cvw/pipelined/src/ieu/extend.sv

///////////////////////////////////////////
// extend.sv
//
// Written: David_Harris@hmc.edu 9 January 2021
// Modified: 
//
// Purpose: 
// 
// A component of the Wally configurable RISC-V project.
// 
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, 
// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software 
// is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT 
// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
///////////////////////////////////////////

`include "wally-config.vh"

module extend (
  input  logic [31:7]       InstrD,
  input  logic [2:0]        ImmSrcD,
  output logic [`XLEN-1:0 ] ExtImmD);

  localparam [`XLEN-1:0] undefined = {(`XLEN){1'bx}}; // could change to 0 after debug
 
//  generate
    always_comb
      case(ImmSrcD) 
                // I-type 
        3'b000:   ExtImmD = {{(`XLEN-12){InstrD[31]}}, InstrD[31:20]};  
                // S-type (stores)
        3'b001:   ExtImmD = {{(`XLEN-12){InstrD[31]}}, InstrD[31:25], InstrD[11:7]}; 
                // B-type (branches)
        3'b010:   ExtImmD = {{(`XLEN-12){InstrD[31]}}, InstrD[7], InstrD[30:25], InstrD[11:8], 1'b0}; 
                // J-type (jal)
        3'b011:   ExtImmD = {{(`XLEN-20){InstrD[31]}}, InstrD[19:12], InstrD[20], InstrD[30:21], 1'b0}; 
                // U-type (lui, auipc)
        3'b100:  ExtImmD = {{(`XLEN-31){InstrD[31]}}, InstrD[30:12], 12'b0}; 
                // Store Conditional: zero offset
        3'b101:  if (`A_SUPPORTED) ExtImmD = 0;
                 else              ExtImmD = undefined;
        default: ExtImmD = undefined; // undefined
      endcase  
//  endgenerate           
endmodule