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Sketch in an AMO ALU

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Luke Wren 2021-12-04 18:52:41 +00:00
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hdl/arith/hazard3_alu.v
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* DO WHAT THE FUCK YOU WANT TO AND DON'T BLAME US PUBLIC LICENSE *
* Version 3, April 2008 *
* *
* Copyright (C) 2018 Luke Wren *
* Copyright (C) 2021 Luke Wren *
* *
* Everyone is permitted to copy and distribute verbatim or modified *
* copies of this license document and accompanying software, and *

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hdl/arith/hazard3_amo_alu.v Normal file
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/**********************************************************************
* DO WHAT THE FUCK YOU WANT TO AND DON'T BLAME US PUBLIC LICENSE *
* Version 3, April 2008 *
* *
* Copyright (C) 2021 Luke Wren *
* *
* Everyone is permitted to copy and distribute verbatim or modified *
* copies of this license document and accompanying software, and *
* changing either is allowed. *
* *
* TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION *
* *
* 0. You just DO WHAT THE FUCK YOU WANT TO. *
* 1. We're NOT RESPONSIBLE WHEN IT DOESN'T FUCKING WORK. *
* *
*********************************************************************/
// Separate ALU for atomic memory operations
`default_nettype none
module hazard3_amo_alu #(
`include "hazard3_config.vh"
,
`include "hazard3_width_const.vh"
) (
input wire [W_MEMOP-1:0] op,
input wire [W_DATA-1:0] op_rs1, // From load
input wire [W_DATA-1:0] op_rs2, // From core
output reg [W_DATA-1:0] result
);
wire sub = op != MEMOP_AMOADD_W;
wire cmp_unsigned = op == MEMOP_AMOMINU_W || op == MEMOP_AMOMAXU_W;
wire [W_DATA-1:0] sum = op_rs1 + (op_rs2 ^ {W_DATA{sub}}) + sub;
wire rs1_lessthan_rs2 =
op_rs1[W_DATA-1] == op_rs2[W_DATA-1] ? sum[W_DATA-1] :
cmp_unsigned ? op_rs2[W_DATA-1] :
op_rs1[W_DATA-1] ;
always @ (*) begin
case(op)
MEMOP_AMOADD_W : result = sum;
MEMOP_AMOXOR_W : result = op_rs1 ^ op_rs2;
MEMOP_AMOAND_W : result = op_rs1 & op_rs2;
MEMOP_AMOOR_W : result = op_rs1 | op_rs2;
MEMOP_AMOMIN_W : result = rs1_lessthan_rs2 ? op_rs1 : op_rs2;
MEMOP_AMOMAX_W : result = rs1_lessthan_rs2 ? op_rs2 : op_rs1;
MEMOP_AMOMINU_W: result = rs1_lessthan_rs2 ? op_rs1 : op_rs2;
MEMOP_AMOMAXU_W: result = rs1_lessthan_rs2 ? op_rs2 : op_rs1;
// AMOSWAP
default: result = op_rs2;
endcase
end
endmodule
`default_nettype wire