Implements a new API to set a function entry hook for profiling.

src/x64/code-stubs-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6402 matching lines @@
   __ movq(r9, FieldOperand(rbx, JSObject::kElementsOffset));
   __ SmiToInteger32(r11, rcx);
   __ StoreNumberToDoubleElements(rax,
                                  r9,
                                  r11,
                                  xmm0,
                                  &slow_elements);
   __ ret(0);
 }
 
+
+void ProfileEntryHookStub::MaybeCallEntryHook(MacroAssembler* masm) {
+  if (entry_hook_ != NULL) {
+    ProfileEntryHookStub stub;
+    masm->CallStub(&stub);
+  }
+}
+
+
+void ProfileEntryHookStub::Generate(MacroAssembler* masm) {
+  // RCX is the only volatile register we must save.
+  __ push(rcx);
+
+  // Calculate the original stack pointer and store it in RDX, the second arg.
+  __ lea(rdx, Operand(rsp, kPointerSize));
+
+  // Calculate the function address to RCX, the first arg.
+  __ movq(rcx, Operand(rdx, 0));
+  __ subq(rcx, Immediate(Assembler::kShortCallInstructionLength));
+
+  // Reserve stack for the first 4 args.
+  __ subq(rsp, Immediate(4 * kPointerSize));
+
+  // Call the entry hook.
+  int64_t hook_location = reinterpret_cast<int64_t>(&entry_hook_);
+  __ movq(rax, hook_location, RelocInfo::NONE);
+  __ call(Operand(rax, 0));
+  __ addq(rsp, Immediate(4 * kPointerSize));
+
+  // Restore RCX.
+  __ pop(rcx);
+  __ ret(0);
+}
+
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64