477 lines
16 KiB
C++
477 lines
16 KiB
C++
//===- BitstreamReader.cpp - BitstreamReader implementation ---------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Bitstream/BitstreamReader.h"
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#include "llvm/ADT/StringRef.h"
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#include <cassert>
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#include <string>
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// BitstreamCursor implementation
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//===----------------------------------------------------------------------===//
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/// Having read the ENTER_SUBBLOCK abbrevid, enter the block.
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Error BitstreamCursor::EnterSubBlock(unsigned BlockID, unsigned *NumWordsP) {
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// Save the current block's state on BlockScope.
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BlockScope.push_back(Block(CurCodeSize));
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BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
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// Add the abbrevs specific to this block to the CurAbbrevs list.
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if (BlockInfo) {
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if (const BitstreamBlockInfo::BlockInfo *Info =
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BlockInfo->getBlockInfo(BlockID)) {
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llvm::append_range(CurAbbrevs, Info->Abbrevs);
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}
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}
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// Get the codesize of this block.
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Expected<uint32_t> MaybeVBR = ReadVBR(bitc::CodeLenWidth);
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if (!MaybeVBR)
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return MaybeVBR.takeError();
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CurCodeSize = MaybeVBR.get();
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if (CurCodeSize > MaxChunkSize)
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return llvm::createStringError(
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std::errc::illegal_byte_sequence,
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"can't read more than %zu at a time, trying to read %u", +MaxChunkSize,
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CurCodeSize);
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SkipToFourByteBoundary();
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Expected<word_t> MaybeNum = Read(bitc::BlockSizeWidth);
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if (!MaybeNum)
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return MaybeNum.takeError();
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word_t NumWords = MaybeNum.get();
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if (NumWordsP)
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*NumWordsP = NumWords;
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if (CurCodeSize == 0)
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return llvm::createStringError(
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std::errc::illegal_byte_sequence,
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"can't enter sub-block: current code size is 0");
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if (AtEndOfStream())
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return llvm::createStringError(
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std::errc::illegal_byte_sequence,
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"can't enter sub block: already at end of stream");
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return Error::success();
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}
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static Expected<uint64_t> readAbbreviatedField(BitstreamCursor &Cursor,
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const BitCodeAbbrevOp &Op) {
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assert(!Op.isLiteral() && "Not to be used with literals!");
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// Decode the value as we are commanded.
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switch (Op.getEncoding()) {
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case BitCodeAbbrevOp::Array:
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case BitCodeAbbrevOp::Blob:
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llvm_unreachable("Should not reach here");
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case BitCodeAbbrevOp::Fixed:
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assert((unsigned)Op.getEncodingData() <= Cursor.MaxChunkSize);
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return Cursor.Read((unsigned)Op.getEncodingData());
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case BitCodeAbbrevOp::VBR:
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assert((unsigned)Op.getEncodingData() <= Cursor.MaxChunkSize);
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return Cursor.ReadVBR64((unsigned)Op.getEncodingData());
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case BitCodeAbbrevOp::Char6:
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if (Expected<unsigned> Res = Cursor.Read(6))
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return BitCodeAbbrevOp::DecodeChar6(Res.get());
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else
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return Res.takeError();
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}
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llvm_unreachable("invalid abbreviation encoding");
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}
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/// skipRecord - Read the current record and discard it.
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Expected<unsigned> BitstreamCursor::skipRecord(unsigned AbbrevID) {
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// Skip unabbreviated records by reading past their entries.
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if (AbbrevID == bitc::UNABBREV_RECORD) {
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Expected<uint32_t> MaybeCode = ReadVBR(6);
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if (!MaybeCode)
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return MaybeCode.takeError();
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unsigned Code = MaybeCode.get();
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Expected<uint32_t> MaybeVBR = ReadVBR(6);
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if (!MaybeVBR)
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return MaybeVBR.get();
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unsigned NumElts = MaybeVBR.get();
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for (unsigned i = 0; i != NumElts; ++i)
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if (Expected<uint64_t> Res = ReadVBR64(6))
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; // Skip!
