Subversion Repositories double_fpu

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

////                                                             ////

////  FPU                                                        ////

////  Floating Point Unit (Double precision)                     ////

////                                                             ////

////  Author: David Lundgren                                     ////

////          davidklun@gmail.com                                ////

////                                                             ////

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

////                                                             ////

//// Copyright (C) 2009 David Lundgren                           ////

////                  davidklun@gmail.com                        ////

////                                                             ////

//// 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.                                 ////

////                                                             ////

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

`timescale 1ns / 100ps

module fpu_sub( clk, rst, enable, opa, opb, fpu_op, sign, diff_2, exponent_2);

input           clk;

input           rst;

input           enable;

input   [63:0]   opa, opb;

input   [2:0]    fpu_op;

output          sign;

output  [55:0]   diff_2;

output  [10:0]   exponent_2;

reg [6:0]        diff_shift;

reg [6:0]        diff_shift_2;

reg   [10:0] exponent_a;

reg   [10:0] exponent_b;

reg   [51:0] mantissa_a;

reg   [51:0] mantissa_b;

reg   expa_gt_expb;

reg   expa_et_expb;

reg   mana_gtet_manb;

reg   a_gtet_b;

reg   sign;

reg   [10:0] exponent_small;

reg   [10:0] exponent_large;

reg   [51:0] mantissa_small;

reg   [51:0] mantissa_large;

reg   small_is_denorm;

reg   large_is_denorm;

reg   large_norm_small_denorm;

reg   small_is_nonzero;

reg   [10:0] exponent_diff;

reg   [54:0] minuend;

reg   [54:0] subtrahend;

reg   [54:0] subtra_shift;

wire   subtra_shift_nonzero = |subtra_shift[54:0];

wire   subtra_fraction_enable = small_is_nonzero & !subtra_shift_nonzero;

wire   [54:0] subtra_shift_2 = { 54'b0, 1'b1 };

reg   [54:0] subtra_shift_3;

reg   [54:0] diff;

reg   diffshift_gt_exponent;

reg   diffshift_et_55; // when the difference = 0

reg   [54:0] diff_1;

reg   [10:0] exponent;

reg   [10:0] exponent_2;

wire   in_norm_out_denorm = (exponent_large > 0) & (exponent== 0);

reg   [55:0] diff_2;

always @(posedge clk)

        begin

                if (rst) begin

                exponent_a <= 0;

                exponent_b <= 0;

                mantissa_a <= 0;

                mantissa_b <= 0;

                expa_gt_expb <= 0;

                expa_et_expb <= 0;

                mana_gtet_manb <= 0;

                a_gtet_b <= 0;

                sign <= 0;

                exponent_small  <= 0;

                exponent_large  <= 0;

                mantissa_small  <= 0;

                mantissa_large  <= 0;

                small_is_denorm <= 0;

                large_is_denorm <= 0;

                large_norm_small_denorm <= 0;

                small_is_nonzero <= 0;

                exponent_diff <= 0;

                minuend <= 0;

                subtrahend <= 0;

                subtra_shift <= 0;

                subtra_shift_3 <= 0;

                diff_shift_2 <= 0;

                diff <= 0;

                diffshift_gt_exponent <= 0;

                diffshift_et_55 <= 0;

                diff_1 <= 0;

                exponent <= 0;

                exponent_2 <= 0;

                diff_2 <= 0;

                end

                else if (enable) begin

                exponent_a <= opa[62:52];

                exponent_b <= opb[62:52];

                mantissa_a <= opa[51:0];

                mantissa_b <= opb[51:0];

                expa_gt_expb <= exponent_a > exponent_b;

                expa_et_expb <= exponent_a == exponent_b;

                mana_gtet_manb <= mantissa_a >= mantissa_b;

                a_gtet_b <= expa_gt_expb | (expa_et_expb & mana_gtet_manb);

                sign <= a_gtet_b ? opa[63] :!opb[63] ^ (fpu_op == 3'b000);

                exponent_small  <= a_gtet_b ? exponent_b : exponent_a;

                exponent_large  <= a_gtet_b ? exponent_a : exponent_b;

                mantissa_small  <= a_gtet_b ? mantissa_b : mantissa_a;

                mantissa_large  <= a_gtet_b ? mantissa_a : mantissa_b;

                small_is_denorm <= !(exponent_small > 0);

                large_is_denorm <= !(exponent_large > 0);

                large_norm_small_denorm <= (small_is_denorm == 1 && large_is_denorm == 0);

                small_is_nonzero <= (exponent_small > 0) | |mantissa_small[51:0];

                exponent_diff <= exponent_large - exponent_small - large_norm_small_denorm;

                minuend <= { !large_is_denorm, mantissa_large, 2'b00 };

                subtrahend <= { !small_is_denorm, mantissa_small, 2'b00 };

                subtra_shift <= subtrahend >> exponent_diff;

                subtra_shift_3 <= subtra_fraction_enable ? subtra_shift_2 : subtra_shift;

                diff_shift_2 <= diff_shift;

                diff <= minuend - subtra_shift_3;

                diffshift_gt_exponent <= diff_shift_2 > exponent_large;

                diffshift_et_55 <= diff_shift_2 == 55;

                diff_1 <= diffshift_gt_exponent ? diff << exponent_large : diff << diff_shift_2;

                exponent <= diffshift_gt_exponent ? 0 : (exponent_large - diff_shift_2);

                exponent_2 <= diffshift_et_55 ? 0 : exponent;

                diff_2 <= in_norm_out_denorm ? { 1'b0, diff_1 >> 1} : {1'b0, diff_1};

                end

        end

always @(diff)

   casex(diff)

