Move lib/Archive to tools/llvm-ar.

llvm-ar is the only tool that needs to write archive files. Every other tool
should be able to use the lib/Object interface.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184083 91177308-0d34-0410-b5e6-96231b3b80d8

9 files changed, 1857 insertions, 4 deletions

diff --git a/tools/llvm-ar/Archive.cpp b/tools/llvm-ar/Archive.cpp
new file mode 100644
index 0000000000..3e9b9b2c25
--- /dev/null
+++ b/tools/llvm-ar/Archive.cpp
@@ -0,0 +1,254 @@
+//===-- Archive.cpp - Generic LLVM archive functions ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the implementation of the Archive and ArchiveMember
+// classes that is common to both reading and writing archives..
+//
+//===----------------------------------------------------------------------===//
+
+#include "Archive.h"
+#include "ArchiveInternals.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/system_error.h"
+#include <cstring>
+#include <memory>
+using namespace llvm;
+
+// getMemberSize - compute the actual physical size of the file member as seen
+// on disk. This isn't the size of member's payload. Use getSize() for that.
+unsigned
+ArchiveMember::getMemberSize() const {
+  // Basically its the file size plus the header size
+  unsigned result =  info.fileSize + sizeof(ArchiveMemberHeader);
+
+  // If it has a long filename, include the name length
+  if (hasLongFilename())
+    result += path.str().length() + 1;
+
+  // If its now odd lengthed, include the padding byte
+  if (result % 2 != 0 )
+    result++;
+
+  return result;
+}
+
+// This default constructor is only use by the ilist when it creates its
+// sentry node. We give it specific static values to make it stand out a bit.
+ArchiveMember::ArchiveMember()
+  : parent(0), path("--invalid--"), flags(0), data(0)
+{
+  info.user = sys::Process::GetCurrentUserId();
+  info.group = sys::Process::GetCurrentGroupId();
+  info.mode = 0777;
+  info.fileSize = 0;
+  info.modTime = sys::TimeValue::now();
+}
+
+// This is the constructor that the Archive class uses when it is building or
+// reading an archive. It just defaults a few things and ensures the parent is
+// set for the iplist. The Archive class fills in the ArchiveMember's data.
+// This is required because correctly setting the data may depend on other
+// things in the Archive.
+ArchiveMember::ArchiveMember(Archive* PAR)
+  : parent(PAR), path(), flags(0), data(0)
+{
+}
+
+// This method allows an ArchiveMember to be replaced with the data for a
+// different file, presumably as an update to the member. It also makes sure
+// the flags are reset correctly.
+bool ArchiveMember::replaceWith(const sys::Path& newFile, std::string* ErrMsg) {
+  bool Exists;
+  if (sys::fs::exists(newFile.str(), Exists) || !Exists) {
+    if (ErrMsg)
+      *ErrMsg = "Can not replace an archive member with a non-existent file";
+    return true;
+  }
+
+  data = 0;
+  path = newFile;
+
+  // SVR4 symbol tables have an empty name
+  if (path.str() == ARFILE_SVR4_SYMTAB_NAME)
+    flags |= SVR4SymbolTableFlag;
+  else
+    flags &= ~SVR4SymbolTableFlag;
+
+  // BSD4.4 symbol tables have a special name
+  if (path.str() == ARFILE_BSD4_SYMTAB_NAME)
+    flags |= BSD4SymbolTableFlag;
+  else
+    flags &= ~BSD4SymbolTableFlag;
+
+  // String table name
+  if (path.str() == ARFILE_STRTAB_NAME)
+    flags |= StringTableFlag;
+  else
+    flags &= ~StringTableFlag;
+
+  // If it has a slash then it has a path
+  bool hasSlash = path.str().find('/') != std::string::npos;
+  if (hasSlash)
+    flags |= HasPathFlag;
+  else
+    flags &= ~HasPathFlag;
+
+  // If it has a slash or its over 15 chars then its a long filename format
+  if (hasSlash || path.str().length() > 15)
+    flags |= HasLongFilenameFlag;
+  else
+    flags &= ~HasLongFilenameFlag;
+
+  // Get the signature and status info
+  const char* signature = (const char*) data;
+  SmallString<4> magic;
+  if (!signature) {
+    sys::fs::get_magic(path.str(), magic.capacity(), magic);
+    signature = magic.c_str();
+    const sys::FileStatus *FSinfo = path.getFileStatus(false, ErrMsg);
+    if (FSinfo)
+      info = *FSinfo;
+    else
+      return true;
+  }
+
+  // Determine what kind of file it is.
+  if (sys::fs::identify_magic(StringRef(signature, 4)) ==
+      sys::fs::file_magic::bitcode)
+    flags |= BitcodeFlag;
+  else
+    flags &= ~BitcodeFlag;
+
+  return false;
+}
+
+// Archive constructor - this is the only constructor that gets used for the
+// Archive class. Everything else (default,copy) is deprecated. This just
+// initializes and maps the file into memory, if requested.
+Archive::Archive(const sys::Path& filename, LLVMContext& C)
+  : archPath(filename), members(), mapfile(0), base(0), symTab(), strtab(),
+    symTabSize(0), firstFileOffset(0), modules(), foreignST(0), Context(C) {
+}
+
+bool
+Archive::mapToMemory(std::string* ErrMsg) {
+  OwningPtr<MemoryBuffer> File;
+  if (error_code ec = MemoryBuffer::getFile(archPath.c_str(), File)) {
+    if (ErrMsg)
+      *ErrMsg = ec.message();
+    return true;
+  }
+  mapfile = File.take();
+  base = mapfile->getBufferStart();
+  return false;
+}
+
+void Archive::cleanUpMemory() {
+  // Shutdown the file mapping
+  delete mapfile;
+  mapfile = 0;
+  base = 0;
+
+  // Forget the entire symbol table
+  symTab.clear();
+  symTabSize = 0;
+
+  firstFileOffset = 0;
+
+  // Free the foreign symbol table member
+  if (foreignST) {
+    delete foreignST;
+    foreignST = 0;
+  }
+
+  // Delete any Modules and ArchiveMember's we've allocated as a result of
+  // symbol table searches.
+  for (ModuleMap::iterator I=modules.begin(), E=modules.end(); I != E; ++I ) {
+    delete I->second.first;
+    delete I->second.second;
+  }
+}
+
+// Archive destructor - just clean up memory
+Archive::~Archive() {
+  cleanUpMemory();
+}
+
+
+
+static void getSymbols(Module*M, std::vector<std::string>& symbols) {
+  // Loop over global variables
+  for (Module::global_iterator GI = M->global_begin(), GE=M->global_end(); GI != GE; ++GI)
+    if (!GI->isDeclaration() && !GI->hasLocalLinkage())
+      if (!GI->getName().empty())
+        symbols.push_back(GI->getName());
+
+  // Loop over functions
+  for (Module::iterator FI = M->begin(), FE = M->end(); FI != FE; ++FI)
+    if (!FI->isDeclaration() && !FI->hasLocalLinkage())
+      if (!FI->getName().empty())
+        symbols.push_back(FI->getName());
+
+  // Loop over aliases
+  for (Module::alias_iterator AI = M->alias_begin(), AE = M->alias_end();
+       AI != AE; ++AI) {
+    if (AI->hasName())
+      symbols.push_back(AI->getName());
+  }
+}
+
+// Get just the externally visible defined symbols from the bitcode
+bool llvm::GetBitcodeSymbols(const sys::Path& fName,
+                             LLVMContext& Context,
+                             std::vector<std::string>& symbols,
+                             std::string* ErrMsg) {
+  OwningPtr<MemoryBuffer> Buffer;
+  if (error_code ec = MemoryBuffer::getFileOrSTDIN(fName.c_str(), Buffer)) {
+    if (ErrMsg) *ErrMsg = "Could not open file '" + fName.str() + "'" + ": "
+                        + ec.message();
+    return true;
+  }
+
+  Module *M = ParseBitcodeFile(Buffer.get(), Context, ErrMsg);
+  if (!M)
+    return true;
+
+  // Get the symbols
+  getSymbols(M, symbols);
+
+  // Done with the module.
+  delete M;
+  return true;
+}
+
+Module*
+llvm::GetBitcodeSymbols(const char *BufPtr, unsigned Length,
+                        const std::string& ModuleID,
+                        LLVMContext& Context,
+                        std::vector<std::string>& symbols,
+                        std::string* ErrMsg) {
+  // Get the module.
+  OwningPtr<MemoryBuffer> Buffer(
+    MemoryBuffer::getMemBufferCopy(StringRef(BufPtr, Length),ModuleID.c_str()));
+
+  Module *M = ParseBitcodeFile(Buffer.get(), Context, ErrMsg);
+  if (!M)
+    return 0;
+
+  // Get the symbols
+  getSymbols(M, symbols);
+
+  // Done with the module. Note that it's the caller's responsibility to delete
+  // the Module.
