diff --git a/clang/include/clang/Serialization/ASTWriter.h b/clang/include/clang/Serialization/ASTWriter.h
--- a/clang/include/clang/Serialization/ASTWriter.h
+++ b/clang/include/clang/Serialization/ASTWriter.h
@@ -447,6 +447,22 @@
   /// User ModuleMaps skipped when writing control block.
   std::set<const FileEntry *> SkippedModuleMaps;
 
+  /// Returns an adjusted \c FileID, accounting for any non-affecting input
+  /// files.
+  FileID getAdjustedFileID(FileID FID) const;
+  /// Returns an adjusted number of \c FileIDs created within the specified \c
+  /// FileID, accounting for any non-affecting input files.
+  unsigned getAdjustedNumCreatedFIDs(FileID FID) const;
+  /// Returns an adjusted \c SourceLocation, accounting for any non-affecting
+  /// input files.
+  SourceLocation getAdjustedLocation(SourceLocation Loc) const;
+  /// Returns an adjusted \c SourceRange, accounting for any non-affecting input
+  /// files.
+  SourceRange getAdjustedRange(SourceRange Range) const;
+  /// Returns an adjusted \c SourceLocation offset, accounting for any
+  /// non-affecting input files.
+  SourceLocation::UIntTy getAdjustedOffset(SourceLocation::UIntTy Offset) const;
+
   /// Retrieve or create a submodule ID for this module.
   unsigned getSubmoduleID(Module *Mod);
 
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2063,7 +2063,7 @@
     Record.push_back(Code);
 
     // Starting offset of this entry within this module, so skip the dummy.
-    Record.push_back(SLoc->getOffset() - 2);
+    Record.push_back(getAdjustedOffset(SLoc->getOffset()) - 2);
     if (SLoc->isFile()) {
       const SrcMgr::FileInfo &File = SLoc->getFile();
       const SrcMgr::ContentCache *Content = &File.getContentCache();
@@ -2086,7 +2086,7 @@
         assert(InputFileIDs[Content->OrigEntry] != 0 && "Missed file entry");
         Record.push_back(InputFileIDs[Content->OrigEntry]);
 
-        Record.push_back(File.NumCreatedFIDs);
+        Record.push_back(getAdjustedNumCreatedFIDs(FID));
 
         FileDeclIDsTy::iterator FDI = FileDeclIDs.find(FID);
         if (FDI != FileDeclIDs.end()) {
@@ -2146,7 +2146,7 @@
       SourceLocation::UIntTy NextOffset = SourceMgr.getNextLocalOffset();
       if (I + 1 != N)
         NextOffset = SourceMgr.getLocalSLocEntry(I + 1).getOffset();
-      Record.push_back(NextOffset - SLoc->getOffset() - 1);
+      Record.push_back(getAdjustedOffset(NextOffset - SLoc->getOffset()) - 1);
       Stream.EmitRecordWithAbbrev(SLocExpansionAbbrv, Record);
     }
   }
@@ -2170,7 +2170,7 @@
   {
     RecordData::value_type Record[] = {
         SOURCE_LOCATION_OFFSETS, SLocEntryOffsets.size(),
-        SourceMgr.getNextLocalOffset() - 1 /* skip dummy */,
+        getAdjustedOffset(SourceMgr.getNextLocalOffset()) - 1 /* skip dummy */,
         SLocEntryOffsetsBase - SourceManagerBlockOffset};
     Stream.EmitRecordWithBlob(SLocOffsetsAbbrev, Record,
                               bytes(SLocEntryOffsets));
@@ -2569,7 +2569,7 @@
     uint64_t Offset = Stream.GetCurrentBitNo() - MacroOffsetsBase;
     assert((Offset >> 32) == 0 && "Preprocessed entity offset too large");
     PreprocessedEntityOffsets.push_back(
-        PPEntityOffset((*E)->getSourceRange(), Offset));
+        PPEntityOffset(getAdjustedRange((*E)->getSourceRange()), Offset));
 
     if (auto *MD = dyn_cast<MacroDefinitionRecord>(*E)) {
       // Record this macro definition's ID.
@@ -3014,7 +3014,7 @@
 
     Record.push_back(FileIDAndFile.second.StateTransitions.size());
     for (auto &StatePoint : FileIDAndFile.second.StateTransitions) {
-      Record.push_back(StatePoint.Offset);
+      Record.push_back(getAdjustedOffset(StatePoint.Offset));
       AddDiagState(StatePoint.State, false);
     }
   }
@@ -5225,12 +5225,42 @@
   Record.push_back(Raw);
 }
 
+FileID ASTWriter::getAdjustedFileID(FileID FID) const {
+  // TODO: Actually adjust this.
+  return FID;
+}
+
+unsigned ASTWriter::getAdjustedNumCreatedFIDs(FileID FID) const {
+  // TODO: Actually adjust this.
+  return PP->getSourceManager()
+      .getLocalSLocEntry(FID.ID)
+      .getFile()
+      .NumCreatedFIDs;
+}
+
+SourceLocation ASTWriter::getAdjustedLocation(SourceLocation Loc) const {
+  // TODO: Actually adjust this.
+  return Loc;
+}
+
+SourceRange ASTWriter::getAdjustedRange(SourceRange Range) const {
+  // TODO: Actually adjust this.
+  return Range;
+}
+
+SourceLocation::UIntTy
+ASTWriter::getAdjustedOffset(SourceLocation::UIntTy Offset) const {
+  // TODO: Actually adjust this.
+  return Offset;
+}
+
 void ASTWriter::AddFileID(FileID FID, RecordDataImpl &Record) {
-  Record.push_back(FID.getOpaqueValue());
+  Record.push_back(getAdjustedFileID(FID).getOpaqueValue());
 }
 
 void ASTWriter::AddSourceLocation(SourceLocation Loc, RecordDataImpl &Record,
                                   SourceLocationSequence *Seq) {
+  Loc = getAdjustedLocation(Loc);
   Record.push_back(SourceLocationEncoding::encode(Loc, Seq));
 }
 
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -2457,11 +2457,12 @@
   SourceLocation Loc = D->getLocation();
   unsigned Index = ID - FirstDeclID;
   if (DeclOffsets.size() == Index)
-    DeclOffsets.emplace_back(Loc, Offset, DeclTypesBlockStartOffset);
+    DeclOffsets.emplace_back(getAdjustedLocation(Loc), Offset,
+                             DeclTypesBlockStartOffset);
   else if (DeclOffsets.size() < Index) {
     // FIXME: Can/should this happen?
     DeclOffsets.resize(Index+1);
-    DeclOffsets[Index].setLocation(Loc);
+    DeclOffsets[Index].setLocation(getAdjustedLocation(Loc));
     DeclOffsets[Index].setBitOffset(Offset, DeclTypesBlockStartOffset);
   } else {
     llvm_unreachable("declarations should be emitted in ID order");