Index: cfe/trunk/include/clang/Basic/SourceManager.h
===================================================================
--- cfe/trunk/include/clang/Basic/SourceManager.h
+++ cfe/trunk/include/clang/Basic/SourceManager.h
@@ -1489,6 +1489,17 @@
   /// \returns true if LHS source location comes before RHS, false otherwise.
   bool isBeforeInTranslationUnit(SourceLocation LHS, SourceLocation RHS) const;
 
+  /// \brief Determines whether the two decomposed source location is in the
+  ///        same translation unit. As a byproduct, it also calculates the order
+  ///        of the source locations in case they are in the same TU.
+  ///
+  /// \returns Pair of bools the first component is true if the two locations
+  ///          are in the same TU. The second bool is true if the first is true
+  ///          and \p LOffs is before \p ROffs.
+  std::pair<bool, bool>
+  isInTheSameTranslationUnit(std::pair<FileID, unsigned> &LOffs,
+                             std::pair<FileID, unsigned> &ROffs) const;
+
   /// \brief Determines the order of 2 source locations in the "source location
   /// address space".
   bool isBeforeInSLocAddrSpace(SourceLocation LHS, SourceLocation RHS) const {
Index: cfe/trunk/lib/Basic/SourceManager.cpp
===================================================================
--- cfe/trunk/lib/Basic/SourceManager.cpp
+++ cfe/trunk/lib/Basic/SourceManager.cpp
@@ -2018,9 +2018,51 @@
   if (LOffs.first.isInvalid() || ROffs.first.isInvalid())
     return LOffs.first.isInvalid() && !ROffs.first.isInvalid();
 
+  std::pair<bool, bool> InSameTU = isInTheSameTranslationUnit(LOffs, ROffs);
+  if (InSameTU.first)
+    return InSameTU.second;
+
+  // If we arrived here, the location is either in a built-ins buffer or
+  // associated with global inline asm. PR5662 and PR22576 are examples.
+
+  StringRef LB = getBuffer(LOffs.first)->getBufferIdentifier();
+  StringRef RB = getBuffer(ROffs.first)->getBufferIdentifier();
+  bool LIsBuiltins = LB == "<built-in>";
+  bool RIsBuiltins = RB == "<built-in>";
+  // Sort built-in before non-built-in.
+  if (LIsBuiltins || RIsBuiltins) {
+    if (LIsBuiltins != RIsBuiltins)
+      return LIsBuiltins;
+    // Both are in built-in buffers, but from different files. We just claim that
+    // lower IDs come first.
+    return LOffs.first < ROffs.first;
+  }
+  bool LIsAsm = LB == "<inline asm>";
+  bool RIsAsm = RB == "<inline asm>";
+  // Sort assembler after built-ins, but before the rest.
+  if (LIsAsm || RIsAsm) {
+    if (LIsAsm != RIsAsm)
+      return RIsAsm;
+    assert(LOffs.first == ROffs.first);
+    return false;
+  }
+  bool LIsScratch = LB == "<scratch space>";
+  bool RIsScratch = RB == "<scratch space>";
+  // Sort scratch after inline asm, but before the rest.
+  if (LIsScratch || RIsScratch) {
+    if (LIsScratch != RIsScratch)
+      return LIsScratch;
+    return LOffs.second < ROffs.second;
+  }
+  llvm_unreachable("Unsortable locations found");
+}
+
+std::pair<bool, bool> SourceManager::isInTheSameTranslationUnit(
+    std::pair<FileID, unsigned> &LOffs,
+    std::pair<FileID, unsigned> &ROffs) const {
   // If the source locations are in the same file, just compare offsets.
   if (LOffs.first == ROffs.first)
-    return LOffs.second < ROffs.second;
+    return std::make_pair(true, LOffs.second < ROffs.second);
 
   // If we are comparing a source location with multiple locations in the same
   // file, we get a big win by caching the result.
@@ -2030,7 +2072,8 @@
   // If we are comparing a source location with multiple locations in the same
   // file, we get a big win by caching the result.
   if (IsBeforeInTUCache.isCacheValid(LOffs.first, ROffs.first))
-    return IsBeforeInTUCache.getCachedResult(LOffs.second, ROffs.second);
+    return std::make_pair(
+        true, IsBeforeInTUCache.getCachedResult(LOffs.second, ROffs.second));
 
   // Okay, we missed in the cache, start updating the cache for this query.
   IsBeforeInTUCache.setQueryFIDs(LOffs.first, ROffs.first,
@@ -2060,44 +2103,12 @@
   // locations within the common file and cache them.
   if (LOffs.first == ROffs.first) {
     IsBeforeInTUCache.setCommonLoc(LOffs.first, LOffs.second, ROffs.second);
-    return IsBeforeInTUCache.getCachedResult(LOffs.second, ROffs.second);
+    return std::make_pair(
+        true, IsBeforeInTUCache.getCachedResult(LOffs.second, ROffs.second));
   }
-
-  // If we arrived here, the location is either in a built-ins buffer or
-  // associated with global inline asm. PR5662 and PR22576 are examples.
-
   // Clear the lookup cache, it depends on a common location.
   IsBeforeInTUCache.clear();
-  StringRef LB = getBuffer(LOffs.first)->getBufferIdentifier();
-  StringRef RB = getBuffer(ROffs.first)->getBufferIdentifier();
-  bool LIsBuiltins = LB == "<built-in>";
-  bool RIsBuiltins = RB == "<built-in>";
-  // Sort built-in before non-built-in.
-  if (LIsBuiltins || RIsBuiltins) {
-    if (LIsBuiltins != RIsBuiltins)
-      return LIsBuiltins;
-    // Both are in built-in buffers, but from different files. We just claim that
-    // lower IDs come first.
-    return LOffs.first < ROffs.first;
-  }
-  bool LIsAsm = LB == "<inline asm>";
-  bool RIsAsm = RB == "<inline asm>";
-  // Sort assembler after built-ins, but before the rest.
-  if (LIsAsm || RIsAsm) {
-    if (LIsAsm != RIsAsm)
-      return RIsAsm;
-    assert(LOffs.first == ROffs.first);
-    return false;
-  }
-  bool LIsScratch = LB == "<scratch space>";
-  bool RIsScratch = RB == "<scratch space>";
-  // Sort scratch after inline asm, but before the rest.
-  if (LIsScratch || RIsScratch) {
-    if (LIsScratch != RIsScratch)
-      return LIsScratch;
-    return LOffs.second < ROffs.second;
-  }
-  llvm_unreachable("Unsortable locations found");
+  return std::make_pair(false, false);
 }
 
 void SourceManager::PrintStats() const {