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changed SC M-to-E fowarding to W-to-E forwarding to improve critical path

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bbracker 2021-06-25 07:18:38 -04:00
parent 2155a4e485
commit 192171826b
3 changed files with 14 additions and 10 deletions
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6
wally-pipelined/src/ieu/controller.sv
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@ -49,7 +49,8 @@ module controller(
// Memory stage control signals
input logic StallM, FlushM,
output logic [1:0] MemRWM,
output logic CSRReadM, CSRWriteM, PrivilegedM,
output logic CSRReadM, CSRWriteM, PrivilegedM,
output logic SCE,
output logic [1:0] AtomicM,
output logic [2:0] Funct3M,
output logic RegWriteM, // for Hazard Unit
@ -202,7 +203,8 @@ module controller(
assign PCSrcE = JumpE | BranchE & BranchTakenE;
assign MemReadE = MemRWE[1];
assign MemReadE = MemRWE[1];
assign SCE = (ResultSrcE == 3'b100);
// Memory stage pipeline control register
flopenrc #(15) controlregM(clk, reset, FlushM, ~StallM,

15
wally-pipelined/src/ieu/forward.sv
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@ -28,13 +28,14 @@
module forward(
// Detect hazards
input logic [4:0] Rs1D, Rs2D, Rs1E, Rs2E, RdE, RdM, RdW,
input logic MemReadE, MulDivE, CSRReadE,
input logic RegWriteM, RegWriteW,
input logic DivDoneE, DivBusyE,
input logic FWriteIntE, FWriteIntM, FWriteIntW,
input logic MemReadE, MulDivE, CSRReadE,
input logic RegWriteM, RegWriteW,
input logic DivDoneE, DivBusyE,
input logic FWriteIntE, FWriteIntM, FWriteIntW,
input logic SCE,
// Forwarding controls
output logic [1:0] ForwardAE, ForwardBE,
output logic FPUStallD, LoadStallD, MulDivStallD, CSRRdStallD
output logic FPUStallD, LoadStallD, MulDivStallD, CSRRdStallD
);
always_comb begin
@ -43,7 +44,7 @@ module forward(
if (Rs1E != 5'b0)
if ((Rs1E == RdM) & RegWriteM) ForwardAE = 2'b10;
else if ((Rs1E == RdW) & (RegWriteW|FWriteIntW)) ForwardAE = 2'b01;
else if ((Rs1E == RdM) & FWriteIntM) ForwardAE = 2'b11;
else if ((Rs1E == RdM) & FWriteIntM) ForwardAE = 2'b11;
if (Rs2E != 5'b0)
if ((Rs2E == RdM) & RegWriteM) ForwardBE = 2'b10;
@ -53,7 +54,7 @@ module forward(
// Stall on dependent operations that finish in Mem Stage and can't bypass in time
assign FPUStallD = FWriteIntE & ((Rs1D == RdE) | (Rs2D == RdE));
assign LoadStallD = MemReadE & ((Rs1D == RdE) | (Rs2D == RdE));
assign LoadStallD = (MemReadE|SCE) & ((Rs1D == RdE) | (Rs2D == RdE));
assign MulDivStallD = MulDivE & ((Rs1D == RdE) | (Rs2D == RdE)) | MulDivE | DivBusyE; // *** extend with stalls for divide
assign CSRRdStallD = CSRReadE & ((Rs1D == RdE) | (Rs2D == RdE));

3
wally-pipelined/src/ieu/ieu.sv
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@ -73,7 +73,8 @@ module ieu (
logic [4:0] ALUControlE;
logic ALUSrcAE, ALUSrcBE;
logic [2:0] ResultSrcW;
logic TargetSrcE;
logic TargetSrcE;
logic SCE;
// forwarding signals
logic [4:0] Rs1D, Rs2D, Rs1E, Rs2E, RdE, RdM, RdW;