Add abilities to generate bitcode buffers from munged bitcode.

lib/Bitcode/NaCl/TestUtils/NaClBitcodeMungeReader.cpp

+//===- NaClBitcodeMungeReader.cpp - Read bitcode record list ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements bitcode reader for NaClBitcodeRecordList and  NaClMungedBitcode.

[jvoung (off chromium), 2015/05/05 00:27:23]

extra space in "  NaClMungedBitcode"

[Karl, 2015/05/05 22:38:03]

Done.

+
+#include "llvm/Bitcode/NaCl/NaClBitcodeMungeUtils.h"
+
+#include "llvm/Bitcode/NaCl/NaClBitcodeHeader.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+using namespace llvm;
+
+namespace {
+
+class BitcodeParser;
+
+// \brief The state associated with parsing a bitcode buffer.
+class BitcodeParseState {
+  BitcodeParseState(const BitcodeParseState&) = delete;
+  BitcodeParseState &operator=(const BitcodeParseState&) = delete;
+public:
+  // \brief Construct the bitcode parse state.
+  //
+  // \param Parser The parser used to parse the bitcode.
+  // \param[out] Records Filled with parsed records.
+  BitcodeParseState(BitcodeParser *Parser,
+                    NaClBitcodeRecordList &Records);
+
+  // List to read records into.
+  NaClBitcodeRecordList &Records;
+  // Listener use to get abbreviations as they are read.

[jvoung (off chromium), 2015/05/05 00:27:23]

"use to get" -> "used to get" ?

[Karl, 2015/05/05 22:38:04]

Done.

+  NaClBitcodeParserListener AbbrevListener;
+  //

[jvoung (off chromium), 2015/05/05 00:27:23]

Dangling "//"

[Karl, 2015/05/05 22:38:03]

Done.

+};
+
+// \brief The bitcode parser to extract bitcode records.
+class BitcodeParser : public NaClBitcodeParser {
+  BitcodeParser(const BitcodeParser &) = delete;
+  BitcodeParser &operator=(const BitcodeParser&) = delete;
+public:
+  // \brief Top-level constructor for a bitcode parser.
+  //
+  // \param Cursor The beginning position of the bitcode to parse.
+  // \param[out] Records Filled with parsed records.
+  BitcodeParser(NaClBitstreamCursor &Cursor,
+                NaClBitcodeRecordList &Records)
+      : NaClBitcodeParser(Cursor),
+        State(new BitcodeParseState(this, Records)) {
+    SetListener(&State->AbbrevListener);
+  }
+
+  virtual ~BitcodeParser() override {

[jvoung (off chromium), 2015/05/05 00:27:23]

Only need one "override" and don't need "virtual"

[Karl, 2015/05/05 22:38:03]

Done.

