clang-r445002/include/llvm/Bitstream/BitstreamWriter.h - platform/prebuilts/clang/host/darwin-x86 - Git at Google

 //===- BitstreamWriter.h - Low-level bitstream writer 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 BitstreamWriter class.  This class can be used to
 // write an arbitrary bitstream, regardless of its contents.
 //
 //===----------------------------------------------------------------------===//

 #ifndef LLVM_BITSTREAM_BITSTREAMWRITER_H
 #define LLVM_BITSTREAM_BITSTREAMWRITER_H

 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Bitstream/BitCodes.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <vector>

 namespace llvm {

 class BitstreamWriter {
   /// Out - The buffer that keeps unflushed bytes.
   SmallVectorImpl<char> &Out;

   /// FS - The file stream that Out flushes to. If FS is nullptr, it does not
   /// support read or seek, Out cannot be flushed until all data are written.
   raw_fd_stream *FS;

   /// FlushThreshold - If FS is valid, this is the threshold (unit B) to flush
   /// FS.
   const uint64_t FlushThreshold;

   /// CurBit - Always between 0 and 31 inclusive, specifies the next bit to use.
   unsigned CurBit;

   /// CurValue - The current value. Only bits < CurBit are valid.
   uint32_t CurValue;

   /// CurCodeSize - This is the declared size of code values used for the
   /// current block, in bits.
   unsigned CurCodeSize;

   /// BlockInfoCurBID - When emitting a BLOCKINFO_BLOCK, this is the currently
   /// selected BLOCK ID.
   unsigned BlockInfoCurBID;

   /// CurAbbrevs - Abbrevs installed at in this block.
   std::vector<std::shared_ptr<BitCodeAbbrev>> CurAbbrevs;

   struct Block {
     unsigned PrevCodeSize;
     size_t StartSizeWord;
     std::vector<std::shared_ptr<BitCodeAbbrev>> PrevAbbrevs;
     Block(unsigned PCS, size_t SSW) : PrevCodeSize(PCS), StartSizeWord(SSW) {}
   };

   /// BlockScope - This tracks the current blocks that we have entered.
   std::vector<Block> 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<std::shared_ptr<BitCodeAbbrev>> Abbrevs;
   };
   std::vector<BlockInfo> BlockInfoRecords;

   void WriteByte(unsigned char Value) {
     Out.push_back(Value);
     FlushToFile();
   }

   void WriteWord(unsigned Value) {
     Value = support::endian::byte_swap<uint32_t, support::little>(Value);
     Out.append(reinterpret_cast<const char *>(&Value),
                reinterpret_cast<const char *>(&Value + 1));
     FlushToFile();
   }

   uint64_t GetNumOfFlushedBytes() const { return FS ? FS->tell() : 0; }

   size_t GetBufferOffset() const { return Out.size() + GetNumOfFlushedBytes(); }

   size_t GetWordIndex() const {
     size_t Offset = GetBufferOffset();
     assert((Offset & 3) == 0 && "Not 32-bit aligned");
     return Offset / 4;
   }

   /// If the related file stream supports reading, seeking and writing, flush
   /// the buffer if its size is above a threshold.
   void FlushToFile() {
     if (!FS)
       return;
     if (Out.size() < FlushThreshold)
       return;
     FS->write((char *)&Out.front(), Out.size());
     Out.clear();
   }

 public:
   /// Create a BitstreamWriter that writes to Buffer \p O.
   ///
   /// \p FS is the file stream that \p O flushes to incrementally. If \p FS is
   /// null, \p O does not flush incrementially, but writes to disk at the end.
   ///
   /// \p FlushThreshold is the threshold (unit M) to flush \p O if \p FS is
   /// valid.
   BitstreamWriter(SmallVectorImpl<char> &O, raw_fd_stream *FS = nullptr,
                   uint32_t FlushThreshold = 512)
       : Out(O), FS(FS), FlushThreshold(FlushThreshold << 20), CurBit(0),
         CurValue(0), CurCodeSize(2) {}

   ~BitstreamWriter() {
     assert(CurBit == 0 && "Unflushed data remaining");
     assert(BlockScope.empty() && CurAbbrevs.empty() && "Block imbalance");
   }

   /// Retrieve the current position in the stream, in bits.
   uint64_t GetCurrentBitNo() const { return GetBufferOffset() * 8 + CurBit; }

   /// Retrieve the number of bits currently used to encode an abbrev ID.
   unsigned GetAbbrevIDWidth() const { return CurCodeSize; }

   //===--------------------------------------------------------------------===//
   // Basic Primitives for emitting bits to the stream.
   //===--------------------------------------------------------------------===//

   /// Backpatch a 32-bit word in the output at the given bit offset
   /// with the specified value.
   void BackpatchWord(uint64_t BitNo, unsigned NewWord) {
     using namespace llvm::support;
     uint64_t ByteNo = BitNo / 8;
     uint64_t StartBit = BitNo & 7;
     uint64_t NumOfFlushedBytes = GetNumOfFlushedBytes();

     if (ByteNo >= NumOfFlushedBytes) {
       assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
                  &Out[ByteNo - NumOfFlushedBytes], StartBit)) &&
              "Expected to be patching over 0-value placeholders");
       endian::writeAtBitAlignment<uint32_t, little, unaligned>(
           &Out[ByteNo - NumOfFlushedBytes], NewWord, StartBit);
       return;
     }

     // If the byte offset to backpatch is flushed, use seek to backfill data.
     // First, save the file position to restore later.
     uint64_t CurPos = FS->tell();

     // Copy data to update into Bytes from the file FS and the buffer Out.
     char Bytes[9]; // Use one more byte to silence a warning from Visual C++.
     size_t BytesNum = StartBit ? 8 : 4;
     size_t BytesFromDisk = std::min(static_cast<uint64_t>(BytesNum), NumOfFlushedBytes - ByteNo);
     size_t BytesFromBuffer = BytesNum - BytesFromDisk;

