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// ============================================================================
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// __
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// \\__/ o\ (C) 2017-2019 Robert Finch, Waterloo
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// \ __ / All rights reserved.
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// \/_// robfinch<remove>@finitron.ca
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// ||
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//
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// FT64_EvalBranch.v
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// - FT64 branch evaluation
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//
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// This source file is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This source file is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//
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// ============================================================================
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//
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`define TRUE 1'b1
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`define BNEI 6'h12
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`define BBc 6'h26
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`define Bcc 6'h30
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`define BEQI 6'h32
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`define BCHK 6'h33
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`define CHK 6'h34
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`define BEQ 3'h0
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`define BNE 3'h1
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`define BLT 3'h2
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`define BGE 3'h3
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`define BLTU 3'h6
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`define BGEU 3'h7
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`define BAND 3'h0
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`define BOR 3'h1
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`define BXOR 3'd2
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`define BNAND 3'h4
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`define BNOR 3'h5
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`define BXNOR 3'd6
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`define IBNE 2'd2
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`define DBNZ 2'd3
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module FT64_EvalBranch(instr, a, b, c, takb);
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parameter WID=64;
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input [47:0] instr;
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input [WID-1:0] a;
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input [WID-1:0] b;
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input [WID-1:0] c;
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output reg takb;
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wire [5:0] opcode = instr[5:0];
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//Evaluate branch condition
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always @*
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case(opcode)
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`Bcc:
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case(instr[15:13])
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`BEQ: takb <= a==b;
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`BNE: takb <= a!=b;
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`BLT: takb <= $signed(a) < $signed(b);
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`BGE: takb <= $signed(a) >= $signed(b);
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`BLTU: takb <= a < b;
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`BGEU: takb <= a >= b;
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default: takb <= `TRUE;
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endcase
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`BLcc:
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case(instr[15:13])
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`BAND: takb <= a != 0 && b != 0;
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`BOR: takb <= a != 0 || b != 0;
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`BXOR: takb <= (a != 0) ^ (b != 0);
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`BNAND: takb <= !(a != 0 && b != 0);
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`BNOR: takb <= !(a != 0 || b != 0);
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`BXNOR: takb <= !((a != 0) ^ (b != 0));
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default: takb <= `TRUE;
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endcase
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`BEQI: takb <= a=={{56{instr[22]}},instr[22:18],instr[15:13]};
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`BNEI: takb <= a!={{56{instr[22]}},instr[22:18],instr[15:13]};
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`BBc:
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case(instr[14:13])
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2'd0: takb <= a[{instr[22:18],instr[15]}]; // BBS
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2'd1: takb <= ~a[{instr[22:18],instr[15]}]; // BBC
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`IBNE: takb <= (a + 64'd1) !=b;
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`DBNZ: takb <= (a - 64'd1) !=b;
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default: takb <= `TRUE;
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endcase
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`CHK,`BCHK: takb <= a >= b && a < c;
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default: takb <= `TRUE;
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endcase
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endmodule
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