diff --git a/src/devirt_t.cpp b/src/devirt_t.cpp
index 5e1dad3..20c3d18 100644
--- a/src/devirt_t.cpp
+++ b/src/devirt_t.cpp
@@ -85,6 +85,19 @@ namespace vm
 
     bool devirt_t::compile( std::vector< std::uint8_t > &obj )
     {
+        llvm::legacy::FunctionPassManager pass_mgr( llvm_module );
+        pass_mgr.add( llvm::createPromoteMemoryToRegisterPass() );
+        pass_mgr.add( llvm::createNewGVNPass() );
+        pass_mgr.add( llvm::createReassociatePass() );
+        pass_mgr.add( llvm::createDeadCodeEliminationPass() );
+        pass_mgr.add( llvm::createInstructionCombiningPass() );
+
+        for ( auto vmp_rtn : vmp_rtns )
+        {
+            pass_mgr.run( *vmp_rtn->llvm_fptr );
+            std::printf( "> opt rtn_0x%p\n", vmp_rtn->rtn_begin );
+        }
+
         llvm::TargetOptions opt;
         llvm::SmallVector< char, 128 > buff;
         llvm::raw_svector_ostream dest( buff );
diff --git a/src/lifters/rdtsc.cpp b/src/lifters/rdtsc.cpp
index c456ff5..4f9b660 100644
--- a/src/lifters/rdtsc.cpp
+++ b/src/lifters/rdtsc.cpp
@@ -8,25 +8,21 @@ namespace vm
             llvm::Function *rdtsc_intrin = nullptr;
             if ( !( rdtsc_intrin = rtn->llvm_module->getFunction( "rdtsc" ) ) )
             {
-                rdtsc_intrin = llvm::Function::Create(
-                    llvm::FunctionType::get( ir_builder->getVoidTy(),
-                                             { llvm::PointerType::get( ir_builder->getInt8Ty(), 0ull ) }, false ),
-                    llvm::GlobalValue::LinkageTypes::ExternalLinkage, "rdtsc", *rtn->llvm_module );
+                rdtsc_intrin = llvm::Function::Create( llvm::FunctionType::get( ir_builder->getVoidTy(), false ),
+                                                       llvm::GlobalValue::LinkageTypes::ExternalLinkage, "rdtsc",
+                                                       *rtn->llvm_module );
 
                 auto entry_block = llvm::BasicBlock::Create( ir_builder->getContext(), "", rdtsc_intrin );
                 auto ib = ir_builder->GetInsertBlock();
                 ir_builder->SetInsertPoint( entry_block );
 
-                std::string asm_str( "rdtsc; sub rbp, 0x08; mov [rcx], edx; mov [rcx+0x04], eax; ret" );
-                auto intrin = llvm::InlineAsm::get( llvm::FunctionType::get( ir_builder->getVoidTy(), false ), asm_str,
-                                                    "", false, false, llvm::InlineAsm::AD_Intel );
+                // TODO: put RDTSC code here...
 
-                ir_builder->CreateCall( intrin );
                 ir_builder->CreateRetVoid();
                 ir_builder->SetInsertPoint( ib );
             }
 
             auto &vmp_rtn = rtn->vmp_rtns.back();
-            ir_builder->CreateCall( rdtsc_intrin, { vmp_rtn->stack } );
+            ir_builder->CreateCall( rdtsc_intrin );
         };
 }
\ No newline at end of file