     // When unaligned, copy existing data into Bytes from the file FS and the
     // buffer Out so that it can be updated before writing. For debug builds
     // read bytes unconditionally in order to check that the existing value is 0
     // as expected.
 #ifdef NDEBUG
     if (StartBit)
 #endif
     {
       FS->seek(ByteNo);
       ssize_t BytesRead = FS->read(Bytes, BytesFromDisk);
       (void)BytesRead; // silence warning
       assert(BytesRead >= 0 && static_cast<size_t>(BytesRead) == BytesFromDisk);
       for (size_t i = 0; i < BytesFromBuffer; ++i)
         Bytes[BytesFromDisk + i] = Out[i];
       assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
                  Bytes, StartBit)) &&
              "Expected to be patching over 0-value placeholders");
     }

     // Update Bytes in terms of bit offset and value.
     endian::writeAtBitAlignment<uint32_t, little, unaligned>(Bytes, NewWord,
                                                              StartBit);

     // Copy updated data back to the file FS and the buffer Out.
     FS->seek(ByteNo);
     FS->write(Bytes, BytesFromDisk);
     for (size_t i = 0; i < BytesFromBuffer; ++i)
       Out[i] = Bytes[BytesFromDisk + i];

     // Restore the file position.
     FS->seek(CurPos);
   }

   void BackpatchWord64(uint64_t BitNo, uint64_t Val) {
     BackpatchWord(BitNo, (uint32_t)Val);
     BackpatchWord(BitNo + 32, (uint32_t)(Val >> 32));
   }

   void Emit(uint32_t Val, unsigned NumBits) {
     assert(NumBits && NumBits <= 32 && "Invalid value size!");
     assert((Val & ~(~0U >> (32-NumBits))) == 0 && "High bits set!");
     CurValue |= Val << CurBit;
     if (CurBit + NumBits < 32) {
       CurBit += NumBits;
       return;
     }

     // Add the current word.
     WriteWord(CurValue);

     if (CurBit)
       CurValue = Val >> (32-CurBit);
     else
       CurValue = 0;
     CurBit = (CurBit+NumBits) & 31;
   }

   void FlushToWord() {
     if (CurBit) {
       WriteWord(CurValue);
       CurBit = 0;
       CurValue = 0;
     }
   }

   void EmitVBR(uint32_t Val, unsigned NumBits) {
     assert(NumBits <= 32 && "Too many bits to emit!");
     uint32_t Threshold = 1U << (NumBits-1);

     // Emit the bits with VBR encoding, NumBits-1 bits at a time.
     while (Val >= Threshold) {
       Emit((Val & ((1 << (NumBits-1))-1)) | (1 << (NumBits-1)), NumBits);
       Val >>= NumBits-1;
     }

     Emit(Val, NumBits);
   }

   void EmitVBR64(uint64_t Val, unsigned NumBits) {
     assert(NumBits <= 32 && "Too many bits to emit!");
     if ((uint32_t)Val == Val)
       return EmitVBR((uint32_t)Val, NumBits);

     uint32_t Threshold = 1U << (NumBits-1);

     // Emit the bits with VBR encoding, NumBits-1 bits at a time.
     while (Val >= Threshold) {
       Emit(((uint32_t)Val & ((1 << (NumBits-1))-1)) |
            (1 << (NumBits-1)), NumBits);
       Val >>= NumBits-1;
     }

     Emit((uint32_t)Val, NumBits);
   }

   /// EmitCode - Emit the specified code.
   void EmitCode(unsigned Val) {
     Emit(Val, CurCodeSize);
   }

   //===--------------------------------------------------------------------===//
   // Block Manipulation
   //===--------------------------------------------------------------------===//

   /// 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 nullptr;
   }

   void EnterSubblock(unsigned BlockID, unsigned CodeLen) {
     // Block header:
     //    [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
     EmitCode(bitc::ENTER_SUBBLOCK);
     EmitVBR(BlockID, bitc::BlockIDWidth);
     EmitVBR(CodeLen, bitc::CodeLenWidth);
     FlushToWord();

     size_t BlockSizeWordIndex = GetWordIndex();
     unsigned OldCodeSize = CurCodeSize;

     // Emit a placeholder, which will be replaced when the block is popped.
     Emit(0, bitc::BlockSizeWidth);

     CurCodeSize = CodeLen;

     // Push the outer block's abbrev set onto the stack, start out with an
     // empty abbrev set.
     BlockScope.emplace_back(OldCodeSize, BlockSizeWordIndex);
     BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);

     // If there is a blockinfo for this BlockID, add all the predefined abbrevs
     // to the abbrev list.
     if (BlockInfo *Info = getBlockInfo(BlockID))
       append_range(CurAbbrevs, Info->Abbrevs);
   }

   void ExitBlock() {
     assert(!BlockScope.empty() && "Block scope imbalance!");
     const Block &B = BlockScope.back();

     // Block tail:
     //    [END_BLOCK, <align4bytes>]
     EmitCode(bitc::END_BLOCK);
     FlushToWord();

     // Compute the size of the block, in words, not counting the size field.
     size_t SizeInWords = GetWordIndex() - B.StartSizeWord - 1;
     uint64_t BitNo = uint64_t(B.StartSizeWord) * 32;

     // Update the block size field in the header of this sub-block.
     BackpatchWord(BitNo, SizeInWords);

     // Restore the inner block's code size and abbrev table.
     CurCodeSize = B.PrevCodeSize;
     CurAbbrevs = std::move(B.PrevAbbrevs);
     BlockScope.pop_back();
   }

