[llvm] r264545 - Bitcode: Split out SimpleBitstreamCursor
Duncan P. N. Exon Smith via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 28 21:52:12 PDT 2016
> On 2016-Mar-28, at 21:51, Mehdi Amini <mehdi.amini at apple.com> wrote:
>
>
>> On Mar 27, 2016, at 3:40 PM, Duncan P. N. Exon Smith via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: dexonsmith
>> Date: Sun Mar 27 17:40:55 2016
>> New Revision: 264545
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=264545&view=rev
>> Log:
>> Bitcode: Split out SimpleBitstreamCursor
>>
>> Split out SimpleBitstreamCursor from BitstreamCursor, which is a
>> lower-level cursor with no knowledge of bitcode blocks, abbreviations,
>> or records. It just knows how to read bits and navigate the stream.
>>
>> This is mainly organizational, to separate the API for manipulating raw
>> bits from that for bitcode concepts like Record and Block.
>>
>> Modified:
>> llvm/trunk/include/llvm/Bitcode/BitstreamReader.h
>> llvm/trunk/lib/Bitcode/Reader/BitstreamReader.cpp
>>
>> Modified: llvm/trunk/include/llvm/Bitcode/BitstreamReader.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Bitcode/BitstreamReader.h?rev=264545&r1=264544&r2=264545&view=diff
>> ==============================================================================
>> --- llvm/trunk/include/llvm/Bitcode/BitstreamReader.h (original)
>> +++ llvm/trunk/include/llvm/Bitcode/BitstreamReader.h Sun Mar 27 17:40:55 2016
>> @@ -128,98 +128,42 @@ public:
>> }
>> };
>>
>> -/// 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 {
>> - BitstreamReader *BitStream;
>> - size_t NextChar;
>> +/// 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 {
>> + BitstreamReader *R = nullptr;
>> + size_t NextChar = 0;
>>
>> // The size of the bicode. 0 if we don't know it yet.
>> - size_t Size;
>> + size_t Size = 0;
>>
>> /// 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.
>> +public:
>> typedef size_t word_t;
>> - word_t CurWord;
>> +
>> +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;
>> -
>> - // 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;
>> -
>> + unsigned BitsInCurWord = 0;
>>
>> public:
>> static const size_t MaxChunkSize = sizeof(word_t) * 8;
>>
>> - BitstreamCursor() { init(nullptr); }
>> -
>> - explicit BitstreamCursor(BitstreamReader &R) { init(&R); }
>> -
>> - void init(BitstreamReader *R) {
>> - freeState();
>> + SimpleBitstreamCursor() = default;
>>
>> - BitStream = R;
>> - NextChar = 0;
>> - Size = 0;
>> - BitsInCurWord = 0;
>> - CurCodeSize = 2;
>> - }
>> -
>> - void freeState();
>> + explicit SimpleBitstreamCursor(BitstreamReader *R) : R(R) {}
>>
>> 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));
>> + return pos == 0 ||
>> + R->getBitcodeBytes().isValidAddress(static_cast<uint64_t>(pos - 1));
>> }
>>
>> bool AtEndOfStream() {
>> @@ -231,72 +175,13 @@ public:
>> 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();
>> - }
>> - }
>> + BitstreamReader *getBitStreamReader() { return R; }
>> + const BitstreamReader *getBitStreamReader() const { return R; }
>>
>> /// Reset the stream to the specified bit number.
>> void JumpToBit(uint64_t BitNo) {
>> @@ -321,7 +206,7 @@ public:
>> uint8_t Array[sizeof(word_t)] = {0};
>>
>> uint64_t BytesRead =
>> - BitStream->getBitcodeBytes().readBytes(Array, sizeof(Array), NextChar);
>> + R->getBitcodeBytes().readBytes(Array, sizeof(Array), NextChar);
>>
>> // If we run out of data, stop at the end of the stream.
>> if (BytesRead == 0) {
>> @@ -416,7 +301,6 @@ public:
>> }
>> }
>>
>> -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.
>> @@ -429,7 +313,140 @@ private:
>>
>> BitsInCurWord = 0;
>> }
>> +
>> + /// Skip to the end of the file.
>> + void skipToEnd() { NextChar = R->getBitcodeBytes().getExtent(); }
>> +};
>> +
>> +/// 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 {
>
> Is the private inheritance intended here?
>
Yes.
