Make return statements single steppable

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, 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.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 602 matching lines @@
   M(PolymorphicInstanceCall)                                                   \
   M(StaticCall)                                                                \
   M(LoadLocal)                                                                 \
   M(PushTemp)                                                                  \
   M(DropTemps)                                                                 \
   M(StoreLocal)                                                                \
   M(StrictCompare)                                                             \
   M(EqualityCompare)                                                           \
   M(RelationalOp)                                                              \
   M(NativeCall)                                                                \
+  M(DebugStepCheck)                                                            \
   M(LoadIndexed)                                                               \
   M(StoreIndexed)                                                              \
   M(StoreInstanceField)                                                        \
   M(LoadStaticField)                                                           \
   M(StoreStaticField)                                                          \
   M(BooleanNegate)                                                             \
   M(InstanceOf)                                                                \
   M(CreateArray)                                                               \
   M(CreateClosure)                                                             \
   M(AllocateObject)                                                            \
@@ skipping 2776 matching lines @@
     return true;
   }
 
  private:
   const NativeBodyNode& ast_node_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeCallInstr);
 };
 
 
+class DebugStepCheckInstr : public TemplateInstruction<0> {
+ public:
+  explicit DebugStepCheckInstr(intptr_t token_pos)
+      : token_pos_(token_pos) {
+  }
+
+  DECLARE_INSTRUCTION(DebugStepCheck)
+
+  intptr_t token_pos() const { return token_pos_; }
+  virtual bool MayThrow() const { return false; }
+  virtual bool CanDeoptimize() const { return false; }
+  virtual EffectSet Effects() const { return EffectSet::None(); }
+  virtual intptr_t ArgumentCount() const { return 0; }
+  virtual Instruction* Canonicalize(FlowGraph* flow_graph);
+
+ private:
+  const intptr_t token_pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(DebugStepCheckInstr);
+};
+
+
 enum StoreBarrierType {
   kNoStoreBarrier,
   kEmitStoreBarrier
 };
 
 
 class StoreInstanceFieldInstr : public TemplateDefinition<2> {
  public:
   StoreInstanceFieldInstr(const Field& field,
                           Value* instance,
@@ skipping 3656 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_