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_mul( clk, rst, enable, opa, opb, sign, product_7, exponent_5);

input           clk;

input           rst;

input           enable;

input   [63:0]   opa, opb;

output          sign;

output  [55:0] product_7;

output  [11:0] exponent_5;

reg [5:0]        product_shift;

reg [5:0]        product_shift_2;

reg   sign;

reg   [51:0] mantissa_a;

reg   [51:0] mantissa_b;

reg   [10:0] exponent_a;

reg   [10:0] exponent_b;

reg             a_is_norm;

reg             b_is_norm;

reg             a_is_zero;

reg             b_is_zero;

reg             in_zero;

reg   [11:0] exponent_terms;

reg    exponent_gt_expoffset;

reg   [11:0] exponent_under;

reg   [11:0] exponent_1;

wire   [11:0] exponent = 0;

reg   [11:0] exponent_2;

reg   exponent_gt_prodshift;

reg   [11:0] exponent_3;

reg   [11:0] exponent_4;

reg  exponent_et_zero;

reg   [52:0] mul_a;

reg   [52:0] mul_b;

reg             [40:0] product_a;

reg             [40:0] product_b;

reg             [40:0] product_c;

reg             [25:0] product_d;

reg             [33:0] product_e;

reg             [33:0] product_f;

reg             [35:0] product_g;

reg             [28:0] product_h;

reg             [28:0] product_i;

reg             [30:0] product_j;

reg             [41:0] sum_0;

reg             [35:0] sum_1;

reg             [41:0] sum_2;

reg             [35:0] sum_3;

reg             [36:0] sum_4;

reg             [27:0] sum_5;

reg             [29:0] sum_6;

reg             [36:0] sum_7;

reg             [30:0] sum_8;

reg   [105:0] product;

reg   [105:0] product_1;

reg   [105:0] product_2;

reg   [105:0] product_3;

reg   [105:0] product_4;

reg   [105:0] product_5;

reg   [105:0] product_6;

reg             product_lsb; // if there are any 1's in the remainder

wire  [55:0] product_7 =  { 1'b0, product_6[105:52], product_lsb };

reg  [11:0] exponent_5;

always @(posedge clk)

begin

        if (rst) begin

                sign <= 0;

                mantissa_a <= 0;

                mantissa_b <= 0;

                exponent_a <= 0;

                exponent_b <= 0;

                a_is_norm <= 0;

                b_is_norm <= 0;

                a_is_zero <= 0;

                b_is_zero <= 0;

                in_zero <= 0;

                exponent_terms <= 0;

                exponent_gt_expoffset <= 0;

                exponent_under <= 0;

                exponent_1 <= 0;

                exponent_2 <= 0;

                exponent_gt_prodshift <= 0;

                exponent_3 <= 0;

                exponent_4 <= 0;

                exponent_et_zero <= 0;

                mul_a <= 0;

                mul_b <= 0;

                product_a <= 0;

                product_b <= 0;

                product_c <= 0;

                product_d <= 0;

                product_e <= 0;

                product_f <= 0;

                product_g <= 0;

                product_h <= 0;

                product_i <= 0;

                product_j <= 0;

                sum_0 <= 0;

                sum_1 <= 0;

                sum_2 <= 0;

                sum_3 <= 0;

                sum_4 <= 0;

                sum_5 <= 0;

                sum_6 <= 0;

                sum_7 <= 0;

                sum_8 <= 0;

                product <= 0;

                product_1 <= 0;

                product_2 <= 0;

                product_3 <= 0;

                product_4 <= 0;

                product_5 <= 0;

                product_6 <= 0;

                product_lsb <= 0;

                exponent_5 <= 0;

                product_shift_2 <= 0;

        end

        else if (enable) begin

                sign <= opa[63] ^ opb[63];

                mantissa_a <= opa[51:0];

                mantissa_b <= opb[51:0];

                exponent_a <= opa[62:52];

                exponent_b <= opb[62:52];

                a_is_norm <= |exponent_a;

