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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  or1200_fpu_post_norm_div                                    ////

////                                                              ////

////  This file is part of the OpenRISC 1200 project              ////

////  http://opencores.org/project,or1k                           ////

////                                                              ////

////  Description                                                 ////

////  post-normalization entity for the division unit             ////

////                                                              ////

////  To Do:                                                      ////

////                                                              ////

////                                                              ////

////  Author(s):                                                  ////

////      - Original design (FPU100) -                            ////

////        Jidan Al-eryani, jidan@gmx.net                        ////

////      - Conv. to Verilog and inclusion in OR1200 -            ////

////        Julius Baxter, julius@opencores.org                   ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

//

//  Copyright (C) 2006, 2010

//

//      This source file may be used and distributed without        

//      restriction provided that this copyright statement is not   

//      removed from the file and that any derivative work contains 

//      the original copyright notice and the associated disclaimer.

//                                                           

//              THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     

//      EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   

//      TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   

//      FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      

//      OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         

//      INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    

//      (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   

//      GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        

//      BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  

//      LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  

//      (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  

//      OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         

//      POSSIBILITY OF SUCH DAMAGE. 

//

module or1200_fpu_post_norm_div

  (

   clk_i,

   opa_i,

   opb_i,

   qutnt_i,

   rmndr_i,

   exp_10_i,

   sign_i,

   rmode_i,

   output_o,

   ine_o

   );

   parameter FP_WIDTH = 32;

   parameter MUL_SERIAL = 0; // 0 for parallel multiplier, 1 for serial

   parameter MUL_COUNT = 11; //11 for parallel multiplier, 34 for serial

   parameter FRAC_WIDTH = 23;

   parameter EXP_WIDTH = 8;

   parameter ZERO_VECTOR = 31'd0;

   parameter INF = 31'b1111111100000000000000000000000;

   parameter QNAN = 31'b1111111110000000000000000000000;

   parameter SNAN = 31'b1111111100000000000000000000001;

   input clk_i;

   input [FP_WIDTH-1:0] opa_i;

   input [FP_WIDTH-1:0] opb_i;

   input [FRAC_WIDTH+3:0] qutnt_i;

   input [FRAC_WIDTH+3:0] rmndr_i;

   input [EXP_WIDTH+1:0]  exp_10_i;

   input                  sign_i;

   input [1:0]             rmode_i;

   output reg [FP_WIDTH-1:0] output_o;

   output reg                ine_o;

   // input&output register wires

   reg [FP_WIDTH-1:0]         s_opa_i;

   reg [FP_WIDTH-1:0]         s_opb_i;

   reg [EXP_WIDTH-1:0]        s_expa;

   reg [EXP_WIDTH-1:0]        s_expb;

   reg [FRAC_WIDTH+3:0]      s_qutnt_i;

   reg [FRAC_WIDTH+3:0]      s_rmndr_i;

   reg [5:0]                  s_r_zeros;

   reg [EXP_WIDTH+1:0]        s_exp_10_i;

   reg                       s_sign_i;

   reg [1:0]                  s_rmode_i;

   wire [FP_WIDTH-1:0]        s_output_o;

   wire                      s_ine_o, s_overflow;

   wire                      s_opa_dn, s_opb_dn;

   wire                      s_qutdn;

   wire [9:0]                 s_exp_10b;

   reg [5:0]                  s_shr1;

   reg [5:0]                  s_shl1;

   wire                      s_shr2;

   reg [8:0]                  s_expo1;

   wire [8:0]                 s_expo2;

   reg [8:0]                  s_expo3;

   reg [26:0]                 s_fraco1;

   wire [24:0]                s_frac_rnd;

   reg [24:0]                 s_fraco2;

   wire                      s_guard, s_round, s_sticky, s_roundup;

   wire                      s_lost;

   wire                      s_op_0, s_opab_0, s_opb_0;

   wire                      s_infa, s_infb;

   wire                      s_nan_in, s_nan_op, s_nan_a, s_nan_b;

   wire                      s_inf_result;

   always @(posedge clk_i)

     begin

        s_opa_i <= opa_i;

        s_opb_i <= opb_i;

        s_expa <= opa_i[30:23];

        s_expb <= opb_i[30:23];

        s_qutnt_i <= qutnt_i;

        s_rmndr_i <= rmndr_i;

        s_exp_10_i <= exp_10_i;

        s_sign_i <= sign_i;

        s_rmode_i <= rmode_i;

     end

   // Output Register

   always @(posedge clk_i)

     begin

        output_o <= s_output_o;

        ine_o   <= s_ine_o;

     end

    // qutnt_i

    // 26 25                    3

    // |  |                     | 

    // h  fffffffffffffffffffffff grs

   //*** Stage 1 ****

   // figure out the exponent and how far the fraction has to be shifted 

   // right or left

   assign s_opa_dn = !(|s_expa) & (|opa_i[22:0]);

   assign s_opb_dn = !(|s_expb) & (|opb_i[22:0]);

   assign s_qutdn =  !s_qutnt_i[26];

   assign s_exp_10b = s_exp_10_i - {9'd0,s_qutdn};

   wire [9:0] v_shr;

   wire [9:0] v_shl;

   assign v_shr = (s_exp_10b[9] | !(|s_exp_10b)) ?

                   (10'd1 - s_exp_10b) - s_qutdn : 0;

   assign v_shl = (s_exp_10b[9] | !(|s_exp_10b)) ?

                   0 :

                   s_exp_10b[8] ?

