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Add a new BitstreamEntry concept, and add two helper methods for walking
through a BitstreamCursor that produce it: advance() and advanceSkippingSubblocks(), representing the two most common ways clients want to walk through bitcode. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172919 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -27,6 +27,11 @@ namespace llvm {
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class Deserializer;
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/// BitstreamReader - This class is used to read from an LLVM bitcode stream,
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/// maintaining information that is global to decoding the entire file. While
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/// a file is being read, multiple cursors can be independently advanced or
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/// skipped around within the file. These are represented by the
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/// BitstreamCursor class.
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class BitstreamReader {
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public:
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/// BlockInfo - This contains information emitted to BLOCKINFO_BLOCK blocks.
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@ -119,9 +124,48 @@ public:
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BlockInfoRecords.back().BlockID = BlockID;
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return BlockInfoRecords.back();
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}
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};
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/// BitstreamEntry - When advancing through a bitstream cursor, each advance can
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/// discover a few different kinds of entries:
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/// Error - Malformed bitcode was found.
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/// EndBlock - We've reached the end of the current block, (or the end of the
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/// file, which is treated like a series of EndBlock records.
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/// SubBlock - This is the start of a new subblock of a specific ID.
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/// Record - This is a record with a specific AbbrevID.
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///
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struct BitstreamEntry {
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enum {
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Error,
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EndBlock,
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SubBlock,
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Record
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} Kind;
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unsigned ID;
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static BitstreamEntry getError() {
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BitstreamEntry E; E.Kind = Error; return E;
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}
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static BitstreamEntry getEndBlock() {
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BitstreamEntry E; E.Kind = EndBlock; return E;
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}
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static BitstreamEntry getSubBlock(unsigned ID) {
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BitstreamEntry E; E.Kind = SubBlock; E.ID = ID; return E;
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}
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static BitstreamEntry getRecord(unsigned AbbrevID) {
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BitstreamEntry E; E.Kind = Record; E.ID = AbbrevID; return E;
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}
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};
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/// BitstreamCursor - This represents a position within a bitcode file. There
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/// may be multiple independent cursors reading within one bitstream, each
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/// maintaining their own local state.
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///
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/// Unlike iterators, BitstreamCursors are heavy-weight objects that should not
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/// be passed by value.
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class BitstreamCursor {
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friend class Deserializer;
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BitstreamReader *BitStream;
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@ -151,6 +195,7 @@ class BitstreamCursor {
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/// BlockScope - This tracks the codesize of parent blocks.
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SmallVector<Block, 8> BlockScope;
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public:
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BitstreamCursor() : BitStream(0), NextChar(0) {
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}
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@ -183,9 +228,6 @@ public:
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void freeState();
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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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bool isEndPos(size_t pos) {
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return BitStream->getBitcodeBytes().isObjectEnd(static_cast<uint64_t>(pos));
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}
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@ -212,6 +254,9 @@ public:
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return isEndPos(NextChar) && BitsInCurWord == 0;
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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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/// GetCurrentBitNo - Return the bit # of the bit we are reading.
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uint64_t GetCurrentBitNo() const {
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return NextChar*CHAR_BIT - BitsInCurWord;
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@ -224,6 +269,46 @@ public:
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return BitStream;
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}
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/// advance - Advance the current bitstream, returning the next entry in the
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/// stream.
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BitstreamEntry advance() {
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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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if (ReadBlockEnd())
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return BitstreamEntry::getError();
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return BitstreamEntry::getEndBlock();
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}
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if (Code == bitc::ENTER_SUBBLOCK)
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return BitstreamEntry::getSubBlock(ReadSubBlockID());
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if (Code == bitc::DEFINE_ABBREV) {
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// We read and accumulate abbrev's, the client can't do anything with
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// them anyway.
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ReadAbbrevRecord();
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continue;
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}
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return BitstreamEntry::getRecord(Code);
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}
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}
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/// advanceSkippingSubblocks - This is a convenience function for clients that
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/// don't expect any subblocks. This just skips over them automatically.
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BitstreamEntry advanceSkippingSubblocks() {
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while (1) {
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// If we found a normal entry, return it.
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BitstreamEntry Entry = advance();
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if (Entry.Kind != BitstreamEntry::SubBlock)
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return Entry;
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// If we found a sub-block, just skip over it and check the next entry.
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if (SkipBlock())
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return BitstreamEntry::getError();
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}
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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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@ -375,12 +460,13 @@ public:
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// [END_BLOCK, <align4bytes>]
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SkipToWord();
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PopBlockScope();
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popBlockScope();
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return false;
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}
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private:
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void PopBlockScope() {
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void popBlockScope() {
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CurCodeSize = BlockScope.back().PrevCodeSize;
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// Delete abbrevs from popped scope.
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@ -443,7 +529,6 @@ public:
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//===--------------------------------------------------------------------===//
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// Abbrev Processing
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//===--------------------------------------------------------------------===//
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void ReadAbbrevRecord();
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bool ReadBlockInfoBlock();
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@ -1737,7 +1737,7 @@ bool BitcodeReader::ParseBitcodeInto(Module *M) {
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// The ranlib in xcode 4 will align archive members by appending newlines
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// to the end of them. If this file size is a multiple of 4 but not 8, we
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// have to read and ignore these final 4 bytes :-(
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if (Stream.GetAbbrevIDWidth() == 2 && Code == 2 &&
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if (Stream.getAbbrevIDWidth() == 2 && Code == 2 &&
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Stream.Read(6) == 2 && Stream.Read(24) == 0xa0a0a &&
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Stream.AtEndOfStream())
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return false;
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@ -150,7 +150,7 @@ unsigned BitstreamCursor::ReadRecord(unsigned AbbrevID,
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// the data, do so to avoid copying it.
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if (BlobStart) {
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*BlobStart = (const char*)BitStream->getBitcodeBytes().getPointer(
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NextChar, NumElts);
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NextChar, NumElts);
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*BlobLen = NumElts;
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} else {
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for (; NumElts; ++NextChar, --NumElts)
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