[dynarmic] remove dead-code interpreter (#3547)

interpreter was never called in practice and doesn't do anything other than just crash

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

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3547
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: DraVee <dravee@eden-emu.dev>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

docs/dynarmic/Design.md

@@ -286,15 +286,6 @@ Exclusive OR (i.e.: XOR)
 
 Memory access.
 
-### Terminal: Interpret
-
-```c++
-SetTerm(IR::Term::Interpret{next})
-```
-
-This terminal instruction calls the interpreter, starting at `next`.
-The interpreter must interpret exactly one instruction.
-
 ### Terminal: ReturnToDispatch
 
 ```c++

docs/dynarmic/README.md

@@ -117,11 +117,6 @@ public:
         MemoryWrite32(vaddr + 4, u32(value >> 32));
     }
 
-    void InterpreterFallback(u32 pc, size_t num_instructions) override {
-        // This is never called in practice.
-        std::terminate();
-    }
-
     void CallSVC(u32 swi) override {
         // Do something.
     }

src/core/arm/dynarmic/arm_dynarmic_32.cpp

@@ -88,13 +88,6 @@ bool DynarmicCallbacks32::MemoryWriteExclusive64(u32 vaddr, u64 value, u64 expec
             m_memory.WriteExclusive64(vaddr, value, expected);
 }
 
-void DynarmicCallbacks32::InterpreterFallback(u32 pc, std::size_t num_instructions) {
-    m_parent.LogBacktrace(m_process);
-    LOG_ERROR(Core_ARM,
-                "Unimplemented instruction @ {:#X} for {} instructions (instr = {:08X})", pc,
-                num_instructions, m_memory.Read32(pc));
-}
-
 void DynarmicCallbacks32::ExceptionRaised(u32 pc, Dynarmic::A32::Exception exception) {
     switch (exception) {
     case Dynarmic::A32::Exception::NoExecuteFault:

src/core/arm/dynarmic/arm_dynarmic_32.h

@@ -43,7 +43,6 @@ public:
     bool MemoryWriteExclusive16(u32 vaddr, u16 value, u16 expected) override;
     bool MemoryWriteExclusive32(u32 vaddr, u32 value, u32 expected) override;
     bool MemoryWriteExclusive64(u32 vaddr, u64 value, u64 expected) override;
-    void InterpreterFallback(u32 pc, std::size_t num_instructions) override;
     void ExceptionRaised(u32 pc, Dynarmic::A32::Exception exception) override;
     void CallSVC(u32 swi) override;
     void AddTicks(u64 ticks) override;

src/core/arm/dynarmic/arm_dynarmic_64.cpp

@@ -102,13 +102,6 @@ bool DynarmicCallbacks64::MemoryWriteExclusive128(u64 vaddr, Dynarmic::A64::Vect
             m_memory.WriteExclusive128(vaddr, value, expected);
 }
 
-void DynarmicCallbacks64::InterpreterFallback(u64 pc, std::size_t num_instructions) {
-    m_parent.LogBacktrace(m_process);
-    LOG_ERROR(Core_ARM, "Unimplemented instruction @ {:#X} for {} instructions (instr = {:08X})", pc,
-        num_instructions, m_memory.Read32(pc));
-    ReturnException(pc, PrefetchAbort);
-}
-
 void DynarmicCallbacks64::InstructionCacheOperationRaised(Dynarmic::A64::InstructionCacheOperation op, u64 value) {
     switch (op) {
     case Dynarmic::A64::InstructionCacheOperation::InvalidateByVAToPoU: {

src/core/arm/dynarmic/arm_dynarmic_64.h

@@ -52,7 +52,6 @@ public:
     bool MemoryWriteExclusive32(u64 vaddr, std::uint32_t value, std::uint32_t expected) override;
     bool MemoryWriteExclusive64(u64 vaddr, std::uint64_t value, std::uint64_t expected) override;
     bool MemoryWriteExclusive128(u64 vaddr, Dynarmic::A64::Vector value, Dynarmic::A64::Vector expected) override;
-    void InterpreterFallback(u64 pc, std::size_t num_instructions) override;
     void InstructionCacheOperationRaised(Dynarmic::A64::InstructionCacheOperation op, u64 value) override;
     void ExceptionRaised(u64 pc, Dynarmic::A64::Exception exception) override;
