Various improvements regarding the way we print code code comments.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 54f117c0d9adafaeb31691af6f6796bd0b277554..967b645c81b9ac132a12276fd9ebc04a3397210e 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -280,6 +280,8 @@ class LInstruction: public ZoneObject {
   LOperand* FirstInput() { return InputAt(0); }
   LOperand* Output() { return HasResult() ? result() : NULL; }
 
+  virtual bool HasInterestingComment(LCodeGen* gen) const { return true; }
+
 #ifdef DEBUG
   void VerifyCall();
 #endif
@@ -381,6 +383,10 @@ class LInstructionGap: public LGap {
  public:
   explicit LInstructionGap(HBasicBlock* block) : LGap(block) { }
 
+  virtual bool HasInterestingComment(LCodeGen* gen) const {
+    return !IsRedundant();
+  }
+
   DECLARE_CONCRETE_INSTRUCTION(InstructionGap, "gap")
 };
 
@@ -389,6 +395,7 @@ class LGoto: public LTemplateInstruction<0, 0, 0> {
  public:
   explicit LGoto(int block_id) : block_id_(block_id) { }
 
+  virtual bool HasInterestingComment(LCodeGen* gen) const;
   DECLARE_CONCRETE_INSTRUCTION(Goto, "goto")
   virtual void PrintDataTo(StringStream* stream);
   virtual bool IsControl() const { return true; }
@@ -436,12 +443,14 @@ class LLabel: public LGap {
   explicit LLabel(HBasicBlock* block)
       : LGap(block), replacement_(NULL) { }
 
+  virtual bool HasInterestingComment(LCodeGen* gen) const { return false; }
   DECLARE_CONCRETE_INSTRUCTION(Label, "label")
 
   virtual void PrintDataTo(StringStream* stream);
 
   int block_id() const { return block()->block_id(); }
   bool is_loop_header() const { return block()->IsLoopHeader(); }
+  bool is_osr_entry() const { return block()->is_osr_entry(); }
   Label* label() { return &label_; }
   LLabel* replacement() const { return replacement_; }
   void set_replacement(LLabel* label) { replacement_ = label; }
@@ -455,6 +464,7 @@ class LLabel: public LGap {
 
 class LParameter: public LTemplateInstruction<1, 0, 0> {
  public:
+  virtual bool HasInterestingComment(LCodeGen* gen) const { return false; }
   DECLARE_CONCRETE_INSTRUCTION(Parameter, "parameter")
 };
 
@@ -472,6 +482,7 @@ class LCallStub: public LTemplateInstruction<1, 0, 0> {
 
 class LUnknownOSRValue: public LTemplateInstruction<1, 0, 0> {
  public:
+  virtual bool HasInterestingComment(LCodeGen* gen) const { return false; }
   DECLARE_CONCRETE_INSTRUCTION(UnknownOSRValue, "unknown-osr-value")
 };
 
@@ -2471,6 +2482,7 @@ class LOsrEntry: public LTemplateInstruction<0, 0, 0> {
  public:
   LOsrEntry();
 
+  virtual bool HasInterestingComment(LCodeGen* gen) const { return false; }
   DECLARE_CONCRETE_INSTRUCTION(OsrEntry, "osr-entry")
 
   LOperand** SpilledRegisterArray() { return register_spills_; }