From 65e9747752eeeaa6c709b37eb6aa5c28185ccc99 Mon Sep 17 00:00:00 2001
From: Shreya Sanghai <ssanghai@hmc.edu>
Date: Wed, 31 Mar 2021 21:56:14 -0400
Subject: [PATCH 1/3] fixed bugs in global history to read latest GHRE
---
wally-pipelined/config/rv64BP/wally-config.vh | 2 +-
wally-pipelined/src/ifu/globalHistoryPredictor.sv | 9 +++++----
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/wally-pipelined/config/rv64BP/wally-config.vh b/wally-pipelined/config/rv64BP/wally-config.vh
index bd053750c..f39c6cee3 100644
--- a/wally-pipelined/config/rv64BP/wally-config.vh
+++ b/wally-pipelined/config/rv64BP/wally-config.vh
@@ -97,5 +97,5 @@
`define TWO_BIT_PRELOAD "../config/rv64icfd/twoBitPredictor.txt"
`define BTB_PRELOAD "../config/rv64icfd/BTBPredictor.txt"
-`define BPTYPE "BPGSHARE" // BPGLOBAL or BPTWOBIT or BPGSHARE
+`define BPTYPE "BPGLOBAL" // BPGLOBAL or BPTWOBIT or BPGSHARE
`define TESTSBP 1
diff --git a/wally-pipelined/src/ifu/globalHistoryPredictor.sv b/wally-pipelined/src/ifu/globalHistoryPredictor.sv
index b9addb381..babafb525 100644
--- a/wally-pipelined/src/ifu/globalHistoryPredictor.sv
+++ b/wally-pipelined/src/ifu/globalHistoryPredictor.sv
@@ -41,12 +41,13 @@ module globalHistoryPredictor
input logic [1:0] UpdatePrediction
);
- logic [k-1:0] GHRF, GHRD, GHRE;
+ logic [k-1:0] GHRF, GHRD, GHRE, GHRENext;
+ assign GHRENext = {PCSrcE, GHRE[k-1:1]};
flopenr #(k) GlobalHistoryRegister(.clk(clk),
.reset(reset),
.en(UpdateEN),
- .d({PCSrcE, GHRF[k-1:1] }),
+ .d(GHRENext),
.q(GHRF));
@@ -66,8 +67,8 @@ module globalHistoryPredictor
.reset(reset),
.RA1(GHRF),
.RD1(PredictionMemory),
- .REN1(1'b1),
- .WA1(GHRE),
+ .REN1(~StallF),
+ .WA1(GHRENext),
.WD1(UpdatePrediction),
.WEN1(UpdateEN),
.BitWEN1(2'b11));
From e33007e30e1418584d8013ffa9a0acea53530a76 Mon Sep 17 00:00:00 2001
From: ShreyaSanghai <ssanghai@hmc.edu>
Date: Thu, 1 Apr 2021 22:22:40 +0530
Subject: [PATCH 2/3] added localHistoryPredictor
---
.../src/ifu/globalHistoryPredictor.sv | 9 +-
.../src/ifu/localHistoryPredictor.sv | 138 ++++++++++++++++++
2 files changed, 141 insertions(+), 6 deletions(-)
create mode 100644 wally-pipelined/src/ifu/localHistoryPredictor.sv
diff --git a/wally-pipelined/src/ifu/globalHistoryPredictor.sv b/wally-pipelined/src/ifu/globalHistoryPredictor.sv
index babafb525..1fd0720fc 100644
--- a/wally-pipelined/src/ifu/globalHistoryPredictor.sv
+++ b/wally-pipelined/src/ifu/globalHistoryPredictor.sv
@@ -37,7 +37,7 @@ module globalHistoryPredictor
output logic [1:0] Prediction,
// update
input logic [`XLEN-1:0] UpdatePC,
- input logic UpdateEN, PCSrcE, /// *** need to add as input from bpred.sv
+ input logic UpdateEN, PCSrcE,
input logic [1:0] UpdatePrediction
);
@@ -55,11 +55,8 @@ module globalHistoryPredictor
logic [1:0] PredictionMemory;
logic DoForwarding, DoForwardingF;
logic [1:0] UpdatePredictionF;
-
- // for gshare xor the PC with the GHR
- // TODO: change in sram memory2 module
- // assign UpdatePCIndex = GHRE ^ UpdatePC;
- // assign LookUpPCIndex = LookUpPC ^ GHR;
+
+
// Make Prediction by reading the correct address in the PHT and also update the new address in the PHT
// GHR referes to the address that the past k branches points to in the prediction stage
// GHRE refers to the address that the past k branches points to in the exectution stage
diff --git a/wally-pipelined/src/ifu/localHistoryPredictor.sv b/wally-pipelined/src/ifu/localHistoryPredictor.sv
new file mode 100644
index 000000000..85f413572
--- /dev/null
+++ b/wally-pipelined/src/ifu/localHistoryPredictor.sv
@@ -0,0 +1,138 @@
+///////////////////////////////////////////
+// locallHistoryPredictor.sv
+//
+// Written: Shreya Sanghai
+// Email: ssanghai@hmc.edu
+// Created: March 16, 2021
+// Modified:
+//
+// Purpose: Global History Branch predictor with parameterized global history register
+//
+// A component of the Wally configurable RISC-V project.
