prevent t bit changes without pipeline flush on arm7

idk what's happening fully and its gonna be slow to emulate most likely
we'll figure this out later

src/ARM.cpp

@@ -201,13 +201,6 @@ void ARMv5::Reset()
     ARM::Reset();
 }
 
-void ARMv4::Reset()
-{
-    Thumb = false;
-
-    ARM::Reset();
-}
-
 
 void ARM::DoSavestate(Savestate* file)
 {
@@ -402,7 +395,6 @@ void ARMv4::JumpTo(u32 addr, bool restorecpsr)
         Cycles += NDS.ARM7MemTimings[CodeCycles][0] + NDS.ARM7MemTimings[CodeCycles][1];
 
         CPSR |= 0x20;
-        Thumb = true;
     }
     else
     {
@@ -416,7 +408,6 @@ void ARMv4::JumpTo(u32 addr, bool restorecpsr)
         Cycles += NDS.ARM7MemTimings[CodeCycles][2] + NDS.ARM7MemTimings[CodeCycles][3];
 
         CPSR &= ~0x20;
-        Thumb = false;
     }
 }
 
@@ -840,11 +831,8 @@ void ARMv4::Execute()
         else
 #endif
         {
-            if (Thumb) // THUMB
+            if (CPSR & 0x20) // THUMB
             {
-                Thumb = (CPSR & 0x20);
-                bool fix = !Thumb;
-
                 if constexpr (mode == CPUExecuteMode::InterpreterGDB)
                     GdbCheckC();
 
@@ -858,22 +846,12 @@ void ARMv4::Execute()
                 else
                 {
                     // actually execute
-                    u32 icode = (CurInstr >> 6) & 0x3FF;
+                    u32 icode = (CurInstr >> 6);
                     ARMInterpreter::THUMBInstrTable[icode](this);
                 }
-                
-                if (fix) [[unlikely]]
-                {
-                    // probably wrong?
-                    // fixup
-                    R[15] &= ~0x3;
-                    NextInstr[1] = CodeRead32(R[15]);
-                }
             }
             else
             {
-                Thumb = (CPSR & 0x20);
-
                 if constexpr (mode == CPUExecuteMode::InterpreterGDB)
                     GdbCheckC();
 

src/ARM.h

@@ -385,8 +385,6 @@ class ARMv4 : public ARM
 public:
     ARMv4(melonDS::NDS& nds, std::optional<GDBArgs> gdb, bool jit);
 
-    void Reset() override;
-
     void FillPipeline() override;
 
     void JumpTo(u32 addr, bool restorecpsr = false) override;
@@ -395,7 +393,7 @@ public:
     template <CPUExecuteMode mode>
     void Execute();
 
-    u32 CodeRead16(u32 addr)
+    u16 CodeRead16(u32 addr)
     {
         return BusRead16(addr);
     }
@@ -405,8 +403,6 @@ public:
         return BusRead32(addr);
     }
 
-    bool Thumb;
-
     bool DataRead8(u32 addr, u32* val) override;
     bool DataRead16(u32 addr, u32* val) override;
     bool DataRead32(u32 addr, u32* val) override;

src/ARMInterpreter.cpp

@@ -126,8 +126,15 @@ void A_MSR_IMM(ARM* cpu)
     if (!(cpu->CurInstr & (1<<22)))
         cpu->UpdateMode(oldpsr, cpu->CPSR);
 
-    if (cpu->Num == 0)
+    if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20))
-    if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20)) cpu->NextInstr[1] &= 0xFFFF; // checkme: probably not the right way to handle this
+    {
+        if (cpu->Num == 0) cpu->NextInstr[1] &= 0xFFFF; // checkme: probably not the right way to handle this
+        else
+        {
+            Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: MSR IMM T bit change on ARM7\n");
+            cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); // keep it from crashing the emulator at least
+        }
+    }
 
     cpu->AddCycles_C();
 }
@@ -178,9 +185,16 @@ void A_MSR_REG(ARM* cpu)
 
     if (!(cpu->CurInstr & (1<<22)))
         cpu->UpdateMode(oldpsr, cpu->CPSR);
-        
+
-    if (cpu->Num == 0)
+    if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20))
-    if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20)) cpu->NextInstr[1] &= 0xFFFF; // checkme: probably not the right way to handle this
+    {
+        if (cpu->Num == 0) cpu->NextInstr[1] &= 0xFFFF; // checkme: probably not the right way to handle this
+        else
+        {
+            Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: MSR REG T bit change on ARM7\n");
+            cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); // keep it from crashing the emulator at least
+        }
+    }
 