   //===--------------------------------------------------------------------===//
   // Record Emission
   //===--------------------------------------------------------------------===//

 private:
   /// EmitAbbreviatedLiteral - Emit a literal value according to its abbrev
   /// record.  This is a no-op, since the abbrev specifies the literal to use.
   template<typename uintty>
   void EmitAbbreviatedLiteral(const BitCodeAbbrevOp &Op, uintty V) {
     assert(Op.isLiteral() && "Not a literal");
     // If the abbrev specifies the literal value to use, don't emit
     // anything.
     assert(V == Op.getLiteralValue() &&
            "Invalid abbrev for record!");
   }

   /// EmitAbbreviatedField - Emit a single scalar field value with the specified
   /// encoding.
   template<typename uintty>
   void EmitAbbreviatedField(const BitCodeAbbrevOp &Op, uintty V) {
     assert(!Op.isLiteral() && "Literals should use EmitAbbreviatedLiteral!");

     // Encode the value as we are commanded.
     switch (Op.getEncoding()) {
     default: llvm_unreachable("Unknown encoding!");
     case BitCodeAbbrevOp::Fixed:
       if (Op.getEncodingData())
         Emit((unsigned)V, (unsigned)Op.getEncodingData());
       break;
     case BitCodeAbbrevOp::VBR:
       if (Op.getEncodingData())
         EmitVBR64(V, (unsigned)Op.getEncodingData());
       break;
     case BitCodeAbbrevOp::Char6:
       Emit(BitCodeAbbrevOp::EncodeChar6((char)V), 6);
       break;
     }
   }

   /// EmitRecordWithAbbrevImpl - This is the core implementation of the record
   /// emission code.  If BlobData is non-null, then it specifies an array of
   /// data that should be emitted as part of the Blob or Array operand that is
   /// known to exist at the end of the record. If Code is specified, then
   /// it is the record code to emit before the Vals, which must not contain
   /// the code.
   template <typename uintty>
   void EmitRecordWithAbbrevImpl(unsigned Abbrev, ArrayRef<uintty> Vals,
                                 StringRef Blob, Optional<unsigned> Code) {
     const char *BlobData = Blob.data();
     unsigned BlobLen = (unsigned) Blob.size();
     unsigned AbbrevNo = Abbrev-bitc::FIRST_APPLICATION_ABBREV;
     assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
     const BitCodeAbbrev *Abbv = CurAbbrevs[AbbrevNo].get();

     EmitCode(Abbrev);

     unsigned i = 0, e = static_cast<unsigned>(Abbv->getNumOperandInfos());
     if (Code) {
       assert(e && "Expected non-empty abbreviation");
       const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i++);

       if (Op.isLiteral())
         EmitAbbreviatedLiteral(Op, Code.getValue());
       else {
         assert(Op.getEncoding() != BitCodeAbbrevOp::Array &&
                Op.getEncoding() != BitCodeAbbrevOp::Blob &&
                "Expected literal or scalar");
         EmitAbbreviatedField(Op, Code.getValue());
       }
     }

     unsigned RecordIdx = 0;
     for (; i != e; ++i) {
       const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
       if (Op.isLiteral()) {
         assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
         EmitAbbreviatedLiteral(Op, Vals[RecordIdx]);
         ++RecordIdx;
       } else if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
         // Array case.
         assert(i + 2 == e && "array op not second to last?");
         const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);

         // If this record has blob data, emit it, otherwise we must have record
         // entries to encode this way.
         if (BlobData) {
           assert(RecordIdx == Vals.size() &&
                  "Blob data and record entries specified for array!");
           // Emit a vbr6 to indicate the number of elements present.
           EmitVBR(static_cast<uint32_t>(BlobLen), 6);

           // Emit each field.
           for (unsigned i = 0; i != BlobLen; ++i)
             EmitAbbreviatedField(EltEnc, (unsigned char)BlobData[i]);

           // Know that blob data is consumed for assertion below.
           BlobData = nullptr;
         } else {
           // Emit a vbr6 to indicate the number of elements present.
           EmitVBR(static_cast<uint32_t>(Vals.size()-RecordIdx), 6);

           // Emit each field.
           for (unsigned e = Vals.size(); RecordIdx != e; ++RecordIdx)
             EmitAbbreviatedField(EltEnc, Vals[RecordIdx]);
         }
       } else if (Op.getEncoding() == BitCodeAbbrevOp::Blob) {
         // If this record has blob data, emit it, otherwise we must have record
         // entries to encode this way.

         if (BlobData) {
           assert(RecordIdx == Vals.size() &&
                  "Blob data and record entries specified for blob operand!");

           assert(Blob.data() == BlobData && "BlobData got moved");
           assert(Blob.size() == BlobLen && "BlobLen got changed");
           emitBlob(Blob);
           BlobData = nullptr;
         } else {
           emitBlob(Vals.slice(RecordIdx));
         }
       } else {  // Single scalar field.
         assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
         EmitAbbreviatedField(Op, Vals[RecordIdx]);
         ++RecordIdx;
       }
     }
     assert(RecordIdx == Vals.size() && "Not all record operands emitted!");
     assert(BlobData == nullptr &&
            "Blob data specified for record that doesn't use it!");
   }

 public:
   /// Emit a blob, including flushing before and tail-padding.
   template <class UIntTy>
   void emitBlob(ArrayRef<UIntTy> Bytes, bool ShouldEmitSize = true) {
     // Emit a vbr6 to indicate the number of elements present.
     if (ShouldEmitSize)
       EmitVBR(static_cast<uint32_t>(Bytes.size()), 6);

     // Flush to a 32-bit alignment boundary.
     FlushToWord();

     // Emit literal bytes.
     for (const auto &B : Bytes) {
       assert(isUInt<8>(B) && "Value too large to emit as byte");
       WriteByte((unsigned char)B);
     }