+  return M;
+}
diff --git a/tools/llvm-ar/Archive.h b/tools/llvm-ar/Archive.h
new file mode 100644
index 0000000000..bd76298c42
--- /dev/null
+++ b/tools/llvm-ar/Archive.h
@@ -0,0 +1,524 @@
+//===-- llvm/Bitcode/Archive.h - LLVM Bitcode Archive -----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header file declares the Archive and ArchiveMember classes that provide
+// manipulation of LLVM Archive files.  The implementation is provided by the
+// lib/Bitcode/Archive library.  This library is used to read and write
+// archive (*.a) files that contain LLVM bitcode files (or others).
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef TOOLS_LLVM_AR_ARCHIVE_H
+#define TOOLS_LLVM_AR_ARCHIVE_H
+
+#include "llvm/ADT/ilist.h"
+#include "llvm/ADT/ilist_node.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/PathV1.h"
+#include <map>
+#include <set>
+
+namespace llvm {
+  class MemoryBuffer;
+
+// Forward declare classes
+class Module;              // From VMCore
+class Archive;             // Declared below
+class ArchiveMemberHeader; // Internal implementation class
+class LLVMContext;         // Global data
+
+/// This class is the main class manipulated by users of the Archive class. It
+/// holds information about one member of the Archive. It is also the element
+/// stored by the Archive's ilist, the Archive's main abstraction. Because of
+/// the special requirements of archive files, users are not permitted to
+/// construct ArchiveMember instances. You should obtain them from the methods
+/// of the Archive class instead.
+/// @brief This class represents a single archive member.
+class ArchiveMember : public ilist_node<ArchiveMember> {
+  /// @name Types
+  /// @{
+  public:
+    /// These flags are used internally by the archive member to specify various
+    /// characteristics of the member. The various "is" methods below provide
+    /// access to the flags. The flags are not user settable.
+    enum Flags {
+      SVR4SymbolTableFlag = 1,     ///< Member is a SVR4 symbol table
+      BSD4SymbolTableFlag = 2,     ///< Member is a BSD4 symbol table
+      BitcodeFlag         = 4,     ///< Member is bitcode
+      HasPathFlag         = 8,     ///< Member has a full or partial path
+      HasLongFilenameFlag = 16,    ///< Member uses the long filename syntax
+      StringTableFlag     = 32     ///< Member is an ar(1) format string table
+    };
+
+  /// @}
+  /// @name Accessors
+  /// @{
+  public:
+    /// @returns the parent Archive instance
+    /// @brief Get the archive associated with this member
+    Archive* getArchive() const          { return parent; }
+
+    /// @returns the path to the Archive's file
+    /// @brief Get the path to the archive member
+    const sys::Path& getPath() const     { return path; }
+
+    /// The "user" is the owner of the file per Unix security. This may not
+    /// have any applicability on non-Unix systems but is a required component
+    /// of the "ar" file format.
+    /// @brief Get the user associated with this archive member.
+    unsigned getUser() const             { return info.getUser(); }
+
+    /// The "group" is the owning group of the file per Unix security. This
+    /// may not have any applicability on non-Unix systems but is a required
+    /// component of the "ar" file format.
+    /// @brief Get the group associated with this archive member.
+    unsigned getGroup() const            { return info.getGroup(); }
+
+    /// The "mode" specifies the access permissions for the file per Unix
+    /// security. This may not have any applicability on non-Unix systems but is
+    /// a required component of the "ar" file format.
+    /// @brief Get the permission mode associated with this archive member.
+    unsigned getMode() const             { return info.getMode(); }
+
+    /// This method returns the time at which the archive member was last
+    /// modified when it was not in the archive.
+    /// @brief Get the time of last modification of the archive member.
+    sys::TimeValue getModTime() const    { return info.getTimestamp(); }
+
+    /// @returns the size of the archive member in bytes.
+    /// @brief Get the size of the archive member.
+    uint64_t getSize() const             { return info.getSize(); }
+
+    /// This method returns the total size of the archive member as it
+    /// appears on disk. This includes the file content, the header, the
+    /// long file name if any, and the padding.
+    /// @brief Get total on-disk member size.
+    unsigned getMemberSize() const;
+
+    /// This method will return a pointer to the in-memory content of the
+    /// archive member, if it is available. If the data has not been loaded
+    /// into memory, the return value will be null.
+    /// @returns a pointer to the member's data.
+    /// @brief Get the data content of the archive member
+    const char* getData() const { return data; }
+
+    /// @returns true iff the member is a SVR4 (non-LLVM) symbol table
+    /// @brief Determine if this member is a SVR4 symbol table.
+    bool isSVR4SymbolTable() const { return flags&SVR4SymbolTableFlag; }
+
+    /// @returns true iff the member is a BSD4.4 (non-LLVM) symbol table
+    /// @brief Determine if this member is a BSD4.4 symbol table.
+    bool isBSD4SymbolTable() const { return flags&BSD4SymbolTableFlag; }
+
+    /// @returns true iff the archive member is the ar(1) string table
+    /// @brief Determine if this member is the ar(1) string table.
+    bool isStringTable() const { return flags&StringTableFlag; }
+
+    /// @returns true iff the archive member is a bitcode file.
+    /// @brief Determine if this member is a bitcode file.
+    bool isBitcode() const { return flags&BitcodeFlag; }
+
+    /// @returns true iff the file name contains a path (directory) component.
+    /// @brief Determine if the member has a path
+    bool hasPath() const { return flags&HasPathFlag; }
+
+    /// Long filenames are an artifact of the ar(1) file format which allows
+    /// up to sixteen characters in its header and doesn't allow a path
+    /// separator character (/). To avoid this, a "long format" member name is
+    /// allowed that doesn't have this restriction. This method determines if
+    /// that "long format" is used for this member.
+    /// @returns true iff the file name uses the long form
+    /// @brief Determine if the member has a long file name
+    bool hasLongFilename() const { return flags&HasLongFilenameFlag; }
+
+    /// This method returns the status info (like Unix stat(2)) for the archive
+    /// member. The status info provides the file's size, permissions, and
+    /// modification time. The contents of the Path::StatusInfo structure, other
+    /// than the size and modification time, may not have utility on non-Unix
+    /// systems.
+    /// @returns the status info for the archive member
+    /// @brief Obtain the status info for the archive member
+    const sys::FileStatus &getFileStatus() const { return info; }
+
+    /// This method causes the archive member to be replaced with the contents
+    /// of the file specified by \p File. The contents of \p this will be
+    /// updated to reflect the new data from \p File. The \p File must exist and
+    /// be readable on entry to this method.
+    /// @returns true if an error occurred, false otherwise
+    /// @brief Replace contents of archive member with a new file.
+    bool replaceWith(const sys::Path &aFile, std::string* ErrMsg);
+
+  /// @}
+  /// @name Data
+  /// @{
+  private:
+    Archive*            parent;   ///< Pointer to parent archive
+    sys::PathWithStatus path;     ///< Path of file containing the member
+    sys::FileStatus     info;     ///< Status info (size,mode,date)
+    unsigned            flags;    ///< Flags about the archive member
+    const char*         data;     ///< Data for the member
+
+  /// @}
+  /// @name Constructors
+  /// @{
+  public:
+    /// The default constructor is only used by the Archive's iplist when it
+    /// constructs the list's sentry node.
+    ArchiveMember();
+
+  private:
+    /// Used internally by the Archive class to construct an ArchiveMember.
+    /// The contents of the ArchiveMember are filled out by the Archive class.
+    explicit ArchiveMember(Archive *PAR);
+
+    // So Archive can construct an ArchiveMember
+    friend class llvm::Archive;
+  /// @}
+};
+
+/// This class defines the interface to LLVM Archive files. The Archive class
+/// presents the archive file as an ilist of ArchiveMember objects. The members
+/// can be rearranged in any fashion either by directly editing the ilist or by
+/// using editing methods on the Archive class (recommended). The Archive
+/// class also provides several ways of accessing the archive file for various
+/// purposes such as editing and linking.  Full symbol table support is provided
+/// for loading only those files that resolve symbols. Note that read
+/// performance of this library is _crucial_ for performance of JIT type
+/// applications and the linkers. Consequently, the implementation of the class
+/// is optimized for reading.
+class Archive {
+
+  /// @name Types
+  /// @{
+  public:
+    /// This is the ilist type over which users may iterate to examine
+    /// the contents of the archive
+    /// @brief The ilist type of ArchiveMembers that Archive contains.