     cpu->AddCycles_C();
 }

src/ARMInterpreter_ALU.cpp

@@ -585,8 +585,17 @@ A_IMPLEMENT_ALU_OP(RSC,)
                !res); \
     if (((cpu->CurInstr>>12) & 0xF) == 15) /* yes this instruction has a secret rd for some reason */ \
     { \
-        if (cpu->Num == 1) cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+        if (cpu->Num == 1) \
-        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: WHO IS USING TST w/ rd == 15???"); \
+        { \
+            u32 oldcpsr = cpu->CPSR; \
+            cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+            if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20)) \
+            { \
+                Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: TST T bit change on ARM7\n"); \
+                cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); /* keep it from crashing the emulator at least */ \
+            } \
+        } \
+        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: TST w/ rd == 15 on ARM9\n"); \
     } \
     if (c) cpu->AddCycles_CI(c); else cpu->AddCycles_C();
 
@@ -600,8 +609,17 @@ A_IMPLEMENT_ALU_TEST(TST,_S)
                !res); \
     if (((cpu->CurInstr>>12) & 0xF) == 15) /* yes this instruction has a secret rd for some reason */ \
     { \
-        if (cpu->Num == 1) cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+        if (cpu->Num == 1) \
-        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: WHO IS USING TEQ w/ rd == 15???"); \
+        { \
+            u32 oldcpsr = cpu->CPSR; \
+            cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+            if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20)) \
+            { \
+                Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: TEQ T bit change on ARM7\n"); \
+                cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); /* keep it from crashing the emulator at least */ \
+            } \
+        } \
+        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: TEQ w/ rd == 15 on ARM9\n"); \
     } \
     if (c) cpu->AddCycles_CI(c); else cpu->AddCycles_C();
 
@@ -617,8 +635,17 @@ A_IMPLEMENT_ALU_TEST(TEQ,_S)
                  OverflowSub(a, b)); \
     if (((cpu->CurInstr>>12) & 0xF) == 15) /* yes this instruction has a secret rd for some reason */ \
     { \
-        if (cpu->Num == 1) cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+        if (cpu->Num == 1) \
-        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: WHO IS USING CMP w/ rd == 15???"); \
+        { \
+            u32 oldcpsr = cpu->CPSR; \
+            cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+            if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20)) \
+            { \
+                Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: CMP T bit change on ARM7\n"); \
+                cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); /* keep it from crashing the emulator at least */ \
+            } \
+        } \
+        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: CMP w/ rd == 15 on ARM9\n"); \
     } \
     if (c) cpu->AddCycles_CI(c); else cpu->AddCycles_C();
 
@@ -634,8 +661,17 @@ A_IMPLEMENT_ALU_TEST(CMP,)
                  OverflowAdd(a, b)); \
     if (((cpu->CurInstr>>12) & 0xF) == 15) /* yes this instruction has a secret rd for some reason */ \
     { \
-        if (cpu->Num == 1) cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+        if (cpu->Num == 1) \
-        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: WHO IS USING CMN w/ rd == 15???"); \
+        { \
+            u32 oldcpsr = cpu->CPSR; \
+            cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+            if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20)) \
+            { \
+                Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: CMN T bit change on ARM7\n"); \
+                cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); /* keep it from crashing the emulator at least */ \
+            } \
+        } \
+        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: CMN w/ rd == 15 on ARM9\n"); \
     } \
     if (c) cpu->AddCycles_CI(c); else cpu->AddCycles_C();
 
@@ -1589,11 +1625,20 @@ void T_CMP_HIREG(ARM* cpu)
                  !res,
                  CarrySub(a, b),
                  OverflowSub(a, b));
-    if (rd == 15) \
+    if (rd == 15)
-    { \
+    {
-        if (cpu->Num == 1) cpu->RestoreCPSR(); /* ARM7TDMI restores cpsr and does ___not___ flush the pipeline. */ \
+        if (cpu->Num == 1)
-        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: CMP HIREG w/ rd == 15."); \
+        {
-    } \
+            u32 oldcpsr = cpu->CPSR;
+            cpu->RestoreCPSR(); // ARM7TDMI restores cpsr and does ___not___ flush the pipeline.
+            if (!(oldpsr & 0x20) && (cpu->CPSR & 0x20))
+            {
+                Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: MSR REG T bit change on ARM7\n");
+                cpu->CPSR = (cpu->CPSR & ~0x20) | (oldpsr & 0x20); // keep it from crashing the emulator at least
+            }
+        }
+        else Platform::Log(Platform::LogLevel::Warn, "UNIMPLEMENTED: CMP HIREG w/ rd == 15 on ARM9\n");
+    }
     cpu->AddCycles_C();
 }