diff --git a/studies/comparator.sv b/studies/comparator.sv new file mode 100644 index 000000000..771236f65 --- /dev/null +++ b/studies/comparator.sv @@ -0,0 +1,50 @@ +/////////////////////////////////////////// +// comparator.sv +// +// Written: David_Harris@hmc.edu, Sarah.Harris@unlv.edu +// Created: 8 December 2021 +// Modified: +// +// Purpose: Branch comparison +// +// Documentation: RISC-V System on Chip Design Chapter 4 (Figure 4.7) +// +// A component of the CORE-V-WALLY configurable RISC-V project. +// +// Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University +// +// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1 +// +// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file +// except in compliance with the License, or, at your option, the Apache License version 2.0. You +// may obtain a copy of the License at +// +// https://solderpad.org/licenses/SHL-2.1/ +// +// Unless required by applicable law or agreed to in writing, any work distributed under the +// 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. +//////////////////////////////////////////////////////////////////////////////////////////////// + +`include "wally-config.vh" + +// This comparator is best +module comparator_dc_flip #(parameter WIDTH=64) ( + input logic [WIDTH-1:0] a, b, // Operands + input logic sgnd, // Signed operands + output logic [1:0] flags); // Output flags: {eq, lt} + + logic eq, lt; // Flags: equal (eq), less than (lt) + logic [WIDTH-1:0] af, bf; // Operands with msb flipped (inverted) when signed + + // For signed numbers, flip most significant bit + assign af = {a[WIDTH-1] ^ sgnd, a[WIDTH-2:0]}; + assign bf = {b[WIDTH-1] ^ sgnd, b[WIDTH-2:0]}; + + // Behavioral description gives best results + assign eq = (a == b); // eq = 1 when operands are equal, 0 otherwise + assign lt = (af < bf); // lt = 1 when a less than b (taking signed operands into account) + assign flags = {eq, lt}; +endmodule + diff --git a/pipelined/src/ppa/ppa.sv b/studies/ppa/ppa.sv similarity index 100% rename from pipelined/src/ppa/ppa.sv rename to studies/ppa/ppa.sv