     void CallSVC(u32 svc) override;

src/core/arm/nce/interpreter_visitor.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
@@ -772,12 +772,8 @@ std::optional<u64> MatchAndExecuteOneInstruction(Core::Memory::Memory& memory, m
     u32 instruction = memory.Read32(pc);
     bool was_executed = false;
 
-    if (auto decoder = Dynarmic::A64::Decode<VisitorBase>(instruction)) {
+    auto decoder = Dynarmic::A64::Decode<VisitorBase>(instruction);
-        was_executed = decoder->get().call(visitor, instruction);
+    was_executed = decoder.get().call(visitor, instruction);
-    } else {
-        LOG_ERROR(Core_ARM, "Unallocated encoding: {:#x}", instruction);
-    }
-
     return was_executed ? std::optional<u64>(pc + 4) : std::nullopt;
 }
 

src/core/hle/service/jit/jit_context.cpp

@@ -116,7 +116,6 @@ public:
 
     void CallSVC(u32 swi) override;
     void ExceptionRaised(u64 pc, Dynarmic::A64::Exception exception) override;
-    void InterpreterFallback(u64 pc, size_t num_instructions) override;
 
     void AddTicks(u64 ticks) override {}
     u64 GetTicksRemaining() override {
@@ -432,11 +431,6 @@ void DynarmicCallbacks64::ExceptionRaised(u64 pc, Dynarmic::A64::Exception excep
     parent.jit->HaltExecution();
 }
 
-void DynarmicCallbacks64::InterpreterFallback(u64 pc, size_t num_instructions) {
-    LOG_CRITICAL(Service_JIT, "Unimplemented instruction PC @ {:08x}", pc);
-    parent.jit->HaltExecution();
-}
-
 JITContext::JITContext(Core::Memory::Memory& memory)
     : impl{std::make_unique<JITContextImpl>(memory)} {}
 

src/dynarmic/src/dynarmic/backend/arm64/emit_arm64_a32.cpp

@@ -36,10 +36,6 @@ oaknut::Label EmitA32Cond(oaknut::CodeGenerator& code, EmitContext&, IR::Cond co
 
 void EmitA32Terminal(oaknut::CodeGenerator& code, EmitContext& ctx, IR::Term::Terminal terminal, IR::LocationDescriptor initial_location, bool is_single_step);
 
-void EmitA32Terminal(oaknut::CodeGenerator&, EmitContext&, IR::Term::Interpret, IR::LocationDescriptor, bool) {
-    UNREACHABLE();
-}
-
 void EmitA32Terminal(oaknut::CodeGenerator& code, EmitContext& ctx, IR::Term::ReturnToDispatch, IR::LocationDescriptor, bool) {
     EmitRelocation(code, ctx, LinkTarget::ReturnToDispatcher);
 }

src/dynarmic/src/dynarmic/backend/arm64/emit_arm64_a64.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -35,10 +35,6 @@ oaknut::Label EmitA64Cond(oaknut::CodeGenerator& code, EmitContext&, IR::Cond co
 
 void EmitA64Terminal(oaknut::CodeGenerator& code, EmitContext& ctx, IR::Term::Terminal terminal, IR::LocationDescriptor initial_location, bool is_single_step);
 
-void EmitA64Terminal(oaknut::CodeGenerator&, EmitContext&, IR::Term::Interpret, IR::LocationDescriptor, bool) {
-    UNREACHABLE();
-}
-
 void EmitA64Terminal(oaknut::CodeGenerator& code, EmitContext& ctx, IR::Term::ReturnToDispatch, IR::LocationDescriptor, bool) {
     EmitRelocation(code, ctx, LinkTarget::ReturnToDispatcher);
 }

src/dynarmic/src/dynarmic/backend/riscv64/emit_riscv64_a32.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -114,10 +114,6 @@ void EmitA32Cond(biscuit::Assembler& as, EmitContext&, IR::Cond cond, biscuit::L
 
 void EmitA32Terminal(biscuit::Assembler& as, EmitContext& ctx, IR::Term::Terminal terminal, IR::LocationDescriptor initial_location, bool is_single_step);
 
-void EmitA32Terminal(biscuit::Assembler&, EmitContext&, IR::Term::Interpret, IR::LocationDescriptor, bool) {
-    UNREACHABLE();
-}
-
 void EmitA32Terminal(biscuit::Assembler& as, EmitContext& ctx, IR::Term::ReturnToDispatch, IR::LocationDescriptor, bool) {
     EmitRelocation(as, ctx, LinkTarget::ReturnFromRunCode);
 }

src/dynarmic/src/dynarmic/backend/x64/a32_emit_x64.cpp

