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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's ALU                                                ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/project,or1k                       ////
////                                                              ////
////  Description                                                 ////
////  ALU                                                         ////
////                                                              ////
////  To Do:                                                      ////
////   - make it smaller and faster                               ////
////                                                              ////
////  Author(s):                                                  ////
////      - Damjan Lampret, lampret@opencores.org                 ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// 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 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source 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 Lesser General Public License for more ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// $Log: or1200_alu.v,v $
// Revision 2.0  2010/06/30 11:00:00  ORSoC
// Minor update: 
// Defines added, flags are corrected. 
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "or1200_defines.v"
 
module or1200_alu(
	a, b, mult_mac_result, macrc_op,
	alu_op, shrot_op, comp_op,
	cust5_op, cust5_limm,
	result, flagforw, flag_we,
	cyforw, cy_we, carry, flag
);
 
parameter width = `OR1200_OPERAND_WIDTH;
 
//
// I/O
//
input	[width-1:0]		a;
input	[width-1:0]		b;
input	[width-1:0]		mult_mac_result;
input				macrc_op;
input	[`OR1200_ALUOP_WIDTH-1:0]	alu_op;
input	[`OR1200_SHROTOP_WIDTH-1:0]	shrot_op;
input	[`OR1200_COMPOP_WIDTH-1:0]	comp_op;
input	[4:0]			cust5_op;
input	[5:0]			cust5_limm;
output	[width-1:0]		result;
output				flagforw;
output				flag_we;
output				cyforw;
output				cy_we;
input				carry;
input         flag;
 
//
// Internal wires and regs
//
reg	[width-1:0]		result;
reg	[width-1:0]		shifted_rotated;
reg	[width-1:0]		result_cust5;
reg				flagforw;
reg				flagcomp;
reg				flag_we;
reg				cy_we;
wire	[width-1:0]		comp_a;
wire	[width-1:0]		comp_b;
`ifdef OR1200_IMPL_ALU_COMP1
wire				a_eq_b;
wire				a_lt_b;
`endif
wire	[width-1:0]		result_sum;
`ifdef OR1200_IMPL_ADDC
wire	[width-1:0]		result_csum;
wire				cy_csum;
`endif
wire	[width-1:0]		result_and;
wire				cy_sum;
`ifdef OR1200_IMPL_SUB
wire				cy_sub;
`endif
reg				cyforw;
 
//
// Combinatorial logic
//
assign comp_a = {a[width-1] ^ comp_op[3] , a[width-2:0]};
assign comp_b = {b[width-1] ^ comp_op[3] , b[width-2:0]};
`ifdef OR1200_IMPL_ALU_COMP1
assign a_eq_b = (comp_a == comp_b);
assign a_lt_b = (comp_a < comp_b);
`endif
`ifdef OR1200_IMPL_SUB
assign cy_sub = a < b;
`endif
assign {cy_sum, result_sum} = a + b;
`ifdef OR1200_IMPL_ADDC
assign {cy_csum, result_csum} = a + b + {`OR1200_OPERAND_WIDTH'd0, carry};
`endif
assign result_and = a & b;
 
//
// Simulation check for bad ALU behavior
//
`ifdef OR1200_WARNINGS
// synopsys translate_off
always @(result) begin
	if (result === 32'bx)
		$display("%t: WARNING: 32'bx detected on ALU result bus. Please check !", $time);
end
// synopsys translate_on
`endif
 
