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 //===- 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/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Bitstream/BitCodes.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <optional>
 #include <vector>
 
 namespace llvm {
 
 class BitstreamWriter {
   /// Owned buffer, used to init Buffer if the provided stream doesn't happen to
   /// be a buffer itself.
   SmallVector<char, 0> OwnBuffer;
   /// Internal buffer for unflushed bytes (unless there is no stream to flush
   /// to, case in which these are "the bytes"). The writer backpatches, so it is
   /// efficient to buffer.
   SmallVectorImpl<char> &Buffer;
 
   /// FS - The file stream that Buffer flushes to. If FS is a raw_fd_stream, the
   /// writer will incrementally flush at subblock boundaries. Otherwise flushing
   /// will happen at the end of BitstreamWriter's lifetime.
   raw_ostream *const FS;
 
   /// FlushThreshold - this is the threshold (unit B) to flush to FS, if FS is a
   /// raw_fd_stream.
   const uint64_t FlushThreshold;
 
   /// CurBit - Always between 0 and 31 inclusive, specifies the next bit to use.
   unsigned CurBit = 0;
 
   /// CurValue - The current value. Only bits < CurBit are valid.
   uint32_t CurValue = 0;
 
   /// CurCodeSize - This is the declared size of code values used for the
   /// current block, in bits.
   unsigned CurCodeSize = 2;
 
   /// BlockInfoCurBID - When emitting a BLOCKINFO_BLOCK, this is the currently
   /// selected BLOCK ID.
   unsigned BlockInfoCurBID = 0;
 
   /// CurAbbrevs - Abbrevs installed at in this block.
   std::vector<std::shared_ptr<BitCodeAbbrev>> CurAbbrevs;
 
   // Support for retrieving a section of the output, for purposes such as
   // checksumming.
   std::optional<size_t> BlockFlushingStartPos;
 
   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 WriteWord(unsigned Value) {
     Value =
         support::endian::byte_swap<uint32_t, llvm::endianness::little>(Value);
     Buffer.append(reinterpret_cast<const char *>(&Value),
                   reinterpret_cast<const char *>(&Value + 1));
   }
 
   uint64_t GetNumOfFlushedBytes() const {
     return fdStream() ? fdStream()->tell() : 0;
   }
 
   size_t GetBufferOffset() const {
     return Buffer.size() + GetNumOfFlushedBytes();
   }
 
   size_t GetWordIndex() const {
     size_t Offset = GetBufferOffset();
     assert((Offset & 3) == 0 && "Not 32-bit aligned");
     return Offset / 4;
   }
 
   void flushAndClear() {
     assert(FS);
     assert(!Buffer.empty());
     assert(!BlockFlushingStartPos &&
            "a call to markAndBlockFlushing should have been paired with a "
            "call to getMarkedBufferAndResumeFlushing");
     FS->write(Buffer.data(), Buffer.size());
     Buffer.clear();
   }
 
   /// If the related file stream is a raw_fd_stream, flush the buffer if its
   /// size is above a threshold. If \p OnClosing is true, flushing happens
   /// regardless of thresholds.
   void FlushToFile(bool OnClosing = false) {
     if (!FS || Buffer.empty())
       return;
     if (OnClosing)
       return flushAndClear();
     if (BlockFlushingStartPos)
       return;
     if (fdStream() && Buffer.size() > FlushThreshold)
       flushAndClear();
   }
 
   raw_fd_stream *fdStream() { return dyn_cast_or_null<raw_fd_stream>(FS); }
 
   const raw_fd_stream *fdStream() const {
     return dyn_cast_or_null<raw_fd_stream>(FS);
   }
 
   SmallVectorImpl<char> &getInternalBufferFromStream(raw_ostream &OutStream) {
     if (auto *SV = dyn_cast<raw_svector_ostream>(&OutStream))
       return SV->buffer();
     return OwnBuffer;
   }
 
 public:
   /// Create a BitstreamWriter over a raw_ostream \p OutStream.
   /// If \p OutStream is a raw_svector_ostream, the BitstreamWriter will write
   /// directly to the latter's buffer. In all other cases, the BitstreamWriter
   /// will use an internal buffer and flush at the end of its lifetime.
   ///
   /// In addition, if \p is a raw_fd_stream supporting seek, tell, and read
   /// (besides write), the BitstreamWriter will also flush incrementally, when a
   /// subblock is finished, and if the FlushThreshold is passed.
   ///
   /// NOTE: \p FlushThreshold's unit is MB.
   BitstreamWriter(raw_ostream &OutStream, uint32_t FlushThreshold = 512)
       : Buffer(getInternalBufferFromStream(OutStream)),
         FS(!isa<raw_svector_ostream>(OutStream) ? &OutStream : nullptr),
         FlushThreshold(uint64_t(FlushThreshold) << 20) {}
 
   /// Convenience constructor for users that start with a vector - avoids
   /// needing to wrap it in a raw_svector_ostream.
   BitstreamWriter(SmallVectorImpl<char> &Buff)
       : Buffer(Buff), FS(nullptr), FlushThreshold(0) {}
 
   ~BitstreamWriter() {
     FlushToWord();
     assert(BlockScope.empty() && CurAbbrevs.empty() && "Block imbalance");
     FlushToFile(/*OnClosing=*/true);
   }
 
