cvw/wally-pipelined/src/muldiv/intdivrestoringstep.sv

///////////////////////////////////////////
// intdivrestoringstep.sv
//
// Written: David_Harris@hmc.edu 2 October 2021
// Modified: 
//
// Purpose: Restoring integer division using a shift register and subtractor
// 
// 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 intdivrestoringstep(
  input  logic [`XLEN-1:0] W, XQ, DAbsB,
  output logic [`XLEN-1:0] WOut, XQOut);

  logic [`XLEN-1:0] WShift, WPrime;
  logic qi, qib;
  
  assign {WShift, XQOut} = {W[`XLEN-2:0], XQ, qi};
  adder #(`XLEN+1) wdsub({1'b0, WShift}, {1'b1, DAbsB}, {qib, WPrime});
  //assign {qib, WPrime} = {1'b0, WShift} + {1'b1, DAbsB}; // effective subtractor, carry out determines quotient bit
  assign qi = ~qib;
  mux2 #(`XLEN) wrestoremux(WShift, WPrime, qi, WOut);
endmodule