| //===- BitstreamReader.h - Low-level bitstream reader interface -*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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/ArrayRef.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/Bitcode/BitCodes.h" |
| #include "llvm/Support/Endian.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/MemoryBuffer.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <climits> |
| #include <cstddef> |
| #include <cstdint> |
| #include <memory> |
| #include <string> |
| #include <utility> |
| #include <vector> |
| |
| namespace llvm { |
| |
| /// This class maintains the abbreviations read from a block info block. |
| class BitstreamBlockInfo { |
| 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<std::shared_ptr<BitCodeAbbrev>> Abbrevs; |
| std::string Name; |
| std::vector<std::pair<unsigned, std::string>> RecordNames; |
| }; |
| |
| private: |
| std::vector<BlockInfo> BlockInfoRecords; |
| |
| public: |
| /// 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.emplace_back(); |
| BlockInfoRecords.back().BlockID = BlockID; |
| return BlockInfoRecords.back(); |
| } |
| }; |
| |
| /// This represents a position within a bitstream. There may be multiple |
| /// independent cursors reading within one bitstream, each maintaining their |
| /// own local state. |
| class SimpleBitstreamCursor { |
| ArrayRef<uint8_t> BitcodeBytes; |
| size_t NextChar = 0; |
| |
| public: |
| /// 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. |
| using word_t = size_t; |
| |
| private: |
| word_t CurWord = 0; |
| |
| /// This is the number of bits in CurWord that are valid. This is always from |
| /// [0...bits_of(size_t)-1] inclusive. |
| unsigned BitsInCurWord = 0; |
| |
| public: |
| static const size_t MaxChunkSize = sizeof(word_t) * 8; |
| |
| SimpleBitstreamCursor() = default; |
| explicit SimpleBitstreamCursor(ArrayRef<uint8_t> BitcodeBytes) |
| : BitcodeBytes(BitcodeBytes) {} |
| explicit SimpleBitstreamCursor(StringRef BitcodeBytes) |
| : BitcodeBytes(reinterpret_cast<const uint8_t *>(BitcodeBytes.data()), |
| BitcodeBytes.size()) {} |
| explicit SimpleBitstreamCursor(MemoryBufferRef BitcodeBytes) |
| : SimpleBitstreamCursor(BitcodeBytes.getBuffer()) {} |
| |
| 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 <= BitcodeBytes.size(); |
| } |
| |
| bool AtEndOfStream() { |
| return BitsInCurWord == 0 && BitcodeBytes.size() <= NextChar; |
| } |
| |
| /// Return the bit # of the bit we are reading. |
| uint64_t GetCurrentBitNo() const { |
| return NextChar*CHAR_BIT - BitsInCurWord; |
| } |
| |
| // Return the byte # of the current bit. |
| uint64_t getCurrentByteNo() const { return GetCurrentBitNo() / 8; } |
| |
| ArrayRef<uint8_t> getBitcodeBytes() const { return BitcodeBytes; } |
| |
| /// Reset the stream to the specified bit number. |
| void JumpToBit(uint64_t BitNo) { |
| size_t ByteNo = size_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); |
| } |
| |
| /// Get a pointer into the bitstream at the specified byte offset. |
| const uint8_t *getPointerToByte(uint64_t ByteNo, uint64_t NumBytes) { |
| return BitcodeBytes.data() + ByteNo; |
| } |
| |
| /// Get a pointer into the bitstream at the specified bit offset. |
| /// |
| /// The bit offset must be on a byte boundary. |
| const uint8_t *getPointerToBit(uint64_t BitNo, uint64_t NumBytes) { |
| assert(!(BitNo % 8) && "Expected bit on byte boundary"); |
| return getPointerToByte(BitNo / 8, NumBytes); |
| } |
| |
| void fillCurWord() { |
| if (NextChar >= BitcodeBytes.size()) |
| report_fatal_error("Unexpected end of file"); |
| |
| // Read the next word from the stream. |
| const uint8_t *NextCharPtr = BitcodeBytes.data() + NextChar; |
| unsigned BytesRead; |
| if (BitcodeBytes.size() >= NextChar + sizeof(word_t)) { |
| BytesRead = sizeof(word_t); |
| CurWord = |
| support::endian::read<word_t, support::little, support::unaligned>( |
| NextCharPtr); |
| } else { |
| // Short read. |
| BytesRead = BitcodeBytes.size() - NextChar; |
| CurWord = 0; |
| for (unsigned B = 0; B != BytesRead; ++B) |
| CurWord |= uint64_t(NextCharPtr[B]) << (B * 8); |
| } |
| NextChar += BytesRead; |
| BitsInCurWord = BytesRead * 8; |
| } |
| |
| word_t Read(unsigned NumBits) { |
