Initial code coverage mapping data, reader, writer + C interface for ProfileData

[arphaman]

Summary

A patch which implements the data structures, the reader, and the writers for the new code coverage mapping system.
Based on the earlier proposal: http://comments.gmane.org/gmane.comp.compilers.clang.devel/37289

[arphaman]

The updated version of the patch that fixes various typos, adds format version to the coverage mapping format, changes the storage of filenames to once per tu, and adds document that describes the actual coverage mapping format.

[bob.wilson]

The documentation is going to need more work. Let’s split that out into a separate patch. At least it helps me understand how the reader and writer work.

[arphaman]

Thanks again for the review, I've implemented the suggested changes. I also merged the coverage mapping data into one section - this reduced the object file size for the test programs by 4.5% on average.

[arphaman]

Updated patch with the 'coverage' namespace, name case fixes and shared encoding constant.

[bob.wilson]

Looks good. Please commit!

[arphaman]

Committed in r213909 and r213910 (forgot to add the new files in the first
one).

2014-07-24 16:17 GMT-07:00 Bob Wilson <[e-mail]>:

Looks good. Please commit!

http://reviews.llvm.org/D4301

include/llvm/ProfileData/CoverageMapping.h

+//=-- CoverageMapping.h - Code coverage mapping support ---------*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Code coverage mapping data is generated by clang and read by
+// llvm-cov to show code coverage statistics for a file.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_PROFILEDATA_COVERAGEMAPPING_H_
+#define LLVM_PROFILEDATA_COVERAGEMAPPING_H_
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/raw_ostream.h"
+#include <system_error>
+
+namespace llvm {
+
+struct CounterExpressions;
+
+enum CoverageMappingVersion { CoverageMappingVersion1 };
+
+/// \brief A Counter is an abstract value that describes how to compute the
+/// execution count for a region of code using the collected profile count data.
+struct Counter {
+  enum CounterKind { Zero, CounterValueReference, Expression };
+  static const unsigned EncodingTagBits = 2;
+  static const unsigned EncodingTagMask = 0x3;
+
+private:
+  CounterKind Kind;
+  unsigned ID;
+
+  Counter(CounterKind Kind, unsigned ID) : Kind(Kind), ID(ID) {}
+
+public:
+  Counter() : Kind(Zero), ID(0) {}
+
+  CounterKind getKind() const { return Kind; }
+
+  bool isZero() const { return Kind == Zero; }
+
+  bool isExpression() const { return Kind == Expression; }
+
+  unsigned getCounterID() const { return ID; }
+
+  unsigned getExpressionID() const { return ID; }
+
+  bool operator==(const Counter &Other) const {
+    return Kind == Other.Kind && ID == Other.ID;
+  }
+
+  /// \brief Return the counter that represents the number zero.
+  static Counter getZero() { return Counter(); }
+
+  /// \brief Return the counter that corresponds to a specific profile counter.
+  static Counter getCounter(unsigned CounterId) {
+    return Counter(CounterValueReference, CounterId);
+  }
+
+  /// \brief Return the counter that corresponds to a specific
+  /// addition counter expression.
+  static Counter getExpression(unsigned ExpressionId) {
+    return Counter(Expression, ExpressionId);
+  }
+};
+
+/// \brief A Counter expression is a value that represents an arithmetic
+/// operation with two counters.
+struct CounterExpression {
+  enum ExprKind { Subtract, Add };
+  ExprKind Kind;
+  Counter LHS, RHS;
+
+  CounterExpression(ExprKind Kind, Counter LHS, Counter RHS)
+      : Kind(Kind), LHS(LHS), RHS(RHS) {}
+
+  bool operator==(const CounterExpression &Other) const {
+    return Kind == Other.Kind && LHS == Other.LHS && RHS == Other.RHS;
+  }
+};
+
+/// \brief A Counter expression builder is used to construct the
+/// counter expressions. It avoids unecessary duplication
+/// and simplifies algebraic expressions.
+class CounterExpressionBuilder {
