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

////                                                             ////

////  FPU                                                        ////

////  Floating Point Unit (Single precision)                     ////

////                                                             ////

////  Author: Rudolf Usselmann                                   ////

////          rudi@asics.ws                                      ////

////                                                             ////

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

////                                                             ////

//// Copyright (C) 2000 Rudolf Usselmann                         ////

////                    rudi@asics.ws                            ////

////                                                             ////

//// 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

/*

FPU Operations (fpu_op):

========================

1 = sub

2 = mul

3 = div

4 =

5 =

6 =

7 =

Rounding Modes (rmode):

=======================

1 = round_to_zero

2 = round_up

3 = round_down

*/

module fpu( clk, rmode, fpu_op, opa, opb, out, inf, snan, qnan, ine, overflow, underflow, zero, div_by_zero);

input           clk;

input   [1:0]    rmode;

input   [2:0]    fpu_op;

input   [31:0]   opa, opb;

output  [31:0]   out;

output          inf, snan, qnan;

output          ine;

output          overflow, underflow;

output          zero;

output          div_by_zero;

parameter       INF  = 31'h7f800000,

                QNAN = 31'h7fc00001,

                SNAN = 31'h7f800001;

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

//

// Local Wires

//

reg             zero;

reg     [31:0]   opa_r, opb_r;           // Input operand registers

reg     [31:0]   out;                    // Output register

reg             div_by_zero;            // Divide by zero output register

wire            signa, signb;           // alias to opX sign

wire            sign_fasu;              // sign output

wire    [26:0]   fracta, fractb;         // Fraction Outputs from EQU block

wire    [7:0]    exp_fasu;               // Exponent output from EQU block

reg     [7:0]    exp_r;                  // Exponent output (registerd)

wire    [26:0]   fract_out_d;            // fraction output

wire            co;                     // carry output

reg     [27:0]   fract_out_q;            // fraction output (registerd)

wire    [30:0]   out_d;                  // Intermediate final result output

wire            overflow_d, underflow_d;// Overflow/Underflow Indicators

reg             overflow, underflow;    // Output registers for Overflow & Underflow

reg             inf, snan, qnan;        // Output Registers for INF, SNAN and QNAN

reg             ine;                    // Output Registers for INE

reg     [1:0]    rmode_r1, rmode_r2,     // Pipeline registers for rounding mode

                rmode_r3;

reg     [2:0]    fpu_op_r1, fpu_op_r2,   // Pipeline registers for fp opration

                fpu_op_r3;

wire            mul_inf, div_inf;

wire            mul_00, div_00;

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

//

// Input Registers

//

always @(posedge clk)

        opa_r <= #1 opa;

always @(posedge clk)

        opb_r <= #1 opb;

always @(posedge clk)

        rmode_r1 <= #1 rmode;

always @(posedge clk)

        rmode_r2 <= #1 rmode_r1;

always @(posedge clk)

        rmode_r3 <= #1 rmode_r2;

always @(posedge clk)

        fpu_op_r1 <= #1 fpu_op;

always @(posedge clk)

        fpu_op_r2 <= #1 fpu_op_r1;

always @(posedge clk)

        fpu_op_r3 <= #1 fpu_op_r2;

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

//

// Exceptions block

//

wire            inf_d, ind_d, qnan_d, snan_d, opa_nan, opb_nan;

wire            opa_00, opb_00;

wire            opa_inf, opb_inf;

wire            opa_dn, opb_dn;

except u0(      .clk(clk),

                .opa(opa_r), .opb(opb_r),

                .inf(inf_d), .ind(ind_d),

                .qnan(qnan_d), .snan(snan_d),

                .opa_nan(opa_nan), .opb_nan(opb_nan),

                .opa_00(opa_00), .opb_00(opb_00),

                .opa_inf(opa_inf), .opb_inf(opb_inf),

                .opa_dn(opa_dn), .opb_dn(opb_dn)

                );

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

//

// Pre-Normalize block

// - Adjusts the numbers to equal exponents and sorts them

// - determine result sign

// - determine actual operation to perform (add or sub)

