Figure out why the program counter never stops increasing after a certain point

.gitignore

@@ -4,6 +4,7 @@ saves/
 .cache/
 .vs/
 .vscode/
+.zed/
 out/
 *.toml
 *.ini

src/backend/Core.cpp

@@ -16,6 +16,8 @@ Core::Core() :
         cpuType = Interpreted;
     } else if (selectedCpu == "jit") {
         cpuType = DynamicRecompiler;
+    } else if (selectedCpu == "cached_interpreter") {
+        cpuType = CachedInterpreter;
     } else {
         panic("Unimplemented CPU type");
     }
@@ -63,7 +65,13 @@ void Core::LoadROM(const std::string &rom_) {
 }
 
 u32 Core::StepCPU() {
-    if (cpuType == Interpreted)
+    if (cpuType == Interpreted) {
+        auto taken = interpreter.Step() + regs.PopStalledCycles();
+        StepRSP(taken);
+        return taken;
+    }
+
+    if (cpuType == CachedInterpreter)
         return interpreter.ExecuteCached() + regs.PopStalledCycles();
 
 #ifdef KAIZEN_JIT_ENABLED
@@ -115,8 +123,6 @@ void Core::Run(const float volumeL, const float volumeR) {
 
                 const u32 taken = StepCPU();
                 cycles += taken;
-
-                StepRSP(taken);
                 frameCycles += taken;
                 Scheduler::GetInstance().Tick(taken);
             }

src/backend/Core.hpp

@@ -10,7 +10,7 @@
 
 namespace n64 {
 struct Core {
-    enum CPUType { Interpreted, DynamicRecompiler, CachedInterpreter } cpuType = Interpreted;
+    enum CPUType { Interpreted, DynamicRecompiler, CachedInterpreter } cpuType = CachedInterpreter;
 
     explicit Core();
 

src/backend/core/Interpreter.cpp

@@ -52,6 +52,18 @@ bool Interpreter::MaybeAdvance() {
         return false;
     }
 
+    regs.push_to_stack_trace(regs.pc);
+    if ((u32)regs.pc == 0x4) {
+        auto &regs = Core::GetRegs();
+        std::sort(regs.stack_trace.begin(), regs.stack_trace.end());
+
+        std::println("Stack trace:");
+        for (int i = 0; i < regs.stack_trace.size(); i++) {
+            std::println("    [{:016X}]", regs.stack_trace[i]);
+        }
+        exit(1);
+    }
+
     regs.oldPC = regs.pc;
     regs.pc = regs.nextPC;
     regs.nextPC += 4;
@@ -101,23 +113,22 @@ u32 DivideAddr(u32 addr, u32 &offset) {
     return addr / MAX_LINES_PER_BLOCK;
 }
 
-CachedLine *CachedState::GetLine(u64 addr) {
+std::shared_ptr<CachedLine> CachedState::GetLine(u64 addr) {
     u32 offset;
     u32 page = DivideAddr(addr, offset);
-    if (blocks[page] && blocks[page]->valid)
+    if (blocks[page])
-        return &blocks[page]->lines[offset];
+        return blocks[page]->lines[offset];
 
     return nullptr;
 }
 
-void CachedState::InsertLine(u64 addr, const CachedLine &line) {
+void CachedState::InsertLine(u64 addr, std::shared_ptr<CachedLine> line) {
     u32 offset;
     u32 page = DivideAddr(addr, offset);
 
     if (!blocks[page])
         blocks[page] = std::make_unique<CachedBlock>();
 
-    blocks[page]->valid = true;
     blocks[page]->lines[offset] = line;
 }
 
@@ -125,8 +136,8 @@ void CachedState::EvictLine(u64 addr) {
     u32 offset;
     u32 page = DivideAddr(addr, offset);
 
-    if (blocks[page] && blocks[page]->valid)
+    if (blocks[page])
-        blocks[page]->valid = false;
+        blocks[page] = nullptr;
 }
 
 u32 Interpreter::ExecuteCached() {
@@ -141,14 +152,13 @@ u32 Interpreter::ExecuteCached() {
 
             Instruction instr = line->code[i];
             DecodeExecute(instr);
-            if (IsBranchLikely(instr) && !regs.delaySlot) {
+
-                line->len -= 1; // Branch likely with false condition, it wasn't taken so don't execute the delay slot
+            Core::GetInstance().StepRSP(1);
-                                // and remove it from the cache
+
-                if (line->len <= 0)
+            // Branch likely with false condition, it wasn't taken so don't execute the delay slot
-                    line->len = 1;
+            if (IsBranchLikely(instr) && !regs.delaySlot)
                 break;
         }
-        }
 
         if (line->cycles == 0)
             Scheduler::GetInstance().SkipToNext();
@@ -182,7 +192,7 @@ u32 Interpreter::ExecuteCached() {
         }
     }
 
