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//===- BitstreamWriter.h - Low-level bitstream writer interface -*- C++ -*-===//
2
//
3
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4
// See https://llvm.org/LICENSE.txt for license information.
5
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6
//
7
//===----------------------------------------------------------------------===//
8
//
9
// This header defines the BitstreamWriter class.  This class can be used to
10
// write an arbitrary bitstream, regardless of its contents.
11
//
12
//===----------------------------------------------------------------------===//
13
 
14
#ifndef LLVM_BITSTREAM_BITSTREAMWRITER_H
15
#define LLVM_BITSTREAM_BITSTREAMWRITER_H
16
 
17
#include "llvm/ADT/ArrayRef.h"
18
#include "llvm/ADT/SmallVector.h"
19
#include "llvm/ADT/StringRef.h"
20
#include "llvm/Bitstream/BitCodes.h"
21
#include "llvm/Support/Endian.h"
22
#include "llvm/Support/MathExtras.h"
23
#include "llvm/Support/raw_ostream.h"
24
#include <algorithm>
25
#include <optional>
26
#include <vector>
27
 
28
namespace llvm {
29
 
30
class BitstreamWriter {
31
  /// Out - The buffer that keeps unflushed bytes.
32
  SmallVectorImpl<char> &Out;
33
 
34
  /// FS - The file stream that Out flushes to. If FS is nullptr, it does not
35
  /// support read or seek, Out cannot be flushed until all data are written.
36
  raw_fd_stream *FS;
37
 
38
  /// FlushThreshold - If FS is valid, this is the threshold (unit B) to flush
39
  /// FS.
40
  const uint64_t FlushThreshold;
41
 
42
  /// CurBit - Always between 0 and 31 inclusive, specifies the next bit to use.
43
  unsigned CurBit;
44
 
45
  /// CurValue - The current value. Only bits < CurBit are valid.
46
  uint32_t CurValue;
47
 
48
  /// CurCodeSize - This is the declared size of code values used for the
49
  /// current block, in bits.
50
  unsigned CurCodeSize;
51
 
52
  /// BlockInfoCurBID - When emitting a BLOCKINFO_BLOCK, this is the currently
53
  /// selected BLOCK ID.
54
  unsigned BlockInfoCurBID;
55
 
56
  /// CurAbbrevs - Abbrevs installed at in this block.
57
  std::vector<std::shared_ptr<BitCodeAbbrev>> CurAbbrevs;
58
 
59
  struct Block {
60
    unsigned PrevCodeSize;
61
    size_t StartSizeWord;
62
    std::vector<std::shared_ptr<BitCodeAbbrev>> PrevAbbrevs;
63
    Block(unsigned PCS, size_t SSW) : PrevCodeSize(PCS), StartSizeWord(SSW) {}
64
  };
65
 
66
  /// BlockScope - This tracks the current blocks that we have entered.
67
  std::vector<Block> BlockScope;
68
 
69
  /// BlockInfo - This contains information emitted to BLOCKINFO_BLOCK blocks.
70
  /// These describe abbreviations that all blocks of the specified ID inherit.
71
  struct BlockInfo {
72
    unsigned BlockID;
73
    std::vector<std::shared_ptr<BitCodeAbbrev>> Abbrevs;
74
  };
75
  std::vector<BlockInfo> BlockInfoRecords;
76
 
77
  void WriteWord(unsigned Value) {
78
    Value = support::endian::byte_swap<uint32_t, support::little>(Value);
79
    Out.append(reinterpret_cast<const char *>(&Value),
80
               reinterpret_cast<const char *>(&Value + 1));
81
  }
82
 
83
  uint64_t GetNumOfFlushedBytes() const { return FS ? FS->tell() : 0; }
84
 
85
  size_t GetBufferOffset() const { return Out.size() + GetNumOfFlushedBytes(); }
86
 
87
  size_t GetWordIndex() const {
88
    size_t Offset = GetBufferOffset();
89
    assert((Offset & 3) == 0 && "Not 32-bit aligned");
90
    return Offset / 4;
91
  }
92
 
