Emit comment with instruction+reason before deopt calls.

src/lithium-codegen.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/lithium-codegen.h"
 
 #if V8_TARGET_ARCH_IA32
 #include "src/ia32/lithium-ia32.h"  // NOLINT
@@ skipping 129 matching lines @@
 
   // Copy the string before recording it in the assembler to avoid
   // issues when the stack allocated buffer goes out of scope.
   size_t length = builder.position();
   Vector<char> copy = Vector<char>::New(static_cast<int>(length) + 1);
   MemCopy(copy.start(), builder.Finalize(), copy.length());
   masm()->RecordComment(copy.start());
 }
 
 
+void LCodeGenBase::DeoptComment(const char* mnemonic, const char* reason) {
+  Comment(";;; deoptimize %s: %s", mnemonic,
+          reason == NULL ? "unknown reason" : reason);
+}
+
+
 int LCodeGenBase::GetNextEmittedBlock() const {
   for (int i = current_block_ + 1; i < graph()->blocks()->length(); ++i) {
     if (!graph()->blocks()->at(i)->IsReachable()) continue;
     if (!chunk_->GetLabel(i)->HasReplacement()) return i;
   }
   return -1;
 }
 
 
 static void AddWeakObjectToCodeDependency(Isolate* isolate,
@@ skipping 67 matching lines @@
   chunk_->AddDeprecationDependency(map);
 }
 
 
 void LCodeGenBase::AddStabilityDependency(Handle<Map> map) {
   if (!map->is_stable()) return Abort(kMapBecameUnstable);
   chunk_->AddStabilityDependency(map);
 }
 
 } }  // namespace v8::internal