+  /// \brief A list of all the counter expressions
+  llvm::SmallVector<CounterExpression, 16> Expressions;
+  /// \brief An array of terms used in expression simplification.
+  llvm::SmallVector<int, 16> Terms;
+
+  /// \brief Return the counter which corresponds to the given expression.
+  ///
+  /// If the given expression is already stored in the builder, a counter
+  /// that references that expression is returned. Otherwise, the given
+  /// expression is added to the builder's collection of expressions.
+  Counter get(const CounterExpression &E);
+
+  /// \brief Convert the expression tree represented by a counter
+  /// into a polynomial in the form of K1Counter1 + .. + KNCounterN
+  /// where K1 .. KN are integer constants that are stored in the Terms array.
+  void ExtractTerms(Counter C, int Sign = 1);
+
+  /// \brief Simplifies the given expression tree
+  /// by getting rid of algebraically redundant operations.
+  Counter Simplify(Counter ExpressionTree);
+
+public:
+  CounterExpressionBuilder(unsigned NumCounterValues);
+
+  ArrayRef<CounterExpression> getExpressions() const { return Expressions; }
+
+  /// \brief Return a counter that represents the expression
+  /// that adds LHS and RHS.
+  Counter Add(Counter LHS, Counter RHS);
+
+  /// \brief Return a counter that represents the expression
+  /// that subtracts RHS from LHS.
+  Counter Subtract(Counter LHS, Counter RHS);
+};
+
+/// \brief A Counter mapping region associates a source range with
+/// a specific counter.
+struct CounterMappingRegion {
+  enum RegionKind {
+    /// \brief A CodeRegion associates some code with a counter
+    CodeRegion,
+
+    /// \brief An ExpansionRegion represents a file expansion region that
+    /// associates a source range with the expansion of a virtual source file,
+    /// such as for a macro instantiation or #include file.
+    ExpansionRegion,
+
+    /// \brief An EmptyRegion represents a source range without code,
+    /// but with a distinct counter.
+    EmptyRegion,
+
+    /// \brief A SkippedRegion represents a source range with code that
+    /// was skipped by a preprocessor or similar means.
+    SkippedRegion
+  };
+
+  Counter Count;
+  unsigned FileID, ExpandedFileID;
+  unsigned LineStart, ColumnStart, LineEnd, ColumnEnd;
+  RegionKind Kind;
+
+  CounterMappingRegion(Counter Count, unsigned FileID, unsigned LineStart,
+                       unsigned ColumnStart, unsigned LineEnd,
+                       unsigned ColumnEnd, RegionKind Kind = CodeRegion)
+      : Count(Count), FileID(FileID), ExpandedFileID(0), LineStart(LineStart),
+        ColumnStart(ColumnStart), LineEnd(LineEnd), ColumnEnd(ColumnEnd),
+        Kind(Kind) {}
+
+  bool operator<(const CounterMappingRegion &Other) const {
+    if (FileID != Other.FileID)
+      return FileID < Other.FileID;
+    if (LineStart == Other.LineStart)
+      return ColumnStart < Other.ColumnStart;
+    return LineStart < Other.LineStart;
+  }
+};
+
+/// \brief A Counter mapping context is used to connect the counters,
+/// expressions and the obtained counter values.
+class CounterMappingContext {
+  ArrayRef<CounterExpression> Expressions;
+  ArrayRef<uint64_t> CounterValues;
+
+public:
+  CounterMappingContext(ArrayRef<CounterExpression> Expressions,
+                        ArrayRef<uint64_t> CounterValues = ArrayRef<uint64_t>())
+      : Expressions(Expressions), CounterValues(CounterValues) {}
+
+  void dump(const Counter &C, llvm::raw_ostream &OS) const;
+  void dump(const Counter &C) const { dump(C, llvm::outs()); }
+
+  /// \brief Return the number of times that a region of code
+  /// associated with this counter was executed.
+  int64_t evaluate(const Counter &C, std::error_code *Error) const;
+  int64_t evaluate(const Counter &C, std::error_code &Error) const {
+    Error.clear();
+    return evaluate(C, &Error);
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_PROFILEDATA_COVERAGEMAPPING_H_