+    typedef iplist<ArchiveMember> MembersList;
+
+    /// @brief Forward mutable iterator over ArchiveMember
+    typedef MembersList::iterator iterator;
+
+    /// @brief Forward immutable iterator over ArchiveMember
+    typedef MembersList::const_iterator const_iterator;
+
+    /// @brief Reverse mutable iterator over ArchiveMember
+    typedef std::reverse_iterator<iterator> reverse_iterator;
+
+    /// @brief Reverse immutable iterator over ArchiveMember
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+
+    /// @brief The in-memory version of the symbol table
+    typedef std::map<std::string,unsigned> SymTabType;
+
+  /// @}
+  /// @name ilist accessor methods
+  /// @{
+  public:
+    inline iterator               begin()        { return members.begin();  }
+    inline const_iterator         begin()  const { return members.begin();  }
+    inline iterator               end  ()        { return members.end();    }
+    inline const_iterator         end  ()  const { return members.end();    }
+
+    inline reverse_iterator       rbegin()       { return members.rbegin(); }
+    inline const_reverse_iterator rbegin() const { return members.rbegin(); }
+    inline reverse_iterator       rend  ()       { return members.rend();   }
+    inline const_reverse_iterator rend  () const { return members.rend();   }
+
+    inline size_t                 size()   const { return members.size();   }
+    inline bool                   empty()  const { return members.empty();  }
+    inline const ArchiveMember&   front()  const { return members.front();  }
+    inline       ArchiveMember&   front()        { return members.front();  }
+    inline const ArchiveMember&   back()   const { return members.back();   }
+    inline       ArchiveMember&   back()         { return members.back();   }
+
+  /// @}
+  /// @name ilist mutator methods
+  /// @{
+  public:
+    /// This method splices a \p src member from an archive (possibly \p this),
+    /// to a position just before the member given by \p dest in \p this. When
+    /// the archive is written, \p src will be written in its new location.
+    /// @brief Move a member to a new location
+    inline void splice(iterator dest, Archive& arch, iterator src)
+      { return members.splice(dest,arch.members,src); }
+
+    /// This method erases a \p target member from the archive. When the
+    /// archive is written, it will no longer contain \p target. The associated
+    /// ArchiveMember is deleted.
+    /// @brief Erase a member.
+    inline iterator erase(iterator target) { return members.erase(target); }
+
+  /// @}
+  /// @name Constructors
+  /// @{
+  public:
+    /// Create an empty archive file and associate it with the \p Filename. This
+    /// method does not actually create the archive disk file. It creates an
+    /// empty Archive object. If the writeToDisk method is called, the archive
+    /// file \p Filename will be created at that point, with whatever content
+    /// the returned Archive object has at that time.
+    /// @returns An Archive* that represents the new archive file.
+    /// @brief Create an empty Archive.
+    static Archive* CreateEmpty(
+      const sys::Path& Filename,///< Name of the archive to (eventually) create.
+      LLVMContext& C            ///< Context to use for global information
+    );
+
+    /// Open an existing archive and load its contents in preparation for
+    /// editing. After this call, the member ilist is completely populated based
+    /// on the contents of the archive file. You should use this form of open if
+    /// you intend to modify the archive or traverse its contents (e.g. for
+    /// printing).
+    /// @brief Open and load an archive file
+    static Archive* OpenAndLoad(
+      const sys::Path& filePath,  ///< The file path to open and load
+      LLVMContext& C,       ///< The context to use for global information
+      std::string* ErrorMessage   ///< An optional error string
+    );
+
+    /// This method opens an existing archive file from \p Filename and reads in
+    /// its symbol table without reading in any of the archive's members. This
+    /// reduces both I/O and cpu time in opening the archive if it is to be used
+    /// solely for symbol lookup (e.g. during linking).  The \p Filename must
+    /// exist and be an archive file or an error will be returned. This form
+    /// of opening the archive is intended for read-only operations that need to
+    /// locate members via the symbol table for link editing.  Since the archve
+    /// members are not read by this method, the archive will appear empty upon
+    /// return. If editing operations are performed on the archive, they will
+    /// completely replace the contents of the archive! It is recommended that
+    /// if this form of opening the archive is used that only the symbol table
+    /// lookup methods (getSymbolTable, findModuleDefiningSymbol, and
+    /// findModulesDefiningSymbols) be used.
+    /// @returns an Archive* that represents the archive file, or null on error.
+    /// @brief Open an existing archive and load its symbols.
+    static Archive* OpenAndLoadSymbols(
+      const sys::Path& Filename,   ///< Name of the archive file to open
+      LLVMContext& C,              ///< The context to use for global info
+      std::string* ErrorMessage=0  ///< An optional error string
+    );
+
+    /// This destructor cleans up the Archive object, releases all memory, and
+    /// closes files. It does nothing with the archive file on disk. If you
+    /// haven't used the writeToDisk method by the time the destructor is
+    /// called, all changes to the archive will be lost.
+    /// @brief Destruct in-memory archive
+    ~Archive();
+
+  /// @}
+  /// @name Accessors
+  /// @{
+  public:
+    /// @returns the path to the archive file.
+    /// @brief Get the archive path.
+    const sys::Path& getPath() { return archPath; }
+
+    /// This method is provided so that editing methods can be invoked directly
+    /// on the Archive's iplist of ArchiveMember. However, it is recommended
+    /// that the usual STL style iterator interface be used instead.
+    /// @returns the iplist of ArchiveMember
+    /// @brief Get the iplist of the members
+    MembersList& getMembers() { return members; }
+
+    /// This method allows direct query of the Archive's symbol table. The
+    /// symbol table is a std::map of std::string (the symbol) to unsigned (the
+    /// file offset). Note that for efficiency reasons, the offset stored in
+    /// the symbol table is not the actual offset. It is the offset from the
+    /// beginning of the first "real" file member (after the symbol table). Use
+    /// the getFirstFileOffset() to obtain that offset and add this value to the
+    /// offset in the symbol table to obtain the real file offset. Note that
+    /// there is purposefully no interface provided by Archive to look up
+    /// members by their offset. Use the findModulesDefiningSymbols and
+    /// findModuleDefiningSymbol methods instead.
+    /// @returns the Archive's symbol table.
+    /// @brief Get the archive's symbol table
+    const SymTabType& getSymbolTable() { return symTab; }
+
+    /// This method returns the offset in the archive file to the first "real"
+    /// file member. Archive files, on disk, have a signature and might have a
+    /// symbol table that precedes the first actual file member. This method
+    /// allows you to determine what the size of those fields are.
+    /// @returns the offset to the first "real" file member  in the archive.
+    /// @brief Get the offset to the first "real" file member  in the archive.
+    unsigned getFirstFileOffset() { return firstFileOffset; }
+
+    /// This method will scan the archive for bitcode modules, interpret them
+    /// and return a vector of the instantiated modules in \p Modules. If an
+    /// error occurs, this method will return true. If \p ErrMessage is not null
+    /// and an error occurs, \p *ErrMessage will be set to a string explaining
+    /// the error that occurred.
+    /// @returns true if an error occurred
+    /// @brief Instantiate all the bitcode modules located in the archive
+    bool getAllModules(std::vector<Module*>& Modules, std::string* ErrMessage);
+
+    /// This accessor looks up the \p symbol in the archive's symbol table and
+    /// returns the associated module that defines that symbol. This method can
+    /// be called as many times as necessary. This is handy for linking the
+    /// archive into another module based on unresolved symbols. Note that the
+    /// Module returned by this accessor should not be deleted by the caller. It
+    /// is managed internally by the Archive class. It is possible that multiple
+    /// calls to this accessor will return the same Module instance because the
+    /// associated module defines multiple symbols.
+    /// @returns The Module* found or null if the archive does not contain a
+    /// module that defines the \p symbol.
+    /// @brief Look up a module by symbol name.
+    Module* findModuleDefiningSymbol(
+      const std::string& symbol,  ///< Symbol to be sought
+      std::string* ErrMessage     ///< Error message storage, if non-zero
+    );
+
+    /// This method is similar to findModuleDefiningSymbol but allows lookup of
+    /// more than one symbol at a time. If \p symbols contains a list of
+    /// undefined symbols in some module, then calling this method is like
+    /// making one complete pass through the archive to resolve symbols but is
+    /// more efficient than looking at the individual members. Note that on
+    /// exit, the symbols resolved by this method will be removed from \p
+    /// symbols to ensure they are not re-searched on a subsequent call. If
+    /// you need to retain the list of symbols, make a copy.
+    /// @brief Look up multiple symbols in the archive.
+    bool findModulesDefiningSymbols(
+      std::set<std::string>& symbols,     ///< Symbols to be sought
+      SmallVectorImpl<Module*>& modules,  ///< The modules matching \p symbols
+      std::string* ErrMessage             ///< Error msg storage, if non-zero
+    );
+
+    /// This method determines whether the archive is a properly formed llvm
+    /// bitcode archive.  It first makes sure the symbol table has been loaded
+    /// and has a non-zero size.  If it does, then it is an archive.  If not,
+    /// then it tries to load all the bitcode modules of the archive.  Finally,
+    /// it returns whether it was successful.
+    /// @returns true if the archive is a proper llvm bitcode archive
+    /// @brief Determine whether the archive is a proper llvm bitcode archive.
