Optimization: Make SVC use RSB

src/backend_x64/emit_x64.cpp

@@ -1674,6 +1674,9 @@ void EmitX64::EmitTerminal(IR::Terminal terminal, Arm::LocationDescriptor initia
     case 6:
         EmitTerminalIf(boost::get<IR::Term::If>(terminal), initial_location);
         return;
+    case 7:
+        EmitTerminalCheckHalt(boost::get<IR::Term::CheckHalt>(terminal), initial_location);
+        return;
     default:
         ASSERT_MSG(0, "Invalid Terminal. Bad programmer.");
         return;
@@ -1776,6 +1779,12 @@ void EmitX64::EmitTerminalIf(IR::Term::If terminal, Arm::LocationDescriptor init
     EmitTerminal(terminal.then_, initial_location);
 }
 
+void EmitX64::EmitTerminalCheckHalt(IR::Term::CheckHalt terminal, Arm::LocationDescriptor initial_location) {
+    code->CMP(8, MDisp(R15, offsetof(JitState, halt_requested)), Imm8(0));
+    code->J_CC(CC_NE, code->GetReturnFromRunCodeAddress(), true);
+    EmitTerminal(terminal.else_, initial_location);
+}
+
 void EmitX64::Patch(Arm::LocationDescriptor desc, CodePtr bb) {
     u8* const save_code_ptr = code->GetWritableCodePtr();
 

src/backend_x64/emit_x64.h

@@ -64,6 +64,7 @@ private:
     void EmitTerminalLinkBlockFast(IR::Term::LinkBlockFast terminal, Arm::LocationDescriptor initial_location);
     void EmitTerminalPopRSBHint(IR::Term::PopRSBHint terminal, Arm::LocationDescriptor initial_location);
     void EmitTerminalIf(IR::Term::If terminal, Arm::LocationDescriptor initial_location);
+    void EmitTerminalCheckHalt(IR::Term::CheckHalt terminal, Arm::LocationDescriptor initial_location);
     void Patch(Arm::LocationDescriptor desc, CodePtr bb);
 
     // Per-block state

src/backend_x64/interface_x64.cpp

@@ -112,10 +112,10 @@ size_t Jit::Run(size_t cycle_count) {
     is_executing = true;
     SCOPE_EXIT({ this->is_executing = false; });
 
-    halt_requested = false;
+    impl->jit_state.halt_requested = false;
 
     size_t cycles_executed = 0;
-    while (cycles_executed < cycle_count && !halt_requested) {
+    while (cycles_executed < cycle_count && !impl->jit_state.halt_requested) {
         cycles_executed += impl->Execute(cycle_count - cycles_executed);
     }
 
@@ -136,7 +136,7 @@ void Jit::Reset() {
 
 void Jit::HaltExecution() {
     ASSERT(is_executing);
-    halt_requested = true;
+    impl->jit_state.halt_requested = true;
 
     // TODO: Uh do other stuff to JitState pls.
 }

src/backend_x64/jitstate.h

@@ -32,6 +32,7 @@ struct JitState {
     u32 guest_MXCSR = 0x00001f80;
     u32 save_host_MXCSR = 0;
     s64 cycles_remaining = 0;
+    bool halt_requested = false;
 
     // Exclusive state
     static constexpr u32 RESERVATION_GRANULE_MASK = 0xFFFFFFF8;

src/frontend/ir/ir.h

@@ -166,6 +166,7 @@ struct LinkBlockFast {
 struct PopRSBHint {};
 
 struct If;
+struct CheckHalt;
 /// A Terminal is the terminal instruction in a MicroBlock.
 using Terminal = boost::variant<
         Invalid,
@@ -174,7 +175,8 @@ using Terminal = boost::variant<
         LinkBlock,
         LinkBlockFast,
         PopRSBHint,
-        boost::recursive_wrapper<If>
+        boost::recursive_wrapper<If>,
+        boost::recursive_wrapper<CheckHalt>
 >;
 
 /**
@@ -188,6 +190,15 @@ struct If {
     Terminal else_;
 };
 
+/**
+ * This terminal instruction checks if a halt was requested. If it wasn't, else_ is
+ * executed.
+ */
+struct CheckHalt {
+    CheckHalt(Terminal else_) : else_(else_) {}
+    Terminal else_;
+};
+
 } // namespace Term
 
 using Term::Terminal;

src/frontend/translate/translate_arm/exception_generating.cpp

@@ -17,9 +17,10 @@ bool ArmTranslatorVisitor::arm_SVC(Cond cond, Imm24 imm24) {
     u32 imm32 = imm24;
     // SVC<c> #<imm24>
     if (ConditionPassed(cond)) {
+        ir.PushRSB(ir.current_location.AdvancePC(4));
         ir.BranchWritePC(ir.Imm32(ir.current_location.PC() + 4));
         ir.CallSupervisor(ir.Imm32(imm32));
-        ir.SetTerm(IR::Term::ReturnToDispatch{});
+        ir.SetTerm(IR::Term::CheckHalt{IR::Term::PopRSBHint{}});
         return false;
     }
     return true;

src/frontend/translate/translate_thumb.cpp

@@ -773,8 +773,9 @@ struct ThumbTranslatorVisitor final {
         u32 imm32 = imm8;
         // SVC #<imm8>
         ir.BranchWritePC(ir.Imm32(ir.current_location.PC() + 2));
+        ir.PushRSB(ir.current_location.AdvancePC(2));
         ir.CallSupervisor(ir.Imm32(imm32));
-        ir.SetTerm(IR::Term::ReturnToDispatch{});
+        ir.SetTerm(IR::Term::CheckHalt{IR::Term::PopRSBHint{}});
         return false;
     }
 

src/interface/interface.h

@@ -99,7 +99,6 @@ public:
     std::string Disassemble(const Arm::LocationDescriptor& descriptor);
 
 private:
-    bool halt_requested = false;
     bool is_executing = false;
 
     struct Impl;