include/llvm/ProfileData/CoverageMappingReader.h

+//=-- CoverageMappingReader.h - Code coverage mapping reader ------*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for reading coverage mapping data for
+// instrumentation based coverage.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_PROFILEDATA_COVERAGEMAPPING_READER_H_
+#define LLVM_PROFILEDATA_COVERAGEMAPPING_READER_H_
+
+#include "llvm/ProfileData/InstrProf.h"
+#include "llvm/ProfileData/CoverageMapping.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/FileSystem.h"
+
+#include <iterator>
+
+namespace llvm {
+
+class ObjectFileCoverageMappingReader;
+
+/// \brief Coverage mapping information for a single function.
+struct CoverageMappingRecord {
+  StringRef FunctionName;
+  ArrayRef<StringRef> Filenames;
+  ArrayRef<CounterExpression> Expressions;
+  ArrayRef<CounterMappingRegion> MappingRegions;
+};
+
+/// \brief A file format agnostic iterator over coverage mapping data.
+class CoverageMappingIterator
+    : public std::iterator<std::input_iterator_tag, CoverageMappingRecord> {
+  ObjectFileCoverageMappingReader *Reader;
+  CoverageMappingRecord Record;
+
+  void Increment();
+
+public:
+  CoverageMappingIterator() : Reader(nullptr) {}
+  CoverageMappingIterator(ObjectFileCoverageMappingReader *Reader)
+      : Reader(Reader) {
+    Increment();
+  }
+
+  CoverageMappingIterator &operator++() {
+    Increment();
+    return *this;
+  }
+  bool operator==(const CoverageMappingIterator &RHS) {
+    return Reader == RHS.Reader;
+  }
+  bool operator!=(const CoverageMappingIterator &RHS) {
+    return Reader != RHS.Reader;
+  }
+  CoverageMappingRecord &operator*() { return Record; }
+  CoverageMappingRecord *operator->() { return &Record; }
+};
+
+/// \brief Base class for the raw coverage mapping and filenames data readers.
+class RawCoverageReader {
+protected:
+  StringRef Data;
+
+  /// \brief Return the error code.
+  std::error_code error(std::error_code EC) { return EC; }
+
+  /// \brief Clear the current error code and return a successful one.
+  std::error_code success() { return error(instrprof_error::success); }
+
+  RawCoverageReader(StringRef Data) : Data(Data) {}
+
+  std::error_code readULEB128(uint64_t &Result);
+  std::error_code readIntMax(uint64_t &Result, uint64_t MaxPlus1);
+  std::error_code readSize(uint64_t &Result);
+  std::error_code readString(StringRef &Result);
+};
+
+/// \brief Reader for the raw coverage filenames.
+class RawCoverageFilenamesReader : public RawCoverageReader {
+  std::vector<StringRef> &Filenames;
+
+  RawCoverageFilenamesReader(const RawCoverageFilenamesReader &)
+      LLVM_DELETED_FUNCTION;
+  RawCoverageFilenamesReader &
+  operator=(const RawCoverageFilenamesReader &) LLVM_DELETED_FUNCTION;
+
+public:
+  RawCoverageFilenamesReader(StringRef Data, std::vector<StringRef> &Filenames)
+      : RawCoverageReader(Data), Filenames(Filenames) {}
+
+  std::error_code read();
+};
+
+/// \brief Reader for the raw coverage mapping data.
+class RawCoverageMappingReader : public RawCoverageReader {
+  StringRef FunctionName;
+  ArrayRef<StringRef> TranslationUnitFilenames;
+  std::vector<StringRef> &Filenames;
+  std::vector<CounterExpression> &Expressions;
+  std::vector<CounterMappingRegion> &MappingRegions;
+
+  RawCoverageMappingReader(const RawCoverageMappingReader &)
+      LLVM_DELETED_FUNCTION;
+  RawCoverageMappingReader &
+  operator=(const RawCoverageMappingReader &) LLVM_DELETED_FUNCTION;
+
+public:
+  RawCoverageMappingReader(StringRef FunctionName, StringRef MappingData,
+                           ArrayRef<StringRef> TranslationUnitFilenames,
+                           std::vector<StringRef> &Filenames,
+                           std::vector<CounterExpression> &Expressions,
+                           std::vector<CounterMappingRegion> &MappingRegions)
+      : RawCoverageReader(MappingData), FunctionName(FunctionName),
+        TranslationUnitFilenames(TranslationUnitFilenames),
+        Filenames(Filenames), Expressions(Expressions),
+        MappingRegions(MappingRegions) {}
+
+  std::error_code read(CoverageMappingRecord &Record);
+
+private:
+  std::error_code decodeCounter(unsigned Value, Counter &C);
+  std::error_code readCounter(Counter &C);
+  std::error_code
+  readMappingRegionsSubArray(std::vector<CounterMappingRegion> &MappingRegions,
+                             unsigned InferredFileID, size_t NumFileIDs);
+};
+
+/// \brief Reader for the coverage mapping data that is emitted by the
+/// frontend and stored in an object file.
+class ObjectFileCoverageMappingReader {
+public:
+  struct ProfileMappingRecord {
+    CoverageMappingVersion Version;
+    StringRef FunctionName;
+    StringRef CoverageMapping;
+    size_t FilenamesBegin;
+    size_t FilenamesSize;
+
+    ProfileMappingRecord(CoverageMappingVersion Version, StringRef FunctionName,
+                         StringRef CoverageMapping, size_t FilenamesBegin,
+                         size_t FilenamesSize)
+        : Version(Version), FunctionName(FunctionName),
+          CoverageMapping(CoverageMapping), FilenamesBegin(FilenamesBegin),
+          FilenamesSize(FilenamesSize) {}
+  };
+
+private:
+  std::error_code LastError;
+  std::unique_ptr<llvm::object::ObjectFile> Object;
+  std::vector<StringRef> Filenames;
+  std::vector<ProfileMappingRecord> MappingRecords;
+  size_t CurrentRecord;
+  std::vector<StringRef> FunctionsFilenames;
+  std::vector<CounterExpression> Expressions;
+  std::vector<CounterMappingRegion> MappingRegions;
+
+  ObjectFileCoverageMappingReader(const ObjectFileCoverageMappingReader &)
+      LLVM_DELETED_FUNCTION;
+  ObjectFileCoverageMappingReader &
+  operator=(const ObjectFileCoverageMappingReader &) LLVM_DELETED_FUNCTION;
+
+  /// \brief Set the current error_code and return same.
+  std::error_code error(std::error_code EC) {
+    LastError = EC;
+    return EC;
+  }
+
+  /// \brief Clear the current error code and return a successful one.
+  std::error_code success() { return error(instrprof_error::success); }
+
+public:
+  ObjectFileCoverageMappingReader(StringRef FileName);
+  ObjectFileCoverageMappingReader(
+      std::unique_ptr<MemoryBuffer> &ObjectBuffer,
+      sys::fs::file_magic Type = sys::fs::file_magic::unknown);
+
+  std::error_code readHeader();
+  std::error_code readNextRecord(CoverageMappingRecord &Record);
+
+  /// Iterator over profile data.
+  CoverageMappingIterator begin() { return CoverageMappingIterator(this); }
+  CoverageMappingIterator end() { return CoverageMappingIterator(); }
+
+  /// \brief Return true if the reader has finished reading the profile data.
+  bool isEOF() { return LastError == instrprof_error::eof; }
+  /// \brief Return true if the reader encountered an error reading profiling
+  /// data.
+  bool hasError() { return LastError && !isEOF(); }
+  /// \brief Get the current error code.
+  std::error_code getError() { return LastError; }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_PROFILEDATA_COVERAGEMAPPING_READER_H_

