Print stop message.

runtime/vm/assembler_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.h"
 #include "vm/heap.h"
 #include "vm/memory_region.h"
 #include "vm/runtime_entry.h"
+#include "vm/stub_code.h"
 
 namespace dart {
 
+DEFINE_FLAG(bool, print_stop_message, true, "Print stop message.");
+
+
 void Assembler::InitializeMemoryWithBreakpoints(uword data, int length) {
   memset(reinterpret_cast<void*>(data), Instr::kBreakPointInstruction, length);
 }
 
 
 void Assembler::call(Register reg) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   Operand operand(reg);
   EmitOperandREX(2, operand, REX_NONE);
   EmitUint8(0xFF);
@@ skipping 1270 matching lines @@
 
 void Assembler::StoreIntoObject(Register object,
                                 const FieldAddress& dest,
                                 Register value) {
   // TODO(iposva): Add write barrier.
   movq(dest, value);
 }
 
 
 void Assembler::Stop(const char* message) {
+  int64_t message_address = reinterpret_cast<int64_t>(message);
+  if (FLAG_print_stop_message) {
+    pushq(Immediate(message_address));
+    call(&StubCode::PrintStopMessageLabel());
+    popq(RAX);

[Ivan Posva, 2012/01/09 17:26:42]

This kills the content of RAX.

How about:
pushq(RAX);
movq(RAX, Immediate(message_address));
call(&StubCode::PrintStopMessageLabel());
popq(RAX);

And the stub expects the parameter value in RAX?

[regis, 2012/01/10 00:09:16]

Done. Using RDI instead of RAX and also preserving TMP, which is used by the
pseudo call instruction.

+  }
   // Emit the lower half and the higher half of the message address as immediate
   // operands in the test rax instructions, followed by the int3 instruction.
   // Execution can be resumed with the 'cont' command in gdb.
-  int64_t message_address = reinterpret_cast<int64_t>(message);
   testl(RAX, Immediate(Utils::Low32Bits(message_address)));
   testl(RAX, Immediate(Utils::High32Bits(message_address)));
   int3();
 }
 
 
 void Assembler::Bind(Label* label) {
   int bound = buffer_.Size();
   ASSERT(!label->IsBound());  // Labels can only be bound once.
   while (label->IsLinked()) {
@@ skipping 172 matching lines @@
   } else {
     EmitRegisterREX(operand, REX_NONE);
   }
   EmitUint8(0xD3);
   EmitOperand(rm, Operand(operand));
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64