//

wire            nan_sign_d, result_zero_sign_d;

reg             sign_fasu_r;

wire    [7:0]    exp_mul;

wire            sign_mul;

reg             sign_mul_r;

wire    [23:0]   fracta_mul, fractb_mul;

wire            inf_mul;

reg             inf_mul_r;

wire    [1:0]    exp_ovf;

reg     [1:0]    exp_ovf_r;

wire            sign_exe;

reg             sign_exe_r;

wire    [2:0]    underflow_fmul_d;

pre_norm u1(.clk(clk),                          // System Clock

        .rmode(rmode_r2),                       // Roundin Mode

        .add(!fpu_op_r1[0]),                     // Add/Sub Input

        .opa(opa_r),  .opb(opb_r),              // Registered OP Inputs

        .opa_nan(opa_nan),                      // OpA is a NAN indicator

        .opb_nan(opb_nan),                      // OpB is a NAN indicator

        .fracta_out(fracta),                    // Equalized and sorted fraction

        .fractb_out(fractb),                    // outputs (Registered)

        .exp_dn_out(exp_fasu),                  // Selected exponent output (registered);

        .sign(sign_fasu),                       // Encoded output Sign (registered)

        .nan_sign(nan_sign_d),                  // Output Sign for NANs (registered)

        .result_zero_sign(result_zero_sign_d),  // Output Sign for zero result (registered)

        .fasu_op(fasu_op)                       // Actual fasu operation output (registered)

        );

always @(posedge clk)

        sign_fasu_r <= #1 sign_fasu;

pre_norm_fmul u2(

                .clk(clk),

                .fpu_op(fpu_op_r1),

                .opa(opa_r), .opb(opb_r),

                .fracta(fracta_mul),

                .fractb(fractb_mul),

                .exp_out(exp_mul),      // FMUL exponent output (registered)

                .sign(sign_mul),        // FMUL sign output (registered)

                .sign_exe(sign_exe),    // FMUL exception sign output (registered)

                .inf(inf_mul),          // FMUL inf output (registered)

                .exp_ovf(exp_ovf),      // FMUL exponnent overflow output (registered)

                .underflow(underflow_fmul_d)

                );

always @(posedge clk)

        sign_mul_r <= #1 sign_mul;

always @(posedge clk)

        sign_exe_r <= #1 sign_exe;

always @(posedge clk)

        inf_mul_r <= #1 inf_mul;

always @(posedge clk)

        exp_ovf_r <= #1 exp_ovf;

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

//

// Add/Sub

//

add_sub27 u3(

        .add(fasu_op),                  // Add/Sub

        .opa(fracta),                   // Fraction A input

        .opb(fractb),                   // Fraction B Input

        .sum(fract_out_d),              // SUM output

        .co(co_d) );                    // Carry Output

always @(posedge clk)

        fract_out_q <= #1 {co_d, fract_out_d};

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

//

// Mul

//

wire    [47:0]   prod;

mul_r2 u5(.clk(clk), .opa(fracta_mul), .opb(fractb_mul), .prod(prod));

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

//

// Divide

//

wire    [49:0]   quo;

wire    [49:0]   fdiv_opa;

wire    [49:0]   remainder;

wire            remainder_00;

reg     [4:0]    div_opa_ldz_d, div_opa_ldz_r1, div_opa_ldz_r2;

always @(fracta_mul)

        casex(fracta_mul[22:0])

           23'b1??????????????????????: div_opa_ldz_d = 1;

           23'b01?????????????????????: div_opa_ldz_d = 2;

           23'b001????????????????????: div_opa_ldz_d = 3;

           23'b0001???????????????????: div_opa_ldz_d = 4;

           23'b00001??????????????????: div_opa_ldz_d = 5;

           23'b000001?????????????????: div_opa_ldz_d = 6;

           23'b0000001????????????????: div_opa_ldz_d = 7;

           23'b00000001???????????????: div_opa_ldz_d = 8;

           23'b000000001??????????????: div_opa_ldz_d = 9;

           23'b0000000001?????????????: div_opa_ldz_d = 10;

           23'b00000000001????????????: div_opa_ldz_d = 11;

           23'b000000000001???????????: div_opa_ldz_d = 12;