include/llvm/ProfileData/CoverageMappingWriter.h

+//=-- CoverageMappingWriter.h - Code coverage mapping writer ------*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for writing coverage mapping data for
+// instrumentation based coverage.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_PROFILEDATA_COVERAGEMAPPING_WRITER_H_
+#define LLVM_PROFILEDATA_COVERAGEMAPPING_WRITER_H_
+
+#include "llvm/ProfileData/CoverageMapping.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+
+/// \brief Writer of the filenames section for the instrumentation
+/// based code coverage.
+class CoverageFilenamesSectionWriter {
+  ArrayRef<StringRef> Filenames;
+
+public:
+  CoverageFilenamesSectionWriter(ArrayRef<StringRef> Filenames)
+      : Filenames(Filenames) {}
+
+  /// \brief Write encoded filenames to the given output stream.
+  void write(raw_ostream &OS);
+};
+
+/// \brief Writer for instrumentation based coverage mapping data.
+class CoverageMappingWriter {
+  ArrayRef<unsigned> VirtualFileMapping;
+  ArrayRef<CounterExpression> Expressions;
+  MutableArrayRef<CounterMappingRegion> MappingRegions;
+
+public:
+  CoverageMappingWriter(ArrayRef<unsigned> VirtualFileMapping,
+                        ArrayRef<CounterExpression> Expressions,
+                        MutableArrayRef<CounterMappingRegion> MappingRegions)
+      : VirtualFileMapping(VirtualFileMapping), Expressions(Expressions),
+        MappingRegions(MappingRegions) {}
+
+  CoverageMappingWriter(ArrayRef<CounterExpression> Expressions,
+                        MutableArrayRef<CounterMappingRegion> MappingRegions)
+      : Expressions(Expressions), MappingRegions(MappingRegions) {}
+
+  /// \brief Write encoded coverage mapping data to the given output stream.
+  void write(raw_ostream &OS);
+};
+
+} // end namespace llvm
+
+#endif // LLVM_PROFILE_COVERAGEMAPPING_WRITER_H_

lib/ProfileData/CMakeLists.txt

   InstrProf.cpp
   InstrProfReader.cpp
   InstrProfWriter.cpp
+  CoverageMapping.cpp
+  CoverageMappingWriter.cpp
+  CoverageMappingReader.cpp
   )

lib/ProfileData/CoverageMapping.cpp

+//=-- CoverageMapping.cpp - Code coverage mapping support ---------*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for clang's and llvm's instrumentation based
+// code coverage.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ProfileData/CoverageMapping.h"
+
+using namespace llvm;
+
+CounterExpressionBuilder::CounterExpressionBuilder(unsigned NumCounterValues) {
+  Terms.resize(NumCounterValues);
+}
+
+Counter CounterExpressionBuilder::get(const CounterExpression &E) {
+  for (unsigned I = 0, S = Expressions.size(); I < S; ++I) {
+    if (Expressions[I] == E)
+      return Counter::getExpression(I);
+  }
+  Expressions.push_back(E);
+  return Counter::getExpression(Expressions.size() - 1);
+}
+
+void CounterExpressionBuilder::ExtractTerms(Counter C, int Sign) {
+  switch (C.getKind()) {
+  case Counter::Zero:
+    break;
+  case Counter::CounterValueReference:
+    Terms[C.getCounterID()] += Sign;
+    break;
+  case Counter::Expression:
+    const auto &E = Expressions[C.getExpressionID()];
+    ExtractTerms(E.LHS, Sign);
+    ExtractTerms(E.RHS, E.Kind == CounterExpression::Subtract ? -Sign : Sign);
+    break;
+  }
+}
+
+Counter CounterExpressionBuilder::Simplify(Counter ExpressionTree) {
+  // Gather constant terms.
+  for (auto &I : Terms)
+    I = 0;
+  ExtractTerms(ExpressionTree);
+
+  Counter C;
+  // Create additions.
+  // Note: the additions are created first
+  // to avoid creation of a tree like ((0 - X) + Y) instead of (Y - X).
+  for (unsigned I = 0, S = Terms.size(); I < S; ++I) {
+    if (Terms[I] <= 0)
+      continue;
+    for (int J = 0; J < Terms[I]; ++J) {
+      if (C.isZero())
+        C = Counter::getCounter(I);
+      else
+        C = get(CounterExpression(CounterExpression::Add, C,
+                                  Counter::getCounter(I)));
+    }
+  }
+
+  // Create subtractions.
+  for (unsigned I = 0, S = Terms.size(); I < S; ++I) {
+    if (Terms[I] >= 0)
+      continue;
+    for (int J = 0; J < (-Terms[I]); ++J)
+      C = get(CounterExpression(CounterExpression::Subtract, C,
+                                Counter::getCounter(I)));
+  }
+  return C;
+}
+
+Counter CounterExpressionBuilder::Add(Counter LHS, Counter RHS) {
+  return Simplify(get(CounterExpression(CounterExpression::Add, LHS, RHS)));
+}
+
+Counter CounterExpressionBuilder::Subtract(Counter LHS, Counter RHS) {
+  return Simplify(
+      get(CounterExpression(CounterExpression::Subtract, LHS, RHS)));
+}
+
+void CounterMappingContext::dump(const Counter &C,
+                                 llvm::raw_ostream &OS) const {
+  switch (C.getKind()) {
+  case Counter::Zero:
+    OS << '0';
+    return;
+  case Counter::CounterValueReference:
+    OS << '#' << C.getCounterID();
+    break;
+  case Counter::Expression: {
+    if (C.getExpressionID() >= Expressions.size())
+      return;
+    const auto &E = Expressions[C.getExpressionID()];
+    OS << '(';
+    dump(E.LHS);
+    OS << (E.Kind == CounterExpression::Subtract ? " - " : " + ");
+    dump(E.RHS);
+    OS << ')';
+    break;
+  }
+  }
+  if (CounterValues.empty())
+    return;
+  std::error_code Error;
+  auto Value = evaluate(C, Error);
+  if (Error)
+    return;
+  OS << '[' << Value << ']';
+}
+
+int64_t CounterMappingContext::evaluate(const Counter &C,
+                                        std::error_code *EC) const {
+  switch (C.getKind()) {
+  case Counter::Zero:
+    return 0;
+  case Counter::CounterValueReference:
+    if (C.getCounterID() >= CounterValues.size()) {
+      if (EC)
+        *EC = std::make_error_code(std::errc::argument_out_of_domain);
+      break;
+    }
+    return CounterValues[C.getCounterID()];
+  case Counter::Expression: {
+    if (C.getExpressionID() >= Expressions.size()) {
+      if (EC)
+        *EC = std::make_error_code(std::errc::argument_out_of_domain);
+      break;
+    }
+    const auto &E = Expressions[C.getExpressionID()];
+    auto LHS = evaluate(E.LHS, EC);
+    if (EC && *EC)
+      return 0;
+    auto RHS = evaluate(E.RHS, EC);
+    if (EC && *EC)
+      return 0;
+    return E.Kind == CounterExpression::Subtract ? LHS - RHS : LHS + RHS;
+  }
+  }
+  return 0;
+}

