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module exe (
input logic clk,
input logic rst,
//-----------------
// Decode Interface
//-----------------
input logic idu_exe_instrVld_ID,
// Register Access
input logic idu_exe_rs1Vld_ID,
input logic [REG_IDX-1:0] idu_exe_rs1Idx_ID,
input logic idu_exe_rs2Vld_ID,
input logic [REG_IDX-1:0] idu_exe_rs2Idx_ID,
// Branch Type
input logic idu_exe_instrJmp_ID,
input logic idu_exe_instrBr_ID,
// ALU information
input alu_op_t idu_exe_aluOp_ID,
// Passthrough Information
input mem_op_t idu_exe_instrMemOp_ID,
input mem_size_t idu_exe_instrMemSize_ID,
input rd_data_sel_t idu_exe_instrRdDataSel_ID,
//-----------------
// Memory Interface
//-----------------
// ALU Result information
output logic [WORD_WID-1:0] exe_mem_aluOpOut_EXE,
// Stall
input logic mem_exe_stallVld_EXE,
// Memory Information
output mem_op_t exe_mem_instrMemOp_EXE,
output mem_size_t exe_mem_instrMemSize_EXE,
// Passthrough information
output rd_data_sel_t exe_mem_instrRdDataSel_EXE,
//-----------------------
// Fetch Branch Interface
//-----------------------
output logic exe_ifu_brRes_EXE,
output logic exe_ifu_brTaken_EXE,
output logic [WORD_WID-1:0] exe_ifu_brPC_EXE,
//--------------------
// Writeback Interface
//--------------------
input logic wb_exe_rdVld_WB,
input logic [REG_IDX-1:0] wb_exe_rdIdx_WB,
input logic [WORD_WID-1:0] wb_exe_rdData_WB
);
logic instrVld_EXE;
// Alu
logic [WORD_WID-1:0] aluSumDiff_EXE;
logic [WORD_WID-1:0] aluSumDiffIn1_EXE;
logic [WORD_WID-1:0] aluSumDiffIn2_EXE;
logic [WORD_WID-1:0] aluLeftShft_EXE;
logic [WORD_WID-1:0] aluRightShft_EXE;
logic [WORD_WID-1:0] aluRightShftUsign_EXE;
logic [WORD_WID-1:0] aluRightShftSext_EXE;
logic [WORD_WID-1:0] aluCmp_EXE;
logic [WORD_WID-1:0] aluCmpSign_EXE;
logic [WORD_WID-1:0] aluCmpUsign_EXE;
logic aluCmpMsbDiff_EXE;
logic aluCmpLowUsign_EXE;
// Branch Resolution
logic [5:0] brResChoice_EXE;
// Reg File
logic [NUM_REG-1:1] [WORD_WID-1:0] regData_XXX;
// Stall Signal
assign stallVld_ID = exe_mem_instrVld_EXE & ~mem_exe_stallVld_EXE;
//--------------------
// Decode Output Flops
//--------------------
// Flop Decode information
AFFR #(.WIDTH(1)) AFFR_EXE_instrVld (.q(exe_mem_instrVld_EXE), .d(idu_exe_instrVld_ID), .en(stallVld_ID), .clk(clk), rst(rst));
AFF #(.DTYPE(alu_op_t)) AFF_EXE_aluOp (.q(idu_exe_aluOp_EXE), .d(idu_exe_aluOp_ID), .en(stallVld_ID), .clk(clk));
AFF #(.WIDTH(WORD_WID)) AFF_EXE_pc (.q(idu_exe_pc_EXE), .d(idu_exe_pc_ID), .en(stallVld_ID), .clk(clk));
AFF #(.WIDTH(1)) AFF_EXE_instrJmp (.q(idu_exe_instrJmp_EXE), .d(idu_exe_instrJmp_ID), .en(stallVld_ID), .clk(clk));
AFF #(.WIDTH(1)) AFF_EXE_brRes (.q(idu_exe_brRes_EXE), .d(brResNxt_EXEM1), .en(stallVld_ID), .clk(clk));
//--------------
// Register File
//--------------
assign rs1WrFwd_ID = wb_exe_rdWrVld_WB & (idu_exe_rs1Idx_ID == wb_exe_rdIdx_WB);
assign rs2WrFwd_ID = wb_exe_rdWrVld_WB & (idu_exe_rs2Idx_ID == wb_exe_rdIdx_WB);
always_ff @(posedge clk) begin
// RS1 Read Port with Forwarding
if (instrRs1Vld_ID) begin
if (idx_exe_rs1Idx == REG_IDX'0) // X0 Register
idu_exe_rs1Data_EXE <= WORD_SIZE'0;
else if (rs1WrFwd_ID) begin // Write Foward
idu_exe_rs1Data_EXE <= wb_exe_rdData_WB;
else // Normal Read
idu_exe_rs1Data_EXE <= regData_XXX[idu_exe_rs1Idx_ID];
end
// RS2 Read Port with Forwarding
if (instrRs2Vld_ID) begin
if (idx_exe_rs2Idx == REG_IDX'0) // X0 Register
idu_exe_rs2Data_EXE <= WORD_WID'0;
else if (rs2WrFwd_ID) begin // Write Foward
idu_exe_rs2Data_EXE <= wb_exe_rdData_WB;
else // Normal Read
idu_exe_rs2Data_EXE <= regData_XXX[idu_exe_rs1Idx_ID];
end
// RD Write Port
