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// Richard CPU
// Copyright (C) 2026 Richard Qin
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// File path: tb/unit/tb_if_id_reg.cc
// Description: IF/ID Pipeline Register unit test
#include <iostream>
#include <iomanip>
#include <cstdint>
#include <cassert>
#include <verilated.h>
#include "Vif_id_reg.h"
int pass_count = 0;
void tick(Vif_id_reg* dut) {
dut->clk = 0;
dut->eval();
dut->clk = 1;
dut->eval();
dut->clk = 0;
dut->eval();
}
void check_reg(uint64_t expected_pc, uint32_t expected_instr, uint64_t actual_pc, uint32_t actual_instr, const char* test_name) {
if (expected_pc == actual_pc && expected_instr == actual_instr) {
std::cout << "\033[32m[PASS] " << test_name << " | PC = 0x" << std::hex << actual_pc << " Instr = 0x" << actual_instr << "\033[0m" << std::dec << std::endl;
pass_count++;
} else {
std::cout << "\033[31m[FAIL] " << test_name << "\n Expected: PC=0x" << std::hex << expected_pc << " Instr=0x" << expected_instr
<< "\n Got: PC=0x" << actual_pc << " Instr=0x" << actual_instr << "\033[0m" << std::dec << std::endl;
assert(false);
}
}
int main(int argc, char** argv) {
Verilated::commandArgs(argc, argv);
Vif_id_reg* dut = new Vif_id_reg;
std::cout << "----------------------------------" << std::endl;
std::cout << " IF/ID Register Test" << std::endl;
std::cout << "----------------------------------" << std::endl;
// --- 1. Init / Reset ---
dut->stall_en = 0;
dut->flush_en = 0;
dut->if_pc = 0x80000000;
dut->if_instr = 0xDEADBEEF;
dut->rst = 1;
tick(dut);
dut->rst = 0;
// After reset, PC should be 0, instr should be NOP (0x00000013)
check_reg(0, 0x00000013, dut->id_pc, dut->id_instr, "Reset_Inserts_NOP");
// --- 2. Normal Propagation ---
dut->if_pc = 0x80001000;
dut->if_instr = 0x02A00093; // ADDI x1, x0, 42
tick(dut);
check_reg(0x80001000, 0x02A00093, dut->id_pc, dut->id_instr, "Normal_Propagation");
// --- 3. Stall (Freeze) ---
dut->if_pc = 0x80001004;
dut->if_instr = 0x000280B3; // New incoming data
dut->stall_en = 1;
tick(dut); // Clock ticks but stall is active
// Register should hold previous values
check_reg(0x80001000, 0x02A00093, dut->id_pc, dut->id_instr, "Stall_Holds_Previous_Data");
dut->if_pc = 0x80001008;
dut->if_instr = 0x008000EF;
tick(dut); // Still stalled
check_reg(0x80001000, 0x02A00093, dut->id_pc, dut->id_instr, "Stall_Multiple_Cycles");
// Release stall
dut->stall_en = 0;
tick(dut);
check_reg(0x80001008, 0x008000EF, dut->id_pc, dut->id_instr, "Release_Stall_Captures_New");
// --- 4. Flush (Insert NOP) ---
dut->if_pc = 0x8000100C;
dut->if_instr = 0xDEADBEEF; // Some invalid instruction
dut->flush_en = 1;
tick(dut);
// PC should be 0, instr should be NOP (0x00000013)
check_reg(0, 0x00000013, dut->id_pc, dut->id_instr, "Flush_Inserts_NOP");
// --- 5. Stall overrides Flush ? OR Flush overrides Stall ? ---
// Usually, in RISC-V pipelines, if we have a branch mispredict (Flush),
// we want to flush even if stalled, OR flush takes priority.
// Based on if_id_reg.sv, `flush_en` has higher priority than `stall_en`.
// Pre-load good data
dut->flush_en = 0;
dut->if_pc = 0x80002000;
dut->if_instr = 0x12345678;
tick(dut);
check_reg(0x80002000, 0x12345678, dut->id_pc, dut->id_instr, "Pre_Flush_Stall_Test");
// Apply simultaneous flush & stall
dut->flush_en = 1;
dut->stall_en = 1;
tick(dut);
check_reg(0, 0x00000013, dut->id_pc, dut->id_instr, "Flush_Overrides_Stall");
std::cout << "----------------------------------" << std::endl;
std::cout << "\033[32mAll " << pass_count << " tests passed!\033[0m" << std::endl;
std::cout << "----------------------------------" << std::endl;
delete dut;
return 0;
}
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