Subversion Repositories openrisc_2011-10-31

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////  or1200_fpu_fcmp                                            ////

////  Single precision Floating Point Compare Unit               ////

////                                                             ////

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

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

////                                                             ////

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////                                                             ////

//// 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        ////

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//// 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.                                 ////

////                                                             ////

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`timescale 1ns / 100ps

module or1200_fpu_fcmp(opa, opb, unordered, altb, blta, aeqb, inf, zero);

input   [31:0]   opa, opb;

output          unordered;

output          altb, blta, aeqb;

output          inf, zero;

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

//

// Local Wire

//

reg             altb, blta, aeqb;

wire            signa, signb;

wire    [7:0]    expa, expb;

wire    [22:0]   fracta, fractb;

wire            expa_ff, expb_ff, fracta_00, fractb_00;

wire            qnan_a, snan_a, qnan_b, snan_b, opa_inf, opb_inf, inf;

wire            qnan, snan, opa_zero, opb_zero;

wire            exp_eq, exp_gt, exp_lt;

wire            fract_eq, fract_gt, fract_lt;

wire            all_zero;

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

//

// Aliases

//

assign  signa = opa[31];

assign  signb = opb[31];

assign   expa = opa[30:23];

assign   expb = opb[30:23];

assign fracta = opa[22:0];

assign fractb = opb[22:0];

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

//

// Exception Logic

//

assign expa_ff = &expa;

assign expb_ff = &expb;

assign fracta_00 = !(|fracta);

assign fractb_00 = !(|fractb);

assign qnan_a =  fracta[22];

assign snan_a = !fracta[22] & |fracta[21:0];

assign qnan_b =  fractb[22];

assign snan_b = !fractb[22] & |fractb[21:0];

assign opa_inf = (expa_ff & fracta_00);

assign opb_inf = (expb_ff & fractb_00);

assign inf  = opa_inf | opb_inf;

assign qnan = (expa_ff & qnan_a) | (expb_ff & qnan_b);

assign snan = (expa_ff & snan_a) | (expb_ff & snan_b);

assign unordered = qnan | snan;

assign opa_zero = !(|expa) & fracta_00;

assign opb_zero = !(|expb) & fractb_00;

assign zero = opa_zero;

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

//

// Comparison Logic

//

assign exp_eq = expa == expb;

assign exp_gt = expa  > expb;

assign exp_lt = expa  < expb;

assign fract_eq = fracta == fractb;

assign fract_gt = fracta  > fractb;

assign fract_lt = fracta  < fractb;

assign all_zero = opa_zero & opb_zero;

always @( qnan or snan or opa_inf or opb_inf or signa or signb or exp_eq or exp_gt or

        exp_lt or fract_eq or fract_gt or fract_lt or all_zero)

        casex( {qnan, snan, opa_inf, opb_inf, signa, signb, exp_eq, exp_gt, exp_lt, fract_eq, fract_gt, fract_lt, all_zero})

           //13'b??_??_??_???_???_?: {altb, blta, aeqb} = 3'b000;

           13'b1?_??_??_???_???_?: {altb, blta, aeqb} = 3'b000; // qnan

           13'b?1_??_??_???_???_?: {altb, blta, aeqb} = 3'b000; // snan

           13'b00_11_00_???_???_?: {altb, blta, aeqb} = 3'b001; // both op INF comparisson

           13'b00_11_01_???_???_?: {altb, blta, aeqb} = 3'b100;

           13'b00_11_10_???_???_?: {altb, blta, aeqb} = 3'b010;

           13'b00_11_11_???_???_?: {altb, blta, aeqb} = 3'b001;

           13'b00_10_00_???_???_?: {altb, blta, aeqb} = 3'b100; // opa INF comparisson

           13'b00_10_01_???_???_?: {altb, blta, aeqb} = 3'b100;

           13'b00_10_10_???_???_?: {altb, blta, aeqb} = 3'b010;

           13'b00_10_11_???_???_?: {altb, blta, aeqb} = 3'b010;

           13'b00_01_00_???_???_?: {altb, blta, aeqb} = 3'b010; // opb INF comparisson

           13'b00_01_01_???_???_?: {altb, blta, aeqb} = 3'b100;

           13'b00_01_10_???_???_?: {altb, blta, aeqb} = 3'b010;

           13'b00_01_11_???_???_?: {altb, blta, aeqb} = 3'b100;

           13'b00_00_10_???_???_0: {altb, blta, aeqb} = 3'b010; //compare base on sign

           13'b00_00_01_???_???_0: {altb, blta, aeqb} = 3'b100; //compare base on sign

           13'b00_00_??_???_???_1: {altb, blta, aeqb} = 3'b001; //compare base on sign both are zero

           13'b00_00_00_010_???_?: {altb, blta, aeqb} = 3'b100; // cmp exp, equal sign

           13'b00_00_00_001_???_?: {altb, blta, aeqb} = 3'b010;

           13'b00_00_11_010_???_?: {altb, blta, aeqb} = 3'b010;

           13'b00_00_11_001_???_?: {altb, blta, aeqb} = 3'b100;

           13'b00_00_00_100_010_?: {altb, blta, aeqb} = 3'b100; // compare fractions, equal sign, equal exp

           13'b00_00_00_100_001_?: {altb, blta, aeqb} = 3'b010;

           13'b00_00_11_100_010_?: {altb, blta, aeqb} = 3'b010;

           13'b00_00_11_100_001_?: {altb, blta, aeqb} = 3'b100;

           13'b00_00_00_100_100_?: {altb, blta, aeqb} = 3'b001;

           13'b00_00_11_100_100_?: {altb, blta, aeqb} = 3'b001;

           default: {altb, blta, aeqb} = 3'bxxx;

        endcase

endmodule // or1200_fpu_fcmp