93
  /// If the related file stream supports reading, seeking and writing, flush
94
  /// the buffer if its size is above a threshold.
95
  void FlushToFile() {
96
    if (!FS)
97
      return;
98
    if (Out.size() < FlushThreshold)
99
      return;
100
    FS->write((char *)&Out.front(), Out.size());
101
    Out.clear();
102
  }
103
 
104
public:
105
  /// Create a BitstreamWriter that writes to Buffer \p O.
106
  ///
107
  /// \p FS is the file stream that \p O flushes to incrementally. If \p FS is
108
  /// null, \p O does not flush incrementially, but writes to disk at the end.
109
  ///
110
  /// \p FlushThreshold is the threshold (unit M) to flush \p O if \p FS is
111
  /// valid. Flushing only occurs at (sub)block boundaries.
112
  BitstreamWriter(SmallVectorImpl<char> &O, raw_fd_stream *FS = nullptr,
113
                  uint32_t FlushThreshold = 512)
114
      : Out(O), FS(FS), FlushThreshold(FlushThreshold << 20), CurBit(0),
115
        CurValue(0), CurCodeSize(2) {}
116
 
117
  ~BitstreamWriter() {
118
    assert(CurBit == 0 && "Unflushed data remaining");
119
    assert(BlockScope.empty() && CurAbbrevs.empty() && "Block imbalance");
120
  }
121
 
122
  /// Retrieve the current position in the stream, in bits.
123
  uint64_t GetCurrentBitNo() const { return GetBufferOffset() * 8 + CurBit; }
124
 
125
  /// Retrieve the number of bits currently used to encode an abbrev ID.
126
  unsigned GetAbbrevIDWidth() const { return CurCodeSize; }
127
 
128
  //===--------------------------------------------------------------------===//
129
  // Basic Primitives for emitting bits to the stream.
130
  //===--------------------------------------------------------------------===//
131
 
132
  /// Backpatch a 32-bit word in the output at the given bit offset
133
  /// with the specified value.
134
  void BackpatchWord(uint64_t BitNo, unsigned NewWord) {
135
    using namespace llvm::support;
136
    uint64_t ByteNo = BitNo / 8;
137
    uint64_t StartBit = BitNo & 7;
138
    uint64_t NumOfFlushedBytes = GetNumOfFlushedBytes();
139
 
140
    if (ByteNo >= NumOfFlushedBytes) {
141
      assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
142
                 &Out[ByteNo - NumOfFlushedBytes], StartBit)) &&
143
             "Expected to be patching over 0-value placeholders");
144
      endian::writeAtBitAlignment<uint32_t, little, unaligned>(
145
          &Out[ByteNo - NumOfFlushedBytes], NewWord, StartBit);
146
      return;
147
    }
148
 
149
    // If the byte offset to backpatch is flushed, use seek to backfill data.
150
    // First, save the file position to restore later.
151
    uint64_t CurPos = FS->tell();
152
 
153
    // Copy data to update into Bytes from the file FS and the buffer Out.
154
    char Bytes[9]; // Use one more byte to silence a warning from Visual C++.
155
    size_t BytesNum = StartBit ? 8 : 4;
156
    size_t BytesFromDisk = std::min(static_cast<uint64_t>(BytesNum), NumOfFlushedBytes - ByteNo);
157
    size_t BytesFromBuffer = BytesNum - BytesFromDisk;
158
 
159
    // When unaligned, copy existing data into Bytes from the file FS and the
160
    // buffer Out so that it can be updated before writing. For debug builds
161
    // read bytes unconditionally in order to check that the existing value is 0
162
    // as expected.
163
#ifdef NDEBUG
164
    if (StartBit)
165
#endif
166
    {
167
      FS->seek(ByteNo);
168
      ssize_t BytesRead = FS->read(Bytes, BytesFromDisk);
169
      (void)BytesRead; // silence warning
170
      assert(BytesRead >= 0 && static_cast<size_t>(BytesRead) == BytesFromDisk);
171
      for (size_t i = 0; i < BytesFromBuffer; ++i)
172
        Bytes[BytesFromDisk + i] = Out[i];
173
      assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
174
                 Bytes, StartBit)) &&
175
             "Expected to be patching over 0-value placeholders");
176
    }
177
 
