#pragma once #ifdef __GNUC__ #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-parameter" #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/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 #include #include namespace llvm { class BitstreamWriter { /// Out - The buffer that keeps unflushed bytes. SmallVectorImpl &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> CurAbbrevs; struct Block { unsigned PrevCodeSize; size_t StartSizeWord; std::vector> PrevAbbrevs; Block(unsigned PCS, size_t SSW) : PrevCodeSize(PCS), StartSizeWord(SSW) {} }; /// BlockScope - This tracks the current blocks that we have entered. std::vector 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> Abbrevs; }; std::vector BlockInfoRecords; void WriteWord(unsigned Value) { Value = support::endian::byte_swap(Value); Out.append(reinterpret_cast(&Value), reinterpret_cast(&Value + 1)); } 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. Flushing only occurs at (sub)block boundaries. BitstreamWriter(SmallVectorImpl &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( &Out[ByteNo - NumOfFlushedBytes], StartBit)) && "Expected to be patching over 0-value placeholders"); endian::writeAtBitAlignment( &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(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(BytesRead) == BytesFromDisk); for (size_t i = 0; i < BytesFromBuffer; ++i) Bytes[BytesFromDisk + i] = Out[i]; assert((!endian::readAtBitAlignment( Bytes, StartBit)) && "Expected to be patching over 0-value placeholders"); } // Update Bytes in terms of bit offset and value. endian::writeAtBitAlignment(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 (BlockInfo &BI : BlockInfoRecords) if (BI.BlockID == BlockID) return &BI; return nullptr; } void EnterSubblock(unsigned BlockID, unsigned CodeLen) { // Block header: // [ENTER_SUBBLOCK, blockid, newcodelen, , 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, ] 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 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 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 void EmitRecordWithAbbrevImpl(unsigned Abbrev, ArrayRef Vals, StringRef Blob, std::optional 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(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(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(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 void emitBlob(ArrayRef Bytes, bool ShouldEmitSize = true) { // Emit a vbr6 to indicate the number of elements present. if (ShouldEmitSize) EmitVBR(static_cast(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); })); Out.append(Bytes.begin(), Bytes.end()); // Align end to 32-bits. while (GetBufferOffset() & 3) Out.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 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(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 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 void EmitRecordWithBlob(unsigned Abbrev, const Container &Vals, StringRef Blob) { EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals), Blob, std::nullopt); } template 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 void EmitRecordWithArray(unsigned Abbrev, const Container &Vals, StringRef Array) { EmitRecordWithAbbrevImpl(Abbrev, ArrayRef(Vals), Array, std::nullopt); } template 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(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 Abbv) { EncodeAbbrev(*Abbv); CurAbbrevs.push_back(std::move(Abbv)); return static_cast(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 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 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 #ifdef __GNUC__ #pragma GCC diagnostic pop #endif