Enable ability to have multiple PNaCl wire format versions.

Modifies PNaCl bitcode reader/writer to accept PNaClVersion=1 as supported,
and all other versions are unsupported and unreadable. The PNaCl bitcode
reader/writer will generate appropriate messages (including what version
is unsupported if applicable).

Also allows command-line option --pnacl-version for setting the PNaClVersion
in the PNaCl bitcode writer.

Also fixes some problems on PNaCl bitcode headers, using common support to
determine when the read/written PNaCl bitcode file is valid.

BUG=None
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/19400002

2 files changed, 34 insertions, 4 deletions

diff --git a/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h b/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
index 8febf95564..4f5f83a17a 100644
--- a/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
+++ b/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
@@ -151,6 +151,12 @@ public:
   /// is readable and supported.
   void InstallFields();
 
+  /// \brief Adds a field to the list of fields in a header. Takes ownership
+  /// of fields added.
+  void push_back(NaClBitcodeHeaderField *Field) {
+    Fields.push_back(Field);
+  }
+
   /// \brief Read the PNaCl bitcode header, The format of the header is:
   ///
   ///    1) 'PEXE' - The four character sequence defining the magic number.
@@ -172,9 +178,9 @@ public:
   // \brief Returns the number of bytes read to consume the header.
   size_t getHeaderSize() { return HeaderSize; }
 
-  /// \brief Returns C string describing why the header describes
-  /// an unsupported PNaCl Bitcode file. Returns 0 if supported.
-  const std::string Unsupported() const { return UnsupportedMessage; }
+  /// \brief Returns string describing why the header describes
+  /// an unsupported PNaCl Bitcode file.
+  const std::string &Unsupported() const { return UnsupportedMessage; }
 
   /// \brief Returns true if supported. That is, it can be run in the
   /// browser.
diff --git a/include/llvm/Bitcode/NaCl/NaClReaderWriter.h b/include/llvm/Bitcode/NaCl/NaClReaderWriter.h
index 53feb8ab86..1eb188a83e 100644
--- a/include/llvm/Bitcode/NaCl/NaClReaderWriter.h
+++ b/include/llvm/Bitcode/NaCl/NaClReaderWriter.h
@@ -30,6 +30,15 @@ namespace llvm {
   /// this takes ownership of 'buffer' and returns a non-null pointer.  On
   /// error, this returns null, *does not* take ownership of Buffer, and fills
   /// in *ErrMsg with an error description if ErrMsg is non-null.
+  ///
+  /// The AcceptSupportedOnly argument is used to decide which PNaCl versions
+  /// of the PNaCl bitcode to accept. There are three forms:
+  ///    1) Readable and supported.
+  ///    2) Readable and unsupported. Allows testing of code before becoming
+  ///       supported, as well as running experiments on the bitcode format.
+  ///    3) Unreadable.
+  /// When AcceptSupportedOnly is true, only form 1 is allowed. When
+  /// AcceptSupportedOnly is false, forms 1 and 2 are allowed.
   Module *getNaClLazyBitcodeModule(MemoryBuffer *Buffer,
                                    LLVMContext &Context,
                                    std::string *ErrMsg = 0,
@@ -39,6 +48,9 @@ namespace llvm {
   /// and prepare for lazy deserialization and streaming of function bodies.
   /// On error, this returns null, and fills in *ErrMsg with an error
   /// description if ErrMsg is non-null.
+  ///
+  /// See getNaClLazyBitcodeModule for an explanation of argument
+  /// AcceptSupportedOnly.
   Module *getNaClStreamedBitcodeModule(const std::string &name,
                                        DataStreamer *streamer,
                                        LLVMContext &Context,
@@ -49,6 +61,9 @@ namespace llvm {
   /// returning the module.  If an error occurs, this returns null and
   /// fills in *ErrMsg if it is non-null.  This method *never* takes
   /// ownership of Buffer.
+  ///
+  /// See getNaClLazyBitcodeModule for an explanation of argument
+  /// AcceptSupportedOnly.
   Module *NaClParseBitcodeFile(MemoryBuffer *Buffer, LLVMContext &Context,
                                std::string *ErrMsg = 0,
                                bool AcceptSupportedOnly = true);
@@ -57,7 +72,16 @@ namespace llvm {
   /// specified raw output stream, using PNaCl wire format.  For
   /// streams where it matters, the given stream should be in "binary"
   /// mode.
-  void NaClWriteBitcodeToFile(const Module *M, raw_ostream &Out);
+  ///
+  /// The AcceptSupportedOnly argument is used to decide which PNaCl versions
+  /// of the PNaCl bitcode to generate. There are two forms:
+  ///    1) Writable and supported.
+  ///    2) Writable and unsupported. Allows testing of code before becoming
+  ///       supported, as well as running experiments on the bitcode format.
+  /// When AcceptSupportedOnly is true, only form 1 is allowed. When
+  /// AcceptSupportedOnly is false, forms 1 and 2 are allowed.
+  void NaClWriteBitcodeToFile(const Module *M, raw_ostream &Out,
+                              bool AcceptSupportedOnly = true);
 
   /// isNaClBitcode - Return true if the given bytes are the magic bytes for
   /// PNaCl bitcode wire format.