if (wb_exe_rdWrVld_WB & (~|wb_exe_rdIdx_WB)) begin
regData_XXX[wb_exe_rdIdx_WB] <= wb_exe_rdData_WB;
end
end
//----
// ALU
//----
// Operand Selection
assign aluIn1_EXE = (aluOp_EXE.rs1Sel == PC) ? pc_EXE : // PC for AUIPC, JAL
(aluOp_EXE.rs1Sel == ZERO) ? WORD_WID'(0) : // 0 for LUI
rs1Data_EXE; // RS1 for other operations
assign aluIn2_EXE = (aluOp_EXE.rs2Sel == RS2) ? rs2Data_EXE : // RS2 for R type operations
aluOp_EXE.immediate; // Immediate for all other operations
// Two's complement negation of aluIn2 if func7 is set (subtract)
assign aluSumDiffIn1_EXE = aluIn1_EXE;
assign aluSumDiffIn2_EXE = ({WORD_WID{aluOp_EXE.func7}} ^ aluIn2_EXE) + aluOp_EXE.func7;
assign aluSumDiff_EXE = aluSumDiffIn1_EXE + aluSumDiffIn2_EXE;
// Shifter, TODO: Explicit signed barrel shifter with sign bit
assign aluRightShftUsign_EXE = aluIn1_EXE >> aluIn2_EXE[4:0];
assign aluRightShftSext_EXE = ~({WORD_WID{1'b1}} >> aluIn2_EXE[4:0]);
assign aluRightShft_EXE = aluRightShftUsgn_EXE | (aluRightShftSext_EXE & {WORD_WID{aluOp_EXE.func7}});
FLIP #( .WIDTH(WORD_WID) ) EXE_aluLeftShft ( .in (aluRightShftUsign_EXE), .out(aluLeftShft_EXE) );
// Set Less Than
assign aluCmpMsbDiff_EXE = aluIn2_EXE ^ aluIn1_EXE;
assign aluCmpLowUsign_EXE = aluIn1_EXE[WORD_WID-2:0] < aluIn2_EXE[WORD_WID-2:0];
assign aluCmpSign_EXE = aluCmpMsbDiff_EXE ? aluIn1_EXE[WORD_WID-1] : aluCmpLowUsign_EXE; // If diff signs (MSB) and in1 negative, then in1 < 0 < in2, else compare low bits
assign aluCmpUSign_EXE = aluCmpMsbDiff_EXE ? aluIn2_EXE[WORD_WID-1] : aluCmpLowUsign_EXE; // If diff MSB and MSB in2[31] == 1, then in1 < in2, else compare low bits
// Bitwise Operations
assign aluXor_EXE = aluIn1_EXE ^ aluIn2_EXE;
assign aluOr_EXE = aluIn1_EXE | aluIn2_EXE;
assign aluAnd_EXE = aluIn1_EXE & aluIn2_EXE;
// ALU Operation Select
assign aluOpRes_EXE[0] = aluSumDiff_EXE;
assign aluOpRes_EXE[1] = aluLeftShft_EXE;
assign aluOpRes_EXE[2] = {(WORD_WID - 1)'(0), aluCmpSign_EXE};
assign aluOpRes_EXE[3] = {(WORD_WID - 1)'(0), aluCmpUSign_EXE};
assign aluOpRes_EXE[4] = aluXor_EXE;
assign aluOpRes_EXE[5] = aluRightShft_EXE;
assign aluOpRes_EXE[6] = aluOr_EXE;
assign aluOpRes_EXE[7] = aluAnd_EXE;
EMUX #(
.WIDTH (WORD_WID),
.INPUTS(8)
) EMUX_exe_aluOpSel (
.in (aluOpResults_EXE),
.out(aluOpOut_EXE),
.sel(aluOp_EXE.func3)
);
// rd is either PC from jump instr or alu output
assign exe_mem_rdData_EXE = instrJmp_EXE ? pc_EXE : aluOpOut_EXE;
//------------------
// Branch Resolution
//------------------
assign exe_ifu_brPC_EXE = aluOpOut_EXE;
assign exe_ifu_brRes_EXE = brRes_EXE;
assign exe_ifu_brTaken_EXE = (brTaken_EXE & idu_exe_instrBr_ID) | idu_exe_instrJmp_ID;
assign brResChoice_EXE[0] = ~|aluXor_EXE;
assign brResChoice_EXE[1] = |aluXor_EXE;
assign brResChoice_EXE[2] = aluCmpSign_EXE;
assign brResChoice_EXE[3] = ~aluCmpSign_EXE;
assign brResChoice_EXE[4] = aluCmpUSign_EXE;
assign brResChoice_EXE[5] = ~aluCmpUSign_EXE;
EMUX #(
.WIDTH (1),
.INPUTS(6)
) EMUX_exe_aluOpSel (
.in (brResChoice_EXE),
.out(brTaken_EXE),
.sel(idu_exe_brOp_ID)
);
//---------------------
// Pipeline passthrough
//---------------------
// Memory
AFF #(.DTYPE(mem_op_t)) AFF_EXE_instRdDataSel (
.q(exe_mem_instrMemOp_EXE),
.d(idu_exe_instrMemOp_ID),
.en(stallVld_ID),
.clk(clk)
);
AFF #(.DTYPE(mem_op_size_t)) AFF_EXE_instMemSize (
.q(exe_mem_instrMemSize_EXE),
.d(idu_exe_instrMemSize_ID),
.en(stallVld_ID),
.clk(clk)
);
// Write Back
AFF #(.DTYPE(rd_data_sel_t)) AFF_EXE_instRdDataSel (
.q(exe_mem_instrRdDataSel_EXE),
.d(idu_exe_instrRdDataSel_ID),
.en(stallVld_ID),
.clk(clk)
);
endmodule
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