+//
+// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy,
+// modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+// OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+///////////////////////////////////////////
+
+`include "wally-config.vh"
+
+module localHistoryPredictor
+ #( parameter int m = 6, // 2^m = number of local history branches
+ parameter int k = 10 // number of past branches stored
+ )
+ (input logic clk,
+ input logic reset,
+ input logic StallF, StallD, StallE, FlushF, FlushD, FlushE,
+ input logic [`XLEN-1:0] LookUpPC,
+ output logic [1:0] Prediction,
+ // update
+ input logic [`XLEN-1:0] UpdatePC,
+ input logic UpdateEN, PCSrcE,
+ input logic [1:0] UpdatePrediction
+
+ );
+
+ logic [2**m-1:0][k-1:0] LHRNextF;
+ logic [k-1:0] LHRD, LHRE, LHRENext, ForwardLHRNext;
+ logic [m-1:0] LookUpPCIndex, UpdatePCIndex;
+ logic [1:0] PredictionMemory;
+ logic DoForwarding, DoForwardingF, DoForwardingPHT, DoForwardingPHTF;
+ logic [1:0] UpdatePredictionF;
+
+ assign LHRENext = {PCSrcE, LHRE[k-1:1]};
+ assign UpdatePCIndex = {UpdatePC[m+1] ^ UpdatePC[1], UpdatePC[m:2]};
+ assign LookUpPCIndex = {LookUpPC[m+1] ^ LookUpPC[1], LookUpPC[m:2]};
+
+// INCASE we do ahead pipelining
+// SRAM2P1R1W #(m,k) LHR(.clk(clk)),
+// .reset(reset),
+// .RA1(LookUpPCIndex), // need hashing function to get correct PC address
+// .RD1(LHRF),
+// .REN1(~StallF),
+// .WA1(UpdatePCIndex),
+// .WD1(LHRENExt),
+// .WEN1(UpdateEN),
+// .BitWEN1(2'b11));
+
+genvar index;
+generate
+ for (index = 0; index < 2**m; index = index +1) begin:index
+
+ flopenr #(k) LocalHistoryRegister(.clk(clk),
+ .reset(reset),
+ .en(UpdateEN && (index == UpdatePCIndex)),
+ .d(LHRENext),
+ .q(LHRNextF[index]));
+ end
+endgenerate
+
+// need to forward when updating to the same address as reading.
+// first we compare to see if the update and lookup addreses are the same
+assign DoForwarding = LookUpPCIndex == UpdatePCIndex;
+assign ForwardLHRNext = DoForwarding ? LHRENext :LHRNextF[LookUpPCIndex];
+
+ // Make Prediction by reading the correct address in the PHT and also update the new address in the PHT
+ // LHR referes to the address that the past k branches points to in the prediction stage
+ // LHRE refers to the address that the past k branches points to in the exectution stage
+ SRAM2P1R1W #(k, 2) PHT(.clk(clk),
+ .reset(reset),
+ .RA1(ForwardLHRNext),
+ .RD1(PredictionMemory),
+ .REN1(~StallF),
+ .WA1(LHRENext),
+ .WD1(UpdatePrediction),
+ .WEN1(UpdateEN),
+ .BitWEN1(2'b11));
+
+
+
+assign DoForwardingPHT = LHRENext == ForwardLHRNext;
+
+ // register the update value and the forwarding signal into the Fetch stage
+ // TODO: add stall logic ***
+ flopr #(1) DoForwardingReg(.clk(clk),
+ .reset(reset),
+ .d(DoForwardingPHT),
+ .q(DoForwardingPHTF));
+
+ flopr #(2) UpdatePredictionReg(.clk(clk),
+ .reset(reset),
+ .d(UpdatePrediction),
+ .q(UpdatePredictionF));
+
+ assign Prediction = DoForwardingPHTF ? UpdatePredictionF : PredictionMemory;
+
+ //pipeline for LHR
+ flopenrc #(k) LHRFReg(.clk(clk),
+ .reset(reset),
+ .en(~StallF),
+ .clear(FlushF),
+ .d(ForwardLHRNext),
+ .q(LHRF));
+
+ flopenrc #(k) LHRDReg(.clk(clk),
+ .reset(reset),
+ .en(~StallD),
+ .clear(FlushD),
+ .d(LHRF),
+ .q(LHRD));
+
+ flopenrc #(k) LHREReg(.clk(clk),
+ .reset(reset),
+ .en(~StallE),
+ .clear(FlushE),
+ .d(LHRD),
+ .q(LHRE));
+
+endmodule
From bf3f4ff5b25ec2d611239d08b9f9107c1f6a97a5 Mon Sep 17 00:00:00 2001
From: Shreya Sanghai <ssanghai@hmc.edu>