| static const unsigned BitsInWord = MaxChunkSize; |
| |
| 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, abort. |
| if (BitsLeft > BitsInCurWord) |
| report_fatal_error("Unexpected end of file"); |
| |
| 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 (true) { |
| 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 (true) { |
| Result |= uint64_t(Piece & ((1U << (NumBits-1))-1)) << NextBit; |
| |
| if ((Piece & (1U << (NumBits-1))) == 0) |
| return Result; |
| |
| NextBit += NumBits-1; |
| Piece = Read(NumBits); |
| } |
| } |
| |
| 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; |
| } |
| |
| /// Skip to the end of the file. |
| void skipToEnd() { NextChar = BitcodeBytes.size(); } |
| }; |
| |
| /// 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, implemented on top of a |
| /// SimpleBitstreamCursor. |
| /// |
| /// Unlike iterators, BitstreamCursors are heavy-weight objects that should not |
| /// be passed by value. |
| class BitstreamCursor : SimpleBitstreamCursor { |
| // This is the declared size of code values used for the current block, in |
| // bits. |
| unsigned CurCodeSize = 2; |
| |
| /// Abbrevs installed at in this block. |
| std::vector<std::shared_ptr<BitCodeAbbrev>> CurAbbrevs; |
| |
| struct Block { |
| unsigned PrevCodeSize; |
| std::vector<std::shared_ptr<BitCodeAbbrev>> PrevAbbrevs; |
| |
| explicit Block(unsigned PCS) : PrevCodeSize(PCS) {} |
| }; |
| |
| /// This tracks the codesize of parent blocks. |
| SmallVector<Block, 8> BlockScope; |
| |
| BitstreamBlockInfo *BlockInfo = nullptr; |
| |
| public: |
| static const size_t MaxChunkSize = sizeof(word_t) * 8; |
| |
| BitstreamCursor() = default; |
| explicit BitstreamCursor(ArrayRef<uint8_t> BitcodeBytes) |
| : SimpleBitstreamCursor(BitcodeBytes) {} |
| explicit BitstreamCursor(StringRef BitcodeBytes) |
| : SimpleBitstreamCursor(BitcodeBytes) {} |
| explicit BitstreamCursor(MemoryBufferRef BitcodeBytes) |
| : SimpleBitstreamCursor(BitcodeBytes) {} |
| |
| using SimpleBitstreamCursor::canSkipToPos; |
| using SimpleBitstreamCursor::AtEndOfStream; |
| using SimpleBitstreamCursor::getBitcodeBytes; |
| using SimpleBitstreamCursor::GetCurrentBitNo; |
| using SimpleBitstreamCursor::getCurrentByteNo; |
| using SimpleBitstreamCursor::getPointerToByte; |
| using SimpleBitstreamCursor::JumpToBit; |
| using SimpleBitstreamCursor::fillCurWord; |
| using SimpleBitstreamCursor::Read; |
| using SimpleBitstreamCursor::ReadVBR; |
| using SimpleBitstreamCursor::ReadVBR64; |
| |
| /// Return the number of bits used to encode an abbrev #. |
| unsigned getAbbrevIDWidth() const { return CurCodeSize; } |
| |
| /// 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 (true) { |
| if (AtEndOfStream()) |
| return BitstreamEntry::getError(); |
| |
| 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 (true) { |
| // 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(); |
| } |
| } |
| |
| 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(); |
| size_t 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; |
| if (AbbrevNo >= CurAbbrevs.size()) |
| report_fatal_error("Invalid abbrev number"); |
| return CurAbbrevs[AbbrevNo].get(); |
| } |
| |
| /// Read the current record and discard it, returning the code for the record. |
| unsigned skipRecord(unsigned AbbrevID); |
| |
| unsigned readRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals, |
| StringRef *Blob = nullptr); |
| |
| //===--------------------------------------------------------------------===// |
| // Abbrev Processing |
| //===--------------------------------------------------------------------===// |
| void ReadAbbrevRecord(); |
| |
| /// Read and return a block info block from the bitstream. If an error was |
| /// encountered, return None. |
| /// |
| /// \param ReadBlockInfoNames Whether to read block/record name information in |
| /// the BlockInfo block. Only llvm-bcanalyzer uses this. |
| Optional<BitstreamBlockInfo> |
| ReadBlockInfoBlock(bool ReadBlockInfoNames = false); |
| |
| /// Set the block info to be used by this BitstreamCursor to interpret |
| /// abbreviated records. |
| void setBlockInfo(BitstreamBlockInfo *BI) { BlockInfo = BI; } |
| }; |
| |
| } // end llvm namespace |
| |
| #endif // LLVM_BITCODE_BITSTREAMREADER_H |