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else
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return Res.takeError();
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return Code;
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}
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const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
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const BitCodeAbbrevOp &CodeOp = Abbv->getOperandInfo(0);
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unsigned Code;
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if (CodeOp.isLiteral())
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Code = CodeOp.getLiteralValue();
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else {
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if (CodeOp.getEncoding() == BitCodeAbbrevOp::Array ||
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CodeOp.getEncoding() == BitCodeAbbrevOp::Blob)
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return llvm::createStringError(
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std::errc::illegal_byte_sequence,
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"Abbreviation starts with an Array or a Blob");
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Expected<uint64_t> MaybeCode = readAbbreviatedField(*this, CodeOp);
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if (!MaybeCode)
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return MaybeCode.takeError();
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Code = MaybeCode.get();
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}
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for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i < e; ++i) {
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const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
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if (Op.isLiteral())
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continue;
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if (Op.getEncoding() != BitCodeAbbrevOp::Array &&
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Op.getEncoding() != BitCodeAbbrevOp::Blob) {
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if (Expected<uint64_t> MaybeField = readAbbreviatedField(*this, Op))
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continue;
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else
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return MaybeField.takeError();
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}
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if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
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// Array case. Read the number of elements as a vbr6.
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Expected<uint32_t> MaybeNum = ReadVBR(6);
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if (!MaybeNum)
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return MaybeNum.takeError();
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unsigned NumElts = MaybeNum.get();
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// Get the element encoding.
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assert(i+2 == e && "array op not second to last?");
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const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
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// Read all the elements.
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// Decode the value as we are commanded.
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switch (EltEnc.getEncoding()) {
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default:
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report_fatal_error("Array element type can't be an Array or a Blob");
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case BitCodeAbbrevOp::Fixed:
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assert((unsigned)EltEnc.getEncodingData() <= MaxChunkSize);
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if (Error Err =
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JumpToBit(GetCurrentBitNo() + static_cast<uint64_t>(NumElts) *
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EltEnc.getEncodingData()))
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return std::move(Err);
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break;
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case BitCodeAbbrevOp::VBR:
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assert((unsigned)EltEnc.getEncodingData() <= MaxChunkSize);
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for (; NumElts; --NumElts)
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if (Expected<uint64_t> Res =
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ReadVBR64((unsigned)EltEnc.getEncodingData()))
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; // Skip!
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else
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return Res.takeError();
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break;
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case BitCodeAbbrevOp::Char6:
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if (Error Err = JumpToBit(GetCurrentBitNo() + NumElts * 6))
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return std::move(Err);
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break;
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}
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continue;
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}
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assert(Op.getEncoding() == BitCodeAbbrevOp::Blob);
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// Blob case. Read the number of bytes as a vbr6.
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Expected<uint32_t> MaybeNum = ReadVBR(6);
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if (!MaybeNum)
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return MaybeNum.takeError();
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unsigned NumElts = MaybeNum.get();
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SkipToFourByteBoundary(); // 32-bit alignment
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// Figure out where the end of this blob will be including tail padding.
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const size_t NewEnd = GetCurrentBitNo() + alignTo(NumElts, 4) * 8;
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// If this would read off the end of the bitcode file, just set the
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// record to empty and return.
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if (!canSkipToPos(NewEnd/8)) {
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skipToEnd();
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break;
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}
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// Skip over the blob.
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if (Error Err = JumpToBit(NewEnd))
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return std::move(Err);
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}
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return Code;
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}
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Expected<unsigned> BitstreamCursor::readRecord(unsigned AbbrevID,
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SmallVectorImpl<uint64_t> &Vals,
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StringRef *Blob) {
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if (AbbrevID == bitc::UNABBREV_RECORD) {
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Expected<uint32_t> MaybeCode = ReadVBR(6);
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if (!MaybeCode)
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return MaybeCode.takeError();
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uint32_t Code = MaybeCode.get();
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Expected<uint32_t> MaybeNumElts = ReadVBR(6);
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if (!MaybeNumElts)
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return MaybeNumElts.takeError();
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uint32_t NumElts = MaybeNumElts.get();
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Vals.reserve(Vals.size() + NumElts);
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for (unsigned i = 0; i != NumElts; ++i)
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if (Expected<uint64_t> MaybeVal = ReadVBR64(6))
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Vals.push_back(MaybeVal.get());
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else
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return MaybeVal.takeError();
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return Code;
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}
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const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
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// Read the record code first.