lib/ProfileData/CoverageMappingReader.cpp

+//=-- CoverageMappingReader.cpp - Code coverage mapping reader ----*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for reading coverage mapping data for
+// instrumentation based coverage.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ProfileData/CoverageMappingReader.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/LEB128.h"
+
+using namespace llvm;
+using namespace llvm::object;
+
+void CoverageMappingIterator::Increment() {
+  // Check if all the records were read or if an error occurred while reading
+  // the next record.
+  if (Reader->readNextRecord(Record))
+    *this = CoverageMappingIterator();
+}
+
+std::error_code RawCoverageReader::readULEB128(uint64_t &Result) {
+  if (Data.size() < 1)
+    return error(instrprof_error::truncated);
+  unsigned N = 0;
+  Result = decodeULEB128(reinterpret_cast<const uint8_t *>(Data.data()), &N);
+  if (N > Data.size())
+    return error(instrprof_error::malformed);
+  Data = Data.substr(N);
+  return success();
+}
+
+std::error_code RawCoverageReader::readIntMax(uint64_t &Result,
+                                              uint64_t MaxPlus1) {
+  if (auto Err = readULEB128(Result))
+    return Err;
+  if (Result >= MaxPlus1)
+    return error(instrprof_error::malformed);
+  return success();
+}
+
+std::error_code RawCoverageReader::readSize(uint64_t &Result) {
+  if (auto Err = readULEB128(Result))
+    return Err;
+  // Sanity check the number.
+  if (Result > Data.size())
+    return error(instrprof_error::malformed);
+  return success();
+}
+
+std::error_code RawCoverageReader::readString(StringRef &Result) {
+  uint64_t Length;
+  if (auto Err = readSize(Length))
+    return Err;
+  Result = Data.substr(0, Length);
+  Data = Data.substr(Length);
+  return success();
+}
+
+std::error_code RawCoverageFilenamesReader::read() {
+  uint64_t NumFilenames;
+  if (auto Err = readSize(NumFilenames))
+    return Err;
+  for (size_t I = 0; I < NumFilenames; ++I) {
+    StringRef Filename;
+    if (auto Err = readString(Filename))
+      return Err;
+    Filenames.push_back(Filename);
+  }
+  return success();
+}
+
+std::error_code RawCoverageMappingReader::decodeCounter(unsigned Value,
+                                                        Counter &C) {
+  auto Tag = Value & Counter::EncodingTagMask;
+  switch (Tag) {
+  case Counter::Zero:
+    C = Counter::getZero();
+    return success();
+  case Counter::CounterValueReference:
+    C = Counter::getCounter(Value >> Counter::EncodingTagBits);
+    return success();
+  default:
+    break;
+  }
+  Tag -= Counter::Expression;
+  switch (Tag) {
+  case CounterExpression::Subtract:
+  case CounterExpression::Add: {
+    auto ID = Value >> Counter::EncodingTagBits;
+    if (ID >= Expressions.size())
+      return error(instrprof_error::malformed);
+    Expressions[ID].Kind = CounterExpression::ExprKind(Tag);
+    C = Counter::getExpression(ID);
+    break;
+  }
+  default:
+    return error(instrprof_error::malformed);
+  }
+  return success();
+}
+
+std::error_code RawCoverageMappingReader::readCounter(Counter &C) {
+  uint64_t EncodedCounter;
+  if (auto Err =
+          readIntMax(EncodedCounter, std::numeric_limits<unsigned>::max()))
+    return Err;
+  if (auto Err = decodeCounter(EncodedCounter, C))
+    return Err;
+  return success();
+}
+
+static unsigned const EncodingExpansionRegionBit = 1
+                                                   << Counter::EncodingTagBits;
+
+static unsigned const EncodingCounterTagAndExpansionRegionTagBits =
+    Counter::EncodingTagBits + 1;
+
+/// \brief Read the sub-array of regions for the given inferred file id.
+/// \param NumFileIDs: the number of file ids that are defined for this
+/// function.
+std::error_code RawCoverageMappingReader::readMappingRegionsSubArray(
+    std::vector<CounterMappingRegion> &MappingRegions, unsigned InferredFileID,
+    size_t NumFileIDs) {
+  uint64_t NumRegions;
+  if (auto Err = readSize(NumRegions))
+    return Err;
+  unsigned LineStart = 0;
+  for (size_t I = 0; I < NumRegions; ++I) {
+    Counter C;
+    CounterMappingRegion::RegionKind Kind = CounterMappingRegion::CodeRegion;
+
+    // Read the combined counter + region kind.
+    uint64_t EncodedCounterAndRegion;
+    if (auto Err = readIntMax(EncodedCounterAndRegion,
+                              std::numeric_limits<unsigned>::max()))
+      return Err;
+    unsigned Tag = EncodedCounterAndRegion & Counter::EncodingTagMask;
