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//=============================================================================

//      (C) 2006-2011  Robert Finch

//      All rights reserved.

//      robfinch@opencores.org

//

//      rolx4.v

//              Rotate or shift left by multiples of four bits.

//

//

//

// This source file is free software: you can redistribute it and/or modify 

// it under the terms of the GNU Lesser General Public License as published 

// by the Free Software Foundation, either version 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file is distributed in the hope that it will be useful,      

// but WITHOUT ANY WARRANTY; without even the implied warranty of           

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            

// GNU General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//                                                                          

//

//      Rotate or arithmetic shift left by 0, 4, 8 or 12 bits.

//      Parameterized with a default width of 32 bits.

//

//      Resource Usage Samples:

//      Ref. SpartanII

//      64 LUTs

//      

//      Webpack 7.1i xc3s1000-4ft256

//      64 LUTs / 32 slices / 11 ns             (32 bits)

//=============================================================================

//

// rol 0,4,8 or 12 bits

module rolx4

#(parameter WID = 32)

(

input op,

input [WID:1] a,

input [1:0] b,

output reg [WID:1] o

);

wire [12:1] opx = {12{op}};

always @(a, b, opx)

begin

        case (b)

        2'd0:   o <= a;

        2'd1:   o <= {a[WID- 4%WID:1],a[WID:WID- 3%WID]&opx[ 4:1]};

        2'd2:   o <= {a[WID- 8%WID:1],a[WID:WID- 7%WID]&opx[ 8:1]};

        2'd3:   o <= {a[WID-12%WID:1],a[WID:WID-11%WID]&opx[12:1]};

        endcase

end

endmodule