Check in LLVM r95781.
diff --git a/lib/Support/StringRef.cpp b/lib/Support/StringRef.cpp
new file mode 100644
index 0000000..ae2640b
--- /dev/null
+++ b/lib/Support/StringRef.cpp
@@ -0,0 +1,274 @@
+//===-- StringRef.cpp - Lightweight String References ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringRef.h"
+
+using namespace llvm;
+
+// MSVC emits references to this into the translation units which reference it.
+#ifndef _MSC_VER
+const size_t StringRef::npos;
+#endif
+
+static char ascii_tolower(char x) {
+  if (x >= 'A' && x <= 'Z')
+    return x - 'A' + 'a';
+  return x;
+}
+
+/// compare_lower - Compare strings, ignoring case.
+int StringRef::compare_lower(StringRef RHS) const {
+  for (size_t I = 0, E = min(Length, RHS.Length); I != E; ++I) {
+    char LHC = ascii_tolower(Data[I]);
+    char RHC = ascii_tolower(RHS.Data[I]);
+    if (LHC != RHC)
+      return LHC < RHC ? -1 : 1;
+  }
+
+  if (Length == RHS.Length)
+        return 0;
+  return Length < RHS.Length ? -1 : 1;
+}
+
+// Compute the edit distance between the two given strings.
+unsigned StringRef::edit_distance(llvm::StringRef Other, 
+                                  bool AllowReplacements) {
+  // The algorithm implemented below is the "classic"
+  // dynamic-programming algorithm for computing the Levenshtein
+  // distance, which is described here:
+  //
+  //   http://en.wikipedia.org/wiki/Levenshtein_distance
+  //
+  // Although the algorithm is typically described using an m x n
+  // array, only two rows are used at a time, so this implemenation
+  // just keeps two separate vectors for those two rows.
+  size_type m = size();
+  size_type n = Other.size();
+
+  const unsigned SmallBufferSize = 64;
+  unsigned SmallBuffer[SmallBufferSize];
+  unsigned *Allocated = 0;
+  unsigned *previous = SmallBuffer;
+  if (2*(n + 1) > SmallBufferSize)
+    Allocated = previous = new unsigned [2*(n+1)];
+  unsigned *current = previous + (n + 1);
+  
+  for (unsigned i = 0; i <= n; ++i) 
+    previous[i] = i;
+
+  for (size_type y = 1; y <= m; ++y) {
+    current[0] = y;
+    for (size_type x = 1; x <= n; ++x) {
+      if (AllowReplacements) {
+        current[x] = min(previous[x-1] + ((*this)[y-1] == Other[x-1]? 0u:1u),
+                         min(current[x-1], previous[x])+1);
+      }
+      else {
+        if ((*this)[y-1] == Other[x-1]) current[x] = previous[x-1];
+        else current[x] = min(current[x-1], previous[x]) + 1;
+      }
+    }
+    
+    unsigned *tmp = current;
+    current = previous;
+    previous = tmp;
+  }
+
+  unsigned Result = previous[n];
+  delete [] Allocated;
+  
+  return Result;
+}
+
+//===----------------------------------------------------------------------===//
+// String Searching
+//===----------------------------------------------------------------------===//
+
+
+/// find - Search for the first string \arg Str in the string.
+///
+/// \return - The index of the first occurence of \arg Str, or npos if not
+/// found.
+size_t StringRef::find(StringRef Str, size_t From) const {
+  size_t N = Str.size();
+  if (N > Length)
+    return npos;
+  for (size_t e = Length - N + 1, i = min(From, e); i != e; ++i)
+    if (substr(i, N).equals(Str))
+      return i;
+  return npos;
+}
+
+/// rfind - Search for the last string \arg Str in the string.
+///
+/// \return - The index of the last occurence of \arg Str, or npos if not
+/// found.
+size_t StringRef::rfind(StringRef Str) const {
+  size_t N = Str.size();
+  if (N > Length)
+    return npos;
+  for (size_t i = Length - N + 1, e = 0; i != e;) {
+    --i;
+    if (substr(i, N).equals(Str))
+      return i;
+  }
+  return npos;
+}
+
+/// find_first_of - Find the first character in the string that is in \arg
+/// Chars, or npos if not found.
+///
+/// Note: O(size() * Chars.size())
+StringRef::size_type StringRef::find_first_of(StringRef Chars,
+                                              size_t From) const {
+  for (size_type i = min(From, Length), e = Length; i != e; ++i)
+    if (Chars.find(Data[i]) != npos)
+      return i;
+  return npos;
+}
+
+/// find_first_not_of - Find the first character in the string that is not
+/// \arg C or npos if not found.
