Add re-entry prediction to avoid std::unordered_map lookups

src/backend_x64/block_of_code.cpp

@@ -82,7 +82,14 @@ void BlockOfCode::RunCode(JitState* jit_state, size_t cycles_to_run) const {
 
     jit_state->cycles_to_run = cycles_to_run;
     jit_state->cycles_remaining = cycles_to_run;
+
+    u32 new_rsb_ptr = (jit_state->rsb_ptr - 1) & JitState::RSBPtrMask;
+    if (jit_state->GetUniqueHash() == jit_state->rsb_location_descriptors[new_rsb_ptr]) {
+        jit_state->rsb_ptr = new_rsb_ptr;
+        run_code_from(jit_state, jit_state->rsb_codeptrs[new_rsb_ptr]);
+    } else {
         run_code(jit_state);
+    }
 }
 
 void BlockOfCode::ReturnFromRunCode(bool mxcsr_already_exited) {
@@ -102,6 +109,14 @@ void BlockOfCode::ForceReturnFromRunCode(bool mxcsr_already_exited) {
 void BlockOfCode::GenRunCode() {
     Xbyak::Label loop, enter_mxcsr_then_loop;
 
+    align();
+    run_code_from = getCurr<RunCodeFromFuncType>();
+
+    ABI_PushCalleeSaveRegistersAndAdjustStack(this);
+    mov(r15, ABI_PARAM1);
+    SwitchMxcsrOnEntry();
+    jmp(ABI_PARAM2);
+
     align();
     run_code = getCurr<RunCodeFuncType>();
 

src/backend_x64/block_of_code.h

@@ -138,7 +138,9 @@ private:
     CodePtr far_code_ptr;
 
     using RunCodeFuncType = void(*)(JitState*);
+    using RunCodeFromFuncType = void(*)(JitState*, u64);
     RunCodeFuncType run_code = nullptr;
+    RunCodeFromFuncType run_code_from = nullptr;
     static constexpr size_t MXCSR_ALREADY_EXITED = 1 << 0;
     static constexpr size_t FORCE_RETURN = 1 << 1;
     std::array<const void*, 4> return_from_run_code;

src/backend_x64/jitstate.cpp

@@ -199,5 +199,9 @@ void JitState::SetFpscr(u32 FPSCR) {
     }
 }
 
+u64 JitState::GetUniqueHash() const {
+    return CPSR_et | FPSCR_mode | (static_cast<u64>(Reg[15]) << 32);
+}
+
 } // namespace BackendX64
 } // namespace Dynarmic

src/backend_x64/jitstate.h

@@ -67,6 +67,8 @@ struct JitState {
     u32 old_FPSCR = 0;
     u32 Fpscr() const;
     void SetFpscr(u32 FPSCR);
+
+    u64 GetUniqueHash() const;
 };
 
 #ifdef _MSC_VER