@@ -1135,19 +1135,6 @@ void A32EmitX64::EmitSetUpperLocationDescriptor(IR::LocationDescriptor new_locat
 }
 
 namespace {
-void EmitTerminalImpl(A32EmitX64& e, IR::Term::Interpret terminal, IR::LocationDescriptor initial_location, bool) {
-    ASSERT(A32::LocationDescriptor{terminal.next}.TFlag() == A32::LocationDescriptor{initial_location}.TFlag() && "Unimplemented");
-    ASSERT(A32::LocationDescriptor{terminal.next}.EFlag() == A32::LocationDescriptor{initial_location}.EFlag() && "Unimplemented");
-    ASSERT(terminal.num_instructions == 1 && "Unimplemented");
-
-    e.code.mov(e.code.ABI_PARAM2.cvt32(), A32::LocationDescriptor{terminal.next}.PC());
-    e.code.mov(e.code.ABI_PARAM3.cvt32(), 1);
-    e.code.mov(MJitStateReg(A32::Reg::PC), e.code.ABI_PARAM2.cvt32());
-    e.code.SwitchMxcsrOnExit();
-    Devirtualize<&A32::UserCallbacks::InterpreterFallback>(e.conf.callbacks).EmitCall(e.code);
-    e.code.ReturnFromRunCode(true);  // TODO: Check cycles
-}
-
 void EmitTerminalImpl(A32EmitX64& e, IR::Term::ReturnToDispatch, IR::LocationDescriptor, bool) {
     e.code.ReturnFromRunCode();
 }

src/dynarmic/src/dynarmic/backend/x64/a64_emit_x64.cpp

@@ -619,16 +619,6 @@ std::string A64EmitX64::LocationDescriptorToFriendlyName(const IR::LocationDescr
 }
 
 namespace {
-void EmitTerminalImpl(A64EmitX64& e, IR::Term::Interpret terminal, IR::LocationDescriptor, bool) {
-    e.code.SwitchMxcsrOnExit();
-    Devirtualize<&A64::UserCallbacks::InterpreterFallback>(e.conf.callbacks).EmitCall(e.code, [&](RegList param) {
-        e.code.mov(param[0], A64::LocationDescriptor{terminal.next}.PC());
-        e.code.mov(qword[e.code.ABI_JIT_PTR + offsetof(A64JitState, pc)], param[0]);
-        e.code.mov(param[1].cvt32(), terminal.num_instructions);
-    });
-    e.code.ReturnFromRunCode(true);  // TODO: Check cycles
-}
-
 void EmitTerminalImpl(A64EmitX64& e, IR::Term::ReturnToDispatch, IR::LocationDescriptor, bool) {
     e.code.ReturnFromRunCode();
 }

src/dynarmic/src/dynarmic/frontend/A32/translate/impl/a32_translate_impl.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -35,11 +35,6 @@ bool TranslatorVisitor::VFPConditionPassed(Cond cond) {
     return ArmConditionPassed(cond);
 }
 
-bool TranslatorVisitor::InterpretThisInstruction() {
-    ir.SetTerm(IR::Term::Interpret(ir.current_location));
-    return false;
-}
-
 bool TranslatorVisitor::UnpredictableInstruction() {
     return RaiseException(Exception::UnpredictableInstruction);
 }

src/dynarmic/src/dynarmic/frontend/A32/translate/impl/a32_translate_impl.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -39,7 +39,6 @@ struct TranslatorVisitor final {
     bool ThumbConditionPassed();
     bool VFPConditionPassed(Cond cond);
 
-    bool InterpretThisInstruction();
     bool UnpredictableInstruction();
     bool UndefinedInstruction();
     bool DecodeError();

src/dynarmic/src/dynarmic/frontend/A32/translate/impl/load_store.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -871,11 +871,11 @@ bool TranslatorVisitor::arm_LDMIB(Cond cond, bool W, Reg n, RegList list) {
 }
 
 bool TranslatorVisitor::arm_LDM_usr() {
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 bool TranslatorVisitor::arm_LDM_eret() {
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 static bool STMHelper(A32::IREmitter& ir, bool W, Reg n, RegList list, IR::U32 start_address, IR::U32 writeback_address) {
@@ -956,7 +956,7 @@ bool TranslatorVisitor::arm_STMIB(Cond cond, bool W, Reg n, RegList list) {
 }
 
 bool TranslatorVisitor::arm_STM_usr() {
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 }  // namespace Dynarmic::A32

