Track prologue offset of Code and use for more precise return addresses

runtime/vm/instructions_x64.h

 // Copyright (c) 2012, 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.
 // Classes that describe assembly patterns as used by inline caches.
 
 #ifndef VM_INSTRUCTIONS_X64_H_
 #define VM_INSTRUCTIONS_X64_H_
 
 #ifndef VM_INSTRUCTIONS_H_
 #error Do not include instructions_ia32.h directly; use instructions.h instead.
@@ skipping 94 matching lines @@
  public:
   explicit ReturnPattern(uword pc) : InstructionPattern(pc) {}
 
   virtual const int* pattern() const;
   virtual int pattern_length_in_bytes() const { return kLengthInBytes; }
 
  private:
   static const int kLengthInBytes = 1;
 };
 
+
+class ProloguePattern : public InstructionPattern {
+ public:
+  explicit ProloguePattern(uword pc) : InstructionPattern(pc) {}
+
+  virtual const int* pattern() const;
+  virtual int pattern_length_in_bytes() const { return kLengthInBytes; }
+
+ private:
+  static const int kLengthInBytes = 4;
+};
+
+
+class SetFramePointerPattern : public InstructionPattern {
+ public:
+  explicit SetFramePointerPattern(uword pc) : InstructionPattern(pc) {}
+
+  virtual const int* pattern() const;
+  virtual int pattern_length_in_bytes() const { return kLengthInBytes; }
+
+ private:
+  static const int kLengthInBytes = 3;
+};
+
 }  // namespace dart
 
 #endif  // VM_INSTRUCTIONS_X64_H_