178
    // Update Bytes in terms of bit offset and value.
179
    endian::writeAtBitAlignment<uint32_t, little, unaligned>(Bytes, NewWord,
180
                                                             StartBit);
181
 
182
    // Copy updated data back to the file FS and the buffer Out.
183
    FS->seek(ByteNo);
184
    FS->write(Bytes, BytesFromDisk);
185
    for (size_t i = 0; i < BytesFromBuffer; ++i)
186
      Out[i] = Bytes[BytesFromDisk + i];
187
 
188
    // Restore the file position.
189
    FS->seek(CurPos);
190
  }
191
 
192
  void BackpatchWord64(uint64_t BitNo, uint64_t Val) {
193
    BackpatchWord(BitNo, (uint32_t)Val);
194
    BackpatchWord(BitNo + 32, (uint32_t)(Val >> 32));
195
  }
196
 
197
  void Emit(uint32_t Val, unsigned NumBits) {
198
    assert(NumBits && NumBits <= 32 && "Invalid value size!");
199
    assert((Val & ~(~0U >> (32-NumBits))) == 0 && "High bits set!");
200
    CurValue |= Val << CurBit;
201
    if (CurBit + NumBits < 32) {
202
      CurBit += NumBits;
203
      return;
204
    }
205
 
206
    // Add the current word.
207
    WriteWord(CurValue);
208
 
209
    if (CurBit)
210
      CurValue = Val >> (32-CurBit);
211
    else
212
      CurValue = 0;
213
    CurBit = (CurBit+NumBits) & 31;
214
  }
215
 
216
  void FlushToWord() {
217
    if (CurBit) {
218
      WriteWord(CurValue);
219
      CurBit = 0;
220
      CurValue = 0;
221
    }
222
  }
223
 
224
  void EmitVBR(uint32_t Val, unsigned NumBits) {
225
    assert(NumBits <= 32 && "Too many bits to emit!");
226
    uint32_t Threshold = 1U << (NumBits-1);
227
 
228
    // Emit the bits with VBR encoding, NumBits-1 bits at a time.
229
    while (Val >= Threshold) {
230
      Emit((Val & ((1 << (NumBits-1))-1)) | (1 << (NumBits-1)), NumBits);
231
      Val >>= NumBits-1;
232
    }
233
 
234
    Emit(Val, NumBits);
235
  }
236
 
237
  void EmitVBR64(uint64_t Val, unsigned NumBits) {
238
    assert(NumBits <= 32 && "Too many bits to emit!");
239
    if ((uint32_t)Val == Val)
240
      return EmitVBR((uint32_t)Val, NumBits);
241
 
242
    uint32_t Threshold = 1U << (NumBits-1);
243
 
244
    // Emit the bits with VBR encoding, NumBits-1 bits at a time.
245
    while (Val >= Threshold) {
246
      Emit(((uint32_t)Val & ((1 << (NumBits - 1)) - 1)) | (1 << (NumBits - 1)),
247
           NumBits);
248
      Val >>= NumBits-1;
249
    }
250
 
251
    Emit((uint32_t)Val, NumBits);
252
  }
253
 
254
  /// EmitCode - Emit the specified code.
255
  void EmitCode(unsigned Val) {
256
    Emit(Val, CurCodeSize);
257
  }
258
 
259
  //===--------------------------------------------------------------------===//
260
  // Block Manipulation
261
  //===--------------------------------------------------------------------===//
262
 
263
  /// getBlockInfo - If there is block info for the specified ID, return it,
264
  /// otherwise return null.
265
  BlockInfo *getBlockInfo(unsigned BlockID) {
266
    // Common case, the most recent entry matches BlockID.
267
    if (!BlockInfoRecords.empty() && BlockInfoRecords.back().BlockID == BlockID)
268
      return &BlockInfoRecords.back();
269
 
