diff --git a/docs/LangRef.html b/docs/LangRef.html
index 7032a19..eea1f03 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -1215,6 +1215,13 @@
   <dt><tt>s<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt>
   <dd>This specifies the alignment for a stack object of a given bit
       <i>size</i>.</dd>
+
+  <dt><tt>n<i>size1</i>:<i>size2</i>:<i>size3</i>...</tt></dt>
+  <dd>This specifies a set of native integer widths for the target CPU
+      in bits.  For example, it might contain "n32" for 32-bit PowerPC,
+      "n32:64" for PowerPC 64, or "n8:16:32:64" for X86-64.  Elements of
+      this set are considered to support most general arithmetic 
+      operations efficiently.</dd>
 </dl>
 
 <p>When constructing the data layout for a given target, LLVM starts with a
diff --git a/include/llvm/Target/TargetData.h b/include/llvm/Target/TargetData.h
index 1ad058c..9630877 100644
--- a/include/llvm/Target/TargetData.h
+++ b/include/llvm/Target/TargetData.h
@@ -70,6 +70,8 @@
   unsigned char PointerABIAlign;       ///< Pointer ABI alignment
   unsigned char PointerPrefAlign;      ///< Pointer preferred alignment
 
+  SmallVector<unsigned char, 8> LegalIntWidths; ///< Legal Integers.
+  
   /// Alignments- Where the primitive type alignment data is stored.
   ///
   /// @sa init().
@@ -78,12 +80,8 @@
   /// we don't.
   SmallVector<TargetAlignElem, 16> Alignments;
   
-  
-  
-  /*!
-    This member is a signal that a requested alignment type and bit width were
-    not found in the SmallVector.
-   */
+  /// InvalidAlignmentElem - This member is a signal that a requested alignment
+  /// type and bit width were not found in the SmallVector.
   static const TargetAlignElem InvalidAlignmentElem;
 
   // Opaque pointer for the StructType -> StructLayout map.
@@ -127,6 +125,7 @@
     PointerMemSize(TD.PointerMemSize),
     PointerABIAlign(TD.PointerABIAlign),
     PointerPrefAlign(TD.PointerPrefAlign),
+    LegalIntWidths(TD.LegalIntWidths),
     Alignments(TD.Alignments),
     LayoutMap(0)
   { }
@@ -137,13 +136,33 @@
   void init(StringRef TargetDescription);
 
   /// Target endianness...
-  bool          isLittleEndian()       const { return     LittleEndian; }
-  bool          isBigEndian()          const { return    !LittleEndian; }
+  bool isLittleEndian() const { return LittleEndian; }
+  bool isBigEndian() const { return !LittleEndian; }
 
   /// getStringRepresentation - Return the string representation of the
   /// TargetData.  This representation is in the same format accepted by the
   /// string constructor above.
   std::string getStringRepresentation() const;
+  
+  
+  /// isIllegalInteger - This function returns true if the specified type is
+  /// known to not be a native integer type supported by the CPU.  For example,
+  /// i64 is not native on most 32-bit CPUs and i37 is not native on any known
+  /// one.  This returns false if the integer width is legal or we don't know.
+  ///
+  /// The width is specified in bits.
+  ///
+  bool isIllegalInteger(unsigned Width) const {
+    // If we don't have information about legal integer types, don't claim the
+    // type is illegal.
+    if (LegalIntWidths.empty()) return false;
+    
+    for (unsigned i = 0, e = LegalIntWidths.size(); i != e; ++i)
+      if (LegalIntWidths[i] == Width)
+        return false;
+    return true;
+  }
+  
   /// Target pointer alignment
   unsigned char getPointerABIAlignment() const { return PointerABIAlign; }
   /// Return target's alignment for stack-based pointers
diff --git a/lib/Target/TargetData.cpp b/lib/Target/TargetData.cpp
index 06c493f..b6b84c5 100644
--- a/lib/Target/TargetData.cpp
+++ b/lib/Target/TargetData.cpp
@@ -139,45 +139,7 @@
   return Result;
 }
 
-/*!
- A TargetDescription string consists of a sequence of hyphen-delimited
- specifiers for target endianness, pointer size and alignments, and various
- primitive type sizes and alignments. A typical string looks something like:
- <br><br>
- "E-p:32:32:32-i1:8:8-i8:8:8-i32:32:32-i64:32:64-f32:32:32-f64:32:64"
- <br><br>
- (note: this string is not fully specified and is only an example.)
- \p
- Alignments come in two flavors: ABI and preferred. ABI alignment (abi_align,
- below) dictates how a type will be aligned within an aggregate and when used
- as an argument.  Preferred alignment (pref_align, below) determines a type's
- alignment when emitted as a global.
- \p
- Specifier string details:
- <br><br>
- <i>[E|e]</i>: Endianness. "E" specifies a big-endian target data model, "e"
- specifies a little-endian target data model.
- <br><br>
- <i>p:@verbatim<size>:<abi_align>:<pref_align>@endverbatim</i>: Pointer size, 
- ABI and preferred alignment.
- <br><br>
- <i>@verbatim<type><size>:<abi_align>:<pref_align>@endverbatim</i>: Numeric type
- alignment. Type is
- one of <i>i|f|v|a</i>, corresponding to integer, floating point, vector, or
- aggregate.  Size indicates the size, e.g., 32 or 64 bits.
- \p
- The default string, fully specified, is:
- <br><br>
- "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64"
- "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64"
- "-v64:64:64-v128:128:128"
- <br><br>
- Note that in the case of aggregates, 0 is the default ABI and preferred
- alignment. This is a special case, where the aggregate's computed worst-case
- alignment will be used.
- */ 
 void TargetData::init(StringRef Desc) {
-  
   LayoutMap = 0;
   LittleEndian = false;
   PointerMemSize = 8;
@@ -210,7 +172,7 @@
     
     assert(!Specifier.empty() && "Can't be empty here");
     
-    switch(Specifier[0]) {
+    switch (Specifier[0]) {
     case 'E':
       LittleEndian = false;
       break;
@@ -252,6 +214,17 @@
       setAlignment(AlignType, ABIAlign, PrefAlign, Size);
       break;
     }
+    case 'n':  // Native integer types.
+      Specifier = Specifier.substr(1);
+      do {
+        if (unsigned Width = getInt(Specifier))
+          LegalIntWidths.push_back(Width);
+        Split = Token.split(':');
+        Specifier = Split.first;
+        Token = Split.second;
+      } while (!Specifier.empty() || !Token.empty());
+      break;
+        
     default:
       break;
     }