+    bool isBitcodeArchive();
+
+  /// @}
+  /// @name Mutators
+  /// @{
+  public:
+    /// This method is the only way to get the archive written to disk. It
+    /// creates or overwrites the file specified when \p this was created
+    /// or opened. The arguments provide options for writing the archive. If
+    /// \p CreateSymbolTable is true, the archive is scanned for bitcode files
+    /// and a symbol table of the externally visible function and global
+    /// variable names is created. If \p TruncateNames is true, the names of the
+    /// archive members will have their path component stripped and the file
+    /// name will be truncated at 15 characters. If \p Compress is specified,
+    /// all archive members will be compressed before being written. If
+    /// \p PrintSymTab is true, the symbol table will be printed to std::cout.
+    /// @returns true if an error occurred, \p error set to error message;
+    /// returns false if the writing succeeded.
+    /// @brief Write (possibly modified) archive contents to disk
+    bool writeToDisk(
+      bool CreateSymbolTable=false,   ///< Create Symbol table
+      bool TruncateNames=false,       ///< Truncate the filename to 15 chars
+      std::string* ErrMessage=0       ///< If non-null, where error msg is set
+    );
+
+    /// This method adds a new file to the archive. The \p filename is examined
+    /// to determine just enough information to create an ArchiveMember object
+    /// which is then inserted into the Archive object's ilist at the location
+    /// given by \p where.
+    /// @returns true if an error occurred, false otherwise
+    /// @brief Add a file to the archive.
+    bool addFileBefore(
+      const sys::Path& filename, ///< The file to be added
+      iterator where,            ///< Insertion point
+      std::string* ErrMsg        ///< Optional error message location
+    );
+
+  /// @}
+  /// @name Implementation
+  /// @{
+  protected:
+    /// @brief Construct an Archive for \p filename and optionally  map it
+    /// into memory.
+    explicit Archive(const sys::Path& filename, LLVMContext& C);
+
+    /// @returns A fully populated ArchiveMember or 0 if an error occurred.
+    /// @brief Parse the header of a member starting at \p At
+    ArchiveMember* parseMemberHeader(
+      const char*&At,    ///< The pointer to the location we're parsing
+      const char*End,    ///< The pointer to the end of the archive
+      std::string* error ///< Optional error message catcher
+    );
+
+    /// @param ErrMessage Set to address of a std::string to get error messages
+    /// @returns false on error
+    /// @brief Check that the archive signature is correct
+    bool checkSignature(std::string* ErrMessage);
+
+    /// @param ErrMessage Set to address of a std::string to get error messages
+    /// @returns false on error
+    /// @brief Load the entire archive.
+    bool loadArchive(std::string* ErrMessage);
+
+    /// @param ErrMessage Set to address of a std::string to get error messages
+    /// @returns false on error
+    /// @brief Load just the symbol table.
+    bool loadSymbolTable(std::string* ErrMessage);
+
+    /// Writes one ArchiveMember to an ofstream. If an error occurs, returns
+    /// false, otherwise true. If an error occurs and error is non-null then
+    /// it will be set to an error message.
+    /// @returns false if writing member succeeded,
+    /// returns true if writing member failed, \p error set to error message.
+    bool writeMember(
+      const ArchiveMember& member, ///< The member to be written
+      std::ofstream& ARFile,       ///< The file to write member onto
+      bool CreateSymbolTable,      ///< Should symbol table be created?
+      bool TruncateNames,          ///< Should names be truncated to 11 chars?
+      std::string* ErrMessage      ///< If non-null, place were error msg is set
+    );
+
+    /// @brief Fill in an ArchiveMemberHeader from ArchiveMember.
+    bool fillHeader(const ArchiveMember&mbr,
+                    ArchiveMemberHeader& hdr,int sz, bool TruncateNames) const;
+
+    /// @brief Maps archive into memory
+    bool mapToMemory(std::string* ErrMsg);
+
+    /// @brief Frees all the members and unmaps the archive file.
+    void cleanUpMemory();
+
+    /// This type is used to keep track of bitcode modules loaded from the
+    /// symbol table. It maps the file offset to a pair that consists of the
+    /// associated ArchiveMember and the Module.
+    /// @brief Module mapping type
+    typedef std::map<unsigned,std::pair<Module*,ArchiveMember*> >
+      ModuleMap;
+
+
+  /// @}
+  /// @name Data
+  /// @{
+  protected:
+    sys::Path archPath;       ///< Path to the archive file we read/write
+    MembersList members;      ///< The ilist of ArchiveMember
+    MemoryBuffer *mapfile;    ///< Raw Archive contents mapped into memory
+    const char* base;         ///< Base of the memory mapped file data
+    SymTabType symTab;        ///< The symbol table
+    std::string strtab;       ///< The string table for long file names
+    unsigned symTabSize;      ///< Size in bytes of symbol table
+    unsigned firstFileOffset; ///< Offset to first normal file.
+    ModuleMap modules;        ///< The modules loaded via symbol lookup.
+    ArchiveMember* foreignST; ///< This holds the foreign symbol table.
+    LLVMContext& Context;     ///< This holds global data.
+  /// @}
+  /// @name Hidden
+  /// @{
+  private:
+    Archive() LLVM_DELETED_FUNCTION;
+    Archive(const Archive&) LLVM_DELETED_FUNCTION;
+    Archive& operator=(const Archive&) LLVM_DELETED_FUNCTION;
+  /// @}
+};
+
+} // End llvm namespace
+
+#endif
diff --git a/tools/llvm-ar/ArchiveInternals.h b/tools/llvm-ar/ArchiveInternals.h
new file mode 100644
index 0000000000..e906d7a059
--- /dev/null
+++ b/tools/llvm-ar/ArchiveInternals.h
@@ -0,0 +1,87 @@
+//===-- lib/Archive/ArchiveInternals.h -------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Internal implementation header for LLVM Archive files.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef TOOLS_LLVM_AR_ARCHIVEINTERNALS_H
+#define TOOLS_LLVM_AR_ARCHIVEINTERNALS_H
+
+#include "Archive.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/TimeValue.h"
+#include <cstring>
+
+#define ARFILE_MAGIC "!<arch>\n"                   ///< magic string
+#define ARFILE_MAGIC_LEN (sizeof(ARFILE_MAGIC)-1)  ///< length of magic string
+#define ARFILE_SVR4_SYMTAB_NAME "/               " ///< SVR4 symtab entry name
+#define ARFILE_BSD4_SYMTAB_NAME "__.SYMDEF SORTED" ///< BSD4 symtab entry name
+#define ARFILE_STRTAB_NAME      "//              " ///< Name of string table
+#define ARFILE_PAD "\n"                            ///< inter-file align padding
+#define ARFILE_MEMBER_MAGIC "`\n"                  ///< fmag field magic #
+
+namespace llvm {
+
+  class LLVMContext;
+
+  /// The ArchiveMemberHeader structure is used internally for bitcode
+  /// archives.
+  /// The header precedes each file member in the archive. This structure is
+  /// defined using character arrays for direct and correct interpretation
+  /// regardless of the endianess of the machine that produced it.
+  /// @brief Archive File Member Header
+  class ArchiveMemberHeader {
+    /// @name Data
+    /// @{
+    public:
+      char name[16];  ///< Name of the file member.
+      char date[12];  ///< File date, decimal seconds since Epoch
+      char uid[6];    ///< user id in ASCII decimal
+      char gid[6];    ///< group id in ASCII decimal
+      char mode[8];   ///< file mode in ASCII octal
+      char size[10];  ///< file size in ASCII decimal
+      char fmag[2];   ///< Always contains ARFILE_MAGIC_TERMINATOR
+
+    /// @}
+    /// @name Methods
+    /// @{
+    public:
+    void init() {
+      memset(name,' ',16);
+      memset(date,' ',12);
+      memset(uid,' ',6);
+      memset(gid,' ',6);
+      memset(mode,' ',8);
+      memset(size,' ',10);
+      fmag[0] = '`';
+      fmag[1] = '\n';
+    }
+
+    bool checkSignature() const {
+      return 0 == memcmp(fmag, ARFILE_MEMBER_MAGIC,2);
+    }
+  };
+  
+  // Get just the externally visible defined symbols from the bitcode
+  bool GetBitcodeSymbols(const sys::Path& fName,
+                          LLVMContext& Context,
+                          std::vector<std::string>& symbols,
+                          std::string* ErrMsg);
+  
+  Module* GetBitcodeSymbols(const char *Buffer, unsigned Length,
+                            const std::string& ModuleID,
+                            LLVMContext& Context,
+                            std::vector<std::string>& symbols,
+                            std::string* ErrMsg);
+}
+
+#endif
+
+// vim: sw=2 ai
diff --git a/tools/llvm-ar/ArchiveReader.cpp b/tools/llvm-ar/ArchiveReader.cpp
new file mode 100644
index 0000000000..8ad01dca0b
--- /dev/null
+++ b/tools/llvm-ar/ArchiveReader.cpp
@@ -0,0 +1,557 @@
+//===-- ArchiveReader.cpp - Read LLVM archive files -------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Builds up standard unix archive files (.a) containing LLVM bitcode.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Archive.h"
+#include "ArchiveInternals.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include <cstdio>
+#include <cstdlib>
+using namespace llvm;
+
+/// Read a variable-bit-rate encoded unsigned integer
+static inline unsigned readInteger(const char*&At, const char*End) {
+  unsigned Shift = 0;
+  unsigned Result = 0;
+
+  do {
+    if (At == End)
+      return Result;
+    Result |= (unsigned)((*At++) & 0x7F) << Shift;
+    Shift += 7;
+  } while (At[-1] & 0x80);
+  return Result;
+}
+
+// This member parses an ArchiveMemberHeader that is presumed to be pointed to
+// by At. The At pointer is updated to the byte just after the header, which
+// can be variable in size.
