llvm-6502/include/llvm/Bitcode/BitstreamReader.h
2014-12-18 05:08:43 +00:00

518 lines
16 KiB
C++

//===- BitstreamReader.h - Low-level bitstream reader interface -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This header defines the BitstreamReader class. This class can be used to
// read an arbitrary bitstream, regardless of its contents.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_BITCODE_BITSTREAMREADER_H
#define LLVM_BITCODE_BITSTREAMREADER_H
#include "llvm/Bitcode/BitCodes.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/StreamingMemoryObject.h"
#include <climits>
#include <string>
#include <vector>
namespace llvm {
class Deserializer;
/// This class is used to read from an LLVM bitcode stream, maintaining
/// information that is global to decoding the entire file. While a file is
/// being read, multiple cursors can be independently advanced or skipped around
/// within the file. These are represented by the BitstreamCursor class.
class BitstreamReader {
public:
/// This contains information emitted to BLOCKINFO_BLOCK blocks. These
/// describe abbreviations that all blocks of the specified ID inherit.
struct BlockInfo {
unsigned BlockID;
std::vector<IntrusiveRefCntPtr<BitCodeAbbrev>> Abbrevs;
std::string Name;
std::vector<std::pair<unsigned, std::string> > RecordNames;
};
private:
std::unique_ptr<MemoryObject> BitcodeBytes;
std::vector<BlockInfo> BlockInfoRecords;
/// This is set to true if we don't care about the block/record name
/// information in the BlockInfo block. Only llvm-bcanalyzer uses this.
bool IgnoreBlockInfoNames;
BitstreamReader(const BitstreamReader&) LLVM_DELETED_FUNCTION;
void operator=(const BitstreamReader&) LLVM_DELETED_FUNCTION;
public:
BitstreamReader() : IgnoreBlockInfoNames(true) {
}
BitstreamReader(const unsigned char *Start, const unsigned char *End)
: IgnoreBlockInfoNames(true) {
init(Start, End);
}
BitstreamReader(std::unique_ptr<MemoryObject> BitcodeBytes)
: BitcodeBytes(std::move(BitcodeBytes)), IgnoreBlockInfoNames(true) {}
BitstreamReader(BitstreamReader &&Other) {
*this = std::move(Other);
}
BitstreamReader &operator=(BitstreamReader &&Other) {
BitcodeBytes = std::move(Other.BitcodeBytes);
// Explicitly swap block info, so that nothing gets destroyed twice.
std::swap(BlockInfoRecords, Other.BlockInfoRecords);
IgnoreBlockInfoNames = Other.IgnoreBlockInfoNames;
return *this;
}
void init(const unsigned char *Start, const unsigned char *End) {
assert(((End-Start) & 3) == 0 &&"Bitcode stream not a multiple of 4 bytes");
BitcodeBytes.reset(getNonStreamedMemoryObject(Start, End));
}
MemoryObject &getBitcodeBytes() { return *BitcodeBytes; }
/// This is called by clients that want block/record name information.
void CollectBlockInfoNames() { IgnoreBlockInfoNames = false; }
bool isIgnoringBlockInfoNames() { return IgnoreBlockInfoNames; }
//===--------------------------------------------------------------------===//
// Block Manipulation
//===--------------------------------------------------------------------===//
/// Return true if we've already read and processed the block info block for
/// this Bitstream. We only process it for the first cursor that walks over
/// it.
bool hasBlockInfoRecords() const { return !BlockInfoRecords.empty(); }
/// If there is block info for the specified ID, return it, otherwise return
/// null.
const BlockInfo *getBlockInfo(unsigned BlockID) const {
// Common case, the most recent entry matches BlockID.
if (!BlockInfoRecords.empty() && BlockInfoRecords.back().BlockID == BlockID)
return &BlockInfoRecords.back();
for (unsigned i = 0, e = static_cast<unsigned>(BlockInfoRecords.size());
i != e; ++i)
if (BlockInfoRecords[i].BlockID == BlockID)
return &BlockInfoRecords[i];
return nullptr;
}
BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
if (const BlockInfo *BI = getBlockInfo(BlockID))
return *const_cast<BlockInfo*>(BI);
// Otherwise, add a new record.