   /// For scenarios where the user wants to access a section of the stream to
   /// (for example) compute some checksum, disable flushing and remember the
   /// position in the internal buffer where that happened. Must be paired with a
   /// call to getMarkedBufferAndResumeFlushing.
   void markAndBlockFlushing() {
     assert(!BlockFlushingStartPos);
     BlockFlushingStartPos = Buffer.size();
   }
 
   /// resumes flushing, but does not flush, and returns the section in the
   /// internal buffer starting from the position marked with
   /// markAndBlockFlushing. The return should be processed before any additional
   /// calls to this object, because those may cause a flush and invalidate the
   /// return.
   StringRef getMarkedBufferAndResumeFlushing() {
     assert(BlockFlushingStartPos);
     size_t Start = *BlockFlushingStartPos;
     BlockFlushingStartPos.reset();
     return {&Buffer[Start], Buffer.size() - Start};
   }
 
   /// 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 byte in the output at the given bit offset with the specified
   /// value.
   void BackpatchByte(uint64_t BitNo, uint8_t NewByte) {
     using namespace llvm::support;
     uint64_t ByteNo = BitNo / 8;
     uint64_t StartBit = BitNo & 7;
     uint64_t NumOfFlushedBytes = GetNumOfFlushedBytes();
 
     if (ByteNo >= NumOfFlushedBytes) {
       assert((!endian::readAtBitAlignment<uint8_t, llvm::endianness::little,
                                           unaligned>(
                  &Buffer[ByteNo - NumOfFlushedBytes], StartBit)) &&
              "Expected to be patching over 0-value placeholders");
       endian::writeAtBitAlignment<uint8_t, llvm::endianness::little, unaligned>(
           &Buffer[ByteNo - NumOfFlushedBytes], NewByte, StartBit);
       return;
     }
 
     // If we don't have a raw_fd_stream, GetNumOfFlushedBytes() should have
     // returned 0, and we shouldn't be here.
     assert(fdStream() != nullptr);
     // If the byte offset to backpatch is flushed, use seek to backfill data.
     // First, save the file position to restore later.
     uint64_t CurPos = fdStream()->tell();
 
     // Copy data to update into Bytes from the file FS and the buffer Out.
     char Bytes[3]; // Use one more byte to silence a warning from Visual C++.
     size_t BytesNum = StartBit ? 2 : 1;
     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 Buffer 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
     {
       fdStream()->seek(ByteNo);
       ssize_t BytesRead = fdStream()->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] = Buffer[i];
       assert((!endian::readAtBitAlignment<uint8_t, llvm::endianness::little,
                                           unaligned>(Bytes, StartBit)) &&
              "Expected to be patching over 0-value placeholders");
     }
 
     // Update Bytes in terms of bit offset and value.
     endian::writeAtBitAlignment<uint8_t, llvm::endianness::little, unaligned>(
         Bytes, NewByte, StartBit);
 
     // Copy updated data back to the file FS and the buffer Out.
     fdStream()->seek(ByteNo);
     fdStream()->write(Bytes, BytesFromDisk);
     for (size_t i = 0; i < BytesFromBuffer; ++i)
       Buffer[i] = Bytes[BytesFromDisk + i];
 
     // Restore the file position.
     fdStream()->seek(CurPos);
   }
 
   void BackpatchHalfWord(uint64_t BitNo, uint16_t Val) {
     BackpatchByte(BitNo, (uint8_t)Val);
     BackpatchByte(BitNo + 8, (uint8_t)(Val >> 8));
   }
 
   void BackpatchWord(uint64_t BitNo, unsigned Val) {
     BackpatchHalfWord(BitNo, (uint16_t)Val);
     BackpatchHalfWord(BitNo + 16, (uint16_t)(Val >> 16));
   }
 
   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 & ((1U << (NumBits - 1)) - 1)) | (1U << (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 & ((1U << (NumBits - 1)) - 1)) |
                (1U << (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 (BlockInfo &BI : BlockInfoRecords)
       if (BI.BlockID == BlockID)
         return &BI;
     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();
     FlushToFile();
   }
 
   //===--------------------------------------------------------------------===//
   // 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, std::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);
       else {
         assert(Op.getEncoding() != BitCodeAbbrevOp::Array &&
                Op.getEncoding() != BitCodeAbbrevOp::Blob &&
                "Expected literal or scalar");
         EmitAbbreviatedField(Op, *Code);
       }
     }
 
     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.
     assert(llvm::all_of(Bytes, [](UIntTy B) { return isUInt<8>(B); }));
     Buffer.append(Bytes.begin(), Bytes.end());
 
     // Align end to 32-bits.
     while (GetBufferOffset() & 3)
       Buffer.push_back(0);
   }
   void emitBlob(StringRef Bytes, bool ShouldEmitSize = true) {
     emitBlob(ArrayRef((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>(std::size(Vals));
       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, ArrayRef(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, ArrayRef(Vals), StringRef(), std::nullopt);
   }
 
   /// 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, ArrayRef(Vals), Blob, std::nullopt);
   }
   template <typename Container>
   void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
                           const char *BlobData, unsigned BlobLen) {
     return EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals),
                                     StringRef(BlobData, BlobLen), std::nullopt);
   }
 
   /// 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, ArrayRef(Vals), Array, std::nullopt);
   }
   template <typename Container>
   void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
                            const char *ArrayData, unsigned ArrayLen) {
     return EmitRecordWithAbbrevImpl(
         Abbrev, ArrayRef(Vals), StringRef(ArrayData, ArrayLen), std::nullopt);
   }
 
   //===--------------------------------------------------------------------===//
   // 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

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