A64: Add ExceptionRaised IR instruction

The purpose of this instruction is to raise exceptions when certain decode-time
issues happen, instead of asserting at translate time. This allows us to
use the translator for code analysis without worrying about unnecessary asserts,
but also provides flexibility for the library user to perform custom behaviour
when one of these states are raised.

include/dynarmic/A64/config.h

@@ -16,6 +16,17 @@ namespace A64 {
 
 using VAddr = std::uint64_t;
 
+enum class Exception {
+    /// An UndefinedFault occured due to executing instruction with an unallocated encoding
+    UnallocatedEncoding,
+    /// An UndefinedFault occured due to executing instruction containing a reserved value
+    ReservedValue,
+    /// An unpredictable instruction is to be executed. Implementation-defined behaviour should now happen.
+    /// This behaviour is up to the user of this library to define.
+    /// Note: Constraints on unpredictable behaviour are specified in the ARMv8 ARM.
+    UnpredictableInstruction,
+};
+
 struct UserCallbacks {
     virtual ~UserCallbacks() = default;
 
@@ -47,6 +58,8 @@ struct UserCallbacks {
     // This callback is called whenever a SVC instruction is executed.
     virtual void CallSVC(std::uint32_t swi) = 0;
 
+    virtual void ExceptionRaised(VAddr pc, Exception exception) = 0;
+
     // Timing-related callbacks
     // ticks ticks have passed
     virtual void AddTicks(std::uint64_t ticks) = 0;