CPU: Fix more load delay slot issues

Fixes Spyro again. b{ltz,gez}(al)? disabled in the recompiler until
issues are fixed.

src/core/cpu_code_cache.cpp

@@ -55,22 +55,23 @@ void CodeCache::Execute()
         break;
     }
 
+  reexecute_block:
+
 #if 0
     const u32 tick = m_system->GetGlobalTickCounter() + m_core->GetPendingTicks();
-    if (tick == 58672386)
+    if (tick == 61033207)
       __debugbreak();
 #endif
 
-  reexecute_block:
+#if 0
+    LogCurrentState();
+#endif
+
     if (m_use_recompiler)
       block->host_code(m_core);
     else
       InterpretCachedBlock(*block);
 
-#if 0
-    LogCurrentState();
-#endif
-
     if (m_core->m_downcount < 0)
       break;
     else if (m_core->HasPendingInterrupt() || !USE_BLOCK_LINKING)
@@ -142,11 +143,14 @@ void CodeCache::LogCurrentState()
   WriteToExecutionLog(
     "tick=%u pc=%08X npc=%08X zero=%08X at=%08X v0=%08X v1=%08X a0=%08X a1=%08X a2=%08X a3=%08X t0=%08X "
     "t1=%08X t2=%08X t3=%08X t4=%08X t5=%08X t6=%08X t7=%08X s0=%08X s1=%08X s2=%08X s3=%08X s4=%08X "
-    "s5=%08X s6=%08X s7=%08X t8=%08X t9=%08X k0=%08X k1=%08X gp=%08X sp=%08X fp=%08X ra=%08X\n",
+    "s5=%08X s6=%08X s7=%08X t8=%08X t9=%08X k0=%08X k1=%08X gp=%08X sp=%08X fp=%08X ra=%08X npc=%08X ldr=%s "
+    "ldv=%08X\n",
     m_system->GetGlobalTickCounter() + m_core->GetPendingTicks(), regs.pc, regs.npc, regs.zero, regs.at, regs.v0,
     regs.v1, regs.a0, regs.a1, regs.a2, regs.a3, regs.t0, regs.t1, regs.t2, regs.t3, regs.t4, regs.t5, regs.t6, regs.t7,
     regs.s0, regs.s1, regs.s2, regs.s3, regs.s4, regs.s5, regs.s6, regs.s7, regs.t8, regs.t9, regs.k0, regs.k1, regs.gp,
-    regs.sp, regs.fp, regs.ra);
+    regs.sp, regs.fp, regs.ra, regs.npc,
+    (m_core->m_next_load_delay_reg == Reg::count) ? "NONE" : GetRegName(m_core->m_next_load_delay_reg),
+    (m_core->m_next_load_delay_reg == Reg::count) ? 0 : m_core->m_next_load_delay_value);
 }
 
 CodeBlockKey CodeCache::GetNextBlockKey() const

src/core/cpu_core.cpp

@@ -94,10 +94,8 @@ bool Core::DoState(StateWrapper& sw)
   sw.Do(&m_branch_was_taken);
   sw.Do(&m_load_delay_reg);
   sw.Do(&m_load_delay_value);
-  sw.Do(&m_load_delay_old_value);
   sw.Do(&m_next_load_delay_reg);
   sw.Do(&m_next_load_delay_value);
-  sw.Do(&m_next_load_delay_old_value);
   sw.Do(&m_cache_control);
   sw.DoBytes(m_dcache.data(), m_dcache.size());
 
@@ -389,6 +387,7 @@ u32 Core::ReadReg(Reg rs)
 void Core::WriteReg(Reg rd, u32 value)
 {
   m_regs.r[static_cast<u8>(rd)] = value;
+  m_load_delay_reg = (rd == m_load_delay_reg) ? Reg::count : m_load_delay_reg;
 