+    uint64_t ExpandedFileID = 0;
+    if (Tag != Counter::Zero) {
+      if (auto Err = decodeCounter(EncodedCounterAndRegion, C))
+        return Err;
+    } else {
+      // Is it an expansion region?
+      if (EncodedCounterAndRegion & EncodingExpansionRegionBit) {
+        Kind = CounterMappingRegion::ExpansionRegion;
+        ExpandedFileID = EncodedCounterAndRegion >>
+                         EncodingCounterTagAndExpansionRegionTagBits;
+        if (ExpandedFileID >= NumFileIDs)
+          return error(instrprof_error::malformed);
+      } else {
+        switch (EncodedCounterAndRegion >>
+                EncodingCounterTagAndExpansionRegionTagBits) {
+        case CounterMappingRegion::CodeRegion:
+          // Don't do anything when we have a code region with a zero counter.
+          break;
+        case CounterMappingRegion::EmptyRegion:
+          Kind = CounterMappingRegion::EmptyRegion;
+          break;
+        case CounterMappingRegion::SkippedRegion:
+          Kind = CounterMappingRegion::SkippedRegion;
+          break;
+        default:
+          return error(instrprof_error::malformed);
+        }
+      }
+    }
+
+    // Read the source range.
+    uint64_t LineStartDelta, ColumnStart, NumLines, ColumnEnd;
+    if (auto Err =
+            readIntMax(LineStartDelta, std::numeric_limits<unsigned>::max()))
+      return Err;
+    if (auto Err =
+            readIntMax(ColumnStart, std::numeric_limits<unsigned>::max()))
+      return Err;
+    if (auto Err = readIntMax(NumLines, std::numeric_limits<unsigned>::max()))
+      return Err;
+    if (auto Err = readIntMax(ColumnEnd, std::numeric_limits<unsigned>::max()))
+      return Err;
+    LineStart += LineStartDelta;
+    // Adjust the column locations for the empty regions that are supposed to
+    // cover whole lines. Those regions should be encoded with the
+    // column range (1 -> std::numeric_limits<unsigned>::max()), but because
+    // the encoded std::numeric_limits<unsigned>::max() is several bytes long,
+    // we set the column range to (0 -> 0) to ensure that the column start and
+    // column end take up one byte each.
+    // The std::numeric_limits<unsigned>::max() is used to represent a column
+    // position at the end of the line without knowing the length of that line.
+    if (ColumnStart == 0 && ColumnEnd == 0) {
+      ColumnStart = 1;
+      ColumnEnd = std::numeric_limits<unsigned>::max();
+    }
+    MappingRegions.push_back(
+        CounterMappingRegion(C, InferredFileID, LineStart, ColumnStart,
+                             LineStart + NumLines, ColumnEnd, Kind));
+    MappingRegions.back().ExpandedFileID = ExpandedFileID;
+  }
+  return success();
+}
+
+std::error_code RawCoverageMappingReader::read(CoverageMappingRecord &Record) {
+
+  // Read the virtual file mapping.
+  llvm::SmallVector<unsigned, 8> VirtualFileMapping;
+  uint64_t NumFileMappings;
+  if (auto Err = readSize(NumFileMappings))
+    return Err;
+  for (size_t I = 0; I < NumFileMappings; ++I) {
+    uint64_t FilenameIndex;
+    if (auto Err = readIntMax(FilenameIndex, TranslationUnitFilenames.size()))
+      return Err;
+    VirtualFileMapping.push_back(FilenameIndex);
+  }
+
+  // Construct the files using unique filenames and virtual file mapping.
+  for (auto I : VirtualFileMapping) {
+    Filenames.push_back(TranslationUnitFilenames[I]);
+  }
+
+  // Read the expressions.
+  uint64_t NumExpressions;
+  if (auto Err = readSize(NumExpressions))
+    return Err;
+  // Create an array of dummy expressions that get the proper counters
+  // when the expressions are read, and the proper kinds when the counters
+  // are decoded.
+  Expressions.resize(
+      NumExpressions,
+      CounterExpression(CounterExpression::Subtract, Counter(), Counter()));
+  for (size_t I = 0; I < NumExpressions; ++I) {
+    if (auto Err = readCounter(Expressions[I].LHS))
+      return Err;
+    if (auto Err = readCounter(Expressions[I].RHS))
+      return Err;
+  }
+
+  // Read the mapping regions sub-arrays.
+  for (unsigned InferredFileID = 0, S = VirtualFileMapping.size();
+       InferredFileID < S; ++InferredFileID) {
+    if (auto Err = readMappingRegionsSubArray(MappingRegions, InferredFileID,
+                                              VirtualFileMapping.size()))
+      return Err;
+  }
+
+  // Set the counters for the expansion regions.
+  // i.e. Counter of expansion region = counter of the first region
