[hydrogen] don't bailout assignments to consts

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index c9a4bf062d3a7c3c6b4c79d36d4abe4959c6d8e2..b994a4501f3e6156c8e5d92cacba7991e50fc07a 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -3447,14 +3447,24 @@ class HStoreGlobalGeneric: public HTemplateInstruction<3> {
 
 class HLoadContextSlot: public HUnaryOperation {
  public:
+  enum Check {
+    kEmpty,
+    kIsHoleCheck

[fschneider, 2011/12/12 09:55:56]

Please rebase your change. It seems to conflict with r10220 which also
introduces harmony-related changes (handling CONST_HARMONY etc.).

Basically you need to change this to have 3 modes here. (no check, const-harmony
hole-check (deoptimizes) and const hole-check (returns undefined).

The HStoreContextSlow will also need to be changed accordingly.

+  };
+
   HLoadContextSlot(HValue* context , int slot_index)
-      : HUnaryOperation(context), slot_index_(slot_index) {
+      : HUnaryOperation(context), slot_index_(slot_index), check_(kEmpty) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetFlag(kDependsOnContextSlots);
   }
 
+  void ForceIsHoleCheck() {
+    check_ = kIsHoleCheck;
+  }
+
   int slot_index() const { return slot_index_; }
+  bool RequiresHoleCheck() const { return check_ == kIsHoleCheck; }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
@@ -3472,21 +3482,32 @@ class HLoadContextSlot: public HUnaryOperation {
 
  private:
   int slot_index_;
+  Check check_;
 };
 
 
 class HStoreContextSlot: public HTemplateInstruction<2> {
  public:
+  enum Check {
+    kEmpty,
+    kIsHoleCheck
+  };
+
   HStoreContextSlot(HValue* context, int slot_index, HValue* value)
-      : slot_index_(slot_index) {
+      : slot_index_(slot_index), check_(kEmpty) {
     SetOperandAt(0, context);
     SetOperandAt(1, value);
     SetFlag(kChangesContextSlots);
   }
 
+  void ForceIsHoleCheck() {
+    check_ = kIsHoleCheck;
+  }
+
   HValue* context() { return OperandAt(0); }
   HValue* value() { return OperandAt(1); }
   int slot_index() const { return slot_index_; }
+  bool RequiresHoleCheck() const { return check_ == kIsHoleCheck; }
 
   bool NeedsWriteBarrier() {
     return StoringValueNeedsWriteBarrier(value());
@@ -3502,6 +3523,7 @@ class HStoreContextSlot: public HTemplateInstruction<2> {
 
  private:
   int slot_index_;
+  Check check_;
 };