Index: llvm/trunk/include/llvm/IR/Argument.h
===================================================================
--- llvm/trunk/include/llvm/IR/Argument.h
+++ llvm/trunk/include/llvm/IR/Argument.h
@@ -64,6 +64,11 @@
   /// containing function, return the number of bytes known to be
   /// dereferenceable. Otherwise, zero is returned.
   uint64_t getDereferenceableBytes() const;
+  
+  /// \brief If this argument has the dereferenceable_or_null attribute on 
+  /// it in its containing function, return the number of bytes known to be
+  /// dereferenceable. Otherwise, zero is returned.
+  uint64_t getDereferenceableOrNullBytes() const;
 
   /// \brief Return true if this argument has the byval attribute on it in its
   /// containing function.
Index: llvm/trunk/include/llvm/IR/CallSite.h
===================================================================
--- llvm/trunk/include/llvm/IR/CallSite.h
+++ llvm/trunk/include/llvm/IR/CallSite.h
@@ -231,7 +231,13 @@
   uint64_t getDereferenceableBytes(uint16_t i) const {
     CALLSITE_DELEGATE_GETTER(getDereferenceableBytes(i));
   }
-
+  
+  /// @brief Extract the number of dereferenceable_or_null bytes for a call or
+  /// parameter (0=unknown).
+  uint64_t getDereferenceableOrNullBytes(uint16_t i) const {
+    CALLSITE_DELEGATE_GETTER(getDereferenceableOrNullBytes(i));
+  }
+  
   /// \brief Return true if the call should not be treated as a call to a
   /// builtin.
   bool isNoBuiltin() const {
Index: llvm/trunk/include/llvm/IR/Function.h
===================================================================
--- llvm/trunk/include/llvm/IR/Function.h
+++ llvm/trunk/include/llvm/IR/Function.h
@@ -248,7 +248,13 @@
   uint64_t getDereferenceableBytes(unsigned i) const {
     return AttributeSets.getDereferenceableBytes(i);
   }
-
+  
+  /// @brief Extract the number of dereferenceable_or_null bytes for a call or
+  /// parameter (0=unknown).
+  uint64_t getDereferenceableOrNullBytes(unsigned i) const {
+    return AttributeSets.getDereferenceableOrNullBytes(i);
+  }
+  
   /// @brief Determine if the function does not access memory.
   bool doesNotAccessMemory() const {
     return AttributeSets.hasAttribute(AttributeSet::FunctionIndex,
Index: llvm/trunk/include/llvm/IR/Instructions.h
===================================================================
--- llvm/trunk/include/llvm/IR/Instructions.h
+++ llvm/trunk/include/llvm/IR/Instructions.h
@@ -1491,6 +1491,12 @@
     return AttributeList.getDereferenceableBytes(i);
   }
 
+  /// \brief Extract the number of dereferenceable_or_null bytes for a call or
+  /// parameter (0=unknown).
+  uint64_t getDereferenceableOrNullBytes(unsigned i) const {
+    return AttributeList.getDereferenceableOrNullBytes(i);
+  }
+  
   /// \brief Return true if the call should not be treated as a call to a
   /// builtin.
   bool isNoBuiltin() const {
@@ -3200,6 +3206,12 @@
   uint64_t getDereferenceableBytes(unsigned i) const {
     return AttributeList.getDereferenceableBytes(i);
   }
+  
+  /// \brief Extract the number of dereferenceable_or_null bytes for a call or
+  /// parameter (0=unknown).
+  uint64_t getDereferenceableOrNullBytes(unsigned i) const {
+    return AttributeList.getDereferenceableOrNullBytes(i);
+  }
 
   /// \brief Return true if the call should not be treated as a call to a
   /// builtin.
Index: llvm/trunk/lib/IR/AttributeImpl.h
===================================================================
--- llvm/trunk/lib/IR/AttributeImpl.h
+++ llvm/trunk/lib/IR/AttributeImpl.h
@@ -166,6 +166,7 @@
   unsigned getAlignment() const;
   unsigned getStackAlignment() const;
   uint64_t getDereferenceableBytes() const;
+  uint64_t getDereferenceableOrNullBytes() const;
   std::string getAsString(bool InAttrGrp) const;
 
   typedef const Attribute *iterator;
Index: llvm/trunk/lib/IR/Attributes.cpp
===================================================================
--- llvm/trunk/lib/IR/Attributes.cpp
+++ llvm/trunk/lib/IR/Attributes.cpp
@@ -532,6 +532,13 @@
   return 0;
 }
 
+uint64_t AttributeSetNode::getDereferenceableOrNullBytes() const {
+  for (iterator I = begin(), E = end(); I != E; ++I)
+    if (I->hasAttribute(Attribute::DereferenceableOrNull))
+      return I->getDereferenceableOrNullBytes();
+  return 0;
+}
+
 std::string AttributeSetNode::getAsString(bool InAttrGrp) const {
   std::string Str;
   for (iterator I = begin(), E = end(); I != E; ++I) {
@@ -957,6 +964,11 @@
   return ASN ? ASN->getDereferenceableBytes() : 0;
 }
 
+uint64_t AttributeSet::getDereferenceableOrNullBytes(unsigned Index) const {
+  AttributeSetNode *ASN = getAttributes(Index);
+  return ASN ? ASN->getDereferenceableOrNullBytes() : 0;
+}
+
 std::string AttributeSet::getAsString(unsigned Index,
                                       bool InAttrGrp) const {
   AttributeSetNode *ASN = getAttributes(Index);
Index: llvm/trunk/lib/IR/Function.cpp
===================================================================
--- llvm/trunk/lib/IR/Function.cpp
+++ llvm/trunk/lib/IR/Function.cpp
@@ -117,6 +117,12 @@
   return getParent()->getDereferenceableBytes(getArgNo()+1);
 }
 
+uint64_t Argument::getDereferenceableOrNullBytes() const {
+  assert(getType()->isPointerTy() &&
+         "Only pointers have dereferenceable bytes");
+  return getParent()->getDereferenceableOrNullBytes(getArgNo()+1);
+}
+
 /// hasNestAttr - Return true if this argument has the nest attribute on
 /// it in its containing function.
 bool Argument::hasNestAttr() const {