Revert "Do not rely on code patching on DBC for lazy deoptimization."

runtime/vm/instructions_dbc.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_DBC.
 #if defined(TARGET_ARCH_DBC)
 
 #include "vm/instructions.h"
 #include "vm/instructions_dbc.h"
 
@@ skipping 150 matching lines @@
   return reinterpret_cast<RawCode*>(
       object_pool_.ObjectAt(target_code_pool_index_));
 }
 
 
 void CallPattern::SetTargetCode(const Code& target_code) const {
   object_pool_.SetObjectAt(target_code_pool_index_, target_code);
 }
 
 
+void CallPattern::InsertDeoptCallAt(uword pc) {
+  const uint8_t argc = Bytecode::IsCallOpcode(Bytecode::At(pc))
+                           ? Bytecode::DecodeArgc(Bytecode::At(pc))
+                           : 0;
+  *reinterpret_cast<Instr*>(pc) = Bytecode::Encode(Bytecode::kDeopt, argc, 0);
+}
+
+
 SwitchableCallPattern::SwitchableCallPattern(uword pc, const Code& code)
     : object_pool_(ObjectPool::Handle(code.GetObjectPool())),
       data_pool_index_(-1),
       target_pool_index_(-1) {
   UNIMPLEMENTED();
 }
 
 
 RawObject* SwitchableCallPattern::data() const {
   return object_pool_.ObjectAt(data_pool_index_);
@@ skipping 23 matching lines @@
 
 
 bool ReturnPattern::IsValid() const {
   UNIMPLEMENTED();
   return false;
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC