llvm-6502/include/llvm/Bitcode/BitstreamReader.h
2009-04-15 04:53:47 +00:00

529 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 BITSTREAM_READER_H
#define BITSTREAM_READER_H
#include "llvm/Bitcode/BitCodes.h"
#include <climits>
#include <vector>
namespace llvm {
class Deserializer;
class BitstreamReader {
const unsigned char *NextChar;
const unsigned char *LastChar;
friend class Deserializer;
/// CurWord - This is the current data we have pulled from the stream but have
/// not returned to the client.
uint32_t CurWord;
/// BitsInCurWord - This is the number of bits in CurWord that are valid. This
/// is always from [0...31] inclusive.
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;
/// 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::vector<BlockInfo> BlockInfoRecords;
/// FirstChar - This remembers the first byte of the stream.
const unsigned char *FirstChar;
public:
BitstreamReader() {
NextChar = FirstChar = LastChar = 0;
CurWord = 0;
BitsInCurWord = 0;
CurCodeSize = 0;
}
BitstreamReader(const unsigned char *Start, const unsigned char *End) {
init(Start, End);
}
void init(const unsigned char *Start, const unsigned char *End) {
NextChar = FirstChar = Start;
LastChar = End;
assert(((End-Start) & 3) == 0 &&"Bitcode stream not a multiple of 4 bytes");
CurWord = 0;
BitsInCurWord = 0;
CurCodeSize = 2;
}
~BitstreamReader() {
// Abbrevs could still exist if the stream was broken. If so, don't leak
// them.
for (unsigned i = 0, e = static_cast<unsigned>(CurAbbrevs.size());
i != e; ++i)
CurAbbrevs[i]->dropRef();
for (unsigned S = 0, e = static_cast<unsigned>(BlockScope.size());
S != e; ++S) {
std::vector<BitCodeAbbrev*> &Abbrevs = BlockScope[S].PrevAbbrevs;
for (unsigned i = 0, e = static_cast<unsigned>(Abbrevs.size());
i != e; ++i)
Abbrevs[i]->dropRef();
}
// 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();
}
}
bool AtEndOfStream() const {
return NextChar == LastChar && BitsInCurWord == 0;
}
/// GetCurrentBitNo - Return the bit # of the bit we are reading.
uint64_t GetCurrentBitNo() const {
return (NextChar-FirstChar)*CHAR_BIT - BitsInCurWord;
}
/// JumpToBit - Reset the stream to the specified bit number.
void JumpToBit(uint64_t BitNo) {
uintptr_t ByteNo = uintptr_t(BitNo/8) & ~3;
uintptr_t WordBitNo = uintptr_t(BitNo) & 31;
assert(ByteNo <= (uintptr_t)(LastChar-FirstChar) && "Invalid location");
// Move the cursor to the right word.
NextChar = FirstChar+ByteNo;
BitsInCurWord = 0;
CurWord = 0;
// Skip over any bits that are already consumed.
if (WordBitNo) {
Read(static_cast<unsigned>(WordBitNo));
}
}
/// GetAbbrevIDWidth - Return the number of bits used to encode an abbrev #.
unsigned GetAbbrevIDWidth() const { return CurCodeSize; }
uint32_t Read(unsigned NumBits) {
// If the field is fully contained by CurWord, return it quickly.
if (BitsInCurWord >= NumBits) {
uint32_t R = CurWord & ((1U << NumBits)-1);
CurWord >>= NumBits;
BitsInCurWord -= NumBits;
return R;
}
// If we run out of data, stop at the end of the stream.
if (NextChar == LastChar) {
CurWord = 0;
BitsInCurWord = 0;
return 0;
}
unsigned R = CurWord;
// Read the next word from the stream.
CurWord = (NextChar[0] << 0) | (NextChar[1] << 8) |
(NextChar[2] << 16) | (NextChar[3] << 24);
NextChar += 4;
// Extract NumBits-BitsInCurWord from what we just read.
unsigned BitsLeft = NumBits-BitsInCurWord;
// Be careful here, BitsLeft is in the range [1..32] inclusive.