BlockInfoRecords.push_back(BlockInfo());
BlockInfoRecords.back().BlockID = BlockID;
return BlockInfoRecords.back();
}
/// Takes block info from the other bitstream reader.
///
/// This is a "take" operation because BlockInfo records are non-trivial, and
/// indeed rather expensive.
void takeBlockInfo(BitstreamReader &&Other) {
assert(!hasBlockInfoRecords());
BlockInfoRecords = std::move(Other.BlockInfoRecords);
}
};
/// When advancing through a bitstream cursor, each advance can discover a few
/// different kinds of entries:
struct BitstreamEntry {
enum {
Error, // Malformed bitcode was found.
EndBlock, // We've reached the end of the current block, (or the end of the
// file, which is treated like a series of EndBlock records.
SubBlock, // This is the start of a new subblock of a specific ID.
Record // This is a record with a specific AbbrevID.
} Kind;
unsigned ID;
static BitstreamEntry getError() {
BitstreamEntry E; E.Kind = Error; return E;
}
static BitstreamEntry getEndBlock() {
BitstreamEntry E; E.Kind = EndBlock; return E;
}
static BitstreamEntry getSubBlock(unsigned ID) {
BitstreamEntry E; E.Kind = SubBlock; E.ID = ID; return E;
}
static BitstreamEntry getRecord(unsigned AbbrevID) {
BitstreamEntry E; E.Kind = Record; E.ID = AbbrevID; return E;
}
};
/// This represents a position within a bitcode file. There may be multiple
/// independent cursors reading within one bitstream, each maintaining their own
/// local state.
///
/// Unlike iterators, BitstreamCursors are heavy-weight objects that should not
/// be passed by value.
class BitstreamCursor {
friend class Deserializer;
BitstreamReader *BitStream;
size_t NextChar;
// The size of the bicode. 0 if we don't know it yet.
size_t Size;
/// This is the current data we have pulled from the stream but have not
/// returned to the client. This is specifically and intentionally defined to
/// follow the word size of the host machine for efficiency. We use word_t in
/// places that are aware of this to make it perfectly explicit what is going
/// on.
typedef size_t word_t;
word_t CurWord;
/// This is the number of bits in CurWord that are valid. This is always from
/// [0...bits_of(size_t)-1] inclusive.
unsigned BitsInCurWord;
// This is the declared size of code values used for the current block, in
// bits.
unsigned CurCodeSize;
/// Abbrevs installed at in this block.
std::vector<IntrusiveRefCntPtr<BitCodeAbbrev>> CurAbbrevs;
struct Block {
unsigned PrevCodeSize;
std::vector<IntrusiveRefCntPtr<BitCodeAbbrev>> PrevAbbrevs;
explicit Block(unsigned PCS) : PrevCodeSize(PCS) {}
};
/// This tracks the codesize of parent blocks.
SmallVector<Block, 8> BlockScope;
public:
BitstreamCursor() { init(nullptr); }
explicit BitstreamCursor(BitstreamReader &R) { init(&R); }
void init(BitstreamReader *R) {
freeState();
BitStream = R;
NextChar = 0;
Size = 0;
BitsInCurWord = 0;
CurCodeSize = 2;
}
void freeState();
bool canSkipToPos(size_t pos) const {
// pos can be skipped to if it is a valid address or one byte past the end.
return pos == 0 || BitStream->getBitcodeBytes().isValidAddress(
static_cast<uint64_t>(pos - 1));
}
bool AtEndOfStream() {
if (BitsInCurWord != 0)
return false;
if (Size != 0)
return Size == NextChar;
fillCurWord();
return BitsInCurWord == 0;
}
/// Return the number of bits used to encode an abbrev #.
unsigned getAbbrevIDWidth() const { return CurCodeSize; }
/// Return the bit # of the bit we are reading.
uint64_t GetCurrentBitNo() const {
return NextChar*CHAR_BIT - BitsInCurWord;
}
BitstreamReader *getBitStreamReader() {
return BitStream;
}
const BitstreamReader *getBitStreamReader() const {
return BitStream;
}
/// Flags that modify the behavior of advance().
enum {
/// If this flag is used, the advance() method does not automatically pop
/// the block scope when the end of a block is reached.