     // Align end to 32-bits.
     while (GetBufferOffset() & 3)
       WriteByte(0);
   }
   void emitBlob(StringRef Bytes, bool ShouldEmitSize = true) {
     emitBlob(makeArrayRef((const uint8_t *)Bytes.data(), Bytes.size()),
              ShouldEmitSize);
   }

   /// EmitRecord - Emit the specified record to the stream, using an abbrev if
   /// we have one to compress the output.
   template <typename Container>
   void EmitRecord(unsigned Code, const Container &Vals, unsigned Abbrev = 0) {
     if (!Abbrev) {
       // If we don't have an abbrev to use, emit this in its fully unabbreviated
       // form.
       auto Count = static_cast<uint32_t>(makeArrayRef(Vals).size());
       EmitCode(bitc::UNABBREV_RECORD);
       EmitVBR(Code, 6);
       EmitVBR(Count, 6);
       for (unsigned i = 0, e = Count; i != e; ++i)
         EmitVBR64(Vals[i], 6);
       return;
     }

     EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), StringRef(), Code);
   }

   /// EmitRecordWithAbbrev - Emit a record with the specified abbreviation.
   /// Unlike EmitRecord, the code for the record should be included in Vals as
   /// the first entry.
   template <typename Container>
   void EmitRecordWithAbbrev(unsigned Abbrev, const Container &Vals) {
     EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), StringRef(), None);
   }

   /// EmitRecordWithBlob - Emit the specified record to the stream, using an
   /// abbrev that includes a blob at the end.  The blob data to emit is
   /// specified by the pointer and length specified at the end.  In contrast to
   /// EmitRecord, this routine expects that the first entry in Vals is the code
   /// of the record.
   template <typename Container>
   void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
                           StringRef Blob) {
     EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), Blob, None);
   }
   template <typename Container>
   void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
                           const char *BlobData, unsigned BlobLen) {
     return EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals),
                                     StringRef(BlobData, BlobLen), None);
   }

   /// EmitRecordWithArray - Just like EmitRecordWithBlob, works with records
   /// that end with an array.
   template <typename Container>
   void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
                            StringRef Array) {
     EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), Array, None);
   }
   template <typename Container>
   void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
                            const char *ArrayData, unsigned ArrayLen) {
     return EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals),
                                     StringRef(ArrayData, ArrayLen), None);
   }

   //===--------------------------------------------------------------------===//
   // Abbrev Emission
   //===--------------------------------------------------------------------===//

 private:
   // Emit the abbreviation as a DEFINE_ABBREV record.
   void EncodeAbbrev(const BitCodeAbbrev &Abbv) {
     EmitCode(bitc::DEFINE_ABBREV);
     EmitVBR(Abbv.getNumOperandInfos(), 5);
     for (unsigned i = 0, e = static_cast<unsigned>(Abbv.getNumOperandInfos());
          i != e; ++i) {
       const BitCodeAbbrevOp &Op = Abbv.getOperandInfo(i);
       Emit(Op.isLiteral(), 1);
       if (Op.isLiteral()) {
         EmitVBR64(Op.getLiteralValue(), 8);
       } else {
         Emit(Op.getEncoding(), 3);
         if (Op.hasEncodingData())
           EmitVBR64(Op.getEncodingData(), 5);
       }
     }
   }
 public:

   /// Emits the abbreviation \p Abbv to the stream.
   unsigned EmitAbbrev(std::shared_ptr<BitCodeAbbrev> Abbv) {
     EncodeAbbrev(*Abbv);
     CurAbbrevs.push_back(std::move(Abbv));
     return static_cast<unsigned>(CurAbbrevs.size())-1 +
       bitc::FIRST_APPLICATION_ABBREV;
   }

   //===--------------------------------------------------------------------===//
   // BlockInfo Block Emission
   //===--------------------------------------------------------------------===//

   /// EnterBlockInfoBlock - Start emitting the BLOCKINFO_BLOCK.
   void EnterBlockInfoBlock() {
     EnterSubblock(bitc::BLOCKINFO_BLOCK_ID, 2);
     BlockInfoCurBID = ~0U;
     BlockInfoRecords.clear();
   }
 private:
   /// SwitchToBlockID - If we aren't already talking about the specified block
   /// ID, emit a BLOCKINFO_CODE_SETBID record.
   void SwitchToBlockID(unsigned BlockID) {
     if (BlockInfoCurBID == BlockID) return;
     SmallVector<unsigned, 2> V;
     V.push_back(BlockID);
     EmitRecord(bitc::BLOCKINFO_CODE_SETBID, V);
     BlockInfoCurBID = BlockID;
   }

   BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
     if (BlockInfo *BI = getBlockInfo(BlockID))
       return *BI;

     // Otherwise, add a new record.
     BlockInfoRecords.emplace_back();
     BlockInfoRecords.back().BlockID = BlockID;
     return BlockInfoRecords.back();
   }

 public:

   /// EmitBlockInfoAbbrev - Emit a DEFINE_ABBREV record for the specified
   /// BlockID.
   unsigned EmitBlockInfoAbbrev(unsigned BlockID, std::shared_ptr<BitCodeAbbrev> Abbv) {
     SwitchToBlockID(BlockID);
     EncodeAbbrev(*Abbv);

     // Add the abbrev to the specified block record.
     BlockInfo &Info = getOrCreateBlockInfo(BlockID);
     Info.Abbrevs.push_back(std::move(Abbv));

     return Info.Abbrevs.size()-1+bitc::FIRST_APPLICATION_ABBREV;
   }
 };


 } // End llvm namespace

 #endif
	//===- BitstreamWriter.h - Low-level bitstream writer 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 BitstreamWriter class. This class can be used to
	// write an arbitrary bitstream, regardless of its contents.
	//
	//===----------------------------------------------------------------------===//

