[dynarmic] restore proper backtraces for A64 (#3794)

trivial changes, fixes hard crashes

Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3794
Reviewed-by: Maufeat <sahyno1996@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

src/core/arm/nce/interpreter_visitor.cpp

@@ -773,7 +773,11 @@ std::optional<u64> MatchAndExecuteOneInstruction(Core::Memory::Memory& memory, m
     bool was_executed = false;
 
     auto decoder = Dynarmic::A64::Decode<VisitorBase>(instruction);
-    was_executed = decoder.get().call(visitor, instruction);
+    if (decoder) {
+        was_executed = decoder->get().call(visitor, instruction);
+    } else {
+        was_executed = false;
+    }
     return was_executed ? std::optional<u64>(pc + 4) : std::nullopt;
 }
 

src/dynarmic/src/dynarmic/frontend/A64/decoder/a64.h

@@ -70,14 +70,15 @@ constexpr DecodeTable<V> GetDecodeTable() {
 
 /// In practice it must always suceed, otherwise something else unrelated would have gone awry
 template<typename V>
-std::reference_wrapper<const Matcher<V>> Decode(u32 instruction) {
+std::optional<std::reference_wrapper<const Matcher<V>>> Decode(u32 instruction) {
     alignas(64) static const auto table = GetDecodeTable<V>();
     const auto& subtable = table[detail::ToFastLookupIndex(instruction)];
     auto iter = std::find_if(subtable.begin(), subtable.end(), [instruction](const auto& matcher) {
         return matcher.Matches(instruction);
     });
-    DEBUG_ASSERT(iter != subtable.end());
-    return std::reference_wrapper<const Matcher<V>>(*iter);
+    return iter != subtable.end()
+        ? std::optional{ std::reference_wrapper<const Matcher<V>>(*iter) }
+        : std::nullopt;
 }
 
 template<typename V>

src/dynarmic/src/dynarmic/frontend/A64/translate/a64_translate.cpp

@@ -25,7 +25,11 @@ void Translate(IR::Block& block, LocationDescriptor descriptor, MemoryReadCodeFu
         const u64 pc = visitor.ir.current_location->PC();
         if (const auto instruction = memory_read_code(pc)) {
             auto decoder = Decode<TranslatorVisitor>(*instruction);
-            should_continue = decoder.get().call(visitor, *instruction);
+            if (decoder) {
+                should_continue = decoder->get().call(visitor, *instruction);
+            } else {
+                should_continue = visitor.RaiseException(Exception::UnallocatedEncoding);
+            }
         } else {
             should_continue = visitor.RaiseException(Exception::NoExecuteFault);
         }
@@ -45,13 +49,15 @@ bool TranslateSingleInstruction(IR::Block& block, LocationDescriptor descriptor,
 
     bool should_continue = true;
     auto const decoder = Decode<TranslatorVisitor>(instruction);
-    should_continue = decoder.get().call(visitor, instruction);
+    if (decoder) {
+        should_continue = decoder->get().call(visitor, instruction);
+    } else {
+        should_continue = false;
+    }
 
     visitor.ir.current_location = visitor.ir.current_location->AdvancePC(4);
     block.CycleCount()++;
-
     block.SetEndLocation(*visitor.ir.current_location);
-
     return should_continue;
 }