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57 lines
2.3 KiB
Systemverilog
57 lines
2.3 KiB
Systemverilog
///////////////////////////////////////////
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// extend.sv
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//
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// Written: David_Harris@hmc.edu, Sarah.Harris@unlv.edu
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// Created: 9 January 2021
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// Modified:
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//
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// Purpose: Produce sign-extended immediates from various formats
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//
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// Documentation: RISC-V System on Chip Design Chapter 4 (Figure 4.3)
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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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module extend (
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input logic [31:7] InstrD, // All instruction bits except opcode (lower 7 bits)
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input logic [2:0] ImmSrcD, // Select what kind of extension to perform
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output logic [`XLEN-1:0 ] ImmExtD); // Extended immediate
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localparam [`XLEN-1:0] undefined = {(`XLEN){1'bx}}; // could change to 0 after debug
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always_comb
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case(ImmSrcD)
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// I-type
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3'b000: ImmExtD = {{(`XLEN-12){InstrD[31]}}, InstrD[31:20]};
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// S-type (stores)
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3'b001: ImmExtD = {{(`XLEN-12){InstrD[31]}}, InstrD[31:25], InstrD[11:7]};
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// B-type (branches)
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3'b010: ImmExtD = {{(`XLEN-12){InstrD[31]}}, InstrD[7], InstrD[30:25], InstrD[11:8], 1'b0};
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// J-type (jal)
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3'b011: ImmExtD = {{(`XLEN-20){InstrD[31]}}, InstrD[19:12], InstrD[20], InstrD[30:21], 1'b0};
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// U-type (lui, auipc)
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3'b100: ImmExtD = {{(`XLEN-31){InstrD[31]}}, InstrD[30:12], 12'b0};
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// Store Conditional: zero offset
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3'b101: if (`A_SUPPORTED) ImmExtD = 0;
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else ImmExtD = undefined;
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default: ImmExtD = undefined; // undefined
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endcase
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endmodule
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