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

runtime/vm/assembler_macros_x64.cc

 // 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.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler_macros.h"
 
 #include "vm/assembler.h"
@@ skipping 48 matching lines @@
   // before a frame is created.
   if (offset != 0) {
     __ addq(Address(RSP, 0), Immediate(-offset));
   }
   if (frame_size != 0) {
     __ subq(RSP, Immediate(frame_size));
   }
 }
 
 
+void AssemblerMacros::EnterDartLeafFrame(Assembler* assembler,
+                                         intptr_t frame_size) {
+  __ EnterFrame(0);
+  Label dart_entry;
+  // Leave room for the saved PC, it will be filled in lazily, leave
+  // uninitialized.
+  __ subq(RSP, Immediate(frame_size + kWordSize));
+#if defined(DEBUG)
+  // Store an invalid object in saved PC slot.
+  __ movq(Address(RBP, -kWordSize), Immediate(kHeapObjectTag));
+#endif
+}
+
+
 void AssemblerMacros::EnterStubFrame(Assembler* assembler) {
   __ EnterFrame(0);
   __ pushq(Immediate(0));  // Push 0 in the saved PC area for stub frames.
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64