src/dynarmic/src/dynarmic/frontend/A32/translate/impl/status_register_access.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -15,7 +15,7 @@ namespace Dynarmic::A32 {
 // CPS<effect> <iflags>{, #<mode>}
 // CPS #<mode>
 bool TranslatorVisitor::arm_CPS() {
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 // MRS<c> <Rd>, <spec_reg>
@@ -107,7 +107,7 @@ bool TranslatorVisitor::arm_MSR_reg(Cond cond, unsigned mask, Reg n) {
 
 // RFE{<amode>} <Rn>{!}
 bool TranslatorVisitor::arm_RFE() {
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 // SETEND <endian_specifier>
@@ -118,7 +118,7 @@ bool TranslatorVisitor::arm_SETEND(bool E) {
 
 // SRS{<amode>} SP{!}, #<mode>
 bool TranslatorVisitor::arm_SRS() {
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 }  // namespace Dynarmic::A32

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

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -68,14 +68,16 @@ constexpr DecodeTable<V> GetDecodeTable() {
     return table;
 }
 
+/// In practice it must always suceed, otherwise something else unrelated would have gone awry
 template<typename V>
-std::optional<std::reference_wrapper<const Matcher<V>>> Decode(u32 instruction) {
+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);
     });
-    return iter != subtable.end() ? std::optional<std::reference_wrapper<const Matcher<V>>>(*iter) : std::nullopt;
+    DEBUG_ASSERT(iter != subtable.end());
+    return std::reference_wrapper<const Matcher<V>>(*iter);
 }
 
 template<typename V>

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

@@ -23,17 +23,12 @@ void Translate(IR::Block& block, LocationDescriptor descriptor, MemoryReadCodeFu
     bool should_continue = true;
     do {
         const u64 pc = visitor.ir.current_location->PC();
-
         if (const auto instruction = memory_read_code(pc)) {
-            if (auto decoder = Decode<TranslatorVisitor>(*instruction)) {
+            auto decoder = Decode<TranslatorVisitor>(*instruction);
-                should_continue = decoder->get().call(visitor, *instruction);
+            should_continue = decoder.get().call(visitor, *instruction);
-            } else {
-                should_continue = visitor.InterpretThisInstruction();
-            }
         } else {
             should_continue = visitor.RaiseException(Exception::NoExecuteFault);
         }
-
         visitor.ir.current_location = visitor.ir.current_location->AdvancePC(4);
         block.CycleCount()++;
     } while (should_continue && !single_step);
@@ -49,11 +44,8 @@ bool TranslateSingleInstruction(IR::Block& block, LocationDescriptor descriptor,
     TranslatorVisitor visitor{block, descriptor, {}};
 
     bool should_continue = true;
-    if (auto decoder = Decode<TranslatorVisitor>(instruction)) {
+    auto const decoder = Decode<TranslatorVisitor>(instruction);
-        should_continue = decoder->get().call(visitor, instruction);
+    should_continue = decoder.get().call(visitor, instruction);
-    } else {
-        should_continue = visitor.InterpretThisInstruction();
-    }
 
     visitor.ir.current_location = visitor.ir.current_location->AdvancePC(4);
     block.CycleCount()++;

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

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -16,11 +16,6 @@
 
 namespace Dynarmic::A64 {
 
-bool TranslatorVisitor::InterpretThisInstruction() {
-    ir.SetTerm(IR::Term::Interpret(*ir.current_location));
-    return false;
-}
-
 bool TranslatorVisitor::UnpredictableInstruction() {
     return RaiseException(Exception::UnpredictableInstruction);
 }

src/dynarmic/src/dynarmic/frontend/A64/translate/impl/impl.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 /* This file is part of the dynarmic project.
