forked from Github_Repos/cvw
52 lines
2.3 KiB
Systemverilog
52 lines
2.3 KiB
Systemverilog
///////////////////////////////////////////
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// intdivrestoringstep.sv
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//
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// Written: David_Harris@hmc.edu 2 October 2021
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// Modified:
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//
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// Purpose: Restoring integer division step. k steps are used in intdivrestoring
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//
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// Documentation: RISC-V System on Chip Design Chapter 12 (Figure 12.19)
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//
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// A component of the CORE-V-WALLY configurable RISC-V project.
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//
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// Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
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//
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// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
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//
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// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file
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// except in compliance with the License, or, at your option, the Apache License version 2.0. You
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// may obtain a copy of the License at
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//
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// https://solderpad.org/licenses/SHL-2.1/
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//
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// Unless required by applicable law or agreed to in writing, any work distributed under the
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// License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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// either express or implied. See the License for the specific language governing permissions
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// and limitations under the License.
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////////////////////////////////////////////////////////////////////////////////////////////////
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`include "wally-config.vh"
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/* verilator lint_off UNOPTFLAT */
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module intdivrestoringstep(
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input logic [`XLEN-1:0] W, // Residual in
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input logic [`XLEN-1:0] XQ, // bits of dividend X and quotient Q in
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input logic [`XLEN-1:0] DAbsB, // complement of absolute value of divisor D (for subtraction)
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output logic [`XLEN-1:0] WOut, // Residual out
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output logic [`XLEN-1:0] XQOut // bits of dividend and quotient out: discard one bit of X, append one bit of Q
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);
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logic [`XLEN-1:0] WShift; // Shift W left by one bit, bringing in most significant bit of X
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logic [`XLEN-1:0] WPrime; // WShift - D, for comparison and possible result
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logic qi, qib; // Quotient digit and its complement
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assign {WShift, XQOut} = {W[`XLEN-2:0], XQ, qi}; // shift W and X/Q left, insert quotient bit at bottom
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adder #(`XLEN+1) wdsub({1'b0, WShift}, {1'b1, DAbsB}, {qib, WPrime}); // effective subtractor, carry out determines quotient bit
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assign qi = ~qib;
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mux2 #(`XLEN) wrestoremux(WShift, WPrime, qi, WOut); // if quotient is zero, restore W
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endmodule
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/* verilator lint_on UNOPTFLAT */
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