           23'b0000000000001??????????: div_opa_ldz_d = 13;

           23'b00000000000001?????????: div_opa_ldz_d = 14;

           23'b000000000000001????????: div_opa_ldz_d = 15;

           23'b0000000000000001???????: div_opa_ldz_d = 16;

           23'b00000000000000001??????: div_opa_ldz_d = 17;

           23'b000000000000000001?????: div_opa_ldz_d = 18;

           23'b0000000000000000001????: div_opa_ldz_d = 19;

           23'b00000000000000000001???: div_opa_ldz_d = 20;

           23'b000000000000000000001??: div_opa_ldz_d = 21;

           23'b0000000000000000000001?: div_opa_ldz_d = 22;

           23'b0000000000000000000000?: div_opa_ldz_d = 23;

        endcase

assign fdiv_opa = !(|opa_r[30:23]) ? {(fracta_mul<<div_opa_ldz_d), 26'h0} : {fracta_mul, 26'h0};

div_r2 u6(.clk(clk), .opa(fdiv_opa), .opb(fractb_mul), .quo(quo), .rem(remainder));

assign remainder_00 = !(|remainder);

always @(posedge clk)

        div_opa_ldz_r1 <= #1 div_opa_ldz_d;

always @(posedge clk)

        div_opa_ldz_r2 <= #1 div_opa_ldz_r1;

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

//

// Normalize Result

//

wire            ine_d;

wire    [47:0]   fract_denorm, fract_div;

wire            sign_d;

reg             sign;

always @(posedge clk)                   // Exponent must be once cycle delayed

        exp_r <= #1 fpu_op_r2[1] ? exp_mul : exp_fasu;

assign fract_div = (opb_dn ? quo[49:2] : {quo[26:0], 21'h0});

assign fract_denorm =  !fpu_op_r3[1] ? {fract_out_q, 20'h0}:

                        fpu_op_r3[0] ? fract_div : prod;

assign sign_d = fpu_op_r2[1] ? sign_mul : sign_fasu;

always @(posedge clk)

        sign <= #1 (rmode_r2==2'h3) ? !sign_d : sign_d;

post_norm u4(.clk(clk),                 // System Clock

        .fpu_op(fpu_op_r3),             // Floating Point Operation

        .sign(sign),                    // Sign of the result

        .rmode(rmode_r3),               // Rounding mode

        .fract_in(fract_denorm),        // Fraction Input

        .exp_ovf(exp_ovf_r),            // Exponent Overflow

        .exp_in(exp_r),                 // Exponent Input

        .opa_dn(opa_dn),                // Operand A Denormalized

        .opb_dn(opb_dn),                // Operand A Denormalized

        .rem_00(remainder_00),          // Diveide Remainder is zero

        .div_opa_ldz(div_opa_ldz_r2),   // Divide opa leading zeros count

        .output_zero(mul_00 | div_00),  // Force output to Zero

        .out(out_d),                    // Normalized output (un-registered)

        .ine(ine_d),                    // Result Inexact output (un-registered)

        .overflow(overflow_d),          // Overflow output (un-registered)

        .underflow(underflow_d)         // Underflow output (un-registered)

        );

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

//

// FPU Outputs

//

reg             fasu_op_r1, fasu_op_r2;

wire    [30:0]   out_fixed;

wire            output_zero_fasu;

wire            output_zero_fdiv;

wire            output_zero_fmul;

reg             inf_mul2;

wire            overflow_fasu;

wire            overflow_fmul;

wire            overflow_fdiv;

wire            inf_fmul;

wire            sign_mul_final;

wire            out_d_00;

wire            sign_div_final;

wire            ine_mul, ine_mula, ine_div, ine_fasu;

wire            underflow_fasu, underflow_fmul, underflow_fdiv;

wire            underflow_fmul1;

reg     [2:0]    underflow_fmul_r;

reg             opa_nan_r;

always @(posedge clk)

        fasu_op_r1 <= #1 fasu_op;

always @(posedge clk)

        fasu_op_r2 <= #1 fasu_op_r1;

always @(posedge clk)

        inf_mul2 <= #1 exp_mul == 8'hff;

