Improvements for x87 stack handling

src/hydrogen-instructions.h

 // Copyright 2012 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 3178 matching lines @@
   }
 
   bool InOldSpace() const { return !HEAP->InNewSpace(*handle_); }
 
   bool ImmortalImmovable() const {
     if (has_int32_value_) {
       return false;
     }
     if (has_double_value_) {
       if (BitCast<int64_t>(double_value_) == BitCast<int64_t>(-0.0) ||
-          isnan(double_value_)) {
+          isnan(double_value_) ||
+          FixedDoubleArray::is_the_hole_nan(double_value_)) {
         return true;
       }
       return false;
     }
 
     ASSERT(!handle_.is_null());
     Heap* heap = isolate()->heap();
     // We should have handled minus_zero_value and nan_value in the
     // has_double_value_ clause above.
     // Dereferencing is safe to compare against immovable singletons.
@@ skipping 10 matching lines @@
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   virtual bool IsConvertibleToInteger() const {
     return has_int32_value_;
   }
 
-  virtual bool EmitAtUses() { return !representation().IsDouble(); }
+  virtual bool EmitAtUses() {
+    return !representation().IsDouble() || ImmortalImmovable();

[danno, 2013/04/08 12:57:27]

Maybe it's better to factor our the special cases for doubles into another
predicate, like IsSpecialDouble() that is used both here and in
ImmortalImmovable.

[mvstanton, 2013/04/08 16:10:14]

I did this kind of refactoring but more in the methods ImmortalImmovable(), and
then below with the new IsTheHole() method. Does that correspond?

+  }
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
   bool IsInteger() { return handle()->IsSmi(); }
   HConstant* CopyToRepresentation(Representation r, Zone* zone) const;
   HConstant* CopyToTruncatedInt32(Zone* zone) const;
   bool HasInteger32Value() const { return has_int32_value_; }
   int32_t Integer32Value() const {
     ASSERT(HasInteger32Value());
     return int32_value_;
   }
   bool HasSmiValue() const {
     return HasInteger32Value() && Smi::IsValid(Integer32Value());
   }
   bool HasDoubleValue() const { return has_double_value_; }
   double DoubleValue() const {
     ASSERT(HasDoubleValue());
     return double_value_;
   }
+  bool IsDoubleCanonicalHole() const {
+    ASSERT(HasDoubleValue());
+    return FixedDoubleArray::is_the_hole_nan(double_value_);
+  }
   bool HasNumberValue() const { return has_double_value_; }
   int32_t NumberValueAsInteger32() const {
     ASSERT(HasNumberValue());
     // Irrespective of whether a numeric HConstant can be safely
     // represented as an int32, we store the (in some cases lossy)
     // representation of the number in int32_value_.
     return int32_value_;
   }
   bool HasStringValue() const {
     if (has_double_value_ || has_int32_value_) return false;
@@ skipping 2411 matching lines @@
     return IsFastSmiElementsKind(elements_kind_);
   }
   ElementsKind elements_kind() const { return elements_kind_; }
   uint32_t index_offset() { return index_offset_; }
   void SetIndexOffset(uint32_t index_offset) { index_offset_ = index_offset; }
   HValue* GetKey() { return key(); }
   void SetKey(HValue* key) { SetOperandAt(1, key); }
   bool IsDehoisted() { return is_dehoisted_; }
   void SetDehoisted(bool is_dehoisted) { is_dehoisted_ = is_dehoisted; }
 
+  bool IsConstantHoleStore() {
+    return value()->IsConstant() &&
+        HConstant::cast(value())->IsDoubleCanonicalHole();

[danno, 2013/04/08 12:57:27]

This predicate seems misleading... it checks only for the double canonical hold,
but not the real hole. Either rename the predicate or add support for testing
for the the_hole constant tagged value.

[mvstanton, 2013/04/08 16:10:14]

Done.

+  }
+
   virtual void SetSideEffectDominator(GVNFlag side_effect, HValue* dominator) {
     ASSERT(side_effect == kChangesNewSpacePromotion);
     new_space_dominator_ = dominator;
   }
 
   HValue* new_space_dominator() const { return new_space_dominator_; }
 
   bool NeedsWriteBarrier() {
     if (value_is_smi()) {
       return false;
@@ skipping 759 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_