270
    for (BlockInfo &BI : BlockInfoRecords)
271
      if (BI.BlockID == BlockID)
272
        return &BI;
273
    return nullptr;
274
  }
275
 
276
  void EnterSubblock(unsigned BlockID, unsigned CodeLen) {
277
    // Block header:
278
    //    [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
279
    EmitCode(bitc::ENTER_SUBBLOCK);
280
    EmitVBR(BlockID, bitc::BlockIDWidth);
281
    EmitVBR(CodeLen, bitc::CodeLenWidth);
282
    FlushToWord();
283
 
284
    size_t BlockSizeWordIndex = GetWordIndex();
285
    unsigned OldCodeSize = CurCodeSize;
286
 
287
    // Emit a placeholder, which will be replaced when the block is popped.
288
    Emit(0, bitc::BlockSizeWidth);
289
 
290
    CurCodeSize = CodeLen;
291
 
292
    // Push the outer block's abbrev set onto the stack, start out with an
293
    // empty abbrev set.
294
    BlockScope.emplace_back(OldCodeSize, BlockSizeWordIndex);
295
    BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
296
 
297
    // If there is a blockinfo for this BlockID, add all the predefined abbrevs
298
    // to the abbrev list.
299
    if (BlockInfo *Info = getBlockInfo(BlockID))
300
      append_range(CurAbbrevs, Info->Abbrevs);
301
  }
302
 
303
  void ExitBlock() {
304
    assert(!BlockScope.empty() && "Block scope imbalance!");
305
    const Block &B = BlockScope.back();
306
 
307
    // Block tail:
308
    //    [END_BLOCK, <align4bytes>]
309
    EmitCode(bitc::END_BLOCK);
310
    FlushToWord();
311
 
312
    // Compute the size of the block, in words, not counting the size field.
313
    size_t SizeInWords = GetWordIndex() - B.StartSizeWord - 1;
314
    uint64_t BitNo = uint64_t(B.StartSizeWord) * 32;
315
 
316
    // Update the block size field in the header of this sub-block.
317
    BackpatchWord(BitNo, SizeInWords);
318
 
319
    // Restore the inner block's code size and abbrev table.
320
    CurCodeSize = B.PrevCodeSize;
321
    CurAbbrevs = std::move(B.PrevAbbrevs);
322
    BlockScope.pop_back();
323
    FlushToFile();
324
  }
325
 
326
  //===--------------------------------------------------------------------===//
327
  // Record Emission
328
  //===--------------------------------------------------------------------===//
329
 
330
private:
331
  /// EmitAbbreviatedLiteral - Emit a literal value according to its abbrev
332
  /// record.  This is a no-op, since the abbrev specifies the literal to use.
333
  template<typename uintty>
334
  void EmitAbbreviatedLiteral(const BitCodeAbbrevOp &Op, uintty V) {
335
    assert(Op.isLiteral() && "Not a literal");
336
    // If the abbrev specifies the literal value to use, don't emit
337
    // anything.
338
    assert(V == Op.getLiteralValue() &&
339
           "Invalid abbrev for record!");
340
  }
341
 
342
  /// EmitAbbreviatedField - Emit a single scalar field value with the specified
343
  /// encoding.
344
  template<typename uintty>
345
  void EmitAbbreviatedField(const BitCodeAbbrevOp &Op, uintty V) {
346
    assert(!Op.isLiteral() && "Literals should use EmitAbbreviatedLiteral!");
347
 
