llvm-6502/include/llvm/Bitcode/BitstreamReader.h
Chris Lattner 519e1475d6 use memcpy instead of dubious union to type pun two values,
thanks to David Blaike for pointing this out.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175032 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-13 04:53:40 +00:00

559 lines
17 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/ADT/OwningPtr.h"
#include "llvm/Bitcode/BitCodes.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/StreamableMemoryObject.h"
#include <climits>
#include <string>
#include <vector>
namespace llvm {
class Deserializer;
/// BitstreamReader - 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:
/// BlockInfo - 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<BitCodeAbbrev*> Abbrevs;
std::string Name;
std::vector<std::pair<unsigned, std::string> > RecordNames;
};
private:
OwningPtr<StreamableMemoryObject> BitcodeBytes;
std::vector<BlockInfo> BlockInfoRecords;
/// IgnoreBlockInfoNames - 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(StreamableMemoryObject *bytes) {
BitcodeBytes.reset(bytes);
}
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));
}
StreamableMemoryObject &getBitcodeBytes() { return *BitcodeBytes; }
~BitstreamReader() {
// Free the BlockInfoRecords.
while (!BlockInfoRecords.empty()) {
BlockInfo &Info = BlockInfoRecords.back();
// Free blockinfo abbrev info.
for (unsigned i = 0, e = static_cast<unsigned>(Info.Abbrevs.size());
i != e; ++i)
Info.Abbrevs[i]->dropRef();
BlockInfoRecords.pop_back();
}
}
/// CollectBlockInfoNames - This is called by clients that want block/record
/// name information.
void CollectBlockInfoNames() { IgnoreBlockInfoNames = false; }
bool isIgnoringBlockInfoNames() { return IgnoreBlockInfoNames; }
//===--------------------------------------------------------------------===//
// Block Manipulation
//===--------------------------------------------------------------------===//
/// hasBlockInfoRecords - 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(); }
/// getBlockInfo - 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 0;
}
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();
}
};
/// BitstreamEntry - When advancing through a bitstream cursor, each advance can
/// discover a few different kinds of entries:
/// 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.
///
struct BitstreamEntry {
enum {
Error,
EndBlock,
SubBlock,
Record
} 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;
}
};
/// BitstreamCursor - 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;
/// CurWord/word_t - 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 uint32_t word_t;
word_t CurWord;
/// BitsInCurWord - This is the number of bits in CurWord that are valid. This
/// is always from [0...31/63] inclusive (depending on word size).
unsigned BitsInCurWord;
// CurCodeSize - This is the declared size of code values used for the current
// block, in bits.
unsigned CurCodeSize;
/// CurAbbrevs - Abbrevs installed at in this block.
std::vector<BitCodeAbbrev*> CurAbbrevs;
struct Block {
unsigned PrevCodeSize;
std::vector<BitCodeAbbrev*> PrevAbbrevs;
explicit Block(unsigned PCS) : PrevCodeSize(PCS) {}
};
/// BlockScope - This tracks the codesize of parent blocks.
SmallVector<Block, 8> BlockScope;
public:
BitstreamCursor() : BitStream(0), NextChar(0) {
}
BitstreamCursor(const BitstreamCursor &RHS) : BitStream(0), NextChar(0) {
operator=(RHS);
}
explicit BitstreamCursor(BitstreamReader &R) : BitStream(&R) {
NextChar = 0;
CurWord = 0;
BitsInCurWord = 0;
CurCodeSize = 2;
}
void init(BitstreamReader &R) {
freeState();
BitStream = &R;
NextChar = 0;
CurWord = 0;
BitsInCurWord = 0;
CurCodeSize = 2;
}
~BitstreamCursor() {
freeState();
}
void operator=(const BitstreamCursor &RHS);
void freeState();
bool isEndPos(size_t pos) {
return BitStream->getBitcodeBytes().isObjectEnd(static_cast<uint64_t>(pos));
}
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));
}
uint32_t getWord(size_t pos) {
uint8_t buf[4] = { 0xFF, 0xFF, 0xFF, 0xFF };
BitStream->getBitcodeBytes().readBytes(pos, sizeof(buf), buf, NULL);
return *reinterpret_cast<support::ulittle32_t *>(buf);
}
bool AtEndOfStream() {
return BitsInCurWord == 0 && isEndPos(NextChar);
}
/// getAbbrevIDWidth - Return the number of bits used to encode an abbrev #.
unsigned getAbbrevIDWidth() const { return CurCodeSize; }
/// GetCurrentBitNo - 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 {
/// AF_DontPopBlockAtEnd - 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,
/// AF_DontAutoprocessAbbrevs - If this flag is used, abbrev entries are
/// returned just like normal records.