> --
> Mehdi
>
>
>
>
>> + // 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<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:
>> + static const size_t MaxChunkSize = sizeof(word_t) * 8;
>> +
>> + BitstreamCursor() = default;
>> +
>> + explicit BitstreamCursor(BitstreamReader &R) { init(&R); }
>> +
>> + void init(BitstreamReader *R) {
>> + freeState();
>> + SimpleBitstreamCursor::operator=(SimpleBitstreamCursor(R));
>> + CurCodeSize = 2;
>> + }
>> +
>> + void freeState();
>> +
>> + using SimpleBitstreamCursor::canSkipToPos;
>> + using SimpleBitstreamCursor::AtEndOfStream;
>> + using SimpleBitstreamCursor::GetCurrentBitNo;
>> + using SimpleBitstreamCursor::getBitStreamReader;
>> + 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 (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();
>> + }
>> + }
>>
>> unsigned ReadCode() {
>> return Read(CurCodeSize);
>>
>> Modified: llvm/trunk/lib/Bitcode/Reader/BitstreamReader.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Reader/BitstreamReader.cpp?rev=264545&r1=264544&r2=264545&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Bitcode/Reader/BitstreamReader.cpp (original)
>> +++ llvm/trunk/lib/Bitcode/Reader/BitstreamReader.cpp Sun Mar 27 17:40:55 2016
>> @@ -32,7 +32,7 @@ bool BitstreamCursor::EnterSubBlock(unsi
>>
>> // Add the abbrevs specific to this block to the CurAbbrevs list.
>> if (const BitstreamReader::BlockInfo *Info =
>> - BitStream->getBlockInfo(BlockID)) {
>> + getBitStreamReader()->getBlockInfo(BlockID)) {
>> CurAbbrevs.insert(CurAbbrevs.end(), Info->Abbrevs.begin(),
>> Info->Abbrevs.end());
>> }
>> @@ -164,7 +164,7 @@ void BitstreamCursor::skipRecord(unsigne
>> // If this would read off the end of the bitcode file, just set the
>> // record to empty and return.
>> if (!canSkipToPos(NewEnd/8)) {
>> - NextChar = BitStream->getBitcodeBytes().getExtent();
>> + skipToEnd();
>> break;
>> }
>>
>> @@ -256,13 +256,14 @@ unsigned BitstreamCursor::readRecord(uns
>> // record to empty and return.
>> if (!canSkipToPos(NewEnd/8)) {
>> Vals.append(NumElts, 0);
>> - NextChar = BitStream->getBitcodeBytes().getExtent();
>> + skipToEnd();
>> break;
>> }
>>
>> // Otherwise, inform the streamer that we need these bytes in memory.
>> - const char *Ptr = (const char*)
>> - BitStream->getBitcodeBytes().getPointer(CurBitPos/8, NumElts);
>> + const char *Ptr =
>> + (const char *)getBitStreamReader()->getBitcodeBytes().getPointer(
>> + CurBitPos / 8, NumElts);
>>
>> // If we can return a reference to the data, do so to avoid copying it.
>> if (Blob) {
>> @@ -320,7 +321,7 @@ void BitstreamCursor::ReadAbbrevRecord()
>>
>> bool BitstreamCursor::ReadBlockInfoBlock() {
>> // If this is the second stream to get to the block info block, skip it.
>> - if (BitStream->hasBlockInfoRecords())
>> + if (getBitStreamReader()->hasBlockInfoRecords())
>> return SkipBlock();
>>
>> if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true;
>> @@ -361,11 +362,13 @@ bool BitstreamCursor::ReadBlockInfoBlock
>> default: break; // Default behavior, ignore unknown content.
>> case bitc::BLOCKINFO_CODE_SETBID:
>> if (Record.size() < 1) return true;
>> - CurBlockInfo = &BitStream->getOrCreateBlockInfo((unsigned)Record[0]);
>> + CurBlockInfo =
>> + &getBitStreamReader()->getOrCreateBlockInfo((unsigned)Record[0]);
>> break;
>> case bitc::BLOCKINFO_CODE_BLOCKNAME: {
>> if (!CurBlockInfo) return true;
>> - if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name.
>> + if (getBitStreamReader()->isIgnoringBlockInfoNames())
>> + break; // Ignore name.
>> std::string Name;
>> for (unsigned i = 0, e = Record.size(); i != e; ++i)
>> Name += (char)Record[i];
>> @@ -374,7 +377,8 @@ bool BitstreamCursor::ReadBlockInfoBlock
>> }
>> case bitc::BLOCKINFO_CODE_SETRECORDNAME: {
>> if (!CurBlockInfo) return true;
>> - if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name.
>> + if (getBitStreamReader()->isIgnoringBlockInfoNames())
>> + break; // Ignore name.
>> std::string Name;
>> for (unsigned i = 1, e = Record.size(); i != e; ++i)
>> Name += (char)Record[i];
>>
>>
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