Add (unsupported experimental) feature allowing byte aligned bitcode.

lib/Bitcode/NaCl/Analysis/NaClCompress.cpp

 //===-- NaClCompress.cpp - Bitcode (abbrev) compression -----------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Analyzes the data in memory buffer, and determines what
@@ skipping 1140 matching lines @@
     MemoryBuffer *MemBuf,
     raw_ostream &Output,
     BlockAbbrevsMapType &BlockAbbrevsMap) {
   // TODO(kschimpf): The current code only extracts abbreviations
   // defined in the bitcode file. This code needs to be updated to
   // collect data distributions and figure out better (global)
   // abbreviations to use.
 
   const unsigned char *BufPtr = (const unsigned char *)MemBuf->getBufferStart();
   const unsigned char *EndBufPtr = BufPtr+MemBuf->getBufferSize();
+  const unsigned char *HeaderPtr = BufPtr;
 
   // First read header and verify it is good.
   NaClBitcodeHeader Header;
-  if (Header.Read(BufPtr, EndBufPtr) || !Header.IsSupported())
+  if (Header.Read(HeaderPtr, EndBufPtr) || !Header.IsSupported())

[jvoung (off chromium), 2015/05/07 18:11:17]

Should this check of Read vs IsSupported be split too? (like NaClObjDump and
Analyze)

[Karl, 2015/05/07 22:18:54]

Good point. Changing.

     return Error("Invalid PNaCl bitcode header");
 
   // Create a bitstream reader to read the bitcode file.
-  NaClBitstreamReader StreamFile(BufPtr, EndBufPtr);
+  NaClBitstreamReader StreamFile(BufPtr, EndBufPtr, Header);
   NaClBitstreamCursor Stream(StreamFile);
 
   // Parse the the bitcode file.
   NaClAnalyzeParser Parser(Flags, Stream, BlockAbbrevsMap);
   while (!Stream.AtEndOfStream()) {
     if (Parser.Parse()) return true;
   }
 
   if (Flags.ShowAbbreviationFrequencies)
     displayAbbreviationFrequencies(Output, Parser.BlockDist, BlockAbbrevsMap);
@@ skipping 195 matching lines @@
   return Parser.ParseThisBlock();
 }
 
 // Reads the bitcode in MemBuf, using the abbreviations in AbbrevsMap,
 // and queues the selected abbrevations for each record into
 // AbbrevsQueueMap.
 static bool chooseAbbrevs(MemoryBuffer *MemBuf, BlockAbbrevsMapType &AbbrevsMap,
                           BlockAbbrevsQueueMap &AbbrevsQueueMap) {
   const unsigned char *BufPtr = (const unsigned char *)MemBuf->getBufferStart();
   const unsigned char *EndBufPtr = BufPtr + MemBuf->getBufferSize();
+  const unsigned char *HeaderPtr = BufPtr;
 
   // Read header. No verification is needed since AnalyzeBitcode has
   // already checked it.
   NaClBitcodeHeader Header;
-  if (Header.Read(BufPtr, EndBufPtr))
+  if (Header.Read(HeaderPtr, EndBufPtr))
     return Error("Invalid PNaCl bitcode header");
 
   // Create the bitcode reader.
-  NaClBitstreamReader StreamFile(BufPtr, EndBufPtr);
+  NaClBitstreamReader StreamFile(BufPtr, EndBufPtr, Header);
   NaClBitstreamCursor Stream(StreamFile);
 
   // Set up the parser.
   NaClAssignAbbrevsParser Parser(Stream, AbbrevsMap, AbbrevsQueueMap);
 
   // Parse the bitcode and choose abbreviations for records.
   while (!Stream.AtEndOfStream()) {
     if (Parser.Parse()) {
       installFrequentlyUsedAbbrevs(AbbrevsMap, AbbrevsQueueMap);
       return true;
@@ skipping 169 matching lines @@
 // Read in bitcode, and write it back out using the abbreviations in
 // BlockAbbrevsMap, from memory buffer MemBuf containing the input
 // bitcode file. The bitcode is copied to Output.
 static bool copyBitcode(const NaClBitcodeCompressor::CompressFlags &Flags,
                         MemoryBuffer *MemBuf, raw_ostream &Output,
                         BlockAbbrevsMapType &BlockAbbrevsMap,
                         BlockAbbrevsQueueMap &AbbrevsQueueMap) {
 
   const unsigned char *BufPtr = (const unsigned char *)MemBuf->getBufferStart();
   const unsigned char *EndBufPtr = BufPtr + MemBuf->getBufferSize();
+  const unsigned char *HeaderPtr = BufPtr;
 
   // Read header. No verification is needed since AnalyzeBitcode has
   // already checked it.
   NaClBitcodeHeader Header;
-  if (Header.Read(BufPtr, EndBufPtr))
+  if (Header.Read(HeaderPtr, EndBufPtr))
     return Error("Invalid PNaCl bitcode header");
 
   // Create the bitcode reader.
-  NaClBitstreamReader StreamFile(BufPtr, EndBufPtr);
+  NaClBitstreamReader StreamFile(BufPtr, EndBufPtr, Header);
   NaClBitstreamCursor Stream(StreamFile);
 
   // Create the bitcode writer.
   SmallVector<char, 0> OutputBuffer;
   OutputBuffer.reserve(256 * 1024);
   NaClBitstreamWriter StreamWriter(OutputBuffer);
 
   // Emit the file header.
   NaClWriteHeader(Header, StreamWriter);
 
@@ skipping 42 matching lines @@
   BlockAbbrevsQueueMap AbbrevsQueueMap;
   bool Result = true;
   if (chooseAbbrevs(MemBuf, BlockAbbrevsMap, AbbrevsQueueMap))
     Result = false;
   else if (copyBitcode(Flags, MemBuf, BitcodeOutput, BlockAbbrevsMap,
                        AbbrevsQueueMap))
     Result = false;
   DeleteContainerSeconds(AbbrevsQueueMap);
   return Result;
 }