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the bits in those bytes. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36861 91177308-0d34-0410-b5e6-96231b3b80d8
466 lines
14 KiB
C++
466 lines
14 KiB
C++
//===- BitstreamReader.h - Low-level bitstream reader interface -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This header defines the BitstreamReader class. This class can be used to
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// read an arbitrary bitstream, regardless of its contents.
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//
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//===----------------------------------------------------------------------===//
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#ifndef BITSTREAM_READER_H
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#define BITSTREAM_READER_H
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#include "llvm/Bitcode/BitCodes.h"
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#include <vector>
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namespace llvm {
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class BitstreamReader {
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const unsigned char *NextChar;
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const unsigned char *LastChar;
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/// CurWord - This is the current data we have pulled from the stream but have
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/// not returned to the client.
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uint32_t CurWord;
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/// BitsInCurWord - This is the number of bits in CurWord that are valid. This
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/// is always from [0...31] inclusive.
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unsigned BitsInCurWord;
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// CurCodeSize - This is the declared size of code values used for the current
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// block, in bits.
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unsigned CurCodeSize;
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/// CurAbbrevs - Abbrevs installed at in this block.
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std::vector<BitCodeAbbrev*> CurAbbrevs;
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struct Block {
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unsigned PrevCodeSize;
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std::vector<BitCodeAbbrev*> PrevAbbrevs;
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explicit Block(unsigned PCS) : PrevCodeSize(PCS) {}
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};
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/// BlockScope - This tracks the codesize of parent blocks.
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SmallVector<Block, 8> BlockScope;
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/// BlockInfo - This contains information emitted to BLOCKINFO_BLOCK blocks.
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/// These describe abbreviations that all blocks of the specified ID inherit.
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struct BlockInfo {
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unsigned BlockID;
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std::vector<BitCodeAbbrev*> Abbrevs;
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};
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std::vector<BlockInfo> BlockInfoRecords;
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/// FirstChar - This remembers the first byte of the stream.
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const unsigned char *FirstChar;
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public:
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BitstreamReader() {
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NextChar = FirstChar = LastChar = 0;
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CurWord = 0;
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BitsInCurWord = 0;
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CurCodeSize = 0;
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}
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BitstreamReader(const unsigned char *Start, const unsigned char *End) {
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init(Start, End);
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}
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void init(const unsigned char *Start, const unsigned char *End) {
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NextChar = FirstChar = Start;
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LastChar = End;
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assert(((End-Start) & 3) == 0 &&"Bitcode stream not a multiple of 4 bytes");
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CurWord = 0;
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BitsInCurWord = 0;
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CurCodeSize = 2;
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}
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~BitstreamReader() {
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// Abbrevs could still exist if the stream was broken. If so, don't leak
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// them.
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for (unsigned i = 0, e = CurAbbrevs.size(); i != e; ++i)
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CurAbbrevs[i]->dropRef();
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for (unsigned S = 0, e = BlockScope.size(); S != e; ++S) {
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std::vector<BitCodeAbbrev*> &Abbrevs = BlockScope[S].PrevAbbrevs;
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for (unsigned i = 0, e = Abbrevs.size(); i != e; ++i)
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Abbrevs[i]->dropRef();
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}
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// Free the BlockInfoRecords.
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while (!BlockInfoRecords.empty()) {
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BlockInfo &Info = BlockInfoRecords.back();
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// Free blockinfo abbrev info.
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for (unsigned i = 0, e = Info.Abbrevs.size(); i != e; ++i)
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Info.Abbrevs[i]->dropRef();
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BlockInfoRecords.pop_back();
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}
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}
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bool AtEndOfStream() const {
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return NextChar == LastChar && BitsInCurWord == 0;
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}
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/// GetCurrentBitNo - Return the bit # of the bit we are reading.
