cvw/pipelined/src/fpu/fclassify.sv

///////////////////////////////////////////
// fclassivy.sv
//
// Written: me@KatherineParry.com
// Modified: 7/5/2022
//
// Purpose: Floating-point classify unit
// 
// A component of the CORE-V-WALLY configurable RISC-V project.
// 
// Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
//
// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
//
// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file 
// except in compliance with the License, or, at your option, the Apache License version 2.0. You 
// may obtain a copy of the License at
//
// https://solderpad.org/licenses/SHL-2.1/
//
// Unless required by applicable law or agreed to in writing, any work distributed under the 
// License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
// either express or implied. See the License for the specific language governing permissions 
// and limitations under the License.
////////////////////////////////////////////////////////////////////////////////////////////////
`include "wally-config.vh"

module fclassify (
    input  logic                Xs,         // sign bit
    input  logic                XNaN,       // is NaN
    input  logic                XSNaN,      // is signaling NaN
    input  logic                XSubnorm,   // is Subnormal
    input  logic                XZero,      // is zero
    input  logic                XInf,       // is infinity
    output logic [`XLEN-1:0]    ClassRes    // classify result
);

    logic PInf, PZero, PNorm, PSubnorm; // is the input a positive infinity/zero/normal/subnormal
    logic NInf, NZero, NNorm, NSubnorm; // is the input a negitive infinity/zero/normal/subnormal
    logic XNorm;                        // is the input normal
   
    // determine the sub categories
    assign XNorm= ~(XNaN | XInf| XSubnorm| XZero);
    assign PInf = ~Xs&XInf;
    assign NInf = Xs&XInf;
    assign PNorm = ~Xs&XNorm;
    assign NNorm = Xs&XNorm;
    assign PSubnorm = ~Xs&XSubnorm;
    assign NSubnorm = Xs&XSubnorm;
    assign PZero = ~Xs&XZero;
    assign NZero = Xs&XZero;

    // determine sub category and combine into the result
    //  bit 0 - -Inf
    //  bit 1 - -Norm
    //  bit 2 - -Subnorm
    //  bit 3 - -Zero
    //  bit 4 - +Zero
    //  bit 5 - +Subnorm
    //  bit 6 - +Norm
    //  bit 7 - +Inf
    //  bit 8 - signaling NaN
    //  bit 9 - quiet NaN
    assign ClassRes = {{`XLEN-10{1'b0}}, XNaN&~XSNaN, XSNaN, PInf, PNorm, PSubnorm, PZero, NZero, NSubnorm, NNorm, NInf};

endmodule