//
// Central part of the ALU
//
always @(alu_op or a or b or result_sum or result_and or macrc_op or shifted_rotated or mult_mac_result or flag or result_cust5 or carry
`ifdef OR1200_IMPL_ADDC
         or result_csum
`endif
) begin
`ifdef OR1200_CASE_DEFAULT
	casex (alu_op)		// synopsys parallel_case
`else
	casex (alu_op)		// synopsys full_case parallel_case
`endif
		`OR1200_ALUOP_FF1: begin
			result = a[0] ? 1 : a[1] ? 2 : a[2] ? 3 : a[3] ? 4 : a[4] ? 5 : a[5] ? 6 : a[6] ? 7 : a[7] ? 8 : a[8] ? 9 : a[9] ? 10 : a[10] ? 11 : a[11] ? 12 : a[12] ? 13 : a[13] ? 14 : a[14] ? 15 : a[15] ? 16 : a[16] ? 17 : a[17] ? 18 : a[18] ? 19 : a[19] ? 20 : a[20] ? 21 : a[21] ? 22 : a[22] ? 23 : a[23] ? 24 : a[24] ? 25 : a[25] ? 26 : a[26] ? 27 : a[27] ? 28 : a[28] ? 29 : a[29] ? 30 : a[30] ? 31 : a[31] ? 32 : 0;
		end
		`OR1200_ALUOP_CUST5 : begin 
				result = result_cust5;
		end
		`OR1200_ALUOP_SHROT : begin 
				result = shifted_rotated;
		end
		`OR1200_ALUOP_ADD : begin
				result = result_sum;
		end
`ifdef OR1200_IMPL_ADDC
		`OR1200_ALUOP_ADDC : begin
				result = result_csum;
		end
`endif
`ifdef OR1200_IMPL_SUB
		`OR1200_ALUOP_SUB : begin
				result = a - b;
		end
`endif
		`OR1200_ALUOP_XOR : begin
				result = a ^ b;
		end
		`OR1200_ALUOP_OR  : begin
				result = a | b;
		end
		`OR1200_ALUOP_IMM : begin
				result = b;
		end
		`OR1200_ALUOP_MOVHI : begin
				if (macrc_op) begin
					result = mult_mac_result;
				end
				else begin
					result = b << 16;
				end
		end
`ifdef OR1200_MULT_IMPLEMENTED
`ifdef OR1200_IMPL_DIV
		`OR1200_ALUOP_DIV,
		`OR1200_ALUOP_DIVU,
`endif
		`OR1200_ALUOP_MUL : begin
				result = mult_mac_result;
		end
`endif
		`OR1200_ALUOP_CMOV: begin
			result = flag ? a : b;
		end
 
`ifdef OR1200_CASE_DEFAULT
		default: begin
`else
		`OR1200_ALUOP_COMP, `OR1200_ALUOP_AND: begin
`endif
			result=result_and;
		end 
	endcase
end
 
//
// l.cust5 custom instructions
//
// Examples for move byte, set bit and clear bit
//
always @(cust5_op or cust5_limm or a or b) begin
	casex (cust5_op)		// synopsys parallel_case
		5'h1 : begin 
			casex (cust5_limm[1:0])
				2'h0: result_cust5 = {a[31:8], b[7:0]};
				2'h1: result_cust5 = {a[31:16], b[7:0], a[7:0]};
				2'h2: result_cust5 = {a[31:24], b[7:0], a[15:0]};
				2'h3: result_cust5 = {b[7:0], a[23:0]};
			endcase
		end
		5'h2 :
			result_cust5 = a | (1 << cust5_limm);
		5'h3 :
			result_cust5 = a & (32'hffffffff ^ (1 << cust5_limm));
//
// *** Put here new l.cust5 custom instructions ***
//
		default: begin
			result_cust5 = a;
		end
	endcase
end
 
//
// Generate flag and flag write enable
//
always @(alu_op or result_sum or result_and or flagcomp
`ifdef OR1200_IMPL_ADDC
         or result_csum
`endif
) begin
	casex (alu_op)		// synopsys parallel_case
`ifdef OR1200_ADDITIONAL_FLAG_MODIFIERS
		`OR1200_ALUOP_ADD : begin
			flagforw = (result_sum == 32'h0000_0000);
			flag_we = 1'b1;
		end
`ifdef OR1200_IMPL_ADDC
		`OR1200_ALUOP_ADDC : begin
			flagforw = (result_csum == 32'h0000_0000);
			flag_we = 1'b1;
		end
`endif
		`OR1200_ALUOP_AND: begin
			flagforw = (result_and == 32'h0000_0000);
			flag_we = 1'b1;
		end
`endif
		`OR1200_ALUOP_COMP: begin
			flagforw = flagcomp;
			flag_we = 1'b1;
		end
		default: begin
			flagforw = flagcomp;
			flag_we = 1'b0;
		end
	endcase
end
 