-    cachedState.InsertLine(block_addr, {code, i, i});
+    cachedState.InsertLine(block_addr, std::make_shared<CachedLine>(code, i, i));
 
     return ExecuteCached();
 }

src/backend/core/Interpreter.hpp

@@ -15,8 +15,7 @@ struct CachedLine {
 };
 
 struct CachedBlock {
-    std::array<CachedLine, MAX_LINES_PER_BLOCK / 4> lines = {};
+    std::array<std::shared_ptr<CachedLine>, MAX_LINES_PER_BLOCK / 4> lines = {};
-    bool valid = false;
 };
 
 using CachedBlocks = std::vector<std::unique_ptr<CachedBlock>>;
@@ -34,8 +33,8 @@ struct CachedState {
         exception = false;
     }
 
-    CachedLine *GetLine(u64);
+    std::shared_ptr<CachedLine> GetLine(u64);
-    void InsertLine(u64, const CachedLine &);
+    void InsertLine(u64, std::shared_ptr<CachedLine>);
     void EvictLine(u64);
 };
 

src/backend/core/RSP.cpp

@@ -83,7 +83,15 @@ auto RSP::Read(const u32 addr) -> u32 {
     case 0x04080000:
         return pc & 0xFFC;
     default:
-    panic("Unimplemented SP register read {:08X}", addr);
+        {
+            auto &regs = Core::GetRegs();
+            std::println("Stack trace:");
+            for (int i = 0; i < regs.stack_trace.size(); i++) {
+                std::println("    [{:016X}]", regs.stack_trace[i]);
+            }
+            panic("Unimplemented SP register read {:08X} (cpu pc: 0x{:016X}, rsp pc: 0x{:04X}, ra: 0x{:016X})", addr,
+                  (u64)regs.oldPC, pc & 0xffc, (u64)regs.gpr[31]);
+        }
     }
 }
 

src/backend/core/registers/Registers.cpp

@@ -6,7 +6,10 @@ namespace n64 {
 #ifdef KAIZEN_JIT_ENABLED
 Registers::Registers(JIT &jit) : jit(jit) { Reset(); }
 #else
-Registers::Registers() { Reset(); }
+Registers::Registers() {
+    stack_trace.resize(0x10000000);
+    Reset();
+}
 #endif
 
 void Registers::Reset() {
@@ -14,6 +17,7 @@ void Registers::Reset() {
     lo = 0;
     delaySlot = false;
     prevDelaySlot = false;
+    std::fill(stack_trace.begin(), stack_trace.end(), 0);
     gpr.fill(0);
     regIsConstant = 1; // first bit is true indicating $zero is constant which yes it is always
 

src/backend/core/registers/Registers.hpp

@@ -48,6 +48,14 @@ struct Registers {
     Cop0 cop0;
     Cop1 cop1;
 
+    std::vector<u64> stack_trace;
+    int stack_count = 0;
+
+    void push_to_stack_trace(s64 val) {
+        stack_trace[stack_count++] = val;
+        stack_count %= stack_trace.size();
+    }
+
     void CpuStall(u32 cycles) { extraCycles += cycles; }
 
     u32 PopStalledCycles() {

src/frontend/Settings/CPUSettings.cpp

@@ -4,7 +4,10 @@
 #include <imgui.h>
 
 CPUSettings::CPUSettings() {
-    if (Options::GetInstance().GetValue<std::string>("cpu", "type") == "jit") {
+    auto selectedCpuType = Options::GetInstance().GetValue<std::string>("cpu", "type");
+    if (selectedCpuType == "jit") {
+        selectedCpuTypeIndex = 2;
+    } else if (selectedCpuType == "cached_interpreter") {
         selectedCpuTypeIndex = 1;
     } else {
         selectedCpuTypeIndex = 0;
@@ -12,7 +15,7 @@ CPUSettings::CPUSettings() {
 }
 
 void CPUSettings::render() {
-    const char *items[] = {"Interpreter",
+    const char *items[] = {"Interpreter", "Cached Interpreter",
 #ifdef KAIZEN_JIT_ENABLED
                            "Dynamic Recompiler"
 #endif
@@ -37,6 +40,8 @@ void CPUSettings::render() {
     if (modified) {
         if (selectedCpuTypeIndex == 0) {
             Options::GetInstance().SetValue<std::string>("cpu", "type", "interpreter");
+        } else if (selectedCpuTypeIndex == 1) {
+            Options::GetInstance().SetValue<std::string>("cpu", "type", "cached_interpreter");
         } else {
             Options::GetInstance().SetValue<std::string>("cpu", "type", "jit");
         }