AF_DontPopBlockAtEnd = 1,
/// If this flag is used, abbrev entries are returned just like normal
/// records.
AF_DontAutoprocessAbbrevs = 2
};
/// Advance the current bitstream, returning the next entry in the stream.
BitstreamEntry advance(unsigned Flags = 0) {
while (1) {
unsigned Code = ReadCode();
if (Code == bitc::END_BLOCK) {
// Pop the end of the block unless Flags tells us not to.
if (!(Flags & AF_DontPopBlockAtEnd) && ReadBlockEnd())
return BitstreamEntry::getError();
return BitstreamEntry::getEndBlock();
}
if (Code == bitc::ENTER_SUBBLOCK)
return BitstreamEntry::getSubBlock(ReadSubBlockID());
if (Code == bitc::DEFINE_ABBREV &&
!(Flags & AF_DontAutoprocessAbbrevs)) {
// We read and accumulate abbrev's, the client can't do anything with
// them anyway.
ReadAbbrevRecord();
continue;
}
return BitstreamEntry::getRecord(Code);
}
}
/// This is a convenience function for clients that don't expect any
/// subblocks. This just skips over them automatically.
BitstreamEntry advanceSkippingSubblocks(unsigned Flags = 0) {
while (1) {
// If we found a normal entry, return it.
BitstreamEntry Entry = advance(Flags);
if (Entry.Kind != BitstreamEntry::SubBlock)
return Entry;
// If we found a sub-block, just skip over it and check the next entry.
if (SkipBlock())
return BitstreamEntry::getError();
}
}
/// Reset the stream to the specified bit number.
void JumpToBit(uint64_t BitNo) {
uintptr_t ByteNo = uintptr_t(BitNo/8) & ~(sizeof(word_t)-1);
unsigned WordBitNo = unsigned(BitNo & (sizeof(word_t)*8-1));
assert(canSkipToPos(ByteNo) && "Invalid location");
// Move the cursor to the right word.
NextChar = ByteNo;
BitsInCurWord = 0;
// Skip over any bits that are already consumed.
if (WordBitNo)
Read(WordBitNo);
}
void fillCurWord() {
assert(Size == 0 || NextChar < (unsigned)Size);
// Read the next word from the stream.
uint8_t Array[sizeof(word_t)] = {0};
uint64_t BytesRead =
BitStream->getBitcodeBytes().readBytes(Array, sizeof(Array), NextChar);
// If we run out of data, stop at the end of the stream.
if (BytesRead == 0) {
Size = NextChar;
return;
}
CurWord =
support::endian::read<word_t, support::little, support::unaligned>(
Array);
NextChar += BytesRead;
BitsInCurWord = BytesRead * 8;
}
word_t Read(unsigned NumBits) {
static const unsigned BitsInWord = sizeof(word_t) * 8;
assert(NumBits && NumBits <= BitsInWord &&
"Cannot return zero or more than BitsInWord bits!");
static const unsigned Mask = sizeof(word_t) > 4 ? 0x3f : 0x1f;
// If the field is fully contained by CurWord, return it quickly.
if (BitsInCurWord >= NumBits) {
word_t R = CurWord & (~word_t(0) >> (BitsInWord - NumBits));
// Use a mask to avoid undefined behavior.
CurWord >>= (NumBits & Mask);
BitsInCurWord -= NumBits;
return R;
}
word_t R = BitsInCurWord ? CurWord : 0;
unsigned BitsLeft = NumBits - BitsInCurWord;
fillCurWord();
// If we run out of data, stop at the end of the stream.
if (BitsLeft > BitsInCurWord)
return 0;
word_t R2 = CurWord & (~word_t(0) >> (BitsInWord - BitsLeft));
// Use a mask to avoid undefined behavior.