   // prevent writes to $zero from going through - better than branching/cmov
   m_regs.zero = 0;
@@ -407,7 +406,6 @@ void Core::WriteRegDelayed(Reg rd, u32 value)
   // save the old value, if something else overwrites this reg we want to preserve it
   m_next_load_delay_reg = rd;
   m_next_load_delay_value = value;
-  m_next_load_delay_old_value = m_regs.r[static_cast<u8>(rd)];
 }
 
 std::optional<u32> Core::ReadCop0Reg(Cop0Reg reg)
@@ -1120,7 +1118,7 @@ void Core::ExecuteInstruction()
 
     case InstructionOp::jal:
     {
-      m_regs.ra = m_regs.npc;
+      WriteReg(Reg::ra, m_regs.npc);
       m_next_instruction_is_branch_delay_slot = true;
       Branch((m_regs.pc & UINT32_C(0xF0000000)) | (inst.j.target << 2));
     }
@@ -1175,7 +1173,7 @@ void Core::ExecuteInstruction()
       // register is still linked even if the branch isn't taken
       const bool link = (rt & u8(0x1E)) == u8(0x10);
       if (link)
-        m_regs.ra = m_regs.npc;
+        WriteReg(Reg::ra, m_regs.npc);
 
       if (branch)
         Branch(m_regs.pc + (inst.i.imm_sext32() << 2));

src/core/cpu_core.h

@@ -106,12 +106,11 @@ private:
   ALWAYS_INLINE void UpdateLoadDelay()
   {
     // the old value is needed in case the delay slot instruction overwrites the same register
-    if (m_load_delay_reg != Reg::count && m_regs.r[static_cast<u8>(m_load_delay_reg)] == m_load_delay_old_value)
+    if (m_load_delay_reg != Reg::count)
       m_regs.r[static_cast<u8>(m_load_delay_reg)] = m_load_delay_value;
 
     m_load_delay_reg = m_next_load_delay_reg;
     m_load_delay_value = m_next_load_delay_value;
-    m_load_delay_old_value = m_next_load_delay_old_value;
     m_next_load_delay_reg = Reg::count;
   }
 
@@ -168,10 +167,8 @@ private:
   // load delays
   Reg m_load_delay_reg = Reg::count;
   u32 m_load_delay_value = 0;
-  u32 m_load_delay_old_value = 0;
   Reg m_next_load_delay_reg = Reg::count;
   u32 m_next_load_delay_value = 0;
-  u32 m_next_load_delay_old_value = 0;
 
   u32 m_cache_control = 0;
 

src/core/cpu_recompiler_code_generator.cpp

@@ -93,7 +93,7 @@ bool CodeGenerator::CompileInstruction(const CodeBlockInstruction& cbi)
 
     case InstructionOp::j:
     case InstructionOp::jal:
-    case InstructionOp::b:
+    //case InstructionOp::b:
     case InstructionOp::beq:
     case InstructionOp::bne:
     case InstructionOp::bgtz:
@@ -812,20 +812,23 @@ void CodeGenerator::InstructionEpilogue(const CodeBlockInstruction& cbi)
 {
   m_register_cache.UpdateLoadDelay();
 
+  if (m_load_delay_dirty)
+  {
+    // we have to invalidate the register cache, since the load delayed register might've been cached
+    Log_DebugPrint("Emitting delay slot flush");
+    EmitFlushInterpreterLoadDelay();
+    m_register_cache.InvalidateAllNonDirtyGuestRegisters();
+    m_load_delay_dirty = false;
+  }
+
   // copy if the previous instruction was a load, reset the current value on the next instruction
   if (m_next_load_delay_dirty)
   {
     Log_DebugPrint("Emitting delay slot flush (with move next)");
-    EmitDelaySlotUpdate(false, false, true);
+    EmitMoveNextInterpreterLoadDelay();
     m_next_load_delay_dirty = false;
     m_load_delay_dirty = true;
   }
-  else if (m_load_delay_dirty)
-  {
-    Log_DebugPrint("Emitting delay slot flush");
-    EmitDelaySlotUpdate(true, false, false);
-    m_load_delay_dirty = false;
-  }
 }
 
 void CodeGenerator::SyncCurrentInstructionPC()

src/core/cpu_recompiler_code_generator.h

@@ -65,7 +65,10 @@ public:
 
   void EmitLoadGuestRegister(HostReg host_reg, Reg guest_reg);
   void EmitStoreGuestRegister(Reg guest_reg, const Value& value);
-  void EmitStoreLoadDelay(Reg reg, const Value& value);
+  void EmitStoreInterpreterLoadDelay(Reg reg, const Value& value);
+  void EmitFlushInterpreterLoadDelay();
+  void EmitMoveNextInterpreterLoadDelay();
+  void EmitCancelInterpreterLoadDelayForReg(Reg reg);
   void EmitLoadCPUStructField(HostReg host_reg, RegSize size, u32 offset);
   void EmitStoreCPUStructField(u32 offset, const Value& value);
   void EmitAddCPUStructField(u32 offset, const Value& value);
@@ -168,7 +171,6 @@ private:
   void SyncCurrentInstructionPC();
   void SyncPC();
   void AddPendingCycles();
-  void EmitDelaySlotUpdate(bool skip_check_for_delay, bool skip_check_old_value, bool move_next);
 