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uint64_t GetCurrentBitNo() const {
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return (NextChar-FirstChar)*8 + ((32-BitsInCurWord) & 31);
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}
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/// JumpToBit - Reset the stream to the specified bit number.
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void JumpToBit(uint64_t BitNo) {
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uintptr_t ByteNo = uintptr_t(BitNo/8) & ~3;
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uintptr_t WordBitNo = uintptr_t(BitNo) & 31;
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assert(ByteNo < (uintptr_t)(LastChar-FirstChar) && "Invalid location");
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// Move the cursor to the right word.
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NextChar = FirstChar+ByteNo;
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BitsInCurWord = 0;
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// Skip over any bits that are already consumed.
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if (WordBitNo) {
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NextChar -= 4;
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Read(WordBitNo);
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}
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}
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/// GetAbbrevIDWidth - Return the number of bits used to encode an abbrev #.
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unsigned GetAbbrevIDWidth() const { return CurCodeSize; }
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uint32_t Read(unsigned NumBits) {
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// If the field is fully contained by CurWord, return it quickly.
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if (BitsInCurWord >= NumBits) {
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uint32_t R = CurWord & ((1U << NumBits)-1);
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CurWord >>= NumBits;
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BitsInCurWord -= NumBits;
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return R;
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}
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// If we run out of data, stop at the end of the stream.
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if (LastChar == NextChar) {
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CurWord = 0;
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BitsInCurWord = 0;
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return 0;
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}
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unsigned R = CurWord;
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// Read the next word from the stream.
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CurWord = (NextChar[0] << 0) | (NextChar[1] << 8) |
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(NextChar[2] << 16) | (NextChar[3] << 24);
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NextChar += 4;
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// Extract NumBits-BitsInCurWord from what we just read.
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unsigned BitsLeft = NumBits-BitsInCurWord;
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// Be careful here, BitsLeft is in the range [1..32] inclusive.
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R |= (CurWord & (~0U >> (32-BitsLeft))) << BitsInCurWord;
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// BitsLeft bits have just been used up from CurWord.
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if (BitsLeft != 32)
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CurWord >>= BitsLeft;
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else
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CurWord = 0;
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BitsInCurWord = 32-BitsLeft;
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return R;
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}
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uint64_t Read64(unsigned NumBits) {
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if (NumBits <= 32) return Read(NumBits);
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uint64_t V = Read(32);
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return V | (uint64_t)Read(NumBits-32) << 32;
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}
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uint32_t ReadVBR(unsigned NumBits) {
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uint32_t Piece = Read(NumBits);
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if ((Piece & (1U << (NumBits-1))) == 0)
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return Piece;
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uint32_t Result = 0;
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unsigned NextBit = 0;
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while (1) {
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Result |= (Piece & ((1U << (NumBits-1))-1)) << NextBit;
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if ((Piece & (1U << (NumBits-1))) == 0)
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return Result;
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NextBit += NumBits-1;
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Piece = Read(NumBits);
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}
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}
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uint64_t ReadVBR64(unsigned NumBits) {
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uint64_t Piece = Read(NumBits);
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if ((Piece & (1U << (NumBits-1))) == 0)
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return Piece;
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uint64_t Result = 0;
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unsigned NextBit = 0;
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while (1) {
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Result |= (Piece & ((1U << (NumBits-1))-1)) << NextBit;
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if ((Piece & (1U << (NumBits-1))) == 0)
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return Result;
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NextBit += NumBits-1;
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Piece = Read(NumBits);
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}
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}
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void SkipToWord() {
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BitsInCurWord = 0;
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CurWord = 0;
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}
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unsigned ReadCode() {
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return Read(CurCodeSize);
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}
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//===--------------------------------------------------------------------===//
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// Block Manipulation
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//===--------------------------------------------------------------------===//
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private:
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/// getBlockInfo - If there is block info for the specified ID, return it,
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/// otherwise return null.
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BlockInfo *getBlockInfo(unsigned BlockID) {
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// Common case, the most recent entry matches BlockID.
