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ultra_embe |
//-----------------------------------------------------------------
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// AltOR32
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// Alternative Lightweight OpenRisc
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// V2.0
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// Ultra-Embedded.com
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// Copyright 2011 - 2013
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//
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// Email: admin@ultra-embedded.com
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//
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// License: LGPL
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//-----------------------------------------------------------------
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//
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// Copyright (C) 2011 - 2013 Ultra-Embedded.com
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//
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// This source file may be used and distributed without
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// restriction provided that this copyright statement is not
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// removed from the file and that any derivative work contains
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// the original copyright notice and the associated disclaimer.
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//
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// This source file is free software; you can redistribute it
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// and/or modify it under the terms of the GNU Lesser General
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// Public License as published by the Free Software Foundation;
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// either version 2.1 of the License, or (at your option) any
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// later version.
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//
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// This source is distributed in the hope that it will be
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// useful, but WITHOUT ANY WARRANTY; without even the implied
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// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the GNU Lesser General Public License for more
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// details.
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//
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// You should have received a copy of the GNU Lesser General
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// Public License along with this source; if not, write to the
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// Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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// Boston, MA 02111-1307 USA
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//-----------------------------------------------------------------
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//-----------------------------------------------------------------
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// Includes
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//-----------------------------------------------------------------
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`include "altor32_defs.v"
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//-----------------------------------------------------------------
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// Module: Load Forwarding Unit
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//-----------------------------------------------------------------
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module altor32_lfu
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(
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// Opcode
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input [7:0] opcode_i /*verilator public*/,
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// Memory load result
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input [31:0] mem_result_i /*verilator public*/,
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input [1:0] mem_offset_i /*verilator public*/,
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// Result
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output reg [31:0] load_result_o /*verilator public*/,
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output reg load_insn_o /*verilator public*/
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);
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//-------------------------------------------------------------------
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// Load forwarding unit
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//-------------------------------------------------------------------
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always @ *
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begin
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load_result_o = 32'h00000000;
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load_insn_o = 1'b0;
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case (opcode_i)
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`INST_OR32_LBS: // l.lbs
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begin
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case (mem_offset_i)
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2'b00 : load_result_o[7:0] = mem_result_i[31:24];
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2'b01 : load_result_o[7:0] = mem_result_i[23:16];
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2'b10 : load_result_o[7:0] = mem_result_i[15:8];
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2'b11 : load_result_o[7:0] = mem_result_i[7:0];
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default : ;
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endcase
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// Sign extend LB
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if (load_result_o[7] == 1'b1)
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load_result_o[31:8] = 24'hFFFFFF;
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load_insn_o = 1'b1;
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end
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`INST_OR32_LBZ: // l.lbz
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begin
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case (mem_offset_i)
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2'b00 : load_result_o[7:0] = mem_result_i[31:24];
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2'b01 : load_result_o[7:0] = mem_result_i[23:16];
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2'b10 : load_result_o[7:0] = mem_result_i[15:8];
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2'b11 : load_result_o[7:0] = mem_result_i[7:0];
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default : ;
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endcase
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load_insn_o = 1'b1;
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end
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`INST_OR32_LHS: // l.lhs
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begin
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case (mem_offset_i)
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2'b00 : load_result_o[15:0] = mem_result_i[31:16];
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2'b10 : load_result_o[15:0] = mem_result_i[15:0];
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default : ;
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endcase
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// Sign extend LH
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if (load_result_o[15] == 1'b1)
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load_result_o[31:16] = 16'hFFFF;
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load_insn_o = 1'b1;
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end
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`INST_OR32_LHZ: // l.lhz
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begin
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case (mem_offset_i)
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2'b00 : load_result_o[15:0] = mem_result_i[31:16];
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2'b10 : load_result_o[15:0] = mem_result_i[15:0];
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default : ;
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endcase
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load_insn_o = 1'b1;
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end
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`INST_OR32_LWZ, `INST_OR32_LWS: // l.lwz l.lws
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begin
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load_result_o = mem_result_i;
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load_insn_o = 1'b1;
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end
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default :
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;
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endcase
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end
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endmodule
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