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::Generate(MacroAssembler* masm) {
+  // Grab the cycle counter immediately.
+  __ db(0x0F);  // rdtsc();

[danno, 2012/07/10 09:37:13]

Add to the assembler?

[Sigurður Ásgeirsson, 2012/07/11 14:50:34]

Gone, as in the ia32 case.

+  __ db(0x31);
+  
+  // RCX is the only volatile register we must save.
+  __ push(rcx);  
+
+  // Move the cycle time from EDX/EAX to R8, which is the third argument.
+  __ movq(r8, rax);
+  __ shl(rdx, Immediate(32));
+  __ addq(r8, rdx);
+
+  // Calculate the original stack pointer and store it in RDX, the second arg.
+  __ lea(rdx, Operand(rsp, 0x8));
+
+  // Calculate the function address to RCX, the first arg.
+  __ movq(rcx, Operand(rdx, 0));
+  __ subq(rcx, Immediate(5));
+
+  // Reserve stack for the first 4 args.
+  __ subq(rsp, Immediate(0x20));
+  
+  // Call the entry hook.
+  int64_t hook_location =
+      reinterpret_cast<int64_t>(V8::GetFunctionEntryHookLocation());
+  __ movq(rax, hook_location, RelocInfo::NONE);
+  __ call(Operand(rax, 0));
+  __ addq(rsp, Immediate(0x20));
+
+  // Restore RCX.
+  __ pop(rcx);
+  __ ret(0);
+}
+
+
+void ProfileEntryHookStub::GenerateAheadOfTime() {
+  ProfileEntryHookStub stub;
+  Handle<Code> code = stub.GetCode();
+  code->set_is_pregenerated(true);

[danno, 2012/07/10 09:37:13]

Why do you need to pre-generate on x64 and ia32 but not on ARM?

[Sigurður Ásgeirsson, 2012/07/11 14:50:34]

I need to discuss this with you, or someone else knowledgeable on the issues.
I'm not sure what the concerns are, but I know that this code stub cannot be
serialized to a snapshot.

+}
+
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64