Add a genuine unary minus instruction to Crankshaft....

src/hydrogen-instructions.h

 // Copyright 2011 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 111 matching lines @@
   V(LoadContextSlot)                           \
   V(LoadElements)                              \
   V(LoadFunctionPrototype)                     \
   V(LoadGlobal)                                \
   V(LoadKeyedFastElement)                      \
   V(LoadKeyedGeneric)                          \
   V(LoadNamedField)                            \
   V(LoadNamedGeneric)                          \
   V(Mod)                                       \
   V(Mul)                                       \
+  V(Neg)                                       \
   V(ObjectLiteral)                             \
   V(OsrEntry)                                  \
   V(OuterContext)                              \
   V(Parameter)                                 \
   V(Power)                                     \
   V(PushArgument)                              \
   V(RegExpLiteral)                             \
   V(Return)                                    \
   V(Sar)                                       \
   V(Shl)                                       \
@@ skipping 1205 matching lines @@
   }
   virtual HType CalculateInferredType() const;
 
   DECLARE_CONCRETE_INSTRUCTION(BitNot, "bit_not")
 
  protected:
   virtual bool DataEquals(HValue* other) const { return true; }
 };
 
 
+class HNeg: public HUnaryOperation {
+ public:
+  explicit HNeg(HValue* value) : HUnaryOperation(value) {
+    set_representation(Representation::Tagged());
+    SetFlag(kFlexibleRepresentation);
+    SetFlag(kCanOverflow);
+    SetAllSideEffects();
+  }
+
+  virtual void RepresentationChanged(Representation to) {
+    if (!to.IsTagged()) {

[Kevin Millikin (Chromium), 2011/02/11 12:12:59]

This function always makes me nervous, because the developer has to understand
that it's not OK to change from an untagged representation back to tagged.

Maybe we should handle the else case here, or assert that if to.IsTagged() then
from.IsTagged().

[fschneider, 2011/02/11 12:44:12]

Done.

+      ClearAllSideEffects();
+      SetFlag(kUseGVN);
+    }
+  }
+
+  virtual Representation RequiredInputRepresentation(int index) const {
+    return representation();
+  }
+
+  virtual HType CalculateInferredType() const;
+  virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
+  virtual void PrintDataTo(StringStream* stream) const;
+  DECLARE_CONCRETE_INSTRUCTION(Neg, "neg")
+
+ protected:
+  virtual bool DataEquals(HValue* other) const { return true; }
+  virtual Range* InferRange();
+};
+
+
 class HUnaryMathOperation: public HUnaryOperation {
  public:
   HUnaryMathOperation(HValue* value, BuiltinFunctionId op)
       : HUnaryOperation(value), op_(op) {
     switch (op) {
       case kMathFloor:
       case kMathRound:
       case kMathCeil:
         set_representation(Representation::Integer32());
         break;
@@ skipping 1827 matching lines @@
   HValue* object() const { return left(); }
   HValue* key() const { return right(); }
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_