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

///////////////////////////////////////////
// redundantmul.sv
//
// Written: David_Harris@hmc.edu and ssanghai@hm.edu 10/11/2021
// Modified: 
//
// Purpose: multiplier with output in redundant carry-sum form
//          This can be faster than a mutiplier that requires a final adder to obtain the nonredundant answer.
//          The module has several implementations controlled by the DESIGN_COMPILER flag.
//          When DESIGN_COMPILER = 1, use the Synopsys DesignWare DW02_multp block.  This will give highest quality results
//                                    but doesn't work in simulation or when using different tools
//          When DESIGN_COMPILER = 2, use the Wally mult_cs block with Radix 2 Booth encoding and a Wallace Tree
//                                    This simulates and synthesizes, but quality of results ae lower than DesignWare
//          Otherwise, just use a nonredundant multiplier and set one word to 0.  This is best for FPGAs, which have
//                                    block multipliers, and also simulates fastest.
// 
// 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 redundantmul #(parameter WIDTH =8)(
  input logic [WIDTH-1:0]    a,b,
  output logic [2*WIDTH-1:0] out0, out1);

  // 

   generate
      if (`DESIGN_COMPILER == 1) 
	begin
        logic [2*WIDTH-1+2:0]     tmp_out0; // DW02_
        logic [2*WIDTH-1+2:0]     tmp_out1;   
	  DW02_multp #(WIDTH, WIDTH, 2*WIDTH+2) mul(.a, .b, .tc(1'b0), .out0(tmp_out0), .out1(tmp_out1));
	  assign out0 = tmp_out0[2*WIDTH-1:0];
	  assign out1 = tmp_out1[2*WIDTH-1:0];
	end
      else if (`DESIGN_COMPILER == 2)
	  mult_cs #(WIDTH) mul(.a, .b, .tc(1'b0), .sum(out0), .carry(out1));
      else begin // force a nonredunant multipler.  This will simulate properly and also is appropriate for FPGAs.
	 assign out0 = a * b;
	 assign out1 = 0;
      end
  endgenerate

endmodule