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assert(Abbv->getNumOperandInfos() != 0 && "no record code in abbreviation?");
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const BitCodeAbbrevOp &CodeOp = Abbv->getOperandInfo(0);
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unsigned Code;
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if (CodeOp.isLiteral())
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Code = CodeOp.getLiteralValue();
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else {
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if (CodeOp.getEncoding() == BitCodeAbbrevOp::Array ||
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CodeOp.getEncoding() == BitCodeAbbrevOp::Blob)
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report_fatal_error("Abbreviation starts with an Array or a Blob");
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if (Expected<uint64_t> MaybeCode = readAbbreviatedField(*this, CodeOp))
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Code = MaybeCode.get();
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else
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return MaybeCode.takeError();
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}
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for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i != e; ++i) {
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const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
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if (Op.isLiteral()) {
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Vals.push_back(Op.getLiteralValue());
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continue;
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}
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if (Op.getEncoding() != BitCodeAbbrevOp::Array &&
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Op.getEncoding() != BitCodeAbbrevOp::Blob) {
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if (Expected<uint64_t> MaybeVal = readAbbreviatedField(*this, Op))
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Vals.push_back(MaybeVal.get());
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else
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return MaybeVal.takeError();
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continue;
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}
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if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
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// Array case. Read the number of elements as a vbr6.
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Expected<uint32_t> MaybeNumElts = ReadVBR(6);
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if (!MaybeNumElts)
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return MaybeNumElts.takeError();
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uint32_t NumElts = MaybeNumElts.get();
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Vals.reserve(Vals.size() + NumElts);
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// Get the element encoding.
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if (i + 2 != e)
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report_fatal_error("Array op not second to last");
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const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
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if (!EltEnc.isEncoding())
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report_fatal_error(
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"Array element type has to be an encoding of a type");
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// Read all the elements.
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switch (EltEnc.getEncoding()) {
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default:
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report_fatal_error("Array element type can't be an Array or a Blob");
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case BitCodeAbbrevOp::Fixed:
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for (; NumElts; --NumElts)
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if (Expected<SimpleBitstreamCursor::word_t> MaybeVal =
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Read((unsigned)EltEnc.getEncodingData()))
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Vals.push_back(MaybeVal.get());
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else
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return MaybeVal.takeError();
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break;
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case BitCodeAbbrevOp::VBR:
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for (; NumElts; --NumElts)
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if (Expected<uint64_t> MaybeVal =
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ReadVBR64((unsigned)EltEnc.getEncodingData()))
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Vals.push_back(MaybeVal.get());
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else
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return MaybeVal.takeError();
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break;
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case BitCodeAbbrevOp::Char6:
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for (; NumElts; --NumElts)
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if (Expected<SimpleBitstreamCursor::word_t> MaybeVal = Read(6))
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Vals.push_back(BitCodeAbbrevOp::DecodeChar6(MaybeVal.get()));
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else
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return MaybeVal.takeError();
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}
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continue;
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}
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assert(Op.getEncoding() == BitCodeAbbrevOp::Blob);
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// Blob case. Read the number of bytes as a vbr6.
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Expected<uint32_t> MaybeNumElts = ReadVBR(6);
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if (!MaybeNumElts)
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return MaybeNumElts.takeError();
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uint32_t NumElts = MaybeNumElts.get();
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SkipToFourByteBoundary(); // 32-bit alignment
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// Figure out where the end of this blob will be including tail padding.
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size_t CurBitPos = GetCurrentBitNo();
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const size_t NewEnd = CurBitPos + alignTo(NumElts, 4) * 8;
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// If this would read off the end of the bitcode file, just set the
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// record to empty and return.
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if (!canSkipToPos(NewEnd/8)) {
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Vals.append(NumElts, 0);
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skipToEnd();
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break;
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}
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// Otherwise, inform the streamer that we need these bytes in memory. Skip
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// over tail padding first, in case jumping to NewEnd invalidates the Blob
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// pointer.
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if (Error Err = JumpToBit(NewEnd))
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return std::move(Err);
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const char *Ptr = (const char *)getPointerToBit(CurBitPos, NumElts);
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// If we can return a reference to the data, do so to avoid copying it.
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if (Blob) {
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*Blob = StringRef(Ptr, NumElts);
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} else {
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// Otherwise, unpack into Vals with zero extension.