	#ifndef LLVM_BITSTREAM_BITSTREAMWRITER_H
	#define LLVM_BITSTREAM_BITSTREAMWRITER_H

	#include "llvm/ADT/ArrayRef.h"
	#include "llvm/ADT/Optional.h"
	#include "llvm/ADT/SmallVector.h"
	#include "llvm/ADT/StringRef.h"
	#include "llvm/Bitstream/BitCodes.h"
	#include "llvm/Support/Endian.h"
	#include "llvm/Support/MathExtras.h"
	#include "llvm/Support/raw_ostream.h"
	#include <algorithm>
	#include <vector>

	namespace llvm {

	class BitstreamWriter {
	/// Out - The buffer that keeps unflushed bytes.
	SmallVectorImpl<char> &Out;

	/// FS - The file stream that Out flushes to. If FS is nullptr, it does not
	/// support read or seek, Out cannot be flushed until all data are written.
	raw_fd_stream *FS;

	/// FlushThreshold - If FS is valid, this is the threshold (unit B) to flush
	/// FS.
	const uint64_t FlushThreshold;

	/// CurBit - Always between 0 and 31 inclusive, specifies the next bit to use.
	unsigned CurBit;

	/// CurValue - The current value. Only bits < CurBit are valid.
	uint32_t CurValue;

	/// CurCodeSize - This is the declared size of code values used for the
	/// current block, in bits.
	unsigned CurCodeSize;

	/// BlockInfoCurBID - When emitting a BLOCKINFO_BLOCK, this is the currently
	/// selected BLOCK ID.
	unsigned BlockInfoCurBID;

	/// CurAbbrevs - Abbrevs installed at in this block.
	std::vector<std::shared_ptr<BitCodeAbbrev>> CurAbbrevs;

	struct Block {
	unsigned PrevCodeSize;
	size_t StartSizeWord;
	std::vector<std::shared_ptr<BitCodeAbbrev>> PrevAbbrevs;
	Block(unsigned PCS, size_t SSW) : PrevCodeSize(PCS), StartSizeWord(SSW) {}
	};

	/// BlockScope - This tracks the current blocks that we have entered.
	std::vector<Block> 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<std::shared_ptr<BitCodeAbbrev>> Abbrevs;
	};
	std::vector<BlockInfo> BlockInfoRecords;

	void WriteByte(unsigned char Value) {
	Out.push_back(Value);
	FlushToFile();
	}

	void WriteWord(unsigned Value) {
	Value = support::endian::byte_swap<uint32_t, support::little>(Value);
	Out.append(reinterpret_cast<const char *>(&Value),
	reinterpret_cast<const char *>(&Value + 1));
	FlushToFile();
	}

	uint64_t GetNumOfFlushedBytes() const { return FS ? FS->tell() : 0; }

	size_t GetBufferOffset() const { return Out.size() + GetNumOfFlushedBytes(); }

	size_t GetWordIndex() const {
	size_t Offset = GetBufferOffset();
	assert((Offset & 3) == 0 && "Not 32-bit aligned");
	return Offset / 4;
	}

	/// If the related file stream supports reading, seeking and writing, flush
	/// the buffer if its size is above a threshold.
	void FlushToFile() {
	if (!FS)
	return;
	if (Out.size() < FlushThreshold)
	return;
	FS->write((char *)&Out.front(), Out.size());
	Out.clear();
	}

	public:
	/// Create a BitstreamWriter that writes to Buffer \p O.
	///
	/// \p FS is the file stream that \p O flushes to incrementally. If \p FS is
	/// null, \p O does not flush incrementially, but writes to disk at the end.
	///
	/// \p FlushThreshold is the threshold (unit M) to flush \p O if \p FS is
	/// valid.
	BitstreamWriter(SmallVectorImpl<char> &O, raw_fd_stream *FS = nullptr,
	uint32_t FlushThreshold = 512)
	: Out(O), FS(FS), FlushThreshold(FlushThreshold << 20), CurBit(0),
	CurValue(0), CurCodeSize(2) {}

	~BitstreamWriter() {
	assert(CurBit == 0 && "Unflushed data remaining");
	assert(BlockScope.empty() && CurAbbrevs.empty() && "Block imbalance");
	}

	/// Retrieve the current position in the stream, in bits.
	uint64_t GetCurrentBitNo() const { return GetBufferOffset() * 8 + CurBit; }

	/// Retrieve the number of bits currently used to encode an abbrev ID.
	unsigned GetAbbrevIDWidth() const { return CurCodeSize; }

	//===--------------------------------------------------------------------===//
	// Basic Primitives for emitting bits to the stream.
	//===--------------------------------------------------------------------===//

	/// Backpatch a 32-bit word in the output at the given bit offset
	/// with the specified value.
	void BackpatchWord(uint64_t BitNo, unsigned NewWord) {
	using namespace llvm::support;
	uint64_t ByteNo = BitNo / 8;
	uint64_t StartBit = BitNo & 7;
	uint64_t NumOfFlushedBytes = GetNumOfFlushedBytes();

	if (ByteNo >= NumOfFlushedBytes) {
	assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
	&Out[ByteNo - NumOfFlushedBytes], StartBit)) &&
	"Expected to be patching over 0-value placeholders");
	endian::writeAtBitAlignment<uint32_t, little, unaligned>(
	&Out[ByteNo - NumOfFlushedBytes], NewWord, StartBit);
	return;
	}

	// If the byte offset to backpatch is flushed, use seek to backfill data.
	// First, save the file position to restore later.
	uint64_t CurPos = FS->tell();