+  // from the expanded file.
+  // Perform multiple passes to correctly propagate the counters through
+  // all the nested expansion regions.
+  for (unsigned Pass = 1, S = VirtualFileMapping.size(); Pass < S; ++Pass) {
+    for (auto &I : MappingRegions) {
+      if (I.Kind == CounterMappingRegion::ExpansionRegion) {
+        for (const auto &J : MappingRegions) {
+          if (J.FileID == I.ExpandedFileID) {
+            I.Count = J.Count;
+            break;
+          }
+        }
+      }
+    }
+  }
+
+  Record.FunctionName = FunctionName;
+  Record.Filenames = Filenames;
+  Record.Expressions = Expressions;
+  Record.MappingRegions = MappingRegions;
+  return success();
+}
+
+ObjectFileCoverageMappingReader::ObjectFileCoverageMappingReader(
+    StringRef FileName)
+    : CurrentRecord(0) {
+  auto File = llvm::object::ObjectFile::createObjectFile(FileName);
+  if (!File)
+    error(File.getError());
+  else
+    Object.reset(File.get());
+}
+
+ObjectFileCoverageMappingReader::ObjectFileCoverageMappingReader(
+    std::unique_ptr<MemoryBuffer> &ObjectBuffer, sys::fs::file_magic Type)
+    : CurrentRecord(0) {
+  auto File = llvm::object::ObjectFile::createObjectFile(ObjectBuffer, Type);
+  if (!File)
+    error(File.getError());
+  else
+    Object.reset(File.get());
+}
+
+namespace {
+/// \brief The coverage mapping data for a single function.
+/// It points to the function's name.
+template <typename IntPtrT> struct CoverageMappingFunctionRecord {
+  IntPtrT FunctionNamePtr;
+  uint32_t FunctionNameSize;
+  uint32_t CoverageMappingSize;
+};
+
+/// \brief The coverage mapping data for a single translation unit.
+/// It points to the array of function coverage mapping records and the encoded
+/// filenames array.
+template <typename IntPtrT> struct CoverageMappingTURecord {
+  uint32_t FunctionRecordsSize;
+  uint32_t FilenamesSize;
+  uint32_t CoverageMappingsSize;
+  uint32_t Version;
+};
+
+/// \brief A helper structure to access the data from a section
+/// in an object file.
+struct SectionData {
+  StringRef Data;
+  uint64_t Address;
+
+  std::error_code load(SectionRef &Section) {
+    if (auto Err = Section.getContents(Data))
+      return Err;
+    return Section.getAddress(Address);
+  }
+
+  std::error_code get(uint64_t Pointer, size_t Size, StringRef &Result) {
+    if (Pointer < Address)
+      return instrprof_error::malformed;
+    auto Offset = Pointer - Address;
+    if (Offset + Size > Data.size())
+      return instrprof_error::malformed;
+    Result = Data.substr(Pointer - Address, Size);
+    return instrprof_error::success;
+  }
+};
+}
+
+template <typename T>
+std::error_code readCoverageMappingData(
+    SectionRef &ProfileNames, SectionRef &CoverageMapping,
+    std::vector<ObjectFileCoverageMappingReader::ProfileMappingRecord> &Records,
+    std::vector<StringRef> &Filenames) {
+  llvm::DenseSet<T> UniqueFunctionMappingData;
+
+  // Get the contents of the given sections.
+  StringRef Data;
+  if (auto Err = CoverageMapping.getContents(Data))
+    return Err;
+  SectionData ProfileNamesData;
+  if (auto Err = ProfileNamesData.load(ProfileNames))
+    return Err;
+
+  // Read the records in the coverage data section.
+  while (!Data.empty()) {
+    if (Data.size() < sizeof(CoverageMappingTURecord<T>))
+      return instrprof_error::malformed;
+    auto TU = reinterpret_cast<const CoverageMappingTURecord<T> *>(Data.data());
+    Data = Data.substr(sizeof(CoverageMappingTURecord<T>));
+    switch (TU->Version) {
+    case CoverageMappingVersion1:
+      break;
+    default:
+      return instrprof_error::unsupported_version;
+    }
+    auto Version = CoverageMappingVersion(TU->Version);
+
+    // Get the function records.
+    auto FunctionRecords =
+        reinterpret_cast<const CoverageMappingFunctionRecord<T> *>(Data.data());
+    if (Data.size() <
+        sizeof(CoverageMappingFunctionRecord<T>) * TU->FunctionRecordsSize)
+      return instrprof_error::malformed;
+    Data = Data.substr(sizeof(CoverageMappingFunctionRecord<T>) *
+                       TU->FunctionRecordsSize);
+
+    // Get the filenames.
+    if (Data.size() < TU->FilenamesSize)
+      return instrprof_error::malformed;
+    auto RawFilenames = Data.substr(0, TU->FilenamesSize);
+    Data = Data.substr(TU->FilenamesSize);
+    size_t FilenamesBegin = Filenames.size();
+    RawCoverageFilenamesReader Reader(RawFilenames, Filenames);
+    if (auto Err = Reader.read())