//
// Generate SR[CY] write enable
//
always @(alu_op or cy_sum
`ifdef OR1200_IMPL_CY
`ifdef OR1200_IMPL_ADDC
	or cy_csum
`endif
`ifdef OR1200_IMPL_SUB
	or cy_sub
`endif
`endif
) begin
	casex (alu_op)		// synopsys parallel_case
`ifdef OR1200_IMPL_CY
		`OR1200_ALUOP_ADD : begin
			cyforw = cy_sum;
			cy_we = 1'b1;
		end
`ifdef OR1200_IMPL_ADDC
		`OR1200_ALUOP_ADDC: begin
			cyforw = cy_csum;
			cy_we = 1'b1;
		end
`endif
`ifdef OR1200_IMPL_SUB
		`OR1200_ALUOP_SUB: begin
			cyforw = cy_sub;
			cy_we = 1'b1;
		end
`endif
`endif
		default: begin
			cyforw = 1'b0;
			cy_we = 1'b0;
		end
	endcase
end
 
//
// Shifts and rotation
//
always @(shrot_op or a or b) begin
	case (shrot_op)		// synopsys parallel_case
	`OR1200_SHROTOP_SLL :
				shifted_rotated = (a << b[4:0]);
		`OR1200_SHROTOP_SRL :
				shifted_rotated = (a >> b[4:0]);
 
`ifdef OR1200_IMPL_ALU_ROTATE
		`OR1200_SHROTOP_ROR :
				shifted_rotated = (a << (6'd32-{1'b0, b[4:0]})) | (a >> b[4:0]);
`endif
		default:
				shifted_rotated = ({32{a[31]}} << (6'd32-{1'b0, b[4:0]})) | a >> b[4:0];
	endcase
end
 
//
// First type of compare implementation
//
`ifdef OR1200_IMPL_ALU_COMP1
always @(comp_op or a_eq_b or a_lt_b) begin
	case(comp_op[2:0])	// synopsys parallel_case
		`OR1200_COP_SFEQ:
			flagcomp = a_eq_b;
		`OR1200_COP_SFNE:
			flagcomp = ~a_eq_b;
		`OR1200_COP_SFGT:
			flagcomp = ~(a_eq_b | a_lt_b);
		`OR1200_COP_SFGE:
			flagcomp = ~a_lt_b;
		`OR1200_COP_SFLT:
			flagcomp = a_lt_b;
		`OR1200_COP_SFLE:
			flagcomp = a_eq_b | a_lt_b;
		default:
			flagcomp = 1'b0;
	endcase
end
`endif
 
//
// Second type of compare implementation
//
`ifdef OR1200_IMPL_ALU_COMP2
always @(comp_op or comp_a or comp_b) begin
	case(comp_op[2:0])	// synopsys parallel_case
		`OR1200_COP_SFEQ:
			flagcomp = (comp_a == comp_b);
		`OR1200_COP_SFNE:
			flagcomp = (comp_a != comp_b);
		`OR1200_COP_SFGT:
			flagcomp = (comp_a > comp_b);
		`OR1200_COP_SFGE:
			flagcomp = (comp_a >= comp_b);
		`OR1200_COP_SFLT:
			flagcomp = (comp_a < comp_b);
		`OR1200_COP_SFLE:
			flagcomp = (comp_a <= comp_b);
		default:
			flagcomp = 1'b0;
	endcase
end
`endif
 
endmodule