R |= (CurWord & (~0U >> (32-BitsLeft))) << BitsInCurWord;
// BitsLeft bits have just been used up from CurWord.
if (BitsLeft != 32)
CurWord >>= BitsLeft;
else
CurWord = 0;
BitsInCurWord = 32-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);
}
}
uint64_t ReadVBR64(unsigned NumBits) {
uint64_t Piece = Read(NumBits);
if ((Piece & (1U << (NumBits-1))) == 0)
return Piece;
uint64_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);
}
}
void SkipToWord() {
BitsInCurWord = 0;
CurWord = 0;
}
unsigned ReadCode() {
return Read(CurCodeSize);
}
//===--------------------------------------------------------------------===//
// Block Manipulation
//===--------------------------------------------------------------------===//
private:
/// getBlockInfo - If there is block info for the specified ID, return it,
/// otherwise return null.
BlockInfo *getBlockInfo(unsigned BlockID) {
// 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;
}
public:
// 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);
SkipToWord();
unsigned NumWords = Read(bitc::BlockSizeWidth);
// Check that the block wasn't partially defined, and that the offset isn't
// bogus.
if (AtEndOfStream() || NextChar+NumWords*4 > LastChar)
return true;
NextChar += NumWords*4;
return false;
}
/// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter
/// the block, and return true if the block is valid.
bool EnterSubBlock(unsigned BlockID, unsigned *NumWordsP = 0) {
// Save the current block's state on BlockScope.
BlockScope.push_back(Block(CurCodeSize));
BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
// Add the abbrevs specific to this block to the CurAbbrevs list.
if (BlockInfo *Info = getBlockInfo(BlockID)) {
for (unsigned i = 0, e = static_cast<unsigned>(Info->Abbrevs.size());
i != e; ++i) {
CurAbbrevs.push_back(Info->Abbrevs[i]);
CurAbbrevs.back()->addRef();
}
}
// Get the codesize of this block.
CurCodeSize = ReadVBR(bitc::CodeLenWidth);
SkipToWord();
unsigned NumWords = Read(bitc::BlockSizeWidth);
if (NumWordsP) *NumWordsP = NumWords;
// Validate that this block is sane.
if (CurCodeSize == 0 || AtEndOfStream() || NextChar+NumWords*4 > LastChar)
return true;
return false;
}
bool ReadBlockEnd() {
if (BlockScope.empty()) return true;
// Block tail:
// [END_BLOCK, <align4bytes>]
SkipToWord();
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) {
assert(Op.isLiteral() && "Not a literal");
// If the abbrev specifies the literal value to use, use it.
Vals.push_back(Op.getLiteralValue());
}
void ReadAbbreviatedField(const BitCodeAbbrevOp &Op,
SmallVectorImpl<uint64_t> &Vals) {
assert(!Op.isLiteral() && "Use ReadAbbreviatedLiteral for literals!");
// Decode the value as we are commanded.
switch (Op.getEncoding()) {
default: assert(0 && "Unknown encoding!");
case BitCodeAbbrevOp::Fixed:
Vals.push_back(Read((unsigned)Op.getEncodingData()));
break;
case BitCodeAbbrevOp::VBR:
Vals.push_back(ReadVBR64((unsigned)Op.getEncodingData()));
break;
case BitCodeAbbrevOp::Char6:
Vals.push_back(BitCodeAbbrevOp::DecodeChar6(Read(6)));
break;
}
}
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];
}
unsigned ReadRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals,
const char **BlobStart = 0, unsigned *BlobLen = 0) {
if (AbbrevID == bitc::UNABBREV_RECORD) {
unsigned Code = ReadVBR(6);
unsigned NumElts = ReadVBR(6);
for (unsigned i = 0; i != NumElts; ++i)
Vals.push_back(ReadVBR64(6));
return Code;
}
const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
if (Op.isLiteral()) {
ReadAbbreviatedLiteral(Op, Vals);
} else if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
// Array case. Read the number of elements as a vbr6.