348
    // Encode the value as we are commanded.
349
    switch (Op.getEncoding()) {
350
    default: llvm_unreachable("Unknown encoding!");
351
    case BitCodeAbbrevOp::Fixed:
352
      if (Op.getEncodingData())
353
        Emit((unsigned)V, (unsigned)Op.getEncodingData());
354
      break;
355
    case BitCodeAbbrevOp::VBR:
356
      if (Op.getEncodingData())
357
        EmitVBR64(V, (unsigned)Op.getEncodingData());
358
      break;
359
    case BitCodeAbbrevOp::Char6:
360
      Emit(BitCodeAbbrevOp::EncodeChar6((char)V), 6);
361
      break;
362
    }
363
  }
364
 
365
  /// EmitRecordWithAbbrevImpl - This is the core implementation of the record
366
  /// emission code.  If BlobData is non-null, then it specifies an array of
367
  /// data that should be emitted as part of the Blob or Array operand that is
368
  /// known to exist at the end of the record. If Code is specified, then
369
  /// it is the record code to emit before the Vals, which must not contain
370
  /// the code.
371
  template <typename uintty>
372
  void EmitRecordWithAbbrevImpl(unsigned Abbrev, ArrayRef<uintty> Vals,
373
                                StringRef Blob, std::optional<unsigned> Code) {
374
    const char *BlobData = Blob.data();
375
    unsigned BlobLen = (unsigned) Blob.size();
376
    unsigned AbbrevNo = Abbrev-bitc::FIRST_APPLICATION_ABBREV;
377
    assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
378
    const BitCodeAbbrev *Abbv = CurAbbrevs[AbbrevNo].get();
379
 
380
    EmitCode(Abbrev);
381
 
382
    unsigned i = 0, e = static_cast<unsigned>(Abbv->getNumOperandInfos());
383
    if (Code) {
384
      assert(e && "Expected non-empty abbreviation");
385
      const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i++);
386
 
387
      if (Op.isLiteral())
388
        EmitAbbreviatedLiteral(Op, *Code);
389
      else {
390
        assert(Op.getEncoding() != BitCodeAbbrevOp::Array &&
391
               Op.getEncoding() != BitCodeAbbrevOp::Blob &&
392
               "Expected literal or scalar");
393
        EmitAbbreviatedField(Op, *Code);
394
      }
395
    }
396
 
397
    unsigned RecordIdx = 0;
398
    for (; i != e; ++i) {
399
      const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
400
      if (Op.isLiteral()) {
401
        assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
402
        EmitAbbreviatedLiteral(Op, Vals[RecordIdx]);
403
        ++RecordIdx;
404
      } else if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
405
        // Array case.
406
        assert(i + 2 == e && "array op not second to last?");
407
        const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
408
 
409
        // If this record has blob data, emit it, otherwise we must have record
410
        // entries to encode this way.
411
        if (BlobData) {
412
          assert(RecordIdx == Vals.size() &&
413
                 "Blob data and record entries specified for array!");
414
          // Emit a vbr6 to indicate the number of elements present.
415
          EmitVBR(static_cast<uint32_t>(BlobLen), 6);
416
 
417
          // Emit each field.
418
          for (unsigned i = 0; i != BlobLen; ++i)
419
            EmitAbbreviatedField(EltEnc, (unsigned char)BlobData[i]);
420
 
421
          // Know that blob data is consumed for assertion below.
422
          BlobData = nullptr;
423
        } else {
424
          // Emit a vbr6 to indicate the number of elements present.
425
          EmitVBR(static_cast<uint32_t>(Vals.size()-RecordIdx), 6);
426
 
427
          // Emit each field.
428
          for (unsigned e = Vals.size(); RecordIdx != e; ++RecordIdx)
429
            EmitAbbreviatedField(EltEnc, Vals[RecordIdx]);
430
        }
431
      } else if (Op.getEncoding() == BitCodeAbbrevOp::Blob) {
432
        // If this record has blob data, emit it, otherwise we must have record
433
        // entries to encode this way.
434
 
435
        if (BlobData) {
436
          assert(RecordIdx == Vals.size() &&
437
                 "Blob data and record entries specified for blob operand!");
438
 