	// Copy data to update into Bytes from the file FS and the buffer Out.
	char Bytes[9]; // Use one more byte to silence a warning from Visual C++.
	size_t BytesNum = StartBit ? 8 : 4;
	size_t BytesFromDisk = std::min(static_cast<uint64_t>(BytesNum), NumOfFlushedBytes - ByteNo);
	size_t BytesFromBuffer = BytesNum - BytesFromDisk;

	// When unaligned, copy existing data into Bytes from the file FS and the
	// buffer Out so that it can be updated before writing. For debug builds
	// read bytes unconditionally in order to check that the existing value is 0
	// as expected.
	#ifdef NDEBUG
	if (StartBit)
	#endif
	{
	FS->seek(ByteNo);
	ssize_t BytesRead = FS->read(Bytes, BytesFromDisk);
	(void)BytesRead; // silence warning
	assert(BytesRead >= 0 && static_cast<size_t>(BytesRead) == BytesFromDisk);
	for (size_t i = 0; i < BytesFromBuffer; ++i)
	Bytes[BytesFromDisk + i] = Out[i];
	assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
	Bytes, StartBit)) &&
	"Expected to be patching over 0-value placeholders");
	}

	// Update Bytes in terms of bit offset and value.
	endian::writeAtBitAlignment<uint32_t, little, unaligned>(Bytes, NewWord,
	StartBit);

	// Copy updated data back to the file FS and the buffer Out.
	FS->seek(ByteNo);
	FS->write(Bytes, BytesFromDisk);
	for (size_t i = 0; i < BytesFromBuffer; ++i)
	Out[i] = Bytes[BytesFromDisk + i];

	// Restore the file position.
	FS->seek(CurPos);
	}

	void BackpatchWord64(uint64_t BitNo, uint64_t Val) {
	BackpatchWord(BitNo, (uint32_t)Val);
	BackpatchWord(BitNo + 32, (uint32_t)(Val >> 32));
	}

	void Emit(uint32_t Val, unsigned NumBits) {
	assert(NumBits && NumBits <= 32 && "Invalid value size!");
	assert((Val & ~(~0U >> (32-NumBits))) == 0 && "High bits set!");
	CurValue \|= Val << CurBit;
	if (CurBit + NumBits < 32) {
	CurBit += NumBits;
	return;
	}

	// Add the current word.
	WriteWord(CurValue);

	if (CurBit)
	CurValue = Val >> (32-CurBit);
	else
	CurValue = 0;
	CurBit = (CurBit+NumBits) & 31;
	}

	void FlushToWord() {
	if (CurBit) {
	WriteWord(CurValue);
	CurBit = 0;
	CurValue = 0;
	}
	}

	void EmitVBR(uint32_t Val, unsigned NumBits) {
	assert(NumBits <= 32 && "Too many bits to emit!");
	uint32_t Threshold = 1U << (NumBits-1);

	// Emit the bits with VBR encoding, NumBits-1 bits at a time.
	while (Val >= Threshold) {
	Emit((Val & ((1 << (NumBits-1))-1)) \| (1 << (NumBits-1)), NumBits);
	Val >>= NumBits-1;
	}

	Emit(Val, NumBits);
	}

	void EmitVBR64(uint64_t Val, unsigned NumBits) {
	assert(NumBits <= 32 && "Too many bits to emit!");
	if ((uint32_t)Val == Val)
	return EmitVBR((uint32_t)Val, NumBits);

	uint32_t Threshold = 1U << (NumBits-1);

	// Emit the bits with VBR encoding, NumBits-1 bits at a time.
	while (Val >= Threshold) {
	Emit(((uint32_t)Val & ((1 << (NumBits-1))-1)) \|
	(1 << (NumBits-1)), NumBits);
	Val >>= NumBits-1;
	}

	Emit((uint32_t)Val, NumBits);
	}

	/// EmitCode - Emit the specified code.
	void EmitCode(unsigned Val) {
	Emit(Val, CurCodeSize);
	}

	//===--------------------------------------------------------------------===//
	// Block Manipulation
	//===--------------------------------------------------------------------===//

	/// 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 nullptr;
	}

	void EnterSubblock(unsigned BlockID, unsigned CodeLen) {
	// Block header:
	// [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
	EmitCode(bitc::ENTER_SUBBLOCK);
	EmitVBR(BlockID, bitc::BlockIDWidth);
	EmitVBR(CodeLen, bitc::CodeLenWidth);
	FlushToWord();

	size_t BlockSizeWordIndex = GetWordIndex();
	unsigned OldCodeSize = CurCodeSize;

	// Emit a placeholder, which will be replaced when the block is popped.
	Emit(0, bitc::BlockSizeWidth);

	CurCodeSize = CodeLen;

	// Push the outer block's abbrev set onto the stack, start out with an
	// empty abbrev set.
	BlockScope.emplace_back(OldCodeSize, BlockSizeWordIndex);
	BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);

	// If there is a blockinfo for this BlockID, add all the predefined abbrevs
	// to the abbrev list.
	if (BlockInfo *Info = getBlockInfo(BlockID))
	append_range(CurAbbrevs, Info->Abbrevs);
	}

	void ExitBlock() {
	assert(!BlockScope.empty() && "Block scope imbalance!");
	const Block &B = BlockScope.back();

	// Block tail:
	// [END_BLOCK, <align4bytes>]
	EmitCode(bitc::END_BLOCK);
	FlushToWord();

	// Compute the size of the block, in words, not counting the size field.
	size_t SizeInWords = GetWordIndex() - B.StartSizeWord - 1;
	uint64_t BitNo = uint64_t(B.StartSizeWord) * 32;

	// Update the block size field in the header of this sub-block.
	BackpatchWord(BitNo, SizeInWords);

	// Restore the inner block's code size and abbrev table.
	CurCodeSize = B.PrevCodeSize;
	CurAbbrevs = std::move(B.PrevAbbrevs);
	BlockScope.pop_back();
	}