unsigned NumElts = ReadVBR(6);
// Get the element encoding.
assert(i+2 == e && "array op not second to last?");
const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
// Read all the elements.
for (; NumElts; --NumElts)
ReadAbbreviatedField(EltEnc, Vals);
} else if (Op.getEncoding() == BitCodeAbbrevOp::Blob) {
// Blob case. Read the number of bytes as a vbr6.
unsigned NumElts = ReadVBR(6);
SkipToWord(); // 32-bit alignment
// Figure out where the end of this blob will be including tail padding.
const unsigned char *NewEnd = NextChar+((NumElts+3)&~3);
// If this would read off the end of the bitcode file, just set the
// record to empty and return.
if (NewEnd > LastChar) {
Vals.append(NumElts, 0);
NextChar = LastChar;
break;
}
// Otherwise, read the number of bytes. If we can return a reference to
// the data, do so to avoid copying it.
if (BlobStart) {
*BlobStart = (const char*)NextChar;
*BlobLen = NumElts;
} else {
for (; NumElts; ++NextChar, --NumElts)
Vals.push_back(*NextChar);
}
// Skip over tail padding.
NextChar = NewEnd;
} else {
ReadAbbreviatedField(Op, Vals);
}
}
unsigned Code = (unsigned)Vals[0];
Vals.erase(Vals.begin());
return Code;
}
unsigned ReadRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals,
const char *&BlobStart, unsigned &BlobLen) {
return ReadRecord(AbbrevID, Vals, &BlobStart, &BlobLen);
}
//===--------------------------------------------------------------------===//
// Abbrev Processing
//===--------------------------------------------------------------------===//
void ReadAbbrevRecord() {
BitCodeAbbrev *Abbv = new BitCodeAbbrev();
unsigned NumOpInfo = ReadVBR(5);
for (unsigned i = 0; i != NumOpInfo; ++i) {
bool IsLiteral = Read(1) ? true : false;
if (IsLiteral) {
Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8)));
continue;
}
BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3);
if (BitCodeAbbrevOp::hasEncodingData(E))
Abbv->Add(BitCodeAbbrevOp(E, ReadVBR64(5)));
else
Abbv->Add(BitCodeAbbrevOp(E));
}
CurAbbrevs.push_back(Abbv);
}
//===--------------------------------------------------------------------===//
// BlockInfo Block Reading
//===--------------------------------------------------------------------===//
private:
BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
if (BlockInfo *BI = getBlockInfo(BlockID))
return *BI;
// Otherwise, add a new record.
BlockInfoRecords.push_back(BlockInfo());
BlockInfoRecords.back().BlockID = BlockID;
return BlockInfoRecords.back();
}
public:
bool ReadBlockInfoBlock() {
if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true;
SmallVector<uint64_t, 64> Record;
BlockInfo *CurBlockInfo = 0;
// Read all the records for this module.
while (1) {
unsigned Code = ReadCode();
if (Code == bitc::END_BLOCK)
return ReadBlockEnd();
if (Code == bitc::ENTER_SUBBLOCK) {
ReadSubBlockID();
if (SkipBlock()) return true;
continue;
}
// Read abbrev records, associate them with CurBID.
if (Code == bitc::DEFINE_ABBREV) {
if (!CurBlockInfo) return true;
ReadAbbrevRecord();
// ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the
// appropriate BlockInfo.
BitCodeAbbrev *Abbv = CurAbbrevs.back();
CurAbbrevs.pop_back();
CurBlockInfo->Abbrevs.push_back(Abbv);
continue;
}
// Read a record.
Record.clear();
switch (ReadRecord(Code, Record)) {
default: break; // Default behavior, ignore unknown content.
case bitc::BLOCKINFO_CODE_SETBID:
if (Record.size() < 1) return true;
CurBlockInfo = &getOrCreateBlockInfo((unsigned)Record[0]);
break;
}
}
}
};
} // End llvm namespace
#endif