Add a HBreak instruction for debugging

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 1845 matching lines @@
     __ j(cc, chunk_->GetAssemblyLabel(left_block));
   } else {
     __ j(cc, chunk_->GetAssemblyLabel(left_block));
     if (cc != always) {
       __ jmp(chunk_->GetAssemblyLabel(right_block));
     }
   }
 }
 
 
+void LCodeGen::DoDebugBreak(LDebugBreak* instr) {
+  __ int3();
+}
+
+
 void LCodeGen::DoBranch(LBranch* instr) {
   int true_block = chunk_->LookupDestination(instr->true_block_id());
   int false_block = chunk_->LookupDestination(instr->false_block_id());
 
   Representation r = instr->hydrogen()->value()->representation();
   if (r.IsInteger32()) {
     Register reg = ToRegister(instr->value());
     __ testl(reg, reg);
     EmitBranch(true_block, false_block, not_zero);
   } else if (r.IsDouble()) {
@@ skipping 3724 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64