439
          assert(Blob.data() == BlobData && "BlobData got moved");
440
          assert(Blob.size() == BlobLen && "BlobLen got changed");
441
          emitBlob(Blob);
442
          BlobData = nullptr;
443
        } else {
444
          emitBlob(Vals.slice(RecordIdx));
445
        }
446
      } else {  // Single scalar field.
447
        assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
448
        EmitAbbreviatedField(Op, Vals[RecordIdx]);
449
        ++RecordIdx;
450
      }
451
    }
452
    assert(RecordIdx == Vals.size() && "Not all record operands emitted!");
453
    assert(BlobData == nullptr &&
454
           "Blob data specified for record that doesn't use it!");
455
  }
456
 
457
public:
458
  /// Emit a blob, including flushing before and tail-padding.
459
  template <class UIntTy>
460
  void emitBlob(ArrayRef<UIntTy> Bytes, bool ShouldEmitSize = true) {
461
    // Emit a vbr6 to indicate the number of elements present.
462
    if (ShouldEmitSize)
463
      EmitVBR(static_cast<uint32_t>(Bytes.size()), 6);
464
 
465
    // Flush to a 32-bit alignment boundary.
466
    FlushToWord();
467
 
468
    // Emit literal bytes.
469
    assert(llvm::all_of(Bytes, [](UIntTy B) { return isUInt<8>(B); }));
470
    Out.append(Bytes.begin(), Bytes.end());
471
 
472
    // Align end to 32-bits.
473
    while (GetBufferOffset() & 3)
474
      Out.push_back(0);
475
  }
476
  void emitBlob(StringRef Bytes, bool ShouldEmitSize = true) {
477
    emitBlob(ArrayRef((const uint8_t *)Bytes.data(), Bytes.size()),
478
             ShouldEmitSize);
479
  }
480
 
481
  /// EmitRecord - Emit the specified record to the stream, using an abbrev if
482
  /// we have one to compress the output.
483
  template <typename Container>
484
  void EmitRecord(unsigned Code, const Container &Vals, unsigned Abbrev = 0) {
485
    if (!Abbrev) {
486
      // If we don't have an abbrev to use, emit this in its fully unabbreviated
487
      // form.
488
      auto Count = static_cast<uint32_t>(std::size(Vals));
489
      EmitCode(bitc::UNABBREV_RECORD);
490
      EmitVBR(Code, 6);
491
      EmitVBR(Count, 6);
492
      for (unsigned i = 0, e = Count; i != e; ++i)
493
        EmitVBR64(Vals[i], 6);
494
      return;
495
    }
496
 
497
    EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals), StringRef(), Code);
498
  }
499
 
500
  /// EmitRecordWithAbbrev - Emit a record with the specified abbreviation.
501
  /// Unlike EmitRecord, the code for the record should be included in Vals as
502
  /// the first entry.
503
  template <typename Container>
504
  void EmitRecordWithAbbrev(unsigned Abbrev, const Container &Vals) {
505
    EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals), StringRef(), std::nullopt);
506
  }
507
 
508
  /// EmitRecordWithBlob - Emit the specified record to the stream, using an
509
  /// abbrev that includes a blob at the end.  The blob data to emit is
510
  /// specified by the pointer and length specified at the end.  In contrast to
511
  /// EmitRecord, this routine expects that the first entry in Vals is the code
512
  /// of the record.
513
  template <typename Container>
514
  void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
515
                          StringRef Blob) {
516
    EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals), Blob, std::nullopt);
517
  }
518
  template <typename Container>
519
  void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals,
520
                          const char *BlobData, unsigned BlobLen) {
521
    return EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals),
522
                                    StringRef(BlobData, BlobLen), std::nullopt);
523
  }
524
 
525
  /// EmitRecordWithArray - Just like EmitRecordWithBlob, works with records
526
  /// that end with an array.
527
  template <typename Container>
528
  void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
529
                           StringRef Array) {
530
    EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals), Array, std::nullopt);
531
  }
532
  template <typename Container>
533
  void EmitRecordWithArray(unsigned Abbrev, const Container &Vals,
534
                           const char *ArrayData, unsigned ArrayLen) {
535
    return EmitRecordWithAbbrevImpl(
536
        Abbrev, ArrayRef(Vals), StringRef(ArrayData, ArrayLen), std::nullopt);
537
  }
538
 