// Force pre-set values for non numerical output

assign mul_inf = (fpu_op_r3==3'b010) & (inf_mul_r | inf_mul2) & (rmode_r3==2'h0);

assign div_inf = (fpu_op_r3==3'b011) & (opb_00 | opa_inf);

assign mul_00 = (fpu_op_r3==3'b010) & (opa_00 | opb_00);

assign div_00 = (fpu_op_r3==3'b011) & (opa_00 | opb_inf);

assign out_fixed = (    (qnan_d | snan_d) |

                        (ind_d & !fasu_op_r2) |

                        ((fpu_op_r3==3'b011) & opb_00 & opa_00) |

                        (((opa_inf & opb_00) | (opb_inf & opa_00 )) & fpu_op_r3==3'b010)

                   )  ? QNAN : INF;

always @(posedge clk)

        out[30:0] <= #1 (mul_inf | div_inf | (inf_d & (fpu_op_r3!=3'b011)) | snan_d | qnan_d) ? out_fixed :

                        out_d;

assign out_d_00 = !(|out_d);

assign sign_mul_final = (sign_exe_r & ((opa_00 & opb_inf) | (opb_00 & opa_inf))) ? !sign_mul_r : sign_mul_r;

assign sign_div_final = (sign_exe_r & (opa_inf & opb_inf)) ? !sign_mul_r : sign_mul_r | (opa_00 & opb_00);

always @(posedge clk)

        out[31] <= #1   ((fpu_op_r3==3'b010) & !(snan_d | qnan_d)) ?    sign_mul_final :

                        ((fpu_op_r3==3'b011) & !(snan_d | qnan_d)) ?    sign_div_final :

                        (snan_d | qnan_d | ind_d) ?                     nan_sign_d :

                        output_zero_fasu ?                              result_zero_sign_d :

                                                                        sign_fasu_r;

// Exception Outputs

assign ine_mula = ((inf_mul_r |  inf_mul2 | opa_inf | opb_inf) & (rmode_r3==2'h1) &

                !((opa_inf & opb_00) | (opb_inf & opa_00 )) & fpu_op_r3[1]);

assign ine_mul  = (ine_mula | ine_d | inf_fmul | out_d_00 | overflow_d | underflow_d) &

                  !opa_00 & !opb_00 & !(snan_d | qnan_d | inf_d);

assign ine_div  = (ine_d | overflow_d | underflow_d) & !(opb_00 | snan_d | qnan_d | inf_d);

assign ine_fasu = (ine_d | overflow_d | underflow_d) & !(snan_d | qnan_d | inf_d);

always @(posedge  clk)

        ine <= #1 !fpu_op_r3[1] ? ine_fasu :

                   fpu_op_r3[0] ? ine_div  : ine_mul;

assign overflow_fasu = overflow_d & !(snan_d | qnan_d | inf_d);

assign overflow_fmul = !inf_d & (inf_mul_r | inf_mul2 | overflow_d) & !(snan_d | qnan_d);

assign overflow_fdiv = (overflow_d & !(opb_00 | inf_d | snan_d | qnan_d));

always @(posedge clk)

        overflow <= #1 !fpu_op_r3[1] ? overflow_fasu :

                        fpu_op_r3[0] ? overflow_fdiv : overflow_fmul;

always @(posedge clk)

        underflow_fmul_r <= #1 underflow_fmul_d;

assign underflow_fmul1 = underflow_fmul_r[0] |

                        (underflow_fmul_r[1] & underflow_d ) |

                        ((opa_dn | opb_dn) & out_d_00 & (prod!=0) & sign) |

                        (underflow_fmul_r[2] & ((out_d[30:23]==0) | (out_d[22:0]==0)));

assign underflow_fasu = underflow_d & !(inf_d | snan_d | qnan_d);

assign underflow_fmul = underflow_fmul1 & !(snan_d | qnan_d | inf_mul_r);

assign underflow_fdiv = underflow_fasu & !opb_00;

always @(posedge clk)

        underflow <= #1 !fpu_op_r3[1] ? underflow_fasu :

