push bytecode decompressor out through APIs. Now the bytecode reader

api's look like this:

ModuleProvider *getBytecodeModuleProvider(
  const std::string &Filename,  ///< Name of file to be read
  BCDecompressor_t *BCDC = Compressor::decompressToNewBuffer,
  std::string* ErrMsg = 0,      ///< Optional error message holder
  BytecodeHandler* H = 0        ///< Optional handler for reader events
);

This is ugly, but allows a client to say:

  getBytecodeModuleProvider("foo", 0);

If they do this, there is no dependency on the compression libraries, saving
codesize.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34012 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bytecode/Reader/Reader.cpp

@@ -1981,7 +1981,7 @@ void BytecodeReader::ParseModule() {
 /// and \p Length parameters.
 bool BytecodeReader::ParseBytecode(volatile BufPtr Buf, unsigned Length,
                                    const std::string &ModuleID,
-                                   Decompressor_t *Decompressor, 
+                                   BCDecompressor_t *Decompressor, 
                                    std::string* ErrMsg) {
 
   /// We handle errors by
@@ -2016,6 +2016,9 @@ bool BytecodeReader::ParseBytecode(volatile BufPtr Buf, unsigned Length,
 
   // If this is a compressed file
   if (Sig == ('l' | ('l' << 8) | ('v' << 16) | ('c' << 24))) {
+    if (!Decompressor) {
+      error("Compressed bytecode found, but not decompressor available");
+    }
 
     // Invoke the decompression of the bytecode. Note that we have to skip the
     // file's magic number which is not part of the compressed block. Hence,