   //////////////////////////////////////////////////////////////////////////
   // Instruction Code Generators

src/core/cpu_recompiler_code_generator_generic.cpp

@@ -17,25 +17,11 @@ void CodeGenerator::EmitStoreGuestRegister(Reg guest_reg, const Value& value)
   EmitStoreCPUStructField(CalculateRegisterOffset(guest_reg), value);
 }
 
-void CodeGenerator::EmitStoreLoadDelay(Reg reg, const Value& value)
+void CodeGenerator::EmitStoreInterpreterLoadDelay(Reg reg, const Value& value)
 {
   DebugAssert(value.size == RegSize_32 && value.IsInHostRegister());
   EmitStoreCPUStructField(offsetof(Core, m_load_delay_reg), Value::FromConstantU8(static_cast<u8>(reg)));
   EmitStoreCPUStructField(offsetof(Core, m_load_delay_value), value);
-
-  // We don't want to allocate a register since this could be in a block exit, so re-use the value.
-  if (m_register_cache.IsGuestRegisterCached(reg))
-  {
-    EmitStoreCPUStructField(offsetof(Core, m_load_delay_old_value), m_register_cache.ReadGuestRegister(reg));
-  }
-  else
-  {
-    EmitPushHostReg(value.host_reg);
-    EmitLoadCPUStructField(value.host_reg, RegSize_32, CalculateRegisterOffset(reg));
-    EmitStoreCPUStructField(offsetof(Core, m_load_delay_old_value), value);
-    EmitPopHostReg(value.host_reg);
-  }
-
   m_load_delay_dirty = true;
 }
 

src/core/cpu_recompiler_code_generator_x64.cpp

@@ -1614,60 +1614,65 @@ void CodeGenerator::EmitStoreGuestMemory(const Value& address, const Value& valu
   SwitchToNearCode();
 }
 
-void CodeGenerator::EmitDelaySlotUpdate(bool skip_check_for_delay, bool skip_check_old_value, bool move_next)
+void CodeGenerator::EmitFlushInterpreterLoadDelay()
 {
   Value reg = m_register_cache.AllocateScratch(RegSize_8);
   Value value = m_register_cache.AllocateScratch(RegSize_32);
 
-  Xbyak::Label skip_flush;
-
   auto load_delay_reg = m_emit->byte[GetCPUPtrReg() + offsetof(Core, m_load_delay_reg)];
-  auto load_delay_old_value = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_load_delay_old_value)];
   auto load_delay_value = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_load_delay_value)];
   auto reg_ptr = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_regs.r[0]) + GetHostReg64(reg.host_reg) * 4];
 
+  Xbyak::Label skip_flush;
+
   // reg = load_delay_reg
   m_emit->movzx(GetHostReg32(reg.host_reg), load_delay_reg);
-  if (!skip_check_old_value)
-    m_emit->mov(GetHostReg32(value), load_delay_old_value);
-
-  if (!skip_check_for_delay)
-  {
-    // if load_delay_reg == Reg::count goto skip_flush
-    m_emit->cmp(GetHostReg32(reg.host_reg), static_cast<u8>(Reg::count));
-    m_emit->je(skip_flush);
-  }
 
-  if (!skip_check_old_value)
-  {
-    // if r[reg] != load_delay_old_value goto skip_flush
-    m_emit->cmp(GetHostReg32(value), reg_ptr);
-    m_emit->jne(skip_flush);
-  }
+  // if load_delay_reg == Reg::count goto skip_flush
+  m_emit->cmp(GetHostReg32(reg.host_reg), static_cast<u8>(Reg::count));
+  m_emit->je(skip_flush);
 
   // r[reg] = load_delay_value
   m_emit->mov(GetHostReg32(value), load_delay_value);
   m_emit->mov(reg_ptr, GetHostReg32(value));
 
