Enable streaming of bitcode

This CL delays reading of function bodies from initial parse until
materialization, allowing overlap of compilation with bitcode download.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149918 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Bitcode/ReaderWriter.h

@@ -17,35 +17,45 @@
 #include <string>
 
 namespace llvm {
-  class Module;
-  class MemoryBuffer;
-  class ModulePass;
   class BitstreamWriter;
+  class MemoryBuffer;
+  class DataStreamer;
   class LLVMContext;
+  class Module;
+  class ModulePass;
   class raw_ostream;
-  
+
   /// getLazyBitcodeModule - Read the header of the specified bitcode buffer
   /// and prepare for lazy deserialization of function bodies.  If successful,
   /// 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.
   Module *getLazyBitcodeModule(MemoryBuffer *Buffer,
-                               LLVMContext& Context,
+                               LLVMContext &Context,
                                std::string *ErrMsg = 0);
 
+  /// getStreamedBitcodeModule - Read the header of the specified stream
+  /// 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.
+  Module *getStreamedBitcodeModule(const std::string &name,
+                                   DataStreamer *streamer,
+                                   LLVMContext &Context,
+                                   std::string *ErrMsg = 0);
+
   /// getBitcodeTargetTriple - Read the header of the specified bitcode
   /// buffer and extract just the triple information. If successful,
   /// this returns a string and *does not* take ownership
   /// of 'buffer'. On error, this returns "", and fills in *ErrMsg
   /// if ErrMsg is non-null.
   std::string getBitcodeTargetTriple(MemoryBuffer *Buffer,
-                                     LLVMContext& Context,
+                                     LLVMContext &Context,
                                      std::string *ErrMsg = 0);
 
   /// ParseBitcodeFile - Read the specified bitcode file, 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.
-  Module *ParseBitcodeFile(MemoryBuffer *Buffer, LLVMContext& Context,
+  Module *ParseBitcodeFile(MemoryBuffer *Buffer, LLVMContext &Context,
                            std::string *ErrMsg = 0);
 
   /// WriteBitcodeToFile - Write the specified module to the specified
@@ -60,8 +70,8 @@ namespace llvm {
   /// createBitcodeWriterPass - Create and return a pass that writes the module
   /// to the specified ostream.
   ModulePass *createBitcodeWriterPass(raw_ostream &Str);
-  
-  
+
+
   /// isBitcodeWrapper - Return true if the given bytes are the magic bytes
   /// for an LLVM IR bitcode wrapper.
   ///
@@ -109,21 +119,24 @@ namespace llvm {
   ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
   ///   ... potentially other gunk ...
   /// };
-  /// 
+  ///
   /// This function is called when we find a file with a matching magic number.
   /// In this case, skip down to the subsection of the file that is actually a
   /// BC file.
-  static inline bool SkipBitcodeWrapperHeader(unsigned char *&BufPtr,
-                                              unsigned char *&BufEnd) {
+  /// If 'VerifyBufferSize' is true, check that the buffer is large enough to
+  /// contain the whole bitcode file.
+  static inline bool SkipBitcodeWrapperHeader(const unsigned char *&BufPtr,
+                                              const unsigned char *&BufEnd,
+                                              bool VerifyBufferSize) {
     enum {
       KnownHeaderSize = 4*4,  // Size of header we read.
       OffsetField = 2*4,      // Offset in bytes to Offset field.
       SizeField = 3*4         // Offset in bytes to Size field.
     };
-    
+
     // Must contain the header!
     if (BufEnd-BufPtr < KnownHeaderSize) return true;
-    
+
     unsigned Offset = ( BufPtr[OffsetField  ]        |
                        (BufPtr[OffsetField+1] << 8)  |
                        (BufPtr[OffsetField+2] << 16) |
@@ -132,9 +145,9 @@ namespace llvm {
                        (BufPtr[SizeField  +1] << 8)  |
                        (BufPtr[SizeField  +2] << 16) |
                        (BufPtr[SizeField  +3] << 24));
-    
+
     // Verify that Offset+Size fits in the file.
-    if (Offset+Size > unsigned(BufEnd-BufPtr))
+    if (VerifyBufferSize && Offset+Size > unsigned(BufEnd-BufPtr))
       return true;
     BufPtr += Offset;
     BufEnd = BufPtr+Size;