                   0 : {9'd0,s_qutdn};

   always @(posedge clk_i)

     if (s_exp_10b[9] | !(|s_exp_10b))

       s_expo1 <= 9'd1;

     else

       s_expo1 <= s_exp_10b[8:0];

   always @(posedge clk_i)

     s_shr1 <= v_shr[6] ? 6'b111111 : v_shr[5:0];

   always @(posedge clk_i)

     s_shl1 <= v_shl[5:0];

   // *** Stage 2 ***

   // Shifting the fraction and rounding

   // shift the fraction

   always @(posedge clk_i)

     if (|s_shr1)

       s_fraco1 <= s_qutnt_i >> s_shr1;

     else

       s_fraco1 <= s_qutnt_i << s_shl1;

   assign s_expo2 = s_fraco1[26] ? s_expo1 : s_expo1 - 9'd1;

   //s_r_zeros <= count_r_zeros(s_qutnt_i);

   always @(s_qutnt_i)

     casex(s_qutnt_i) // synopsys full_case parallel_case

       27'b??????????????????????????1: s_r_zeros <=  0;

       27'b?????????????????????????10: s_r_zeros <=  1;

       27'b????????????????????????100: s_r_zeros <=  2;

       27'b???????????????????????1000: s_r_zeros <=  3;

       27'b??????????????????????10000: s_r_zeros <=  4;

       27'b?????????????????????100000: s_r_zeros <=  5;

       27'b????????????????????1000000: s_r_zeros <=  6;

       27'b???????????????????10000000: s_r_zeros <=  7;

       27'b??????????????????100000000: s_r_zeros <=  8;

       27'b?????????????????1000000000: s_r_zeros <=  9;

       27'b????????????????10000000000: s_r_zeros <=  10;

       27'b???????????????100000000000: s_r_zeros <=  11;

       27'b??????????????1000000000000: s_r_zeros <=  12;

       27'b?????????????10000000000000: s_r_zeros <=  13;

       27'b????????????100000000000000: s_r_zeros <=  14;

       27'b???????????1000000000000000: s_r_zeros <=  15;

       27'b??????????10000000000000000: s_r_zeros <=  16;

       27'b?????????100000000000000000: s_r_zeros <=  17;

       27'b????????1000000000000000000: s_r_zeros <=  18;

       27'b???????10000000000000000000: s_r_zeros <=  19;

       27'b??????100000000000000000000: s_r_zeros <=  20;

       27'b?????1000000000000000000000: s_r_zeros <=  21;

       27'b????10000000000000000000000: s_r_zeros <=  22;

       27'b???100000000000000000000000: s_r_zeros <=  23;

       27'b??1000000000000000000000000: s_r_zeros <=  24;

       27'b?10000000000000000000000000: s_r_zeros <=  25;

       27'b100000000000000000000000000: s_r_zeros <=  26;

       27'b000000000000000000000000000: s_r_zeros <=  27;

     endcase // casex (s_qutnt_i)

   assign s_lost = (s_shr1+{5'd0,s_shr2}) > s_r_zeros;

   // ***Stage 3***

   // Rounding

   assign s_guard = s_fraco1[2];

   assign s_round = s_fraco1[1];

   assign s_sticky = s_fraco1[0] | (|s_rmndr_i);

   assign s_roundup = s_rmode_i==2'b00 ? // round to nearest even

                      s_guard & ((s_round | s_sticky) | s_fraco1[3]) :

                      s_rmode_i==2'b10 ? // round up

                      (s_guard | s_round | s_sticky) & !s_sign_i :

                      s_rmode_i==2'b11 ? // round down

                      (s_guard | s_round | s_sticky) & s_sign_i :

                      0; // round to zero(truncate = no rounding)

   assign s_frac_rnd = s_roundup ?{1'b0,s_fraco1[26:3]} + 1 :

                       {1'b0,s_fraco1[26:3]};

   assign s_shr2 = s_frac_rnd[24];

   always @(posedge clk_i)

     begin

        s_expo3 <= s_shr2 ? s_expo2 + "1" : s_expo2;

        s_fraco2 <= s_shr2 ? {1'b0,s_frac_rnd[24:1]} : s_frac_rnd;

     end

   //

   // ***Stage 4****

   // Output

   assign s_op_0 = !((|s_opa_i[30:0]) & (|s_opb_i[30:0]));

   assign s_opab_0 = !((|s_opa_i[30:0]) | (|s_opb_i[30:0]));

   assign s_opb_0 = !(|s_opb_i[30:0]);

   assign s_infa = &s_expa;

   assign s_infb = &s_expb;

   assign s_nan_a = s_infa & (|s_opa_i[22:0]);

   assign s_nan_b = s_infb & (|s_opb_i[22:0]);

   assign s_nan_in = s_nan_a | s_nan_b;

   assign s_nan_op = (s_infa & s_infb) | s_opab_0; // 0 / 0, inf / inf

   assign s_inf_result = (&s_expo3[7:0]) | s_expo3[8] | s_opb_0;

   assign s_overflow =  s_inf_result & !(s_infa) & !s_opb_0;

   assign s_ine_o =  !s_op_0 &

                     (s_lost | (|s_fraco1[2:0]) | s_overflow | (|s_rmndr_i));

   assign s_output_o = (s_nan_in | s_nan_op) ?

                       {s_sign_i,QNAN} :

                       s_infa  | s_overflow | s_inf_result ?

                       {s_sign_i,INF} :

                       s_op_0 | s_infb ?

                       {s_sign_i,ZERO_VECTOR} :

                       {s_sign_i,s_expo3[7:0],s_fraco2[22:0]};

endmodule // or1200_fpu_post_norm_div