commit bd3556ff994ac7b4a2ed1d220bb926745deb5544
Author: Florian Zaruba <fl.zaruba@be4web.net>
Date:   Sat Mar 18 19:55:23 2017 +0100

    Added simple register file and README

diff --git a/README.md b/README.md
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+# Ariane RISC-V CPU
+
+6 stage, out-of-order RISC-V CPU
+
+## Regfile
+
+The register file has two read ports and one write port. 
diff --git a/regfile.sv b/regfile.sv
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+// Copyright 2015 ETH Zurich and University of Bologna.
+// Copyright and related rights are licensed under the Solderpad Hardware
+// License, Version 0.51 (the “License”); you may not use this file except in
+// compliance with the License.  You may obtain a copy of the License at
+// http://solderpad.org/licenses/SHL-0.51. Unless required by applicable law
+// or agreed to in writing, software, hardware and materials distributed under
+// this 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.
+
+////////////////////////////////////////////////////////////////////////////////
+// Engineer:       Francesco Conti - f.conti@unibo.it                         //
+//                                                                            //
+// Additional contributions by:                                               //
+//                 Michael Gautschi - gautschi@iis.ee.ethz.ch                 //
+//                                                                            //
+// Design Name:    RISC-V register file                                       //
+// Project Name:   RI5CY                                                      //
+// Language:       SystemVerilog                                              //
+//                                                                            //
+// Description:    Register file with 31x 32 bit wide registers. Register 0   //
+//                 is fixed to 0. This register file is based on flip-flops.  //
+//                 Also supports the fp-register file now if FPU=1            //
+//                                                                            //
+////////////////////////////////////////////////////////////////////////////////
+
+module regfile
+#(
+    parameter ADDR_WIDTH    = 5,
+    parameter DATA_WIDTH    = 32
+)
+(
+    // Clock and Reset
+    input  logic                   clk,
+    input  logic                   rst_n,
+
+    input  logic                   test_en_i,
+
+    //Read port R1
+    input  logic [ADDR_WIDTH-1:0]  raddr_a_i,
+    output logic [DATA_WIDTH-1:0]  rdata_a_o,
+
+    //Read port R2
+    input  logic [ADDR_WIDTH-1:0]  raddr_b_i,
+    output logic [DATA_WIDTH-1:0]  rdata_b_o,
+
+    // Write port W1
+    input logic [ADDR_WIDTH-1:0]   waddr_a_i,
+    input logic [DATA_WIDTH-1:0]   wdata_a_i,
+    input logic                    we_a_i
+);
+
+  // number of integer registers
+  localparam    NUM_WORDS     = 2**ADDR_WIDTH;
+
+  // integer register file
+  logic [NUM_WORDS-1:0][DATA_WIDTH-1:0] rf_reg;
+
+  genvar i,j;
+  generate
+
+    // R0 is nil
+    // Being explicit because of Verilator misunderstanding the always zero comb
+    always_ff @(posedge clk or negedge rst_n) begin
+      if(~rst_n) begin
+        // R0 is nil
+        rf_reg[0] <= 32'b0;
+      end else begin
+        // R0 is nil
+        rf_reg[0] <= 32'b0;
+      end
+    end
+
+    // loop from 1 to NUM_WORDS-1 as R0 is nil
+    for (i = 1; i < NUM_WORDS; i++)
+    begin : rf_gen
+
+      always_ff @(posedge clk, negedge rst_n)
+      begin : register_write_behavioral
+        if (rst_n == 1'b0) begin
+          rf_reg[i] <= 32'b0;
+        end else begin
+          if(we_a_i)
+            rf_reg[$unsigned(waddr_a_i)] <= wdata_a_i;
+        end
+      end
+
+    end
+
+
+  endgenerate
+
+assign rdata_a_o = rf_reg[raddr_a_i[4:0]];
+assign rdata_b_o = rf_reg[raddr_b_i[4:0]];
+
+endmodule
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