	//===--------------------------------------------------------------------===//
	// Record Emission
	//===--------------------------------------------------------------------===//

	private:
	/// EmitAbbreviatedLiteral - Emit a literal value according to its abbrev
	/// record. This is a no-op, since the abbrev specifies the literal to use.
	template<typename uintty>
	void EmitAbbreviatedLiteral(const BitCodeAbbrevOp &Op, uintty V) {
	assert(Op.isLiteral() && "Not a literal");
	// If the abbrev specifies the literal value to use, don't emit
	// anything.
	assert(V == Op.getLiteralValue() &&
	"Invalid abbrev for record!");
	}

	/// EmitAbbreviatedField - Emit a single scalar field value with the specified
	/// encoding.
	template<typename uintty>
	void EmitAbbreviatedField(const BitCodeAbbrevOp &Op, uintty V) {
	assert(!Op.isLiteral() && "Literals should use EmitAbbreviatedLiteral!");

	// Encode the value as we are commanded.
	switch (Op.getEncoding()) {
	default: llvm_unreachable("Unknown encoding!");
	case BitCodeAbbrevOp::Fixed:
	if (Op.getEncodingData())
	Emit((unsigned)V, (unsigned)Op.getEncodingData());
	break;
	case BitCodeAbbrevOp::VBR:
	if (Op.getEncodingData())
	EmitVBR64(V, (unsigned)Op.getEncodingData());
	break;
	case BitCodeAbbrevOp::Char6:
	Emit(BitCodeAbbrevOp::EncodeChar6((char)V), 6);
	break;
	}
	}

	/// EmitRecordWithAbbrevImpl - This is the core implementation of the record
	/// emission code. If BlobData is non-null, then it specifies an array of
	/// data that should be emitted as part of the Blob or Array operand that is
	/// known to exist at the end of the record. If Code is specified, then
	/// it is the record code to emit before the Vals, which must not contain
	/// the code.
	template <typename uintty>
	void EmitRecordWithAbbrevImpl(unsigned Abbrev, ArrayRef<uintty> Vals,
	StringRef Blob, Optional<unsigned> Code) {
	const char *BlobData = Blob.data();
	unsigned BlobLen = (unsigned) Blob.size();
	unsigned AbbrevNo = Abbrev-bitc::FIRST_APPLICATION_ABBREV;
	assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
	const BitCodeAbbrev *Abbv = CurAbbrevs[AbbrevNo].get();

	EmitCode(Abbrev);

	unsigned i = 0, e = static_cast<unsigned>(Abbv->getNumOperandInfos());
	if (Code) {
	assert(e && "Expected non-empty abbreviation");
	const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i++);

	if (Op.isLiteral())
	EmitAbbreviatedLiteral(Op, Code.getValue());
	else {
	assert(Op.getEncoding() != BitCodeAbbrevOp::Array &&
	Op.getEncoding() != BitCodeAbbrevOp::Blob &&
	"Expected literal or scalar");
	EmitAbbreviatedField(Op, Code.getValue());
	}
	}

	unsigned RecordIdx = 0;
	for (; i != e; ++i) {
	const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
	if (Op.isLiteral()) {
	assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
	EmitAbbreviatedLiteral(Op, Vals[RecordIdx]);
	++RecordIdx;
	} else if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
	// Array case.
	assert(i + 2 == e && "array op not second to last?");
	const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);

	// If this record has blob data, emit it, otherwise we must have record
	// entries to encode this way.
	if (BlobData) {
	assert(RecordIdx == Vals.size() &&
	"Blob data and record entries specified for array!");
	// Emit a vbr6 to indicate the number of elements present.
	EmitVBR(static_cast<uint32_t>(BlobLen), 6);

	// Emit each field.
	for (unsigned i = 0; i != BlobLen; ++i)
	EmitAbbreviatedField(EltEnc, (unsigned char)BlobData[i]);

	// Know that blob data is consumed for assertion below.
	BlobData = nullptr;
	} else {
	// Emit a vbr6 to indicate the number of elements present.
	EmitVBR(static_cast<uint32_t>(Vals.size()-RecordIdx), 6);

	// Emit each field.
	for (unsigned e = Vals.size(); RecordIdx != e; ++RecordIdx)
	EmitAbbreviatedField(EltEnc, Vals[RecordIdx]);
	}
	} else if (Op.getEncoding() == BitCodeAbbrevOp::Blob) {
	// If this record has blob data, emit it, otherwise we must have record
	// entries to encode this way.

	if (BlobData) {
	assert(RecordIdx == Vals.size() &&
	"Blob data and record entries specified for blob operand!");

	assert(Blob.data() == BlobData && "BlobData got moved");
	assert(Blob.size() == BlobLen && "BlobLen got changed");
	emitBlob(Blob);
	BlobData = nullptr;
	} else {
	emitBlob(Vals.slice(RecordIdx));
	}
	} else { // Single scalar field.
	assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
	EmitAbbreviatedField(Op, Vals[RecordIdx]);
	++RecordIdx;
	}
	}
	assert(RecordIdx == Vals.size() && "Not all record operands emitted!");
	assert(BlobData == nullptr &&
	"Blob data specified for record that doesn't use it!");
	}

	public:
	/// Emit a blob, including flushing before and tail-padding.
	template <class UIntTy>
	void emitBlob(ArrayRef<UIntTy> Bytes, bool ShouldEmitSize = true) {
	// Emit a vbr6 to indicate the number of elements present.
	if (ShouldEmitSize)
	EmitVBR(static_cast<uint32_t>(Bytes.size()), 6);

	// Flush to a 32-bit alignment boundary.
	FlushToWord();