+ArchiveMember*
+Archive::parseMemberHeader(const char*& At, const char* End, std::string* error)
+{
+  if (At + sizeof(ArchiveMemberHeader) >= End) {
+    if (error)
+      *error = "Unexpected end of file";
+    return 0;
+  }
+
+  // Cast archive member header
+  const ArchiveMemberHeader* Hdr = (const ArchiveMemberHeader*)At;
+  At += sizeof(ArchiveMemberHeader);
+
+  int flags = 0;
+  int MemberSize = atoi(Hdr->size);
+  assert(MemberSize >= 0);
+
+  // Check the size of the member for sanity
+  if (At + MemberSize > End) {
+    if (error)
+      *error = "invalid member length in archive file";
+    return 0;
+  }
+
+  // Check the member signature
+  if (!Hdr->checkSignature()) {
+    if (error)
+      *error = "invalid file member signature";
+    return 0;
+  }
+
+  // Convert and check the member name
+  // The empty name ( '/' and 15 blanks) is for a foreign (non-LLVM) symbol
+  // table. The special name "//" and 14 blanks is for a string table, used
+  // for long file names. This library doesn't generate either of those but
+  // it will accept them. If the name starts with #1/ and the remainder is
+  // digits, then those digits specify the length of the name that is
+  // stored immediately following the header. Anything else is a regular, short
+  // filename that is terminated with a '/' and blanks.
+
+  std::string pathname;
+  switch (Hdr->name[0]) {
+    case '#':
+      if (Hdr->name[1] == '1' && Hdr->name[2] == '/') {
+        if (isdigit(Hdr->name[3])) {
+          unsigned len = atoi(&Hdr->name[3]);
+          const char *nulp = (const char *)memchr(At, '\0', len);
+          pathname.assign(At, nulp != 0 ? (uintptr_t)(nulp - At) : len);
+          At += len;
+          MemberSize -= len;
+          flags |= ArchiveMember::HasLongFilenameFlag;
+        } else {
+          if (error)
+            *error = "invalid long filename";
+          return 0;
+        }
+      }
+      break;
+    case '/':
+      if (Hdr->name[1]== '/') {
+        if (0 == memcmp(Hdr->name, ARFILE_STRTAB_NAME, 16)) {
+          pathname.assign(ARFILE_STRTAB_NAME);
+          flags |= ArchiveMember::StringTableFlag;
+        } else {
+          if (error)
+            *error = "invalid string table name";
+          return 0;
+        }
+      } else if (Hdr->name[1] == ' ') {
+        if (0 == memcmp(Hdr->name, ARFILE_SVR4_SYMTAB_NAME, 16)) {
+          pathname.assign(ARFILE_SVR4_SYMTAB_NAME);
+          flags |= ArchiveMember::SVR4SymbolTableFlag;
+        } else {
+          if (error)
+            *error = "invalid SVR4 symbol table name";
+          return 0;
+        }
+      } else if (isdigit(Hdr->name[1])) {
+        unsigned index = atoi(&Hdr->name[1]);
+        if (index < strtab.length()) {
+          const char* namep = strtab.c_str() + index;
+          const char* endp = strtab.c_str() + strtab.length();
+          const char* p = namep;
+          const char* last_p = p;
+          while (p < endp) {
+            if (*p == '\n' && *last_p == '/') {
+              pathname.assign(namep, last_p - namep);
+              flags |= ArchiveMember::HasLongFilenameFlag;
+              break;
+            }
+            last_p = p;
+            p++;
+          }
+          if (p >= endp) {
+            if (error)
+              *error = "missing name terminator in string table";
+            return 0;
+          }
+        } else {
+          if (error)
+            *error = "name index beyond string table";
+          return 0;
+        }
+      }
+      break;
+    case '_':
+      if (Hdr->name[1] == '_' &&
+          (0 == memcmp(Hdr->name, ARFILE_BSD4_SYMTAB_NAME, 16))) {
+        pathname.assign(ARFILE_BSD4_SYMTAB_NAME);
+        flags |= ArchiveMember::BSD4SymbolTableFlag;
+        break;
+      }
+      /* FALL THROUGH */
+
+    default:
+      const char* slash = (const char*) memchr(Hdr->name, '/', 16);
+      if (slash == 0)
+        slash = Hdr->name + 16;
+      pathname.assign(Hdr->name, slash - Hdr->name);
+      break;
+  }
+
+  // Determine if this is a bitcode file
+  if (sys::fs::identify_magic(StringRef(At, 4)) ==
+      sys::fs::file_magic::bitcode)
+    flags |= ArchiveMember::BitcodeFlag;
+  else
+    flags &= ~ArchiveMember::BitcodeFlag;
+
+  // Instantiate the ArchiveMember to be filled
+  ArchiveMember* member = new ArchiveMember(this);
+
+  // Fill in fields of the ArchiveMember
+  member->parent = this;
+  member->path.set(pathname);
+  member->info.fileSize = MemberSize;
+  member->info.modTime.fromEpochTime(atoi(Hdr->date));
+  unsigned int mode;
+  sscanf(Hdr->mode, "%o", &mode);
+  member->info.mode = mode;
+  member->info.user = atoi(Hdr->uid);
+  member->info.group = atoi(Hdr->gid);
+  member->flags = flags;
+  member->data = At;
+
+  return member;
+}
+
+bool
+Archive::checkSignature(std::string* error) {
+  // Check the magic string at file's header
+  if (mapfile->getBufferSize() < 8 || memcmp(base, ARFILE_MAGIC, 8)) {
+    if (error)
+      *error = "invalid signature for an archive file";
+    return false;
+  }
+  return true;
+}
+
+// This function loads the entire archive and fully populates its ilist with
+// the members of the archive file. This is typically used in preparation for
+// editing the contents of the archive.
+bool
+Archive::loadArchive(std::string* error) {
+
+  // Set up parsing
+  members.clear();
+  symTab.clear();
+  const char *At = base;
+  const char *End = mapfile->getBufferEnd();
+
+  if (!checkSignature(error))
+    return false;
+
+  At += 8;  // Skip the magic string.
+
+  bool foundFirstFile = false;
+  while (At < End) {
+    // parse the member header
+    const char* Save = At;
+    ArchiveMember* mbr = parseMemberHeader(At, End, error);
+    if (!mbr)
+      return false;
+
+    // check if this is the foreign symbol table
+    if (mbr->isSVR4SymbolTable() || mbr->isBSD4SymbolTable()) {
+      // We just save this but don't do anything special
+      // with it. It doesn't count as the "first file".
+      if (foreignST) {
+        // What? Multiple foreign symbol tables? Just chuck it
+        // and retain the last one found.
+        delete foreignST;
+      }
+      foreignST = mbr;
+      At += mbr->getSize();
+      if ((intptr_t(At) & 1) == 1)
+        At++;
+    } else if (mbr->isStringTable()) {
+      // Simply suck the entire string table into a string
+      // variable. This will be used to get the names of the
+      // members that use the "/ddd" format for their names
+      // (SVR4 style long names).
+      strtab.assign(At, mbr->getSize());
+      At += mbr->getSize();
+      if ((intptr_t(At) & 1) == 1)
+        At++;
+      delete mbr;
+    } else {
+      // This is just a regular file. If its the first one, save its offset.
+      // Otherwise just push it on the list and move on to the next file.
+      if (!foundFirstFile) {
+        firstFileOffset = Save - base;
+        foundFirstFile = true;
+      }
+      members.push_back(mbr);
+      At += mbr->getSize();
+      if ((intptr_t(At) & 1) == 1)
+        At++;
+    }
+  }
+  return true;
+}
+
+// Open and completely load the archive file.