    55'b1??????????????????????????????????????????????????????: diff_shift <=  0;

        55'b01?????????????????????????????????????????????????????: diff_shift <=  1;

        55'b001????????????????????????????????????????????????????: diff_shift <=  2;

        55'b0001???????????????????????????????????????????????????: diff_shift <=  3;

        55'b00001??????????????????????????????????????????????????: diff_shift <=  4;

        55'b000001?????????????????????????????????????????????????: diff_shift <=  5;

        55'b0000001????????????????????????????????????????????????: diff_shift <=  6;

        55'b00000001???????????????????????????????????????????????: diff_shift <=  7;

        55'b000000001??????????????????????????????????????????????: diff_shift <=  8;

        55'b0000000001?????????????????????????????????????????????: diff_shift <=  9;

        55'b00000000001????????????????????????????????????????????: diff_shift <=  10;

        55'b000000000001???????????????????????????????????????????: diff_shift <=  11;

        55'b0000000000001??????????????????????????????????????????: diff_shift <=  12;

        55'b00000000000001?????????????????????????????????????????: diff_shift <=  13;

        55'b000000000000001????????????????????????????????????????: diff_shift <=  14;

        55'b0000000000000001???????????????????????????????????????: diff_shift <=  15;

        55'b00000000000000001??????????????????????????????????????: diff_shift <=  16;

        55'b000000000000000001?????????????????????????????????????: diff_shift <=  17;

        55'b0000000000000000001????????????????????????????????????: diff_shift <=  18;

        55'b00000000000000000001???????????????????????????????????: diff_shift <=  19;

        55'b000000000000000000001??????????????????????????????????: diff_shift <=  20;

        55'b0000000000000000000001?????????????????????????????????: diff_shift <=  21;

        55'b00000000000000000000001????????????????????????????????: diff_shift <=  22;

        55'b000000000000000000000001???????????????????????????????: diff_shift <=  23;

        55'b0000000000000000000000001??????????????????????????????: diff_shift <=  24;

        55'b00000000000000000000000001?????????????????????????????: diff_shift <=  25;

        55'b000000000000000000000000001????????????????????????????: diff_shift <=  26;

        55'b0000000000000000000000000001???????????????????????????: diff_shift <=  27;

        55'b00000000000000000000000000001??????????????????????????: diff_shift <=  28;

        55'b000000000000000000000000000001?????????????????????????: diff_shift <=  29;

        55'b0000000000000000000000000000001????????????????????????: diff_shift <=  30;

        55'b00000000000000000000000000000001???????????????????????: diff_shift <=  31;

        55'b000000000000000000000000000000001??????????????????????: diff_shift <=  32;

        55'b0000000000000000000000000000000001?????????????????????: diff_shift <=  33;

        55'b00000000000000000000000000000000001????????????????????: diff_shift <=  34;

        55'b000000000000000000000000000000000001???????????????????: diff_shift <=  35;

        55'b0000000000000000000000000000000000001??????????????????: diff_shift <=  36;

        55'b00000000000000000000000000000000000001?????????????????: diff_shift <=  37;

        55'b000000000000000000000000000000000000001????????????????: diff_shift <=  38;

        55'b0000000000000000000000000000000000000001???????????????: diff_shift <=  39;

        55'b00000000000000000000000000000000000000001??????????????: diff_shift <=  40;

        55'b000000000000000000000000000000000000000001?????????????: diff_shift <=  41;

        55'b0000000000000000000000000000000000000000001????????????: diff_shift <=  42;

        55'b00000000000000000000000000000000000000000001???????????: diff_shift <=  43;

        55'b000000000000000000000000000000000000000000001??????????: diff_shift <=  44;

        55'b0000000000000000000000000000000000000000000001?????????: diff_shift <=  45;

        55'b00000000000000000000000000000000000000000000001????????: diff_shift <=  46;

        55'b000000000000000000000000000000000000000000000001???????: diff_shift <=  47;

        55'b0000000000000000000000000000000000000000000000001??????: diff_shift <=  48;

    55'b00000000000000000000000000000000000000000000000001?????: diff_shift <=  49;

        55'b000000000000000000000000000000000000000000000000001????: diff_shift <=  50;

        55'b0000000000000000000000000000000000000000000000000001???: diff_shift <=  51;

        55'b00000000000000000000000000000000000000000000000000001??: diff_shift <=  52;

        55'b000000000000000000000000000000000000000000000000000001?: diff_shift <=  53;

        55'b0000000000000000000000000000000000000000000000000000001: diff_shift <=  54;

        55'b0000000000000000000000000000000000000000000000000000000: diff_shift <=  55;

        endcase

endmodule