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if (!BlockInfoRecords.empty() && BlockInfoRecords.back().BlockID == BlockID)
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return &BlockInfoRecords.back();
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for (unsigned i = 0, e = BlockInfoRecords.size(); i != e; ++i)
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if (BlockInfoRecords[i].BlockID == BlockID)
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return &BlockInfoRecords[i];
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return 0;
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}
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public:
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// Block header:
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// [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
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/// ReadSubBlockID - Having read the ENTER_SUBBLOCK code, read the BlockID for
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/// the block.
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unsigned ReadSubBlockID() {
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return ReadVBR(bitc::BlockIDWidth);
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}
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/// SkipBlock - Having read the ENTER_SUBBLOCK abbrevid and a BlockID, skip
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/// over the body of this block. If the block record is malformed, return
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/// true.
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bool SkipBlock() {
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// Read and ignore the codelen value. Since we are skipping this block, we
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// don't care what code widths are used inside of it.
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ReadVBR(bitc::CodeLenWidth);
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SkipToWord();
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unsigned NumWords = Read(bitc::BlockSizeWidth);
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// Check that the block wasn't partially defined, and that the offset isn't
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// bogus.
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if (AtEndOfStream() || NextChar+NumWords*4 > LastChar)
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return true;
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NextChar += NumWords*4;
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return false;
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}
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/// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, read and enter
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/// the block, returning the BlockID of the block we just entered.
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bool EnterSubBlock(unsigned BlockID, unsigned *NumWordsP = 0) {
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// Save the current block's state on BlockScope.
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BlockScope.push_back(Block(CurCodeSize));
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BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
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// Add the abbrevs specific to this block to the CurAbbrevs list.
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if (BlockInfo *Info = getBlockInfo(BlockID)) {
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for (unsigned i = 0, e = Info->Abbrevs.size(); i != e; ++i) {
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CurAbbrevs.push_back(Info->Abbrevs[i]);
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CurAbbrevs.back()->addRef();
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}
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}
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// Get the codesize of this block.
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CurCodeSize = ReadVBR(bitc::CodeLenWidth);
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SkipToWord();
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unsigned NumWords = Read(bitc::BlockSizeWidth);
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if (NumWordsP) *NumWordsP = NumWords;
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// Validate that this block is sane.
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if (CurCodeSize == 0 || AtEndOfStream() || NextChar+NumWords*4 > LastChar)
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return true;
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return false;
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}
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bool ReadBlockEnd() {
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if (BlockScope.empty()) return true;
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// Block tail:
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// [END_BLOCK, <align4bytes>]
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SkipToWord();
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CurCodeSize = BlockScope.back().PrevCodeSize;
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// Delete abbrevs from popped scope.
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for (unsigned i = 0, e = CurAbbrevs.size(); i != e; ++i)
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CurAbbrevs[i]->dropRef();
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BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
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BlockScope.pop_back();
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return false;
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}
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//===--------------------------------------------------------------------===//
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// Record Processing
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//===--------------------------------------------------------------------===//
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private:
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void ReadAbbreviatedField(const BitCodeAbbrevOp &Op,
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SmallVectorImpl<uint64_t> &Vals) {
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if (Op.isLiteral()) {
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// If the abbrev specifies the literal value to use, use it.
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Vals.push_back(Op.getLiteralValue());
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} else {
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// Decode the value as we are commanded.
