forked from Github_Repos/cvw
9172e52286
Added performance counters to individually track branches; jumps, jump register, jal, and jalr; return. jump and jump register are special cases of jal and jalr. Similarlly return is a special case of jalr. Also added counters to track if the branch direction was wrong, btb target wrong, or the ras target was wrong. Finally added one more counter to track if the BP incorrectly predicts a non-cfi instruction.
81 lines
2.6 KiB
Systemverilog
81 lines
2.6 KiB
Systemverilog
///////////////////////////////////////////
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// RASPredictor.sv
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//
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// Written: Ross Thomposn
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// Email: ross1728@gmail.com
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// Created: February 15, 2021
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// Modified:
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//
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// Purpose: 2 bit saturating counter predictor with parameterized table depth.
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//
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// A component of the Wally configurable RISC-V project.
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//
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// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
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// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy,
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// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
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// is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
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// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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///////////////////////////////////////////
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`include "wally-config.vh"
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module RASPredictor
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#(parameter int StackSize = 16
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)
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(input logic clk,
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input logic reset,
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input logic pop,
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output logic [`XLEN-1:0] popPC,
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input logic push,
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input logic incr,
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input logic [`XLEN-1:0] pushPC
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);
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logic CounterEn;
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localparam Depth = $clog2(StackSize);
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logic [Depth-1:0] PtrD, PtrQ, PtrP1, PtrM1;
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logic [StackSize-1:0] [`XLEN-1:0] memory;
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integer index;
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assign CounterEn = pop | push | incr;
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assign PtrD = pop ? PtrM1 : PtrP1;
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assign PtrM1 = PtrQ - 1'b1;
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assign PtrP1 = PtrQ + 1'b1;
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// may have to handle a push and an incr at the same time.
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// *** what happens if jal is executing and there is a return being flushed in Decode?
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flopenr #(Depth) PTR(.clk(clk),
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.reset(reset),
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.en(CounterEn),
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.d(PtrD),
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.q(PtrQ));
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// RAS must be reset.
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always_ff @ (posedge clk, posedge reset) begin
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if(reset) begin
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for(index=0; index<StackSize; index++)
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memory[index] <= {`XLEN{1'b0}};
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end else if(push) begin
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memory[PtrP1] <= #1 pushPC;
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end
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end
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assign popPC = memory[PtrQ];
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endmodule
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