  * Copyright (c) 2018 MerryMage
  * SPDX-License-Identifier: 0BSD
@@ -24,7 +27,6 @@ struct TranslatorVisitor final {
     A64::IREmitter ir;
     TranslationOptions options;
 
-    bool InterpretThisInstruction();
     bool UnpredictableInstruction();
     bool DecodeError();
     bool ReservedValue();

src/dynarmic/src/dynarmic/frontend/A64/translate/impl/simd_three_same_extra.cpp

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 /* This file is part of the dynarmic project.
  * Copyright (c) 2018 MerryMage
  * SPDX-License-Identifier: 0BSD
@@ -63,9 +66,7 @@ bool TranslatorVisitor::FCMLA_vec(bool Q, Imm<2> size, Vec Vm, Imm<2> rot, Vec V
     const size_t esize = 8U << size.ZeroExtend();
 
     // TODO: Currently we don't support half-precision floating point
-    if (esize == 16) {
+    ASSERT(esize != 16);
-        return InterpretThisInstruction();
-    }
 
     const size_t datasize = Q ? 128 : 64;
     const size_t num_elements = datasize / esize;
@@ -134,9 +135,7 @@ bool TranslatorVisitor::FCADD_vec(bool Q, Imm<2> size, Vec Vm, Imm<1> rot, Vec V
     const size_t esize = 8U << size.ZeroExtend();
 
     // TODO: Currently we don't support half-precision floating point
-    if (esize == 16) {
+    ASSERT(esize != 16);
-        return InterpretThisInstruction();
-    }
 
     const size_t datasize = Q ? 128 : 64;
     const size_t num_elements = datasize / esize;

src/dynarmic/src/dynarmic/frontend/A64/translate/impl/simd_vector_x_indexed_element.cpp

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -223,9 +223,7 @@ bool TranslatorVisitor::FCMLA_elt(bool Q, Imm<2> size, Imm<1> L, Imm<1> M, Imm<4
     const size_t esize = 8U << size.ZeroExtend();
 
     // TODO: We don't support the half-precision floating point variant yet.
-    if (esize == 16) {
+    ASSERT(esize != 16);
-        return InterpretThisInstruction();
-    }
 
     const size_t index = [=] {
         if (size == 0b01) {

src/dynarmic/src/dynarmic/frontend/A64/translate/impl/system.cpp

@@ -118,7 +118,7 @@ bool TranslatorVisitor::MSR_reg(Imm<1> o0, Imm<3> op1, Imm<4> CRn, Imm<4> CRm, I
     default:
         break;
     }
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 bool TranslatorVisitor::MRS(Imm<1> o0, Imm<3> op1, Imm<4> CRn, Imm<4> CRm, Imm<3> op2, Reg Rt) {
@@ -158,7 +158,7 @@ bool TranslatorVisitor::MRS(Imm<1> o0, Imm<3> op1, Imm<4> CRn, Imm<4> CRm, Imm<3
         X(64, Rt, ir.GetTPIDRRO());
         return true;
     }
-    return InterpretThisInstruction();
+    UNREACHABLE();
 }
 
 }  // namespace Dynarmic::A64

src/dynarmic/src/dynarmic/interface/A32/config.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -103,9 +103,6 @@ struct UserCallbacks : public TranslateCallbacks {
     // A conservative implementation that always returns false is safe.
     virtual bool IsReadOnlyMemory(VAddr /*vaddr*/) { return false; }
 
-    /// The interpreter must execute exactly num_instructions starting from PC.
-    virtual void InterpreterFallback(VAddr pc, size_t num_instructions) = 0;
-
     // This callback is called whenever a SVC instruction is executed.
     virtual void CallSVC(std::uint32_t swi) = 0;
 

src/dynarmic/src/dynarmic/interface/A64/config.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -118,9 +118,6 @@ struct UserCallbacks {
     // A conservative implementation that always returns false is safe.
     virtual bool IsReadOnlyMemory(VAddr /*vaddr*/) { return false; }
 
-    /// The interpreter must execute exactly num_instructions starting from PC.