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switch (Op.getEncoding()) {
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default: assert(0 && "Unknown encoding!");
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case BitCodeAbbrevOp::Fixed:
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Vals.push_back(Read((unsigned)Op.getEncodingData()));
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break;
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case BitCodeAbbrevOp::VBR:
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Vals.push_back(ReadVBR64((unsigned)Op.getEncodingData()));
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break;
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case BitCodeAbbrevOp::Char6:
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Vals.push_back(BitCodeAbbrevOp::DecodeChar6(Read(6)));
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break;
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}
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}
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}
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public:
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unsigned ReadRecord(unsigned AbbrevID, SmallVectorImpl<uint64_t> &Vals) {
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if (AbbrevID == bitc::UNABBREV_RECORD) {
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unsigned Code = ReadVBR(6);
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unsigned NumElts = ReadVBR(6);
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for (unsigned i = 0; i != NumElts; ++i)
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Vals.push_back(ReadVBR64(6));
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return Code;
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}
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unsigned AbbrevNo = AbbrevID-bitc::FIRST_APPLICATION_ABBREV;
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assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
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BitCodeAbbrev *Abbv = CurAbbrevs[AbbrevNo];
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for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
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const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
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if (Op.isLiteral() || Op.getEncoding() != BitCodeAbbrevOp::Array) {
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ReadAbbreviatedField(Op, Vals);
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} else {
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// Array case. Read the number of elements as a vbr6.
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unsigned NumElts = ReadVBR(6);
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// Get the element encoding.
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assert(i+2 == e && "array op not second to last?");
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const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
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// Read all the elements.
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for (; NumElts; --NumElts)
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ReadAbbreviatedField(EltEnc, Vals);
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}
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}
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unsigned Code = (unsigned)Vals[0];
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Vals.erase(Vals.begin());
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return Code;
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}
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//===--------------------------------------------------------------------===//
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// Abbrev Processing
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//===--------------------------------------------------------------------===//
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void ReadAbbrevRecord() {
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BitCodeAbbrev *Abbv = new BitCodeAbbrev();
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unsigned NumOpInfo = ReadVBR(5);
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for (unsigned i = 0; i != NumOpInfo; ++i) {
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bool IsLiteral = Read(1);
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if (IsLiteral) {
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Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8)));
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continue;
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}
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BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3);
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if (BitCodeAbbrevOp::hasEncodingData(E))
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Abbv->Add(BitCodeAbbrevOp(E, ReadVBR64(5)));
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else
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Abbv->Add(BitCodeAbbrevOp(E));
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}
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CurAbbrevs.push_back(Abbv);
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}
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//===--------------------------------------------------------------------===//
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// BlockInfo Block Reading
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//===--------------------------------------------------------------------===//
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private:
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BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
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if (BlockInfo *BI = getBlockInfo(BlockID))
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return *BI;
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// Otherwise, add a new record.
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BlockInfoRecords.push_back(BlockInfo());
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BlockInfoRecords.back().BlockID = BlockID;
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return BlockInfoRecords.back();
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}
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public:
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bool ReadBlockInfoBlock() {
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if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true;
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SmallVector<uint64_t, 64> Record;
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BlockInfo *CurBlockInfo = 0;
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// Read all the records for this module.
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while (1) {
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unsigned Code = ReadCode();
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if (Code == bitc::END_BLOCK)
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return ReadBlockEnd();
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if (Code == bitc::ENTER_SUBBLOCK) {
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ReadSubBlockID();
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if (SkipBlock()) return true;
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continue;
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}
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// Read abbrev records, associate them with CurBID.
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if (Code == bitc::DEFINE_ABBREV) {
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if (!CurBlockInfo) return true;
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ReadAbbrevRecord();
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// ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the
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// appropriate BlockInfo.
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BitCodeAbbrev *Abbv = CurAbbrevs.back();
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CurAbbrevs.pop_back();
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CurBlockInfo->Abbrevs.push_back(Abbv);
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continue;
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}
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// Read a record.
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Record.clear();
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switch (ReadRecord(Code, Record)) {
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default: break; // Default behavior, ignore unknown content.
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case bitc::BLOCKINFO_CODE_SETBID:
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if (Record.size() < 1) return true;
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CurBlockInfo = &getOrCreateBlockInfo((unsigned)Record[0]);
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break;
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}
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}
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}
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};
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} // End llvm namespace
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#endif
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