, prescaleOld );

#ifdef ISSUE_1836_replace_overflow_libcom

    mem_fx[0] = L_shr_sat( mem_fx[0], diff );