diff --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -1744,7 +1744,7 @@
     assert(ID != -1 && "Using FileID sentinel value");
     if (ID < 0)
       return getLoadedSLocEntryByID(ID, Invalid);
-    return getLocalSLocEntry(static_cast<unsigned>(ID), Invalid);
+    return getLocalSLocEntry(static_cast<unsigned>(ID));
   }
 
   const SrcMgr::SLocEntry &
@@ -1779,6 +1779,21 @@
     return SLocOffset < getSLocEntryByID(FID.ID+1).getOffset();
   }
 
+  /// A small optimization over isOffsetInFileID for when the caller has
+  /// already determined the FileID to be local, as opposed to loaded and the
+  /// SlocOffset to be before the NextLocalOffset. The more generic
+  /// isOffsetInFileID method should be preferred.
+  inline bool isOffsetInLocalFileID(FileID FID, unsigned SLocOffset) const {
+    assert(SLocOffset < NextLocalOffset && "SLocOffset non-local");
+    assert(FID.ID > 0 && "FID non-local or invalid");
+    const unsigned ID = static_cast<unsigned>(FID.ID);
+    if (SLocOffset < getLocalSLocEntry(ID).getOffset())
+      return false;
+    if (ID + 1 == LocalSLocEntryTable.size())
+      return true;
+    return SLocOffset < getLocalSLocEntry(ID + 1).getOffset();
+  }
+
   /// Returns the previous in-order FileID or an invalid FileID if there
   /// is no previous one.
   FileID getPreviousFileID(FileID FID) const;
diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -861,11 +861,8 @@
     --I;
     if (I->getOffset() <= SLocOffset) {
       FileID Res = FileID::get(int(I - LocalSLocEntryTable.begin()));
-
-      // If this isn't an expansion, remember it.  We have good locality across
-      // FileID lookups.
-      if (!I->isExpansion())
-        LastFileIDLookup = Res;
+      // Remember it.  We have good locality across FileID lookups.
+      LastFileIDLookup = Res;
       NumLinearScans += NumProbes+1;
       return Res;
     }
@@ -882,11 +879,8 @@
   unsigned LessIndex = 0;
   NumProbes = 0;
   while (true) {
-    bool Invalid = false;
     unsigned MiddleIndex = (GreaterIndex-LessIndex)/2+LessIndex;
-    unsigned MidOffset = getLocalSLocEntry(MiddleIndex, &Invalid).getOffset();
-    if (Invalid)
-      return FileID::get(0);
+    unsigned MidOffset = getLocalSLocEntry(MiddleIndex).getOffset();
 
     ++NumProbes;
 
@@ -898,15 +892,10 @@
     }
 
     // If the middle index contains the value, succeed and return.
-    // FIXME: This could be made faster by using a function that's aware of
-    // being in the local area.
-    if (isOffsetInFileID(FileID::get(MiddleIndex), SLocOffset)) {
-      FileID Res = FileID::get(MiddleIndex);
-
-      // If this isn't a macro expansion, remember it.  We have good locality
-      // across FileID lookups.
-      if (!LocalSLocEntryTable[MiddleIndex].isExpansion())
-        LastFileIDLookup = Res;
+    FileID Res = FileID::get(MiddleIndex);
+    if (isOffsetInLocalFileID(Res, SLocOffset)) {
+      // Remember it.  We have good locality across FileID lookups.
+      LastFileIDLookup = Res;
       NumBinaryProbes += NumProbes;
       return Res;
     }
@@ -944,9 +933,7 @@
     const SrcMgr::SLocEntry &E = getLoadedSLocEntry(I);
     if (E.getOffset() <= SLocOffset) {
       FileID Res = FileID::get(-int(I) - 2);
-
-      if (!E.isExpansion())
-        LastFileIDLookup = Res;
+      LastFileIDLookup = Res;
       NumLinearScans += NumProbes + 1;
       return Res;
     }
@@ -979,8 +966,7 @@
 
     if (isOffsetInFileID(FileID::get(-int(MiddleIndex) - 2), SLocOffset)) {
       FileID Res = FileID::get(-int(MiddleIndex) - 2);
-      if (!E.isExpansion())
-        LastFileIDLookup = Res;
+      LastFileIDLookup = Res;
       NumBinaryProbes += NumProbes;
       return Res;
     }
@@ -1695,10 +1681,7 @@
   // The location we're looking for isn't in the main file; look
   // through all of the local source locations.
   for (unsigned I = 0, N = local_sloc_entry_size(); I != N; ++I) {
-    bool Invalid = false;
-    const SLocEntry &SLoc = getLocalSLocEntry(I, &Invalid);
-    if (Invalid)
-      return FileID();
+    const SLocEntry &SLoc = getLocalSLocEntry(I);
 
     if (SLoc.isFile() && SLoc.getFile().getContentCache() &&
         SLoc.getFile().getContentCache()->OrigEntry == SourceFile)