implement changing thumb bit. and bkpt ig

probably wrong

src/ARM.cpp

@@ -201,6 +201,13 @@ void ARMv5::Reset()
     ARM::Reset();
 }
 
+void ARMv4::Reset()
+{
+    Thumb = false;
+
+    ARM::Reset();
+}
+
 
 void ARM::DoSavestate(Savestate* file)
 {
@@ -395,6 +402,7 @@ void ARMv4::JumpTo(u32 addr, bool restorecpsr)
         Cycles += NDS.ARM7MemTimings[CodeCycles][0] + NDS.ARM7MemTimings[CodeCycles][1];
 
         CPSR |= 0x20;
+        Thumb = true;
     }
     else
     {
@@ -408,6 +416,7 @@ void ARMv4::JumpTo(u32 addr, bool restorecpsr)
         Cycles += NDS.ARM7MemTimings[CodeCycles][2] + NDS.ARM7MemTimings[CodeCycles][3];
 
         CPSR &= ~0x20;
+        Thumb = false;
     }
 }
 
@@ -724,7 +733,12 @@ void ARMv5::Execute()
                     ARMInterpreter::A_BLX_IMM(this);
                 }
                 else
-                    AddCycles_C();
+                {
+                    if ((((CurInstr >> 4) & 0xF) | ((CurInstr >> 16) & 0xFF0)) == 0x127)
+                        ARMInterpreter::A_BKPT(this); // always passes regardless of condition code
+                    else
+                        AddCycles_C();
+                }
             }
 
             // TODO optimize this shit!!!
@@ -826,8 +840,11 @@ void ARMv4::Execute()
         else
 #endif
         {
-            if (CPSR & 0x20) // THUMB
+            if (Thumb) // THUMB
             {
+                Thumb = (CPSR & 0x20);
+                bool fix = !Thumb;
+
                 if constexpr (mode == CPUExecuteMode::InterpreterGDB)
                     GdbCheckC();
 
@@ -841,12 +858,22 @@ void ARMv4::Execute()
                 else
                 {
                     // actually execute
-                    u32 icode = (CurInstr >> 6);
+                    u32 icode = (CurInstr >> 6) & 0x3FF;
                     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

@@ -385,6 +385,8 @@ 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;
@@ -393,7 +395,7 @@ public:
     template <CPUExecuteMode mode>
     void Execute();
 
-    u16 CodeRead16(u32 addr)
+    u32 CodeRead16(u32 addr)
     {
         return BusRead16(addr);
     }
@@ -403,6 +405,8 @@ 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

@@ -69,6 +69,14 @@ void T_UNK(ARM* cpu)
     cpu->JumpTo(cpu->ExceptionBase + 0x04);
 }
 
+void A_BKPT(ARM* cpu)
+{
+    if (cpu->Num == 1) A_UNK(cpu); // checkme
+    
+    Log(LogLevel::Warn, "BKPT: "); // combine with the prefetch abort warning message
+    ((ARMv5*)cpu)->PrefetchAbort();
+}
+
 
 
 void A_MSR_IMM(ARM* cpu)
@@ -105,9 +113,6 @@ void A_MSR_IMM(ARM* cpu)
     //if (cpu->CurInstr & (1<<18)) mask |= 0x00FF0000; // unused by arm 7 & 9
     if (cpu->CurInstr & (1<<19)) mask |= ((cpu->Num==1) ? 0xF0000000 : 0xF8000000);
 
-    if (!(cpu->CurInstr & (1<<22)))
-        mask &= 0xFFFFFFDF;
-
     if ((cpu->CPSR & 0x1F) == 0x10) mask &= 0xFFFFFF00;
 
     u32 val = ROR((cpu->CurInstr & 0xFF), ((cpu->CurInstr >> 7) & 0x1E));
@@ -121,6 +126,9 @@ 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)) cpu->NextInstr[1] &= 0xFFFF; // checkme: probably not the right way to handle this
+
     cpu->AddCycles_C();
 }
 
@@ -158,9 +166,6 @@ void A_MSR_REG(ARM* cpu)
     //if (cpu->CurInstr & (1<<18)) mask |= 0x00FF0000; // unused by arm 7 & 9
     if (cpu->CurInstr & (1<<19)) mask |= ((cpu->Num==1) ? 0xF0000000 : 0xF8000000);
 
-    if (!(cpu->CurInstr & (1<<22)))
-        mask &= 0xFFFFFFDF;
-
     if ((cpu->CPSR & 0x1F) == 0x10) mask &= 0xFFFFFF00;
 
     u32 val = cpu->R[cpu->CurInstr & 0xF];
@@ -173,6 +178,9 @@ 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)) cpu->NextInstr[1] &= 0xFFFF; // checkme: probably not the right way to handle this
 
     cpu->AddCycles_C();
 }

src/ARMInterpreter.h

@@ -36,6 +36,7 @@ void A_MRS(ARM* cpu);
 void A_MCR(ARM* cpu);
 void A_MRC(ARM* cpu);
 void A_SVC(ARM* cpu);
+void A_BKPT(ARM* cpu);
 
 void T_SVC(ARM* cpu);
 

src/ARM_InstrInfo.cpp

@@ -194,6 +194,7 @@ const u32 A_BX = A_BranchAlways | A_Read0 | ak(ak_BX);
 const u32 A_BLX_REG = A_BranchAlways | A_Link | A_Read0 | ak(ak_BLX_REG);
 
 const u32 A_UNK = A_BranchAlways | A_Link | ak(ak_UNK);
+const u32 A_BKPT = A_BranchAlways | A_Link | ak(ak_UNK);
 const u32 A_MSR_IMM = ak(ak_MSR_IMM);
 const u32 A_MSR_REG = A_Read0 | ak(ak_MSR_REG);
 const u32 A_MRS = A_Write12 | ak(ak_MRS);

src/ARM_InstrTable.h

@@ -130,7 +130,7 @@ INSTRFUNC_PROTO(ARMInstrTable[4096]) =
 
     // 0001 0010 0000
     A_MSR_REG, A_BX, A_UNK, A_BLX_REG,
-    A_UNK, A_QSUB, A_UNK, A_UNK,
+    A_UNK, A_QSUB, A_UNK, A_BKPT,
     A_SMLAWy, A_UNK, A_SMULWy, A_STRH_REG,
     A_SMLAWy, A_LDRD_REG, A_SMULWy, A_STRD_REG,