                b_is_norm <= |exponent_b;

                a_is_zero <= !(|opa[62:0]);

                b_is_zero <= !(|opb[62:0]);

                in_zero <= a_is_zero | b_is_zero;

                exponent_terms <= exponent_a + exponent_b + !a_is_norm + !b_is_norm;

                exponent_gt_expoffset <= exponent_terms > 1021;

                exponent_under <= 1022 - exponent_terms;

                exponent_1 <= exponent_terms - 1022;

                exponent_2 <= exponent_gt_expoffset ? exponent_1 : exponent;

                exponent_gt_prodshift <= exponent_2 > product_shift_2;

                exponent_3 <= exponent_2 - product_shift;

                exponent_4 <= exponent_gt_prodshift ? exponent_3 : exponent;

                exponent_et_zero <= exponent_4 == 0;

                mul_a <= { a_is_norm, mantissa_a };

                mul_b <= { b_is_norm, mantissa_b };

                product_a <= mul_a[23:0] * mul_b[16:0];

                product_b <= mul_a[23:0] * mul_b[33:17];

                product_c <= mul_a[23:0] * mul_b[50:34];

                product_d <= mul_a[23:0] * mul_b[52:51];

                product_e <= mul_a[40:24] * mul_b[16:0];

                product_f <= mul_a[40:24] * mul_b[33:17];

                product_g <= mul_a[40:24] * mul_b[52:34];

                product_h <= mul_a[52:41] * mul_b[16:0];

                product_i <= mul_a[52:41] * mul_b[33:17];

                product_j <= mul_a[52:41] * mul_b[52:34];

                sum_0 <= product_a[40:17] + product_b;

                sum_1 <= sum_0[41:7] + product_e;

                sum_2 <= sum_1[35:10] + product_c;

                sum_3 <= sum_2[41:7] + product_h;

                sum_4 <= sum_3 + product_f;

                sum_5 <= sum_4[36:10] + product_d;

                sum_6 <= sum_5[27:7] + product_i;

                sum_7 <= sum_6 + product_g;

                sum_8 <= sum_7[36:17] + product_j;

                product <= { sum_8, sum_7[16:0], sum_5[6:0], sum_4[9:0], sum_2[6:0],

                                        sum_1[9:0], sum_0[6:0], product_a[16:0] };

                product_1 <= product >> exponent_under;

                product_2 <= exponent_gt_expoffset ? product : product_1;

                product_3 <= product_2 << product_shift_2;

                product_4 <= product_2 << exponent_2;

                product_5 <= exponent_gt_prodshift ? product_3  : product_4;

                product_6 <= exponent_et_zero ? product_5 >> 1 : product_5;

                product_lsb <= |product_6[51:0];

                exponent_5 <= in_zero ? 12'b0 : exponent_4;

                product_shift_2 <= product_shift; // redundant register

                        // reduces fanout on product_shift

        end

end

always @(product)

   casex(product)

    106'b1?????????????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  0;

        106'b01????????????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  1;

        106'b001???????????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  2;

        106'b0001??????????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  3;

        106'b00001?????????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  4;

        106'b000001????????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  5;

        106'b0000001???????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  6;

        106'b00000001??????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  7;

        106'b000000001?????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  8;

        106'b0000000001????????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  9;

        106'b00000000001???????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  10;

        106'b000000000001??????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  11;

        106'b0000000000001?????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  12;

        106'b00000000000001????????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  13;

        106'b000000000000001???????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  14;

        106'b0000000000000001??????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  15;

        106'b00000000000000001?????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  16;

        106'b000000000000000001????????????????????????????????????????????????????????????????????????????????????????: product_shift <=  17;

        106'b0000000000000000001???????????????????????????????????????????????????????????????????????????????????????: product_shift <=  18;

        106'b00000000000000000001??????????????????????????????????????????????????????????????????????????????????????: product_shift <=  19;

        106'b000000000000000000001?????????????????????????????????????????????????????????????????????????????????????: product_shift <=  20;