-  // if !move_next load_delay_reg = Reg::count
-  if (!move_next)
-    m_emit->mov(load_delay_reg, static_cast<u8>(Reg::count));
+  // load_delay_reg = Reg::count
+  m_emit->mov(load_delay_reg, static_cast<u8>(Reg::count));
 
   m_emit->L(skip_flush);
+}
 
-  if (move_next)
-  {
-    auto next_load_delay_reg = m_emit->byte[GetCPUPtrReg() + offsetof(Core, m_next_load_delay_reg)];
-    auto next_load_delay_old_value = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_next_load_delay_old_value)];
-    auto next_load_delay_value = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_next_load_delay_value)];
-    m_emit->mov(GetHostReg32(value), next_load_delay_value);
-    m_emit->mov(GetHostReg8(reg), next_load_delay_reg);
-    m_emit->mov(load_delay_value, GetHostReg32(value));
-    m_emit->mov(GetHostReg32(value), next_load_delay_old_value);
-    m_emit->mov(load_delay_reg, GetHostReg8(reg));
-    m_emit->mov(load_delay_old_value, GetHostReg32(value));
-    m_emit->mov(next_load_delay_reg, static_cast<u8>(Reg::count));
-  }
+void CodeGenerator::EmitMoveNextInterpreterLoadDelay()
+{
+  Value reg = m_register_cache.AllocateScratch(RegSize_8);
+  Value value = m_register_cache.AllocateScratch(RegSize_32);
+
+  auto load_delay_reg = m_emit->byte[GetCPUPtrReg() + offsetof(Core, m_load_delay_reg)];
+  auto load_delay_value = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_load_delay_value)];
+  auto next_load_delay_reg = m_emit->byte[GetCPUPtrReg() + offsetof(Core, m_next_load_delay_reg)];
+  auto next_load_delay_value = m_emit->dword[GetCPUPtrReg() + offsetof(Core, m_next_load_delay_value)];
+
+  m_emit->mov(GetHostReg32(value), next_load_delay_value);
+  m_emit->mov(GetHostReg8(reg), next_load_delay_reg);
+  m_emit->mov(load_delay_value, GetHostReg32(value));
+  m_emit->mov(load_delay_reg, GetHostReg8(reg));
+  m_emit->mov(next_load_delay_reg, static_cast<u8>(Reg::count));
+}
+
+void CodeGenerator::EmitCancelInterpreterLoadDelayForReg(Reg reg)
+{
+  auto load_delay_reg = m_emit->byte[GetCPUPtrReg() + offsetof(Core, m_load_delay_reg)];
+
+  Xbyak::Label skip_cancel;
+
+  // if load_delay_reg != reg goto skip_cancel
+  m_emit->cmp(load_delay_reg, static_cast<u8>(reg));
+  m_emit->jne(skip_cancel);
+
+  // load_delay_reg = Reg::count
+  m_emit->mov(load_delay_reg, static_cast<u8>(Reg::count));
+
+  m_emit->L(skip_cancel);
 }
 
 template<typename T>
@@ -1746,7 +1751,9 @@ void CodeGenerator::EmitBranch(Condition condition, Reg lr_reg, bool always_link
     old_npc = m_register_cache.ReadGuestRegister(Reg::npc, false, true);
     if (always_link)
     {
-      // can't cache because we have two branches
+      // Can't cache because we have two branches. Load delay cancel is due to the immediate flush afterwards,
+      // if we don't cancel it, at the end of the instruction the value we write can be overridden.
+      EmitCancelInterpreterLoadDelayForReg(lr_reg);
       m_register_cache.WriteGuestRegister(lr_reg, std::move(old_npc));
       m_register_cache.FlushGuestRegister(lr_reg, true, true);
     }
@@ -1760,7 +1767,9 @@ void CodeGenerator::EmitBranch(Condition condition, Reg lr_reg, bool always_link
   // save the old PC if we want to
   if (lr_reg != Reg::count && !always_link)
   {
-    // can't cache because we have two branches
+    // Can't cache because we have two branches. Load delay cancel is due to the immediate flush afterwards,
+    // if we don't cancel it, at the end of the instruction the value we write can be overridden.
+    EmitCancelInterpreterLoadDelayForReg(lr_reg);
     m_register_cache.WriteGuestRegister(lr_reg, std::move(old_npc));
     m_register_cache.FlushGuestRegister(lr_reg, true, true);
   }
@@ -1807,6 +1816,10 @@ void CodeGenerator::EmitRaiseException(Exception excode, Condition condition /*
                      Value::FromConstantU8(static_cast<u8>(excode)));
     m_register_cache.FlushAllGuestRegisters(true, true);
     m_register_cache.FlushLoadDelay(true);
+
+    // PC should be synced at this point. If we leave the 4 on here for this instruction, we mess up npc.
+    Assert(m_delayed_pc_add == 4);
+    m_delayed_pc_add = 0;
     return;
   }
 