+Archive*
+Archive::OpenAndLoad(const sys::Path& File, LLVMContext& C,
+                     std::string* ErrorMessage) {
+  OwningPtr<Archive> result ( new Archive(File, C));
+  if (result->mapToMemory(ErrorMessage))
+    return NULL;
+  if (!result->loadArchive(ErrorMessage))
+    return NULL;
+  return result.take();
+}
+
+// Get all the bitcode modules from the archive
+bool
+Archive::getAllModules(std::vector<Module*>& Modules,
+                       std::string* ErrMessage) {
+
+  for (iterator I=begin(), E=end(); I != E; ++I) {
+    if (I->isBitcode()) {
+      std::string FullMemberName = archPath.str() +
+        "(" + I->getPath().str() + ")";
+      MemoryBuffer *Buffer =
+        MemoryBuffer::getMemBufferCopy(StringRef(I->getData(), I->getSize()),
+                                       FullMemberName.c_str());
+      
+      Module *M = ParseBitcodeFile(Buffer, Context, ErrMessage);
+      delete Buffer;
+      if (!M)
+        return true;
+
+      Modules.push_back(M);
+    }
+  }
+  return false;
+}
+
+// Load just the symbol table from the archive file
+bool
+Archive::loadSymbolTable(std::string* ErrorMsg) {
+
+  // Set up parsing
+  members.clear();
+  symTab.clear();
+  const char *At = base;
+  const char *End = mapfile->getBufferEnd();
+
+  // Make sure we're dealing with an archive
+  if (!checkSignature(ErrorMsg))
+    return false;
+
+  At += 8; // Skip signature
+
+  // Parse the first file member header
+  const char* FirstFile = At;
+  ArchiveMember* mbr = parseMemberHeader(At, End, ErrorMsg);
+  if (!mbr)
+    return false;
+
+  if (mbr->isSVR4SymbolTable() || mbr->isBSD4SymbolTable()) {
+    // Skip the foreign symbol table, we don't do anything with it
+    At += mbr->getSize();
+    if ((intptr_t(At) & 1) == 1)
+      At++;
+    delete mbr;
+
+    // Read the next one
+    FirstFile = At;
+    mbr = parseMemberHeader(At, End, ErrorMsg);
+    if (!mbr) {
+      delete mbr;
+      return false;
+    }
+  }
+
+  if (mbr->isStringTable()) {
+    // Process the string table entry
+    strtab.assign((const char*)mbr->getData(), mbr->getSize());
+    At += mbr->getSize();
+    if ((intptr_t(At) & 1) == 1)
+      At++;
+    delete mbr;
+    // Get the next one
+    FirstFile = At;
+    mbr = parseMemberHeader(At, End, ErrorMsg);
+    if (!mbr) {
+      delete mbr;
+      return false;
+    }
+  }
+
+  // There's no symbol table in the file. We have to rebuild it from scratch
+  // because the intent of this method is to get the symbol table loaded so
+  // it can be searched efficiently.
+  // Add the member to the members list
+  members.push_back(mbr);
+
+  firstFileOffset = FirstFile - base;
+  return true;
+}
+
+// Open the archive and load just the symbol tables
+Archive* Archive::OpenAndLoadSymbols(const sys::Path& File,
+                                     LLVMContext& C,
+                                     std::string* ErrorMessage) {
+  OwningPtr<Archive> result ( new Archive(File, C) );
+  if (result->mapToMemory(ErrorMessage))
+    return NULL;
+  if (!result->loadSymbolTable(ErrorMessage))
+    return NULL;
+  return result.take();
+}
+
+// Look up one symbol in the symbol table and return the module that defines
+// that symbol.
+Module*
+Archive::findModuleDefiningSymbol(const std::string& symbol, 
+                                  std::string* ErrMsg) {
+  SymTabType::iterator SI = symTab.find(symbol);
+  if (SI == symTab.end())
+    return 0;
+
+  // The symbol table was previously constructed assuming that the members were
+  // written without the symbol table header. Because VBR encoding is used, the
+  // values could not be adjusted to account for the offset of the symbol table
+  // because that could affect the size of the symbol table due to VBR encoding.
+  // We now have to account for this by adjusting the offset by the size of the
+  // symbol table and its header.
+  unsigned fileOffset =
+    SI->second +                // offset in symbol-table-less file
+    firstFileOffset;            // add offset to first "real" file in archive
+
+  // See if the module is already loaded
+  ModuleMap::iterator MI = modules.find(fileOffset);
+  if (MI != modules.end())
+    return MI->second.first;
+
+  // Module hasn't been loaded yet, we need to load it
+  const char* modptr = base + fileOffset;
+  ArchiveMember* mbr = parseMemberHeader(modptr, mapfile->getBufferEnd(),
+                                         ErrMsg);
+  if (!mbr)
+    return 0;
+
+  // Now, load the bitcode module to get the Module.
+  std::string FullMemberName = archPath.str() + "(" +
+    mbr->getPath().str() + ")";
+  MemoryBuffer *Buffer =
+    MemoryBuffer::getMemBufferCopy(StringRef(mbr->getData(), mbr->getSize()),
+                                   FullMemberName.c_str());
+  
+  Module *m = getLazyBitcodeModule(Buffer, Context, ErrMsg);
+  if (!m)
+    return 0;
+
+  modules.insert(std::make_pair(fileOffset, std::make_pair(m, mbr)));
+
+  return m;
+}
+
+// Look up multiple symbols in the symbol table and return a set of
+// Modules that define those symbols.
+bool
+Archive::findModulesDefiningSymbols(std::set<std::string>& symbols,
+                                    SmallVectorImpl<Module*>& result,
+                                    std::string* error) {
+  if (!mapfile || !base) {
+    if (error)
+      *error = "Empty archive invalid for finding modules defining symbols";
+    return false;
+  }
+
+  if (symTab.empty()) {
+    // We don't have a symbol table, so we must build it now but lets also
+    // make sure that we populate the modules table as we do this to ensure
+    // that we don't load them twice when findModuleDefiningSymbol is called
+    // below.
+
+    // Get a pointer to the first file
+    const char* At  = base + firstFileOffset;
+    const char* End = mapfile->getBufferEnd();
+
+    while ( At < End) {
+      // Compute the offset to be put in the symbol table
+      unsigned offset = At - base - firstFileOffset;
+
+      // Parse the file's header
+      ArchiveMember* mbr = parseMemberHeader(At, End, error);
+      if (!mbr)
+        return false;
+
+      // If it contains symbols
+      if (mbr->isBitcode()) {
+        // Get the symbols
+        std::vector<std::string> symbols;
+        std::string FullMemberName = archPath.str() + "(" +
+          mbr->getPath().str() + ")";
+        Module* M = 
+          GetBitcodeSymbols(At, mbr->getSize(), FullMemberName, Context,
+                            symbols, error);
+
+        if (M) {
+          // Insert the module's symbols into the symbol table
+          for (std::vector<std::string>::iterator I = symbols.begin(),
+               E=symbols.end(); I != E; ++I ) {
+            symTab.insert(std::make_pair(*I, offset));
+          }
+          // Insert the Module and the ArchiveMember into the table of
+          // modules.
+          modules.insert(std::make_pair(offset, std::make_pair(M, mbr)));
+        } else {
+          if (error)
+            *error = "Can't parse bitcode member: " + 
+              mbr->getPath().str() + ": " + *error;
+          delete mbr;
+          return false;
+        }
+      }
+
+      // Go to the next file location
+      At += mbr->getSize();
+      if ((intptr_t(At) & 1) == 1)
+        At++;
+    }
+  }
+
+  // At this point we have a valid symbol table (one way or another) so we
+  // just use it to quickly find the symbols requested.
+
+  SmallPtrSet<Module*, 16> Added;
+  for (std::set<std::string>::iterator I=symbols.begin(),
+         Next = I,
+         E=symbols.end(); I != E; I = Next) {
+    // Increment Next before we invalidate it.
+    ++Next;
+
+    // See if this symbol exists
+    Module* m = findModuleDefiningSymbol(*I,error);
+    if (!m)
+      continue;
+    bool NewMember = Added.insert(m);
+    if (!NewMember)
+      continue;
+
+    // The symbol exists, insert the Module into our result.
+    result.push_back(m);
+
+    // Remove the symbol now that its been resolved.
+    symbols.erase(I);
+  }
+  return true;
+}
+
+bool Archive::isBitcodeArchive() {
+  // Make sure the symTab has been loaded. In most cases this should have been
+  // done when the archive was constructed, but still,  this is just in case.
+  if (symTab.empty())
+    if (!loadSymbolTable(0))
+      return false;
+
+  // Now that we know it's been loaded, return true
+  // if it has a size
+  if (symTab.size()) return true;
+
+  // We still can't be sure it isn't a bitcode archive
+  if (!loadArchive(0))
+    return false;
+
+  std::vector<Module *> Modules;
+  std::string ErrorMessage;
+
+  // Scan the archive, trying to load a bitcode member.  We only load one to
+  // see if this works.
+  for (iterator I = begin(), E = end(); I != E; ++I) {
+    if (!I->isBitcode())
+      continue;
+    
+    std::string FullMemberName = 
+      archPath.str() + "(" + I->getPath().str() + ")";
+
+    MemoryBuffer *Buffer =
+      MemoryBuffer::getMemBufferCopy(StringRef(I->getData(), I->getSize()),
+                                     FullMemberName.c_str());
+    Module *M = ParseBitcodeFile(Buffer, Context);
+    delete Buffer;
+    if (!M)
+      return false;  // Couldn't parse bitcode, not a bitcode archive.