        106'b0000000000000000000001????????????????????????????????????????????????????????????????????????????????????: product_shift <=  21;

        106'b00000000000000000000001???????????????????????????????????????????????????????????????????????????????????: product_shift <=  22;

        106'b000000000000000000000001??????????????????????????????????????????????????????????????????????????????????: product_shift <=  23;

        106'b0000000000000000000000001?????????????????????????????????????????????????????????????????????????????????: product_shift <=  24;

        106'b00000000000000000000000001????????????????????????????????????????????????????????????????????????????????: product_shift <=  25;

        106'b000000000000000000000000001???????????????????????????????????????????????????????????????????????????????: product_shift <=  26;

        106'b0000000000000000000000000001??????????????????????????????????????????????????????????????????????????????: product_shift <=  27;

        106'b00000000000000000000000000001?????????????????????????????????????????????????????????????????????????????: product_shift <=  28;

        106'b000000000000000000000000000001????????????????????????????????????????????????????????????????????????????: product_shift <=  29;

        106'b0000000000000000000000000000001???????????????????????????????????????????????????????????????????????????: product_shift <=  30;

        106'b00000000000000000000000000000001??????????????????????????????????????????????????????????????????????????: product_shift <=  31;

        106'b000000000000000000000000000000001?????????????????????????????????????????????????????????????????????????: product_shift <=  32;

        106'b0000000000000000000000000000000001????????????????????????????????????????????????????????????????????????: product_shift <=  33;

        106'b00000000000000000000000000000000001???????????????????????????????????????????????????????????????????????: product_shift <=  34;

        106'b000000000000000000000000000000000001??????????????????????????????????????????????????????????????????????: product_shift <=  35;

        106'b0000000000000000000000000000000000001?????????????????????????????????????????????????????????????????????: product_shift <=  36;

        106'b00000000000000000000000000000000000001????????????????????????????????????????????????????????????????????: product_shift <=  37;

        106'b000000000000000000000000000000000000001???????????????????????????????????????????????????????????????????: product_shift <=  38;

        106'b0000000000000000000000000000000000000001??????????????????????????????????????????????????????????????????: product_shift <=  39;

        106'b00000000000000000000000000000000000000001?????????????????????????????????????????????????????????????????: product_shift <=  40;

        106'b000000000000000000000000000000000000000001????????????????????????????????????????????????????????????????: product_shift <=  41;

        106'b0000000000000000000000000000000000000000001???????????????????????????????????????????????????????????????: product_shift <=  42;

        106'b00000000000000000000000000000000000000000001??????????????????????????????????????????????????????????????: product_shift <=  43;

        106'b000000000000000000000000000000000000000000001?????????????????????????????????????????????????????????????: product_shift <=  44;

        106'b0000000000000000000000000000000000000000000001????????????????????????????????????????????????????????????: product_shift <=  45;

        106'b00000000000000000000000000000000000000000000001???????????????????????????????????????????????????????????: product_shift <=  46;

        106'b000000000000000000000000000000000000000000000001??????????????????????????????????????????????????????????: product_shift <=  47;

        106'b0000000000000000000000000000000000000000000000001?????????????????????????????????????????????????????????: product_shift <=  48;

    106'b00000000000000000000000000000000000000000000000001????????????????????????????????????????????????????????: product_shift <=  49;

        106'b000000000000000000000000000000000000000000000000001???????????????????????????????????????????????????????: product_shift <=  50;

        106'b0000000000000000000000000000000000000000000000000001??????????????????????????????????????????????????????: product_shift <=  51;

        106'b00000000000000000000000000000000000000000000000000001?????????????????????????????????????????????????????: product_shift <=  52;

        106'b000000000000000000000000000000000000000000000000000000????????????????????????????????????????????????????: product_shift <=  53;

          // It's not necessary to go past 53, because you will only get more than 53 zeros

          // when multiplying 2 denormalized numbers together, in which case you will underflow

        endcase

endmodule