+StringRef::size_type StringRef::find_first_not_of(char C, size_t From) const {
+  for (size_type i = min(From, Length), e = Length; i != e; ++i)
+    if (Data[i] != C)
+      return i;
+  return npos;
+}
+
+/// find_first_not_of - Find the first character in the string that is not
+/// in the string \arg Chars, or npos if not found.
+///
+/// Note: O(size() * Chars.size())
+StringRef::size_type StringRef::find_first_not_of(StringRef Chars,
+                                                  size_t From) const {
+  for (size_type i = min(From, Length), e = Length; i != e; ++i)
+    if (Chars.find(Data[i]) == npos)
+      return i;
+  return npos;
+}
+
+
+//===----------------------------------------------------------------------===//
+// Helpful Algorithms
+//===----------------------------------------------------------------------===//
+
+/// count - Return the number of non-overlapped occurrences of \arg Str in
+/// the string.
+size_t StringRef::count(StringRef Str) const {
+  size_t Count = 0;
+  size_t N = Str.size();
+  if (N > Length)
+    return 0;
+  for (size_t i = 0, e = Length - N + 1; i != e; ++i)
+    if (substr(i, N).equals(Str))
+      ++Count;
+  return Count;
+}
+
+/// GetAsUnsignedInteger - Workhorse method that converts a integer character
+/// sequence of radix up to 36 to an unsigned long long value.
+static bool GetAsUnsignedInteger(StringRef Str, unsigned Radix,
+                                 unsigned long long &Result) {
+  // Autosense radix if not specified.
+  if (Radix == 0) {
+    if (Str.startswith("0x")) {
+      Str = Str.substr(2);
+      Radix = 16;
+    } else if (Str.startswith("0b")) {
+      Str = Str.substr(2);
+      Radix = 2;
+    } else if (Str.startswith("0"))
+      Radix = 8;
+    else
+      Radix = 10;
+  }
+  
+  // Empty strings (after the radix autosense) are invalid.
+  if (Str.empty()) return true;
+  
+  // Parse all the bytes of the string given this radix.  Watch for overflow.
+  Result = 0;
+  while (!Str.empty()) {
+    unsigned CharVal;
+    if (Str[0] >= '0' && Str[0] <= '9')
+      CharVal = Str[0]-'0';
+    else if (Str[0] >= 'a' && Str[0] <= 'z')
+      CharVal = Str[0]-'a'+10;
+    else if (Str[0] >= 'A' && Str[0] <= 'Z')
+      CharVal = Str[0]-'A'+10;
+    else
+      return true;
+    
+    // If the parsed value is larger than the integer radix, the string is
+    // invalid.
+    if (CharVal >= Radix)
+      return true;
+    
+    // Add in this character.
+    unsigned long long PrevResult = Result;
+    Result = Result*Radix+CharVal;
+    
+    // Check for overflow.
+    if (Result < PrevResult)
+      return true;
+
+    Str = Str.substr(1);
+  }
+  
+  return false;
+}
+
+bool StringRef::getAsInteger(unsigned Radix, unsigned long long &Result) const {
+  return GetAsUnsignedInteger(*this, Radix, Result);
+}
+
+
+bool StringRef::getAsInteger(unsigned Radix, long long &Result) const {
+  unsigned long long ULLVal;
+  
+  // Handle positive strings first.
+  if (empty() || front() != '-') {
+    if (GetAsUnsignedInteger(*this, Radix, ULLVal) ||
+        // Check for value so large it overflows a signed value.
+        (long long)ULLVal < 0)
+      return true;
+    Result = ULLVal;
+    return false;
+  }
+  
+  // Get the positive part of the value.
+  if (GetAsUnsignedInteger(substr(1), Radix, ULLVal) ||
+      // Reject values so large they'd overflow as negative signed, but allow
+      // "-0".  This negates the unsigned so that the negative isn't undefined
+      // on signed overflow.
+      (long long)-ULLVal > 0)
+    return true;
+  
+  Result = -ULLVal;
+  return false;
+}
+
+bool StringRef::getAsInteger(unsigned Radix, int &Result) const {
+  long long Val;
+  if (getAsInteger(Radix, Val) ||
+      (int)Val != Val)
+    return true;
+  Result = Val;
+  return false;
+}
+
+bool StringRef::getAsInteger(unsigned Radix, unsigned &Result) const {
+  unsigned long long Val;
+  if (getAsInteger(Radix, Val) ||
+      (unsigned)Val != Val)
+    return true;
+  Result = Val;
+  return false;
+}