+    delete M;
+    return true;
+  }
+  
+  return false;
+}
diff --git a/tools/llvm-ar/ArchiveWriter.cpp b/tools/llvm-ar/ArchiveWriter.cpp
new file mode 100644
index 0000000000..24f5dbc0dc
--- /dev/null
+++ b/tools/llvm-ar/ArchiveWriter.cpp
@@ -0,0 +1,429 @@
+//===-- ArchiveWriter.cpp - Write LLVM archive files ----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Builds up an LLVM archive file (.a) containing LLVM bitcode.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Archive.h"
+#include "ArchiveInternals.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/system_error.h"
+#include <fstream>
+#include <iomanip>
+#include <ostream>
+using namespace llvm;
+
+// Write an integer using variable bit rate encoding. This saves a few bytes
+// per entry in the symbol table.
+static inline void writeInteger(unsigned num, std::ofstream& ARFile) {
+  while (1) {
+    if (num < 0x80) { // done?
+      ARFile << (unsigned char)num;
+      return;
+    }
+
+    // Nope, we are bigger than a character, output the next 7 bits and set the
+    // high bit to say that there is more coming...
+    ARFile << (unsigned char)(0x80 | ((unsigned char)num & 0x7F));
+    num >>= 7;  // Shift out 7 bits now...
+  }
+}
+
+// Compute how many bytes are taken by a given VBR encoded value. This is needed
+// to pre-compute the size of the symbol table.
+static inline unsigned numVbrBytes(unsigned num) {
+
+  // Note that the following nested ifs are somewhat equivalent to a binary
+  // search. We split it in half by comparing against 2^14 first. This allows
+  // most reasonable values to be done in 2 comparisons instead of 1 for
+  // small ones and four for large ones. We expect this to access file offsets
+  // in the 2^10 to 2^24 range and symbol lengths in the 2^0 to 2^8 range,
+  // so this approach is reasonable.
+  if (num < 1<<14) {
+    if (num < 1<<7)
+      return 1;
+    else
+      return 2;
+  }
+  if (num < 1<<21)
+    return 3;
+
+  if (num < 1<<28)
+    return 4;
+  return 5; // anything >= 2^28 takes 5 bytes
+}
+
+// Create an empty archive.
+Archive* Archive::CreateEmpty(const sys::Path& FilePath, LLVMContext& C) {
+  Archive* result = new Archive(FilePath, C);
+  return result;
+}
+
+// Fill the ArchiveMemberHeader with the information from a member. If
+// TruncateNames is true, names are flattened to 15 chars or less. The sz field
+// is provided here instead of coming from the mbr because the member might be
+// stored compressed and the compressed size is not the ArchiveMember's size.
+// Furthermore compressed files have negative size fields to identify them as
+// compressed.
+bool
+Archive::fillHeader(const ArchiveMember &mbr, ArchiveMemberHeader& hdr,
+                    int sz, bool TruncateNames) const {
+
+  // Set the permissions mode, uid and gid
+  hdr.init();
+  char buffer[32];
+  sprintf(buffer, "%-8o", mbr.getMode());
+  memcpy(hdr.mode,buffer,8);
+  sprintf(buffer,  "%-6u", mbr.getUser());
+  memcpy(hdr.uid,buffer,6);
+  sprintf(buffer,  "%-6u", mbr.getGroup());
+  memcpy(hdr.gid,buffer,6);
+
+  // Set the last modification date
+  uint64_t secondsSinceEpoch = mbr.getModTime().toEpochTime();
+  sprintf(buffer,"%-12u", unsigned(secondsSinceEpoch));
+  memcpy(hdr.date,buffer,12);
+
+  // Get rid of trailing blanks in the name
+  std::string mbrPath = mbr.getPath().str();
+  size_t mbrLen = mbrPath.length();
+  while (mbrLen > 0 && mbrPath[mbrLen-1] == ' ') {
+    mbrPath.erase(mbrLen-1,1);
+    mbrLen--;
+  }
+
+  // Set the name field in one of its various flavors.
+  bool writeLongName = false;
+  if (mbr.isStringTable()) {
+    memcpy(hdr.name,ARFILE_STRTAB_NAME,16);
+  } else if (mbr.isSVR4SymbolTable()) {
+    memcpy(hdr.name,ARFILE_SVR4_SYMTAB_NAME,16);
+  } else if (mbr.isBSD4SymbolTable()) {
+    memcpy(hdr.name,ARFILE_BSD4_SYMTAB_NAME,16);
+  } else if (TruncateNames) {
+    const char* nm = mbrPath.c_str();
+    unsigned len = mbrPath.length();
+    size_t slashpos = mbrPath.rfind('/');
+    if (slashpos != std::string::npos) {
+      nm += slashpos + 1;
+      len -= slashpos +1;
+    }
+    if (len > 15)
+      len = 15;
+    memcpy(hdr.name,nm,len);
+    hdr.name[len] = '/';
+  } else if (mbrPath.length() < 16 && mbrPath.find('/') == std::string::npos) {
+    memcpy(hdr.name,mbrPath.c_str(),mbrPath.length());
+    hdr.name[mbrPath.length()] = '/';
+  } else {
+    std::string nm = "#1/";
+    nm += utostr(mbrPath.length());
+    memcpy(hdr.name,nm.data(),nm.length());
+    if (sz < 0)
+      sz -= mbrPath.length();
+    else
+      sz += mbrPath.length();
+    writeLongName = true;
+  }
+
+  // Set the size field
+  if (sz < 0) {
+    buffer[0] = '-';
+    sprintf(&buffer[1],"%-9u",(unsigned)-sz);
+  } else {
+    sprintf(buffer, "%-10u", (unsigned)sz);
+  }
+  memcpy(hdr.size,buffer,10);
+
+  return writeLongName;
+}
+
+// Insert a file into the archive before some other member. This also takes care
+// of extracting the necessary flags and information from the file.
+bool
+Archive::addFileBefore(const sys::Path& filePath, iterator where,
+                        std::string* ErrMsg) {
+  bool Exists;
+  if (sys::fs::exists(filePath.str(), Exists) || !Exists) {
+    if (ErrMsg)
+      *ErrMsg = "Can not add a non-existent file to archive";
+    return true;
+  }
+
+  ArchiveMember* mbr = new ArchiveMember(this);
+
+  mbr->data = 0;
+  mbr->path = filePath;
+  const sys::FileStatus *FSInfo = mbr->path.getFileStatus(false, ErrMsg);
+  if (!FSInfo) {
+    delete mbr;
+    return true;
+  }
+  mbr->info = *FSInfo;
+
+  unsigned flags = 0;
+  bool hasSlash = filePath.str().find('/') != std::string::npos;
+  if (hasSlash)
+    flags |= ArchiveMember::HasPathFlag;
+  if (hasSlash || filePath.str().length() > 15)
+    flags |= ArchiveMember::HasLongFilenameFlag;
+
+  sys::fs::file_magic type;
+  if (sys::fs::identify_magic(mbr->path.str(), type))
+    type = sys::fs::file_magic::unknown;
+  switch (type) {
+    case sys::fs::file_magic::bitcode:
+      flags |= ArchiveMember::BitcodeFlag;
+      break;
+    default:
+      break;
+  }
+  mbr->flags = flags;
+  members.insert(where,mbr);
+  return false;
+}
+
+// Write one member out to the file.
+bool
+Archive::writeMember(
+  const ArchiveMember& member,
+  std::ofstream& ARFile,
+  bool CreateSymbolTable,
+  bool TruncateNames,
+  std::string* ErrMsg
+) {
+
+  unsigned filepos = ARFile.tellp();
+  filepos -= 8;
+
+  // Get the data and its size either from the
+  // member's in-memory data or directly from the file.
+  size_t fSize = member.getSize();
+  const char *data = (const char*)member.getData();
+  MemoryBuffer *mFile = 0;
+  if (!data) {
+    OwningPtr<MemoryBuffer> File;
+    if (error_code ec = MemoryBuffer::getFile(member.getPath().c_str(), File)) {
+      if (ErrMsg)
+        *ErrMsg = ec.message();
+      return true;
+    }
+    mFile = File.take();
+    data = mFile->getBufferStart();
+    fSize = mFile->getBufferSize();
+  }
+
+  // Now that we have the data in memory, update the
+  // symbol table if it's a bitcode file.