+    if (EnclosingParser == nullptr)
+      delete State;
+  }
+
+  bool ParseBlock(unsigned BlockID) override {
+    BitcodeParser NestedParser(BlockID, this);
+    return NestedParser.ParseThisBlock();
+  }
+
+  void EnterBlock(unsigned NumWords) override {
+    NaClRecordVector Values;
+    Values.push_back(GetBlockID());
+    Values.push_back(Record.GetCursor().getAbbrevIDWidth());
+    std::unique_ptr<NaClBitcodeAbbrevRecord> AbbrevRec(
+        new NaClBitcodeAbbrevRecord(naclbitc::ENTER_SUBBLOCK,
+                                    naclbitc::BLK_CODE_ENTER,
+                                    Values));
+    State->Records.push_back(std::move(AbbrevRec));
+  }
+
+  void ExitBlock() override {
+    NaClRecordVector Values;
+    std::unique_ptr<NaClBitcodeAbbrevRecord> AbbrevRec(
+        new NaClBitcodeAbbrevRecord(naclbitc::END_BLOCK,
+                                    naclbitc::BLK_CODE_EXIT,
+                                    Values));
+    State->Records.push_back(std::move(AbbrevRec));
+  }
+
+  void ProcessRecord() override {
+    std::unique_ptr<NaClBitcodeAbbrevRecord> AbbrevRec(
+        new NaClBitcodeAbbrevRecord(Record.GetAbbreviationIndex(),
+                                    Record.GetCode(),
+                                    Record.GetValues()));
+    State->Records.push_back(std::move(AbbrevRec));
+  }
+
+  void SetBID() override {
+    ProcessRecord();
+  }
+
+  void ProcessAbbreviation(unsigned BlockID,
+                           NaClBitCodeAbbrev *Abbrev,
+                           bool IsLocal) override {
+    ProcessRecord();
+  }
+
+private:
+  // \brief Nested constructor for blocks within the bitcode buffer.
+  //
+  // \param BlockID The identifying constant associated with the block.
+  // \param EnclosingParser The bitcode parser parsing the enclosing block.
+  BitcodeParser(unsigned BlockID, BitcodeParser *EnclosingParser)
+      : NaClBitcodeParser(BlockID, EnclosingParser),
+        State(EnclosingParser->State) {}
+
+  // The state of the bitcode parser.
+  BitcodeParseState* State;
+};
+
+BitcodeParseState::BitcodeParseState(BitcodeParser *Parser,
+                                     NaClBitcodeRecordList &Records)
+    : Records(Records), AbbrevListener(Parser) {}
+
+} // end of anonymous namespace
+
+void llvm::readNaClBitcodeRecordList(
+    NaClBitcodeRecordList &RecordList,
+    std::unique_ptr<MemoryBuffer> InputBuffer) {
+  if (InputBuffer->getBufferSize() % 4 != 0)
+    report_fatal_error("Bitcode stream must be a multiple of 4 bytes in length");

[jvoung (off chromium), 2015/05/05 00:27:23]

just a little too long for 80 cols

[Karl, 2015/05/05 22:38:03]

Done.

+
+  const unsigned char *BufPtr =
+      (const unsigned char *) InputBuffer->getBufferStart();
+  const unsigned char *EndBufPtr = BufPtr + InputBuffer->getBufferSize();
+  const unsigned char *HeaderPtr = BufPtr;
+
+  // Read header and verify it is good.
+  NaClBitcodeHeader Header;
+  if (Header.Read(HeaderPtr, EndBufPtr) || !Header.IsSupported())
+    report_fatal_error("Invalid PNaCl bitcode header.\n");
+
+  NaClBitstreamReader Reader(BufPtr, EndBufPtr, Header.getHeaderSize());
+  NaClBitstreamCursor Cursor(Reader);
+
+  // Parse the bitcode buffer.
+  BitcodeParser Parser(Cursor, RecordList);
+
+  while (!Parser.AtEndOfStream()) {

[jvoung (off chromium), 2015/05/05 00:27:22]

There are a couple of instances of code that are very similar to this block
(e.g., Analyzer, Compress, and ObjDump files). They use "Cursor.AtEndOfStream()"
directly. So, is it necessary to introduce the AtEndOfStream() wrapper in
NaClBitcodeParser, or at least should the similar code be kept similar?

[Karl, 2015/05/05 22:38:03]

The problem I discovered was that this pattern was making a potentially bad
assumption by assuming that the cursor passed into the parser was the same as
the one used by the parser. I fixed this instance by adding the wrapper. I was
planning on fixing the other places as well with a separate wrapper.

Perhaps I should follow the other cases, and fix them all in a separate CL.
Changing the code to match the other cases (like Analyzer, Compress and
ObjDump).

+    if (Parser.Parse())
+      report_fatal_error("Malformed records founds, unable to continue");
+  }
+}
+
+
+NaClMungedBitcode::NaClMungedBitcode(std::unique_ptr<MemoryBuffer> InputBuffer)
+    : BaseRecords(new NaClBitcodeRecordList()) {
+  readNaClBitcodeRecordList(*BaseRecords, std::move(InputBuffer));
+}