                         fpu_op_r3[0] ? underflow_fdiv : underflow_fmul;

always @(posedge clk)

        snan <= #1 snan_d;

// synopsys translate_off

wire            mul_uf_del;

wire            uf2_del, ufb2_del, ufc2_del,  underflow_d_del;

wire            co_del;

wire    [30:0]   out_d_del;

wire            ov_fasu_del, ov_fmul_del;

wire    [2:0]    fop;

wire    [4:0]    ldza_del;

wire    [49:0]   quo_del;

delay1  #0 ud000(clk, underflow_fmul1, mul_uf_del);

delay1  #0 ud001(clk, underflow_fmul_r[0], uf2_del);

delay1  #0 ud002(clk, underflow_fmul_r[1], ufb2_del);

delay1  #0 ud003(clk, underflow_d, underflow_d_del);

delay1  #0 ud004(clk, test.u0.u4.exp_out1_co, co_del);

delay1  #0 ud005(clk, underflow_fmul_r[2], ufc2_del);

delay1 #30 ud006(clk, out_d, out_d_del);

delay1  #0 ud007(clk, overflow_fasu, ov_fasu_del);

delay1  #0 ud008(clk, overflow_fmul, ov_fmul_del);

delay1  #2 ud009(clk, fpu_op_r3, fop);

delay3  #4 ud010(clk, div_opa_ldz_d, ldza_del);

delay1  #49 ud012(clk, quo, quo_del);

always @(test.error_event)

   begin

        #0.2

        $display("muf: %b uf0: %b uf1: %b uf2: %b, tx0: %b, co: %b, out_d: %h (%h %h), ov_fasu: %b, ov_fmul: %b, fop: %h",

                        mul_uf_del, uf2_del, ufb2_del, ufc2_del, underflow_d_del, co_del, out_d_del, out_d_del[30:23], out_d_del[22:0],

                        ov_fasu_del, ov_fmul_del, fop );

        $display("ldza: %h, quo: %b",

                        ldza_del, quo_del);

   end

// synopsys translate_on

// Status Outputs

always @(posedge clk)

        qnan <= #1      snan_d | qnan_d | (ind_d & !fasu_op_r2) |

                        (opa_00 & opb_00 & fpu_op_r3==3'b011) |

                        (((opa_inf & opb_00) | (opb_inf & opa_00 )) & fpu_op_r3==3'b010);

assign inf_fmul =       (((inf_mul_r | inf_mul2) & (rmode_r3==2'h0)) | opa_inf | opb_inf) &

                        !((opa_inf & opb_00) | (opb_inf & opa_00 )) &

                        fpu_op_r3==3'b010;

always @(posedge clk)

        inf <= #1       !(qnan_d | snan_d) & (

                                                ((&out_d[30:23]) & !(|out_d[22:0]) & !(opb_00 & fpu_op_r3==3'b011)) |

                                                (inf_d & !(ind_d & !fasu_op_r2) & !fpu_op_r3[1]) |

                                                inf_fmul |

                                                (!opa_00 & opb_00 & fpu_op_r3==3'b011) |

                                                (fpu_op_r3==3'b011 & opa_inf & !opb_inf)

                                        );

assign output_zero_fasu = out_d_00 & !(inf_d | snan_d | qnan_d);

assign output_zero_fdiv = (div_00 | (out_d_00 & !opb_00)) & !(opa_inf & opb_inf) &

                          !(opa_00 & opb_00) & !(qnan_d | snan_d);

assign output_zero_fmul = (out_d_00 | opa_00 | opb_00) &

                          !(inf_mul_r | inf_mul2 | opa_inf | opb_inf | snan_d | qnan_d) &

                          !(opa_inf & opb_00) & !(opb_inf & opa_00);

always @(posedge clk)

        zero <= #1      fpu_op_r3==3'b011 ?     output_zero_fdiv :

                        fpu_op_r3==3'b010 ?     output_zero_fmul :

                                                output_zero_fasu ;

always @(posedge clk)

        opa_nan_r <= #1 !opa_nan & fpu_op_r2==3'b011;

always @(posedge clk)

        div_by_zero <= #1 opa_nan_r & !opa_00 & !opa_inf & opb_00;

endmodule