+  if (CreateSymbolTable && member.isBitcode()) {
+    std::vector<std::string> symbols;
+    std::string FullMemberName = archPath.str() + "(" + member.getPath().str()
+      + ")";
+    Module* M =
+      GetBitcodeSymbols(data, fSize, FullMemberName, Context, symbols, ErrMsg);
+
+    // If the bitcode parsed successfully
+    if ( M ) {
+      for (std::vector<std::string>::iterator SI = symbols.begin(),
+           SE = symbols.end(); SI != SE; ++SI) {
+
+        std::pair<SymTabType::iterator,bool> Res =
+          symTab.insert(std::make_pair(*SI,filepos));
+
+        if (Res.second) {
+          symTabSize += SI->length() +
+                        numVbrBytes(SI->length()) +
+                        numVbrBytes(filepos);
+        }
+      }
+      // We don't need this module any more.
+      delete M;
+    } else {
+      delete mFile;
+      if (ErrMsg)
+        *ErrMsg = "Can't parse bitcode member: " + member.getPath().str()
+          + ": " + *ErrMsg;
+      return true;
+    }
+  }
+
+  int hdrSize = fSize;
+
+  // Compute the fields of the header
+  ArchiveMemberHeader Hdr;
+  bool writeLongName = fillHeader(member,Hdr,hdrSize,TruncateNames);
+
+  // Write header to archive file
+  ARFile.write((char*)&Hdr, sizeof(Hdr));
+
+  // Write the long filename if its long
+  if (writeLongName) {
+    ARFile.write(member.getPath().str().data(),
+                 member.getPath().str().length());
+  }
+
+  // Write the (possibly compressed) member's content to the file.
+  ARFile.write(data,fSize);
+
+  // Make sure the member is an even length
+  if ((ARFile.tellp() & 1) == 1)
+    ARFile << ARFILE_PAD;
+
+  // Close the mapped file if it was opened
+  delete mFile;
+  return false;
+}
+
+// Write the entire archive to the file specified when the archive was created.
+// This writes to a temporary file first. Options are for creating a symbol
+// table, flattening the file names (no directories, 15 chars max) and
+// compressing each archive member.
+bool
+Archive::writeToDisk(bool CreateSymbolTable, bool TruncateNames,
+                     std::string* ErrMsg)
+{
+  // Make sure they haven't opened up the file, not loaded it,
+  // but are now trying to write it which would wipe out the file.
+  if (members.empty() && mapfile && mapfile->getBufferSize() > 8) {
+    if (ErrMsg)
+      *ErrMsg = "Can't write an archive not opened for writing";
+    return true;
+  }
+
+  // Create a temporary file to store the archive in
+  sys::Path TmpArchive = archPath;
+  if (TmpArchive.createTemporaryFileOnDisk(ErrMsg))
+    return true;
+
+  // Make sure the temporary gets removed if we crash
+  sys::RemoveFileOnSignal(TmpArchive.str());
+
+  // Create archive file for output.
+  std::ios::openmode io_mode = std::ios::out | std::ios::trunc |
+                               std::ios::binary;
+  std::ofstream ArchiveFile(TmpArchive.c_str(), io_mode);
+
+  // Check for errors opening or creating archive file.
+  if (!ArchiveFile.is_open() || ArchiveFile.bad()) {
+    TmpArchive.eraseFromDisk();
+    if (ErrMsg)
+      *ErrMsg = "Error opening archive file: " + archPath.str();
+    return true;
+  }
+
+  // If we're creating a symbol table, reset it now
+  if (CreateSymbolTable) {
+    symTabSize = 0;
+    symTab.clear();
+  }
+
+  // Write magic string to archive.
+  ArchiveFile << ARFILE_MAGIC;
+
+  // Loop over all member files, and write them out. Note that this also
+  // builds the symbol table, symTab.
+  for (MembersList::iterator I = begin(), E = end(); I != E; ++I) {
+    if (writeMember(*I, ArchiveFile, CreateSymbolTable,
+                     TruncateNames, ErrMsg)) {
+      TmpArchive.eraseFromDisk();
+      ArchiveFile.close();
+      return true;
+    }
+  }
+
+  // Close archive file.
+  ArchiveFile.close();
+
+  // Write the symbol table
+  if (CreateSymbolTable) {
+    // At this point we have written a file that is a legal archive but it
+    // doesn't have a symbol table in it. To aid in faster reading and to
+    // ensure compatibility with other archivers we need to put the symbol
+    // table first in the file. Unfortunately, this means mapping the file
+    // we just wrote back in and copying it to the destination file.
+    sys::Path FinalFilePath = archPath;
+
+    // Map in the archive we just wrote.
+    {
+    OwningPtr<MemoryBuffer> arch;
+    if (error_code ec = MemoryBuffer::getFile(TmpArchive.c_str(), arch)) {
+      if (ErrMsg)
+        *ErrMsg = ec.message();
+      return true;
+    }
+    const char* base = arch->getBufferStart();
+
+    // Open another temporary file in order to avoid invalidating the
+    // mmapped data
+    if (FinalFilePath.createTemporaryFileOnDisk(ErrMsg))
+      return true;
+    sys::RemoveFileOnSignal(FinalFilePath.str());
+
+    std::ofstream FinalFile(FinalFilePath.c_str(), io_mode);
+    if (!FinalFile.is_open() || FinalFile.bad()) {
+      TmpArchive.eraseFromDisk();
+      if (ErrMsg)
+        *ErrMsg = "Error opening archive file: " + FinalFilePath.str();
+      return true;
+    }
+
+    // Write the file magic number
+    FinalFile << ARFILE_MAGIC;
+
+    // If there is a foreign symbol table, put it into the file now. Most
+    // ar(1) implementations require the symbol table to be first but llvm-ar
+    // can deal with it being after a foreign symbol table. This ensures
+    // compatibility with other ar(1) implementations as well as allowing the
+    // archive to store both native .o and LLVM .bc files, both indexed.
+    if (foreignST) {
+      if (writeMember(*foreignST, FinalFile, false, false, ErrMsg)) {
+        FinalFile.close();
+        TmpArchive.eraseFromDisk();
+        return true;
+      }
+    }
+
+    // Copy the temporary file contents being sure to skip the file's magic
+    // number.
+    FinalFile.write(base + sizeof(ARFILE_MAGIC)-1,
+      arch->getBufferSize()-sizeof(ARFILE_MAGIC)+1);
+
+    // Close up shop
+    FinalFile.close();
+    } // free arch.
+
+    // Move the final file over top of TmpArchive
+    if (FinalFilePath.renamePathOnDisk(TmpArchive, ErrMsg))
+      return true;
+  }
+
+  // Before we replace the actual archive, we need to forget all the
+  // members, since they point to data in that old archive. We need to do
+  // this because we cannot replace an open file on Windows.
+  cleanUpMemory();
+
+  if (TmpArchive.renamePathOnDisk(archPath, ErrMsg))
+    return true;
+
+  // Set correct read and write permissions after temporary file is moved
+  // to final destination path.
+  if (archPath.makeReadableOnDisk(ErrMsg))
+    return true;
+  if (archPath.makeWriteableOnDisk(ErrMsg))
+    return true;
+
+  return false;
+}
diff --git a/tools/llvm-ar/CMakeLists.txt b/tools/llvm-ar/CMakeLists.txt
index 70eb7603fd..68095df714 100644
--- a/tools/llvm-ar/CMakeLists.txt
+++ b/tools/llvm-ar/CMakeLists.txt
@@ -1,7 +1,10 @@
-set(LLVM_LINK_COMPONENTS archive)
+set(LLVM_LINK_COMPONENTS support bitreader)
 
 add_llvm_tool(llvm-ar
   llvm-ar.cpp
+  ArchiveWriter.cpp
+  ArchiveReader.cpp
+  Archive.cpp
   )
 
 # TODO: Support check-local.
diff --git a/tools/llvm-ar/LLVMBuild.txt b/tools/llvm-ar/LLVMBuild.txt
index 1f61a32014..236b4659f7 100644
--- a/tools/llvm-ar/LLVMBuild.txt
+++ b/tools/llvm-ar/LLVMBuild.txt
@@ -19,4 +19,3 @@
 type = Tool
 name = llvm-ar
 parent = Tools
-required_libraries = Archive
diff --git a/tools/llvm-ar/Makefile b/tools/llvm-ar/Makefile
index fafb14bc12..9e782cfca5 100644
--- a/tools/llvm-ar/Makefile
+++ b/tools/llvm-ar/Makefile
@@ -9,7 +9,7 @@
 
 LEVEL := ../..
 TOOLNAME := llvm-ar
-LINK_COMPONENTS := archive
+LINK_COMPONENTS := bitreader support
 
 # This tool has no plugins, optimize startup time.
 TOOL_NO_EXPORTS := 1
diff --git a/tools/llvm-ar/llvm-ar.cpp b/tools/llvm-ar/llvm-ar.cpp
index 243a845e3c..2a4a3deecd 100644
--- a/tools/llvm-ar/llvm-ar.cpp
+++ b/tools/llvm-ar/llvm-ar.cpp
@@ -12,8 +12,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "Archive.h"
 #include "llvm/IR/LLVMContext.h"
-#include "llvm/Bitcode/Archive.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileSystem.h"