diff --git a/clang/lib/Frontend/LayoutOverrideSource.cpp b/clang/lib/Frontend/LayoutOverrideSource.cpp
new file mode 100644
index 0000000..3af2cc2
--- /dev/null
+++ b/clang/lib/Frontend/LayoutOverrideSource.cpp
@@ -0,0 +1,206 @@
+//===--- LayoutOverrideSource.cpp --Override Record Layouts ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/Frontend/LayoutOverrideSource.h"
+#include "clang/AST/Decl.h"
+#include "llvm/Support/raw_ostream.h"
+#include <fstream>
+#include <string>
+
+using namespace clang;
+
+/// \brief Parse a simple identifier.
+std::string parseName(StringRef S) {
+  unsigned Offset = 0;
+  while (Offset < S.size() &&
+         (isalpha(S[Offset]) || S[Offset] == '_' ||
+          (Offset > 0 && isdigit(S[Offset]))))
+    ++Offset;
+  
+  return S.substr(0, Offset).str();
+}
+
+LayoutOverrideSource::LayoutOverrideSource(llvm::StringRef Filename) {
+  std::ifstream Input(Filename.str().c_str());
+  if (!Input.is_open())
+    return;
+  
+  // Parse the output of -fdump-record-layouts.
+  std::string CurrentType;
+  Layout CurrentLayout;
+  bool ExpectingType = false;
+  
+  while (Input.good()) {
+    std::string Line;
+    getline(Input, Line);
+    
+    StringRef LineStr(Line);
+
+    // Determine whether the following line will start a 
+    if (LineStr.find("*** Dumping AST Record Layout") != StringRef::npos)  {
+      // Flush the last type/layout, if there is one.
+      if (!CurrentType.empty())
+        Layouts[CurrentType] = CurrentLayout;
+      CurrentLayout = Layout();
+      
+      ExpectingType = true;
+      continue;
+    }
+    
+    // If we're expecting a type, grab it.
+    if (ExpectingType) {
+      ExpectingType = false;
+      
+      StringRef::size_type Pos;
+      if ((Pos = LineStr.find("struct ")) != StringRef::npos)
+        LineStr = LineStr.substr(Pos + strlen("struct "));
+      else if ((Pos = LineStr.find("class ")) != StringRef::npos)
+        LineStr = LineStr.substr(Pos + strlen("class "));
+      else if ((Pos = LineStr.find("union ")) != StringRef::npos)
+        LineStr = LineStr.substr(Pos + strlen("union "));
+      else
+        continue;
+      
+      // Find the name of the type.
+      CurrentType = parseName(LineStr);
+      CurrentLayout = Layout();
+      continue;
+    }
+    
+    // Check for the size of the type.
+    StringRef::size_type Pos = LineStr.find("Size:");
+    if (Pos != StringRef::npos) {
+      // Skip past the "Size:" prefix.
+      LineStr = LineStr.substr(Pos + strlen("Size:"));
+      
+      unsigned long long Size = 0;
+      (void)LineStr.getAsInteger(10, Size);
+      CurrentLayout.Size = Size;
+      continue;
+    }
+
+    // Check for the alignment of the type.
+    Pos = LineStr.find("Alignment:");
+    if (Pos != StringRef::npos) {
+      // Skip past the "Alignment:" prefix.
+      LineStr = LineStr.substr(Pos + strlen("Alignment:"));
+      
+      unsigned long long Alignment = 0;
+      (void)LineStr.getAsInteger(10, Alignment);
+      CurrentLayout.Align = Alignment;
+      continue;
+    }
+    
+    // Check for the size/alignment of the type.
+    Pos = LineStr.find("sizeof=");
+    if (Pos != StringRef::npos) {
+      /* Skip past the sizeof= prefix. */
+      LineStr = LineStr.substr(Pos + strlen("sizeof="));
+
+      // Parse size.
+      unsigned long long Size = 0;
+      (void)LineStr.getAsInteger(10, Size);
+      CurrentLayout.Size = Size;
+
+      Pos = LineStr.find("align=");
+      if (Pos != StringRef::npos) {
+        /* Skip past the align= prefix. */
+        LineStr = LineStr.substr(Pos + strlen("align="));
+        
+        // Parse alignment.
+        unsigned long long Alignment = 0;
+        (void)LineStr.getAsInteger(10, Alignment);
+        CurrentLayout.Align = Alignment;
+      }
+      
+      continue;
+    }
+    
+    // Check for the field offsets of the type.
+    Pos = LineStr.find("FieldOffsets: [");
+    if (Pos == StringRef::npos)
+      continue;
+
+    LineStr = LineStr.substr(Pos + strlen("FieldOffsets: ["));
+    while (!LineStr.empty() && isdigit(LineStr[0])) {
+      // Parse this offset.
+      unsigned Idx = 1;
+      while (Idx < LineStr.size() && isdigit(LineStr[Idx]))
+        ++Idx;
+      
+      unsigned long long Offset = 0;
+      (void)LineStr.substr(0, Idx).getAsInteger(10, Offset);
+      
+      CurrentLayout.FieldOffsets.push_back(Offset);
+      
+      // Skip over this offset, the following comma, and any spaces.
+      LineStr = LineStr.substr(Idx + 1);
+      while (!LineStr.empty() && isspace(LineStr[0]))
+        LineStr = LineStr.substr(1);
+    }
+  }
+  
+  // Flush the last type/layout, if there is one.
+  if (!CurrentType.empty())
+    Layouts[CurrentType] = CurrentLayout;
+}
+
+bool 
+LayoutOverrideSource::layoutRecordType(const RecordDecl *Record,
+  uint64_t &Size, uint64_t &Alignment,
+  llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets,
+  llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets,
+  llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets) 
+{
+  // We can't override unnamed declarations.
+  if (!Record->getIdentifier())
+    return false;
+  
+  // Check whether we have a layout for this record.
+  llvm::StringMap<Layout>::iterator Known = Layouts.find(Record->getName());
+  if (Known == Layouts.end())
+    return false;
+  
+  // Provide field layouts.
+  unsigned NumFields = 0;
+  for (RecordDecl::field_iterator F = Record->field_begin(), 
+                               FEnd = Record->field_end();
+       F != FEnd; ++F, ++NumFields) {
+    if (NumFields >= Known->second.FieldOffsets.size())
+      continue;
+    
+    FieldOffsets[*F] = Known->second.FieldOffsets[NumFields];
+  }
+  
+  // Wrong number of fields.
+  if (NumFields != Known->second.FieldOffsets.size())
+    return false;
+  
+  Size = Known->second.Size;
+  Alignment = Known->second.Align;
+  return true;
+}
+
+void LayoutOverrideSource::dump() {
+  llvm::raw_ostream &OS = llvm::errs();
+  for (llvm::StringMap<Layout>::iterator L = Layouts.begin(), 
+                                      LEnd = Layouts.end();
+       L != LEnd; ++L) {
+    OS << "Type: blah " << L->first() << '\n';
+    OS << "  Size:" << L->second.Size << '\n';
+    OS << "  Alignment:" << L->second.Align << '\n';
+    OS << "  FieldOffsets: [";
+    for (unsigned I = 0, N = L->second.FieldOffsets.size(); I != N; ++I) {
+      if (I)
+        OS << ", ";
+      OS << L->second.FieldOffsets[I];
+    }
+    OS << "]\n";
+  }
+}
+