-    virtual void InterpreterFallback(VAddr pc, size_t num_instructions) = 0;
-
     // This callback is called whenever a SVC instruction is executed.
     virtual void CallSVC(std::uint32_t swi) = 0;
 

src/dynarmic/src/dynarmic/ir/basic_block.cpp

@@ -77,9 +77,6 @@ static std::string TerminalToString(const Terminal& terminal_variant) noexcept {
         std::string operator()(const Term::Invalid&) const {
             return "<invalid terminal>";
         }
-        std::string operator()(const Term::Interpret& terminal) const {
-            return fmt::format("Interpret{{{}}}", terminal.next);
-        }
         std::string operator()(const Term::ReturnToDispatch&) const {
             return "ReturnToDispatch{}";
         }

src/dynarmic/src/dynarmic/ir/opt_passes.cpp

@@ -638,43 +638,6 @@ static void A64GetSetElimination(IR::Block& block) {
     }
 }
 
-static void A64MergeInterpretBlocksPass(IR::Block& block, A64::UserCallbacks* cb) {
-    const auto is_interpret_instruction = [cb](A64::LocationDescriptor location) {
-        const auto instruction = cb->MemoryReadCode(location.PC());
-        if (!instruction)
-            return false;
-
-        IR::Block new_block{location};
-        A64::TranslateSingleInstruction(new_block, location, *instruction);
-
-        if (!new_block.Instructions().empty())
-            return false;
-
-        const IR::Terminal terminal = new_block.GetTerminal();
-        if (auto term = boost::get<IR::Term::Interpret>(&terminal)) {
-            return term->next == location;
-        }
-
-        return false;
-    };
-
-    IR::Terminal terminal = block.GetTerminal();
-    auto term = boost::get<IR::Term::Interpret>(&terminal);
-    if (!term)
-        return;
-
-    A64::LocationDescriptor location{term->next};
-    size_t num_instructions = 1;
-
-    while (is_interpret_instruction(location.AdvancePC(static_cast<int>(num_instructions * 4)))) {
-        num_instructions++;
-    }
-
-    term->num_instructions = num_instructions;
-    block.ReplaceTerminal(terminal);
-    block.CycleCount() += num_instructions - 1;
-}
-
 using Op = Dynarmic::IR::Opcode;
 
 static IR::Value Value(bool is_32_bit, u64 value) {
@@ -1504,9 +1467,6 @@ void Optimize(IR::Block& block, const A64::UserConfig& conf, const Optimization:
         Optimization::ConstantPropagation(block);
         Optimization::DeadCodeElimination(block);
     }
-    if (conf.HasOptimization(OptimizationFlag::MiscIROpt)) {
-        Optimization::A64MergeInterpretBlocksPass(block, conf.callbacks);
-    }
     Optimization::IdentityRemovalPass(block);
     if (!conf.HasOptimization(OptimizationFlag::DisableVerification)) {
         Optimization::VerificationPass(block);

src/dynarmic/src/dynarmic/ir/terminal.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -19,17 +19,6 @@ namespace Term {
 
 struct Invalid {};
 
-/**
- * This terminal instruction calls the interpreter, starting at `next`.
- * The interpreter must interpret exactly `num_instructions` instructions.
- */
-struct Interpret {
-    explicit Interpret(const LocationDescriptor& next_)
-            : next(next_) {}
-    LocationDescriptor next;  ///< Location at which interpretation starts.
-    size_t num_instructions = 1;
-};
-
 /**
  * This terminal instruction returns control to the dispatcher.
  * The dispatcher will use the current cpu state to determine what comes next.
@@ -83,7 +72,6 @@ struct CheckHalt;
 /// A Terminal is the terminal instruction in a MicroBlock.
 using Terminal = boost::variant<
     Invalid,
-    Interpret,
     ReturnToDispatch,
     LinkBlock,
     LinkBlockFast,

src/dynarmic/tests/A32/fuzz_arm.cpp

@@ -59,8 +59,6 @@ bool AnyLocationDescriptorForTerminalHas(IR::Terminal terminal, Fn fn) {
             return fn(t.next);
         } else if constexpr (std::is_same_v<T, IR::Term::PopRSBHint>) {
             return false;
-        } else if constexpr (std::is_same_v<T, IR::Term::Interpret>) {
-            return fn(t.next);
         } else if constexpr (std::is_same_v<T, IR::Term::FastDispatchHint>) {
             return false;
         } else if constexpr (std::is_same_v<T, IR::Term::If>) {
@@ -85,10 +83,6 @@ bool ShouldTestInst(u32 instruction, u32 pc, bool is_thumb, bool is_last_inst, A
         return false;
     }
 
-    if (auto terminal = block.GetTerminal(); boost::get<IR::Term::Interpret>(&terminal)) {
-        return false;
-    }
-
     if (AnyLocationDescriptorForTerminalHas(block.GetTerminal(), [&](IR::LocationDescriptor ld) { return A32::LocationDescriptor{ld}.PC() <= pc; })) {
         return false;
     }

src/dynarmic/tests/A32/testenv.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 /* This file is part of the dynarmic project.
