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module decode
import riscv_types::*;
#(
)
(
input logic clk,
input logic rst_l,
// I-MEM Interface
input logic [31:0] imem_id_instr_ID,
// Fetch Interface
input logic [31:0] imem_id_pc_ID
// Dispatch Interface
);
// OpCode
opcode_t instrOpCode_ID;
// Instruction Type
logic instrTypeR_ID;
logic instrTypeI_ID;
logic instrTypeS_ID;
logic instrTypeB_ID;
logic instrTypeU_ID;
logic instrTypeJ_ID;
// Immediate
logic [31:0] instrImm_ID;
logic instrImmSign_ID;
// Register Indices
logic [4:0] instrRs1Idx_ID;
logic instrRs1Vld_ID;
logic [4:0] instrRs2Idx_ID;
logic instrRs2Vld_ID;
logic [4:0] instrRdIdx_ID;
logic instrRdVld_ID;
// Funct3 and Funct7
logic [2:0] instrFunct3_ID;
logic instrFunct7_ID;
// Control Bits
// Memory Op
mem_op_t instrMemOp_ID;
// Branch OP
brjmp_op_t instrBrJmpOp_ID;
// ALU Operand Selection
aluSelOp1_t instrAluOp1_ID;
aluSelOp2_t instrAluOp2_ID;
// DEBUG: Display decode instr
always_ff @(clk) begin : f_print_decode
$display("OpCode: %s", instrOpCode_ID.name());
$display("Immediate: %0d", instrImm_ID);
$display("Memory: %s", instrMemOp_ID.name());
$display("Branch: %s", instrBrJmpOp_ID.name());
$display("ALU Sel 1: %s", instrAluOp1_ID.name());
$display("ALU Sel 2: %s", instrAluOp2_ID.name());
$display("Funct3: %0x", instrFunct3_ID);
$display("Funct7: %0x", instrFunct7_ID);
end
// Instruction Type Decode
// FIXME: Add support for FENCE + ECALL + EBREAK + CSRs
assign instrTypeI_ID = (instrOpCode_ID == INSTR_TYPE_IMM)
| (instrOpCode_ID == INSTR_TYPE_JALR)
| (instrOpCode_ID == INSTR_TYPE_LD);
assign instrTypeU_ID = (instrOpCode_ID == INSTR_TYPE_LUI)
| (instrOpCode_ID == INSTR_TYPE_AUIPC);
assign instrTypeR_ID = (instrOpCode_ID == INSTR_TYPE_REG);
assign instrTypeS_ID = (instrOpCode_ID == INSTR_TYPE_ST);
assign instrTypeB_ID = (instrOpCode_ID == INSTR_TYPE_BR);
assign instrTypeJ_ID = (instrOpCode_ID == INSTR_TYPE_JAL);
// Register Index Decode
assign instrRs1Idx_ID = imem_id_instr_ID[19:15];
assign instrRs1Vld_ID = instrTypeR_ID | instrTypeI_ID | instrTypeS_ID | instrTypeB_ID;
assign instrRs2Idx_ID = imem_id_instr_ID[24:20];
assign instrRs2Vld_ID = instrTypeR_ID | instrTypeS_ID | instrTypeB_ID;
assign instrRdIdx_ID = imem_id_instr_ID[11:7];
assign instrRdVld_ID = instrTypeR_ID | instrTypeI_ID | instrTypeU_ID | instrTypeJ_ID;
// Func Bit decode
assign instrFunct7_ID = imem_id_instr_ID[30];
assign instrFunct3_ID = imem_id_instr_ID[14:12];
// Instruction Type (OpCode) Decode
assign instrImmSign_ID = imem_id_instr_ID[31];
assign instrOpCode_ID = opcode_t'(imem_id_instr_ID[6:0]);
// Immediate Decode
assign instrImm_ID[0] = instrTypeJ_ID ? imem_id_instr_ID[25] : // Bit 25 for I-Type
instrTypeS_ID ? imem_id_instr_ID[7] : // Bit 7 for S-Type
'0; // All other instructions set to 0
assign instrImm_ID[4:1] = instrTypeI_ID ? imem_id_instr_ID[24:21] : // I-Type bits
(instrTypeS_ID | instrTypeB_ID) ? imem_id_instr_ID[11:8] : // S-Type + B-Type bits
'0; // All other instructions set to 0
assign instrImm_ID[10:5] = instrTypeU_ID ? '0 : imem_id_instr_ID[30:25]; // Only J type is an immediate instruction that doesn't have it in 30:25
assign instrImm_ID[11] = (instrTypeI_ID | instrTypeS_ID) ? imem_id_instr_ID[31] :
(instrTypeB_ID) ? imem_id_instr_ID[7] :
(instrTypeJ_ID) ? imem_id_instr_ID[20] :
'0;
assign instrImm_ID[19:12] = (instrTypeU_ID | instrTypeJ_ID) ? imem_id_instr_ID[19:12] : { 8{instrImmSign_ID}}; // Only J and U types use 19:12 as not sign bit
assign instrImm_ID[31:20] = (instrTypeU_ID) ? imem_id_instr_ID[31:20] : {12{instrImmSign_ID}}; // Only U type use 31:20 as not sign bit
// Control Bits
assign instrMemOp_ID = (instrOpCode_ID == INSTR_TYPE_ST) ? MEM_OP_STORE :
(instrOpCode_ID == INSTR_TYPE_LD) ? MEM_OP_LOAD :
MEM_OP_NONE;
assign instrBrJmpOp_ID = (instrOpCode_ID == INSTR_TYPE_JALR) ? REG_IMM_OFFSET :
(instrOpCode_ID == INSTR_TYPE_BR | instrOpCode_ID == INSTR_TYPE_JAL) ? PC_IMM_OFFSET :
OFFSET_NONE;
assign instrAluOp1_ID = (instrOpCode_ID == INSTR_TYPE_AUIPC) | (instrOpCode_ID == INSTR_TYPE_JAL) ? PC : // Loading PC for AUIPC, PC Offset for JAL
(instrOpCode_ID == INSTR_TYPE_LUI) ? OP_NONE : // Only loading immediate for LUI
RS1; // All else use RS1 value
assign instrAluOp2_ID = (instrOpCode_ID == INSTR_TYPE_REG) ? RS2 : IMM; // Only R2R needs non-immediate op in ALU
endmodule
|