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auto *UPtr = reinterpret_cast<const unsigned char *>(Ptr);
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Vals.append(UPtr, UPtr + NumElts);
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}
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}
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return Code;
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}
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Error BitstreamCursor::ReadAbbrevRecord() {
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auto Abbv = std::make_shared<BitCodeAbbrev>();
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Expected<uint32_t> MaybeNumOpInfo = ReadVBR(5);
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if (!MaybeNumOpInfo)
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return MaybeNumOpInfo.takeError();
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unsigned NumOpInfo = MaybeNumOpInfo.get();
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for (unsigned i = 0; i != NumOpInfo; ++i) {
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Expected<word_t> MaybeIsLiteral = Read(1);
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if (!MaybeIsLiteral)
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return MaybeIsLiteral.takeError();
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bool IsLiteral = MaybeIsLiteral.get();
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if (IsLiteral) {
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Expected<uint64_t> MaybeOp = ReadVBR64(8);
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if (!MaybeOp)
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return MaybeOp.takeError();
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Abbv->Add(BitCodeAbbrevOp(MaybeOp.get()));
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continue;
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}
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Expected<word_t> MaybeEncoding = Read(3);
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if (!MaybeEncoding)
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return MaybeEncoding.takeError();
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BitCodeAbbrevOp::Encoding E =
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(BitCodeAbbrevOp::Encoding)MaybeEncoding.get();
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if (BitCodeAbbrevOp::hasEncodingData(E)) {
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Expected<uint64_t> MaybeData = ReadVBR64(5);
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if (!MaybeData)
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return MaybeData.takeError();
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uint64_t Data = MaybeData.get();
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// As a special case, handle fixed(0) (i.e., a fixed field with zero bits)
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// and vbr(0) as a literal zero. This is decoded the same way, and avoids
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// a slow path in Read() to have to handle reading zero bits.
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if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) &&
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Data == 0) {
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Abbv->Add(BitCodeAbbrevOp(0));
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continue;
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}
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if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) &&
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Data > MaxChunkSize)
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report_fatal_error(
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"Fixed or VBR abbrev record with size > MaxChunkData");
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Abbv->Add(BitCodeAbbrevOp(E, Data));
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} else
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Abbv->Add(BitCodeAbbrevOp(E));
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}
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if (Abbv->getNumOperandInfos() == 0)
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report_fatal_error("Abbrev record with no operands");
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CurAbbrevs.push_back(std::move(Abbv));
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return Error::success();
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}
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Expected<Optional<BitstreamBlockInfo>>
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BitstreamCursor::ReadBlockInfoBlock(bool ReadBlockInfoNames) {
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if (llvm::Error Err = EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID))
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return std::move(Err);
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BitstreamBlockInfo NewBlockInfo;
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SmallVector<uint64_t, 64> Record;
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BitstreamBlockInfo::BlockInfo *CurBlockInfo = nullptr;
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// Read all the records for this module.
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while (true) {
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Expected<BitstreamEntry> MaybeEntry =
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advanceSkippingSubblocks(AF_DontAutoprocessAbbrevs);
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if (!MaybeEntry)
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return MaybeEntry.takeError();
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BitstreamEntry Entry = MaybeEntry.get();
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switch (Entry.Kind) {
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case llvm::BitstreamEntry::SubBlock: // Handled for us already.
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case llvm::BitstreamEntry::Error:
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return None;
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case llvm::BitstreamEntry::EndBlock:
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return std::move(NewBlockInfo);
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case llvm::BitstreamEntry::Record:
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// The interesting case.
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break;
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}
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// Read abbrev records, associate them with CurBID.
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if (Entry.ID == bitc::DEFINE_ABBREV) {
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if (!CurBlockInfo) return None;
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if (Error Err = ReadAbbrevRecord())
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return std::move(Err);
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// ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the
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// appropriate BlockInfo.
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CurBlockInfo->Abbrevs.push_back(std::move(CurAbbrevs.back()));
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CurAbbrevs.pop_back();
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continue;
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}
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// Read a record.
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Record.clear();
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Expected<unsigned> MaybeBlockInfo = readRecord(Entry.ID, Record);
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if (!MaybeBlockInfo)
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return MaybeBlockInfo.takeError();
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switch (MaybeBlockInfo.get()) {
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default:
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break; // Default behavior, ignore unknown content.
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case bitc::BLOCKINFO_CODE_SETBID:
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if (Record.size() < 1)
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return None;
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CurBlockInfo = &NewBlockInfo.getOrCreateBlockInfo((unsigned)Record[0]);
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break;
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case bitc::BLOCKINFO_CODE_BLOCKNAME: {
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if (!CurBlockInfo)
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return None;
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if (!ReadBlockInfoNames)
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break; // Ignore name.
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CurBlockInfo->Name = std::string(Record.begin(), Record.end());
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break;
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}
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case bitc::BLOCKINFO_CODE_SETRECORDNAME: {
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if (!CurBlockInfo) return None;
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if (!ReadBlockInfoNames)
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break; // Ignore name.
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CurBlockInfo->RecordNames.emplace_back(
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(unsigned)Record[0], std::string(Record.begin() + 1, Record.end()));
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break;
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}
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}
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}
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}
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