@@ -97,10 +97,6 @@ public:
         MemoryWrite32(vaddr + 4, static_cast<u32>(value >> 32));
     }
 
-    void InterpreterFallback(u32 pc, size_t num_instructions) override {
-        UNREACHABLE(); //ASSERT(false && "InterpreterFallback({:08x} && {}) code = {:08x}", pc, num_instructions, *MemoryReadCode(pc));
-    }
-
     void CallSVC(std::uint32_t swi) override {
         UNREACHABLE(); //ASSERT(false && "CallSVC({})", swi);
     }
@@ -190,10 +186,6 @@ public:
         return true;
     }
 
-    void InterpreterFallback(std::uint32_t pc, size_t num_instructions) override {
-        UNREACHABLE(); //ASSERT(false && "InterpreterFallback({:016x} && {})", pc, num_instructions);
-    }
-
     void CallSVC(std::uint32_t swi) override {
         UNREACHABLE(); //ASSERT(false && "CallSVC({})", swi);
     }

src/dynarmic/tests/A64/fibonacci.cpp

@@ -69,11 +69,6 @@ public:
         MemoryWrite64(vaddr + 8, value[1]);
     }
 
-    void InterpreterFallback(u64, size_t) override {
-        // This is never called in practice.
-        std::terminate();
-    }
-
     void CallSVC(u32) override {
         // Do something.
     }

src/dynarmic/tests/A64/fuzz_with_unicorn.cpp

@@ -43,8 +43,6 @@ static bool ShouldTestInst(u32 instruction, u64 pc, bool is_last_inst) {
     bool should_continue = A64::TranslateSingleInstruction(block, location, instruction);
     if (!should_continue && !is_last_inst)
         return false;
-    if (auto terminal = block.GetTerminal(); boost::get<IR::Term::Interpret>(&terminal))
-        return false;
     for (const auto& ir_inst : block.instructions) {
         switch (ir_inst.GetOpcode()) {
         case IR::Opcode::A64ExceptionRaised:

src/dynarmic/tests/A64/testenv.h

@@ -105,10 +105,6 @@ public:
         return true;
     }
 
-    void InterpreterFallback(u64 pc, size_t num_instructions) override {
-        UNREACHABLE(); // ASSERT(false&& "InterpreterFallback({:016x} && {})", pc, num_instructions);
-    }
-
     void CallSVC(std::uint32_t swi) override {
         UNREACHABLE(); //ASSERT(false && "CallSVC({})", swi);
     }
@@ -208,10 +204,6 @@ public:
         return true;
     }
 
-    void InterpreterFallback(u64 pc, size_t num_instructions) override {
-        ASSERT(ignore_invalid_insn && "InterpreterFallback");
-    }
-
     void CallSVC(std::uint32_t swi) override {
         UNREACHABLE(); //ASSERT(false && "CallSVC({})", swi);
     }

src/dynarmic/tests/print_info.cpp

@@ -152,9 +152,6 @@ public:
         MemoryWrite32(vaddr + 4, static_cast<u32>(value >> 32));
     }
 
-    void InterpreterFallback(u32 pc, size_t num_instructions) override {
-        fmt::print("> InterpreterFallback({:08x}, {}) code = {:08x}\n", pc, num_instructions, *MemoryReadCode(pc));
-    }
     void CallSVC(std::uint32_t swi) override {
         fmt::print("> CallSVC({})\n", swi);
     }

src/dynarmic/tests/test_generator.cpp

@@ -50,10 +50,6 @@ namespace {
 using namespace Dynarmic;
 
 bool ShouldTestInst(IR::Block& block) {
-    if (auto terminal = block.GetTerminal(); boost::get<IR::Term::Interpret>(&terminal)) {
-        return false;
-    }
-
     for (const auto& ir_inst : block.instructions) {
         switch (ir_inst.GetOpcode()) {
         // A32