Date: Thu, 1 Apr 2021 13:40:08 -0400
Subject: [PATCH 3/3] fixed minor bugs in localHistory
---
wally-pipelined/config/rv32ic/wally-config.vh | 2 +-
wally-pipelined/config/rv64ic/wally-config.vh | 2 +-
wally-pipelined/config/rv64icfd/wally-config.vh | 2 +-
wally-pipelined/src/ifu/bpred.sv | 13 +++++++++++++
wally-pipelined/src/ifu/localHistoryPredictor.sv | 4 ++--
5 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/wally-pipelined/config/rv32ic/wally-config.vh b/wally-pipelined/config/rv32ic/wally-config.vh
index fadbe36c6..f369c19bc 100644
--- a/wally-pipelined/config/rv32ic/wally-config.vh
+++ b/wally-pipelined/config/rv32ic/wally-config.vh
@@ -94,5 +94,5 @@
`define TWO_BIT_PRELOAD "../config/rv32ic/twoBitPredictor.txt"
`define BTB_PRELOAD "../config/rv32ic/BTBPredictor.txt"
-`define BPTYPE "BPGSHARE" // BPGLOBAL or BPTWOBIT or BPGSHARE
+`define BPTYPE "BPLOCALPAg" // BPGLOBAL or BPTWOBIT or BPGSHARE
`define TESTSBP 0
diff --git a/wally-pipelined/config/rv64ic/wally-config.vh b/wally-pipelined/config/rv64ic/wally-config.vh
index b27a5e1c6..9cfb5a8e5 100644
--- a/wally-pipelined/config/rv64ic/wally-config.vh
+++ b/wally-pipelined/config/rv64ic/wally-config.vh
@@ -97,5 +97,5 @@
`define TWO_BIT_PRELOAD "../config/rv64ic/twoBitPredictor.txt"
`define BTB_PRELOAD "../config/rv64ic/BTBPredictor.txt"
-`define BPTYPE "BPGSHARE" // BPGLOBAL or BPTWOBIT or BPGSHARE
+`define BPTYPE "BPLOCALPAg" // BPGLOBAL or BPTWOBIT or BPGSHARE
`define TESTSBP 0
diff --git a/wally-pipelined/config/rv64icfd/wally-config.vh b/wally-pipelined/config/rv64icfd/wally-config.vh
index 853b86855..6ea013d96 100644
--- a/wally-pipelined/config/rv64icfd/wally-config.vh
+++ b/wally-pipelined/config/rv64icfd/wally-config.vh
@@ -97,5 +97,5 @@
`define TWO_BIT_PRELOAD "../config/rv64icfd/twoBitPredictor.txt"
`define BTB_PRELOAD "../config/rv64icfd/BTBPredictor.txt"
-`define BPTYPE "BPGSHARE" // BPGLOBAL or BPTWOBIT or BPGSHARE
+`define BPTYPE "BPGLOBAL" // BPGLOBAL or BPTWOBIT or BPGSHARE
`define TESTSBP 0
diff --git a/wally-pipelined/src/ifu/bpred.sv b/wally-pipelined/src/ifu/bpred.sv
index a96d43536..56ee1624e 100644
--- a/wally-pipelined/src/ifu/bpred.sv
+++ b/wally-pipelined/src/ifu/bpred.sv
@@ -104,6 +104,19 @@ module bpred
.PCSrcE(PCSrcE),
.UpdatePrediction(UpdateBPPredE));
end
+ else if (`BPTYPE == "BPLOCALPAg") begin:Predictor
+
+ localHistoryPredictor DirPredictor(.clk(clk),
+ .reset(reset),
+ .*, // Stalls and flushes
+ .LookUpPC(PCNextF),
+ .Prediction(BPPredF),
+ // update
+ .UpdatePC(PCE),
+ .UpdateEN(InstrClassE[0] & ~StallE),
+ .PCSrcE(PCSrcE),
+ .UpdatePrediction(UpdateBPPredE));
+ end
endgenerate
diff --git a/wally-pipelined/src/ifu/localHistoryPredictor.sv b/wally-pipelined/src/ifu/localHistoryPredictor.sv
index 85f413572..ef33bbc81 100644
--- a/wally-pipelined/src/ifu/localHistoryPredictor.sv
+++ b/wally-pipelined/src/ifu/localHistoryPredictor.sv
@@ -44,7 +44,7 @@ module localHistoryPredictor
);
logic [2**m-1:0][k-1:0] LHRNextF;
- logic [k-1:0] LHRD, LHRE, LHRENext, ForwardLHRNext;
+ logic [k-1:0] LHRF, LHRD, LHRE, LHRENext, ForwardLHRNext;
logic [m-1:0] LookUpPCIndex, UpdatePCIndex;
logic [1:0] PredictionMemory;
logic DoForwarding, DoForwardingF, DoForwardingPHT, DoForwardingPHTF;
@@ -67,7 +67,7 @@ module localHistoryPredictor
genvar index;
generate
- for (index = 0; index < 2**m; index = index +1) begin:index
+ for (index = 0; index < 2**m; index = index +1) begin
flopenr #(k) LocalHistoryRegister(.clk(clk),
.reset(reset),