539
  //===--------------------------------------------------------------------===//
540
  // Abbrev Emission
541
  //===--------------------------------------------------------------------===//
542
 
543
private:
544
  // Emit the abbreviation as a DEFINE_ABBREV record.
545
  void EncodeAbbrev(const BitCodeAbbrev &Abbv) {
546
    EmitCode(bitc::DEFINE_ABBREV);
547
    EmitVBR(Abbv.getNumOperandInfos(), 5);
548
    for (unsigned i = 0, e = static_cast<unsigned>(Abbv.getNumOperandInfos());
549
         i != e; ++i) {
550
      const BitCodeAbbrevOp &Op = Abbv.getOperandInfo(i);
551
      Emit(Op.isLiteral(), 1);
552
      if (Op.isLiteral()) {
553
        EmitVBR64(Op.getLiteralValue(), 8);
554
      } else {
555
        Emit(Op.getEncoding(), 3);
556
        if (Op.hasEncodingData())
557
          EmitVBR64(Op.getEncodingData(), 5);
558
      }
559
    }
560
  }
561
public:
562
 
563
  /// Emits the abbreviation \p Abbv to the stream.
564
  unsigned EmitAbbrev(std::shared_ptr<BitCodeAbbrev> Abbv) {
565
    EncodeAbbrev(*Abbv);
566
    CurAbbrevs.push_back(std::move(Abbv));
567
    return static_cast<unsigned>(CurAbbrevs.size())-1 +
568
      bitc::FIRST_APPLICATION_ABBREV;
569
  }
570
 
571
  //===--------------------------------------------------------------------===//
572
  // BlockInfo Block Emission
573
  //===--------------------------------------------------------------------===//
574
 
575
  /// EnterBlockInfoBlock - Start emitting the BLOCKINFO_BLOCK.
576
  void EnterBlockInfoBlock() {
577
    EnterSubblock(bitc::BLOCKINFO_BLOCK_ID, 2);
578
    BlockInfoCurBID = ~0U;
579
    BlockInfoRecords.clear();
580
  }
581
private:
582
  /// SwitchToBlockID - If we aren't already talking about the specified block
583
  /// ID, emit a BLOCKINFO_CODE_SETBID record.
584
  void SwitchToBlockID(unsigned BlockID) {
585
    if (BlockInfoCurBID == BlockID) return;
586
    SmallVector<unsigned, 2> V;
587
    V.push_back(BlockID);
588
    EmitRecord(bitc::BLOCKINFO_CODE_SETBID, V);
589
    BlockInfoCurBID = BlockID;
590
  }
591
 
592
  BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
593
    if (BlockInfo *BI = getBlockInfo(BlockID))
594
      return *BI;
595
 
596
    // Otherwise, add a new record.
597
    BlockInfoRecords.emplace_back();
598
    BlockInfoRecords.back().BlockID = BlockID;
599
    return BlockInfoRecords.back();
600
  }
601
 
602
public:
603
 
604
  /// EmitBlockInfoAbbrev - Emit a DEFINE_ABBREV record for the specified
605
  /// BlockID.
606
  unsigned EmitBlockInfoAbbrev(unsigned BlockID, std::shared_ptr<BitCodeAbbrev> Abbv) {
607
    SwitchToBlockID(BlockID);
608
    EncodeAbbrev(*Abbv);
609
 
610
    // Add the abbrev to the specified block record.
611
    BlockInfo &Info = getOrCreateBlockInfo(BlockID);
612
    Info.Abbrevs.push_back(std::move(Abbv));
613
 
614
    return Info.Abbrevs.size()-1+bitc::FIRST_APPLICATION_ABBREV;
615
  }
616
};
617
 
618
 
619
} // End llvm namespace
620
 
621
#endif