src/core/cpu_recompiler_register_cache.cpp

@@ -509,6 +509,9 @@ void RegisterCache::WriteGuestRegisterDelayed(Reg guest_reg, Value&& value)
     m_load_delay_value.ReleaseAndClear();
   }
 
+  // two load delay case with interpreter load delay
+  m_code_generator.EmitCancelInterpreterLoadDelayForReg(guest_reg);
+
   // set up the load delay at the end of this instruction
   Value& cache_value = m_next_load_delay_value;
   Assert(m_next_load_delay_register == Reg::count);
@@ -561,7 +564,7 @@ void RegisterCache::WriteLoadDelayToCPU(bool clear)
   if (m_load_delay_register != Reg::count)
   {
     Log_DebugPrintf("Flushing pending load delay of %s", GetRegName(m_load_delay_register));
-    m_code_generator.EmitStoreLoadDelay(m_load_delay_register, m_load_delay_value);
+    m_code_generator.EmitStoreInterpreterLoadDelay(m_load_delay_register, m_load_delay_value);
     if (clear)
     {
       m_load_delay_register = Reg::count;
@@ -573,17 +576,18 @@ void RegisterCache::WriteLoadDelayToCPU(bool clear)
 void RegisterCache::FlushLoadDelay(bool clear)
 {
   Assert(m_next_load_delay_register == Reg::count);
-  if (m_load_delay_register == Reg::count)
-    return;
-
-  // if this is an exception exit, write the new value to the CPU register file, but keep it tracked for the next
-  // non-exception-raised path. TODO: push/pop whole state would avoid this issue
-  m_code_generator.EmitStoreGuestRegister(m_load_delay_register, m_load_delay_value);
 
-  if (clear)
+  if (m_load_delay_register != Reg::count)
   {
-    m_load_delay_register = Reg::count;
-    m_load_delay_value.ReleaseAndClear();
+    // if this is an exception exit, write the new value to the CPU register file, but keep it tracked for the next
+    // non-exception-raised path. TODO: push/pop whole state would avoid this issue
+    m_code_generator.EmitStoreGuestRegister(m_load_delay_register, m_load_delay_value);
+
+    if (clear)
+    {
+      m_load_delay_register = Reg::count;
+      m_load_delay_value.ReleaseAndClear();
+    }
   }
 }
 
@@ -627,6 +631,16 @@ void RegisterCache::InvalidateGuestRegister(Reg guest_reg)
   cache_value.Clear();
 }
 
+void RegisterCache::InvalidateAllNonDirtyGuestRegisters()
+{
+  for (u8 reg = 0; reg < static_cast<u8>(Reg::count); reg++)
+  {
+    Value& cache_value = m_guest_reg_cache[reg];
+    if (cache_value.IsValid() && !cache_value.IsDirty())
+      InvalidateGuestRegister(static_cast<Reg>(reg));
+  }
+}
+
 void RegisterCache::FlushAllGuestRegisters(bool invalidate, bool clear_dirty)
 {
   for (u8 reg = 0; reg < static_cast<u8>(Reg::count); reg++)
@@ -694,4 +708,5 @@ void RegisterCache::AppendRegisterToOrder(Reg reg)
   m_guest_register_order[0] = reg;
   m_guest_register_order_count++;
 }
+
 } // namespace CPU::Recompiler

src/core/cpu_recompiler_register_cache.h

@@ -257,6 +257,7 @@ public:
   void FlushGuestRegister(Reg guest_reg, bool invalidate, bool clear_dirty);
   void InvalidateGuestRegister(Reg guest_reg);
 
+  void InvalidateAllNonDirtyGuestRegisters();
   void FlushAllGuestRegisters(bool invalidate, bool clear_dirty);
   bool EvictOneGuestRegister();