[llvm-commits] CVS: llvm/include/llvm/Constants.h

[Chris Lattner]

Changes in directory llvm/include/llvm:

Constants.h updated: 1.42 -> 1.43

---
Log message:

Add a new ConstantAggregateZero class, to fix PR239.  This makes zero 
initializers for constant structs and arrays take constant space, instead of
space proportinal to the number of elements.  This reduces the memory usage of
the LLVM compiler by hundreds of megabytes when compiling some nasty SPEC95 
benchmarks.


---
Diffs of the changes:  (+36 -20)

Index: llvm/include/llvm/Constants.h
diff -u llvm/include/llvm/Constants.h:1.42 llvm/include/llvm/Constants.h:1.43
--- llvm/include/llvm/Constants.h:1.42	Sat Feb 14 22:14:40 2004
+++ llvm/include/llvm/Constants.h	Sat Feb 14 23:52:14 2004
@@ -309,6 +309,36 @@
   }
 };
 
+//===---------------------------------------------------------------------------
+/// ConstantAggregateZero - All zero aggregate value
+///
+class ConstantAggregateZero : public Constant {
+  friend struct ConstantCreator<ConstantAggregateZero, Type, char>;
+  ConstantAggregateZero(const ConstantAggregateZero &);      // DO NOT IMPLEMENT
+protected:
+  ConstantAggregateZero(const Type *Ty) : Constant(Ty) {}
+public:
+  /// get() - static factory method for creating a null aggregate.  It is
+  /// illegal to call this method with a non-aggregate type.
+  static Constant *get(const Type *Ty);
+
+  /// isNullValue - Return true if this is the value that would be returned by
+  /// getNullValue.
+  virtual bool isNullValue() const { return true; }
+
+  virtual void destroyConstant();
+  virtual void replaceUsesOfWithOnConstant(Value *From, Value *To,
+                                           bool DisableChecking = false);
+
+  /// Methods for support type inquiry through isa, cast, and dyn_cast:
+  ///
+  static inline bool classof(const ConstantAggregateZero *) { return true; }
+  static bool classof(const Constant *CPV);
+  static inline bool classof(const Value *V) {
+    return isa<Constant>(V) && classof(cast<Constant>(V));
+  }
+};
+
 
 //===---------------------------------------------------------------------------
 /// ConstantArray - Constant Array Declarations
@@ -345,19 +375,9 @@
   inline const std::vector<Use> &getValues() const { return Operands; }
 
   /// isNullValue - Return true if this is the value that would be returned by
-  /// getNullValue.
-  virtual bool isNullValue() const {
-    // FIXME: This should be made to be MUCH faster.  Just check against well
-    // known null value!
-    if (getNumOperands()) {
-      const Constant *First = cast<Constant>(getOperand(0));
-      if (!First->isNullValue()) return false;
-      for (unsigned i = 1, e = getNumOperands(); i != e; ++i)
-        if (cast<Constant>(getOperand(i)) != First)
-          return false; 
-    }
-    return true;
-  }
+  /// getNullValue.  This always returns false because zero arrays are always
+  /// created as ConstantAggregateZero objects.
+  virtual bool isNullValue() const { return false; }
 
   virtual void destroyConstant();
   virtual void replaceUsesOfWithOnConstant(Value *From, Value *To,
@@ -395,14 +415,10 @@
   inline const std::vector<Use> &getValues() const { return Operands; }
 
   /// isNullValue - Return true if this is the value that would be returned by
-  /// getNullValue.
+  /// getNullValue.  This always returns false because zero structs are always
+  /// created as ConstantAggregateZero objects.
   virtual bool isNullValue() const {
-    // FIXME: This should be made to be MUCH faster.  Just check against well
-    // known null value!
-    for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
-      if (!cast<Constant>(getOperand(i))->isNullValue())
-        return false; 
-    return true;
+    return false;
   }
 
   virtual void destroyConstant();