CurWord >>= (BitsLeft & Mask);
BitsInCurWord -= BitsLeft;
R |= R2 << (NumBits - BitsLeft);
return R;
}
uint32_t ReadVBR(unsigned NumBits) {
uint32_t Piece = Read(NumBits);
if ((Piece & (1U << (NumBits-1))) == 0)
return Piece;
uint32_t Result = 0;
unsigned NextBit = 0;
while (1) {
Result |= (Piece & ((1U << (NumBits-1))-1)) << NextBit;
if ((Piece & (1U << (NumBits-1))) == 0)
return Result;
NextBit += NumBits-1;
Piece = Read(NumBits);
}
}
// Read a VBR that may have a value up to 64-bits in size. The chunk size of
// the VBR must still be <= 32 bits though.
uint64_t ReadVBR64(unsigned NumBits) {
uint32_t Piece = Read(NumBits);
if ((Piece & (1U << (NumBits-1))) == 0)
return uint64_t(Piece);
uint64_t Result = 0;
unsigned NextBit = 0;
while (1) {
Result |= uint64_t(Piece & ((1U << (NumBits-1))-1)) << NextBit;
if ((Piece & (1U << (NumBits-1))) == 0)
return Result;
NextBit += NumBits-1;
Piece = Read(NumBits);
}
}
private:
void SkipToFourByteBoundary() {
// If word_t is 64-bits and if we've read less than 32 bits, just dump
// the bits we have up to the next 32-bit boundary.
if (sizeof(word_t) > 4 &&
BitsInCurWord >= 32) {
CurWord >>= BitsInCurWord-32;
BitsInCurWord = 32;
return;
}
BitsInCurWord = 0;
}
public:
unsigned ReadCode() {
return Read(CurCodeSize);
}
// Block header:
// [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
/// Having read the ENTER_SUBBLOCK code, read the BlockID for the block.
unsigned ReadSubBlockID() {
return ReadVBR(bitc::BlockIDWidth);
}
/// Having read the ENTER_SUBBLOCK abbrevid and a BlockID, skip over the body
/// of this block. If the block record is malformed, return true.
bool SkipBlock() {
// Read and ignore the codelen value. Since we are skipping this block, we
// don't care what code widths are used inside of it.
ReadVBR(bitc::CodeLenWidth);
SkipToFourByteBoundary();
unsigned NumFourBytes = Read(bitc::BlockSizeWidth);
// Check that the block wasn't partially defined, and that the offset isn't
// bogus.
size_t SkipTo = GetCurrentBitNo() + NumFourBytes*4*8;
if (AtEndOfStream() || !canSkipToPos(SkipTo/8))
return true;
JumpToBit(SkipTo);
return false;
}
/// Having read the ENTER_SUBBLOCK abbrevid, enter the block, and return true
/// if the block has an error.
bool EnterSubBlock(unsigned BlockID, unsigned *NumWordsP = nullptr);
bool ReadBlockEnd() {
if (BlockScope.empty()) return true;
// Block tail:
// [END_BLOCK, <align4bytes>]
SkipToFourByteBoundary();
popBlockScope();
return false;
}
private:
void popBlockScope() {
CurCodeSize = BlockScope.back().PrevCodeSize;
CurAbbrevs = std::move(BlockScope.back().PrevAbbrevs);
BlockScope.pop_back();
}
//===--------------------------------------------------------------------===//
// Record Processing
//===--------------------------------------------------------------------===//
public:
/// Return the abbreviation for the specified AbbrevId.
const BitCodeAbbrev *getAbbrev(unsigned AbbrevID) {
unsigned AbbrevNo = AbbrevID-bitc::FIRST_APPLICATION_ABBREV;
assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
return CurAbbrevs[AbbrevNo].get();
}
/// Read the current record and discard it.
void skipRecord(unsigned AbbrevID);
unsigned readRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals,
StringRef *Blob = nullptr);
//===--------------------------------------------------------------------===//
// Abbrev Processing
//===--------------------------------------------------------------------===//
void ReadAbbrevRecord();
bool ReadBlockInfoBlock();
};
} // End llvm namespace
#endif