Recognize leaf functions: skip stack check and populating the pc slot, store the pc slot lazily in …

runtime/vm/assembler_macros_x64.h

 // Copyright (c) 2011, 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.
 // The class 'AssemblerMacros' contains assembler instruction groups that
 // are used in Dart.
 
 #ifndef VM_ASSEMBLER_MACROS_X64_H_
 #define VM_ASSEMBLER_MACROS_X64_H_
 
 #ifndef VM_ASSEMBLER_MACROS_H_
@@ skipping 31 matching lines @@
   //   pc (used to derive the RawInstruction Object of the dart code)
   //   locals space  <=== RSP
   //   .....
   // This code sets this up with the sequence:
   //   pushq rbp
   //   movq rbp, rsp
   //   call L
   //   L: <code to adjust saved pc if there is any intrinsification code>
   //   .....
   static void EnterDartFrame(Assembler* assembler, intptr_t frame_size);
+  // Populates pc local slot lazily.
+  static void EnterDartLeafFrame(Assembler* assembler, intptr_t frame_size);
 
   // Set up a stub frame so that the stack traversal code can easily identify
   // a stub frame.
   // The stub frame layout is as follows:
   //   ....
   //   ret PC
   //   saved RBP
   //   pc (used to derive the RawInstruction Object of the stub)
   //   .....
   // This code sets this up with the sequence:
@@ skipping 10 matching lines @@
   //   pushq rbp          (size is 1 byte)
   //   movq rbp, rsp      (size is 3 bytes)
   //   call L             (size is 5 bytes)
   //   L:
   static const intptr_t kOffsetOfSavedPCfromEntrypoint = 9;
 };
 
 }  // namespace dart.
 
 #endif  // VM_ASSEMBLER_MACROS_X64_H_