AF_DontAutoprocessAbbrevs = 2
};
/// advance - 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);
}
}
/// advanceSkippingSubblocks - 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();
}
}
/// JumpToBit - 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;
CurWord = 0;
// Skip over any bits that are already consumed.
if (WordBitNo) {
if (sizeof(word_t) > 4)
Read64(WordBitNo);
else
Read(WordBitNo);
}
}
uint32_t Read(unsigned NumBits) {
assert(NumBits && NumBits <= 32 &&
"Cannot return zero or more than 32 bits!");
// If the field is fully contained by CurWord, return it quickly.
if (BitsInCurWord >= NumBits) {
uint32_t R = uint32_t(CurWord) & (~0U >> (32-NumBits));
CurWord >>= NumBits;
BitsInCurWord -= NumBits;
return R;
}
// If we run out of data, stop at the end of the stream.
if (isEndPos(NextChar)) {
CurWord = 0;
BitsInCurWord = 0;
return 0;
}
uint32_t R = uint32_t(CurWord);
// Read the next word from the stream.
uint8_t Array[sizeof(word_t)] = {0};
BitStream->getBitcodeBytes().readBytes(NextChar, sizeof(Array),
Array, NULL);
// Handle big-endian byte-swapping if necessary.
support::detail::packed_endian_specific_integral
<word_t, support::little, support::unaligned> EndianValue;
memcpy(&EndianValue, Array, sizeof(Array));
CurWord = EndianValue;
NextChar += sizeof(word_t);
// Extract NumBits-BitsInCurWord from what we just read.
unsigned BitsLeft = NumBits-BitsInCurWord;
// Be careful here, BitsLeft is in the range [1..32]/[1..64] inclusive.
R |= uint32_t((CurWord & (word_t(~0ULL) >> (sizeof(word_t)*8-BitsLeft)))
<< BitsInCurWord);
// BitsLeft bits have just been used up from CurWord. BitsLeft is in the
// range [1..32]/[1..64] so be careful how we shift.
if (BitsLeft != sizeof(word_t)*8)
CurWord >>= BitsLeft;
else
CurWord = 0;
BitsInCurWord = sizeof(word_t)*8-BitsLeft;
return R;
}
uint64_t Read64(unsigned NumBits) {
if (NumBits <= 32) return Read(NumBits);
uint64_t V = Read(32);
return V | (uint64_t)Read(NumBits-32) << 32;
}
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);
}
}
// ReadVBR64 - 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;
CurWord = 0;
}
public:
unsigned ReadCode() {
return Read(CurCodeSize);
}
// Block header:
// [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
/// ReadSubBlockID - Having read the ENTER_SUBBLOCK code, read the BlockID for
/// the block.
unsigned ReadSubBlockID() {
return ReadVBR(bitc::BlockIDWidth);
}
/// SkipBlock - 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;
}
/// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter
/// the block, and return true if the block has an error.
bool EnterSubBlock(unsigned BlockID, unsigned *NumWordsP = 0);
bool ReadBlockEnd() {
if (BlockScope.empty()) return true;
// Block tail:
// [END_BLOCK, <align4bytes>]
SkipToFourByteBoundary();
popBlockScope();
return false;
}
private:
void popBlockScope() {
CurCodeSize = BlockScope.back().PrevCodeSize;
// Delete abbrevs from popped scope.
for (unsigned i = 0, e = static_cast<unsigned>(CurAbbrevs.size());
i != e; ++i)
CurAbbrevs[i]->dropRef();
BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
BlockScope.pop_back();
}
//===--------------------------------------------------------------------===//
// Record Processing
//===--------------------------------------------------------------------===//
private:
void readAbbreviatedLiteral(const BitCodeAbbrevOp &Op,
SmallVectorImpl<uint64_t> &Vals);
void readAbbreviatedField(const BitCodeAbbrevOp &Op,
SmallVectorImpl<uint64_t> &Vals);
void skipAbbreviatedField(const BitCodeAbbrevOp &Op);
public:
/// getAbbrev - 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];
}
/// skipRecord - Read the current record and discard it.
void skipRecord(unsigned AbbrevID);
unsigned readRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals,
StringRef *Blob = 0);
//===--------------------------------------------------------------------===//
// Abbrev Processing
//===--------------------------------------------------------------------===//
void ReadAbbrevRecord();
bool ReadBlockInfoBlock();
};
} // End llvm namespace
#endif