	// Emit literal bytes.
	for (const auto &B : Bytes) {
	assert(isUInt<8>(B) && "Value too large to emit as byte");
	WriteByte((unsigned char)B);
	}

	// Align end to 32-bits.
	while (GetBufferOffset() & 3)
	WriteByte(0);
	}
	void emitBlob(StringRef Bytes, bool ShouldEmitSize = true) {
	emitBlob(makeArrayRef((const uint8_t *)Bytes.data(), Bytes.size()),
	ShouldEmitSize);
	}

	/// EmitRecord - Emit the specified record to the stream, using an abbrev if
	/// we have one to compress the output.
	template <typename Container>
	void EmitRecord(unsigned Code, const Container &Vals, unsigned Abbrev = 0) {
	if (!Abbrev) {
	// If we don't have an abbrev to use, emit this in its fully unabbreviated
	// form.
	auto Count = static_cast<uint32_t>(makeArrayRef(Vals).size());
	EmitCode(bitc::UNABBREV_RECORD);
	EmitVBR(Code, 6);
	EmitVBR(Count, 6);
	for (unsigned i = 0, e = Count; i != e; ++i)
	EmitVBR64(Vals[i], 6);
	return;
	}

	EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), StringRef(), Code);
	}

	/// EmitRecordWithAbbrev - Emit a record with the specified abbreviation.
	/// Unlike EmitRecord, the code for the record should be included in Vals as
	/// the first entry.
	template <typename Container>
	void EmitRecordWithAbbrev(unsigned Abbrev, const Container &Vals) {
	EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), StringRef(), None);
	}

	/// EmitRecordWithBlob - Emit the specified record to the stream, using an
	/// abbrev that includes a blob at the end. The blob data to emit is
	/// specified by the pointer and length specified at the end. In contrast to
	/// EmitRecord, this routine expects that the first entry in Vals is the code
	/// of the record.
	template <typename Container>
	void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
	StringRef Blob) {
	EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), Blob, None);
	}
	template <typename Container>
	void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
	const char *BlobData, unsigned BlobLen) {
	return EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals),
	StringRef(BlobData, BlobLen), None);
	}

	/// EmitRecordWithArray - Just like EmitRecordWithBlob, works with records
	/// that end with an array.
	template <typename Container>
	void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
	StringRef Array) {
	EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals), Array, None);
	}
	template <typename Container>
	void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
	const char *ArrayData, unsigned ArrayLen) {
	return EmitRecordWithAbbrevImpl(Abbrev, makeArrayRef(Vals),
	StringRef(ArrayData, ArrayLen), None);
	}

	//===--------------------------------------------------------------------===//
	// Abbrev Emission
	//===--------------------------------------------------------------------===//

	private:
	// Emit the abbreviation as a DEFINE_ABBREV record.
	void EncodeAbbrev(const BitCodeAbbrev &Abbv) {
	EmitCode(bitc::DEFINE_ABBREV);
	EmitVBR(Abbv.getNumOperandInfos(), 5);
	for (unsigned i = 0, e = static_cast<unsigned>(Abbv.getNumOperandInfos());
	i != e; ++i) {
	const BitCodeAbbrevOp &Op = Abbv.getOperandInfo(i);
	Emit(Op.isLiteral(), 1);
	if (Op.isLiteral()) {
	EmitVBR64(Op.getLiteralValue(), 8);
	} else {
	Emit(Op.getEncoding(), 3);
	if (Op.hasEncodingData())
	EmitVBR64(Op.getEncodingData(), 5);
	}
	}
	}
	public:

	/// Emits the abbreviation \p Abbv to the stream.
	unsigned EmitAbbrev(std::shared_ptr<BitCodeAbbrev> Abbv) {
	EncodeAbbrev(*Abbv);
	CurAbbrevs.push_back(std::move(Abbv));
	return static_cast<unsigned>(CurAbbrevs.size())-1 +
	bitc::FIRST_APPLICATION_ABBREV;
	}

	//===--------------------------------------------------------------------===//
	// BlockInfo Block Emission
	//===--------------------------------------------------------------------===//

	/// EnterBlockInfoBlock - Start emitting the BLOCKINFO_BLOCK.
	void EnterBlockInfoBlock() {
	EnterSubblock(bitc::BLOCKINFO_BLOCK_ID, 2);
	BlockInfoCurBID = ~0U;
	BlockInfoRecords.clear();
	}
	private:
	/// SwitchToBlockID - If we aren't already talking about the specified block
	/// ID, emit a BLOCKINFO_CODE_SETBID record.
	void SwitchToBlockID(unsigned BlockID) {
	if (BlockInfoCurBID == BlockID) return;
	SmallVector<unsigned, 2> V;
	V.push_back(BlockID);
	EmitRecord(bitc::BLOCKINFO_CODE_SETBID, V);
	BlockInfoCurBID = BlockID;
	}

	BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
	if (BlockInfo *BI = getBlockInfo(BlockID))
	return *BI;

	// Otherwise, add a new record.
	BlockInfoRecords.emplace_back();
	BlockInfoRecords.back().BlockID = BlockID;
	return BlockInfoRecords.back();
	}

	public:

	/// EmitBlockInfoAbbrev - Emit a DEFINE_ABBREV record for the specified
	/// BlockID.
	unsigned EmitBlockInfoAbbrev(unsigned BlockID, std::shared_ptr<BitCodeAbbrev> Abbv) {
	SwitchToBlockID(BlockID);
	EncodeAbbrev(*Abbv);

	// Add the abbrev to the specified block record.
	BlockInfo &Info = getOrCreateBlockInfo(BlockID);
	Info.Abbrevs.push_back(std::move(Abbv));

	return Info.Abbrevs.size()-1+bitc::FIRST_APPLICATION_ABBREV;
	}
	};


	} // End llvm namespace

	#endif