+      return Err;
+
+    // Get the coverage mappings.
+    if (Data.size() < TU->CoverageMappingsSize)
+      return instrprof_error::malformed;
+    auto CoverageMappings = Data.substr(0, TU->CoverageMappingsSize);
+    Data = Data.substr(TU->CoverageMappingsSize);
+
+    for (unsigned I = 0; I < TU->FunctionRecordsSize; ++I) {
+      auto &MappingRecord = FunctionRecords[I];
+
+      // Get the coverage mapping.
+      if (CoverageMappings.size() < MappingRecord.CoverageMappingSize)
+        return instrprof_error::malformed;
+      auto Mapping =
+          CoverageMappings.substr(0, MappingRecord.CoverageMappingSize);
+      CoverageMappings =
+          CoverageMappings.substr(MappingRecord.CoverageMappingSize);
+
+      // Ignore this record if we already have a record that points to the same
+      // function name.
+      // This is useful to ignore the redundant records for the functions
+      // with ODR linkage.
+      if (UniqueFunctionMappingData.count(MappingRecord.FunctionNamePtr))
+        continue;
+      UniqueFunctionMappingData.insert(MappingRecord.FunctionNamePtr);
+      StringRef FunctionName;
+      if (auto Err = ProfileNamesData.get(MappingRecord.FunctionNamePtr,
+                                          MappingRecord.FunctionNameSize,
+                                          FunctionName))
+        return Err;
+      Records.push_back(ObjectFileCoverageMappingReader::ProfileMappingRecord(
+          Version, FunctionName, Mapping, FilenamesBegin,
+          Filenames.size() - FilenamesBegin));
+    }
+  }
+
+  return instrprof_error::success;
+}
+
+std::error_code ObjectFileCoverageMappingReader::readHeader() {
+  if (!Object)
+    return getError();
+  auto BytesInAddress = Object->getBytesInAddress();
+  if (BytesInAddress != 4 && BytesInAddress != 8)
+    return error(instrprof_error::malformed);
+
+  // Look for the sections that we are interested in.
+  int FoundSectionCount = 0;
+  SectionRef ProfileNames, CoverageMapping;
+  for (const auto &Section : Object->sections()) {
+    StringRef Name;
+    if (auto Err = Section.getName(Name))
+      return Err;
+    if (Name == "__llvm_prf_names") {
+      ProfileNames = Section;
+    } else if (Name == "__llvm_covmap") {
+      CoverageMapping = Section;
+    } else
+      continue;
+    ++FoundSectionCount;
+  }
+  if (FoundSectionCount != 2)
+    return error(instrprof_error::bad_header);
+
+  // Load the data from the found sections.
+  std::error_code Err;
+  if (BytesInAddress == 4)
+    Err = readCoverageMappingData<uint32_t>(ProfileNames, CoverageMapping,
+                                            MappingRecords, Filenames);
+  else
+    Err = readCoverageMappingData<uint64_t>(ProfileNames, CoverageMapping,
+                                            MappingRecords, Filenames);
+  if (Err)
+    return error(Err);
+
+  return success();
+}
+
+std::error_code
+ObjectFileCoverageMappingReader::readNextRecord(CoverageMappingRecord &Record) {
+  if (CurrentRecord >= MappingRecords.size())
+    return error(instrprof_error::eof);
+
+  FunctionsFilenames.clear();
+  Expressions.clear();
+  MappingRegions.clear();
+  auto &R = MappingRecords[CurrentRecord];
+  RawCoverageMappingReader Reader(
+      R.FunctionName, R.CoverageMapping,
+      makeArrayRef(Filenames.data() + R.FilenamesBegin, R.FilenamesSize),
+      FunctionsFilenames, Expressions, MappingRegions);
+  if (auto Err = Reader.read(Record))
+    return Err;
+  ++CurrentRecord;
+  return success();
+}

lib/ProfileData/CoverageMappingWriter.cpp

+//=-- CoverageMappingWriter.cpp - Code coverage mapping writer -------------=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for writing coverage mapping data for
+// instrumentation based coverage.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ProfileData/CoverageMappingWriter.h"
+#include "llvm/Support/LEB128.h"
+
+using namespace llvm;
+
+void CoverageFilenamesSectionWriter::write(raw_ostream &OS) {
+  encodeULEB128(Filenames.size(), OS);
+  for (const auto &Filename : Filenames) {
+    encodeULEB128(Filename.size(), OS);
+    OS << Filename;
+  }
+}
+
+namespace {
+/// \brief Gather only the expressions that are used by the mapping
+/// regions in this function.
+class CounterExpressionsMinimizer {
+  ArrayRef<CounterExpression> Expressions;
+  llvm::SmallVector<CounterExpression, 16> UsedExpressions;
+  std::vector<unsigned> AdjustedExpressionIDs;
+
+public:
+  void mark(Counter C) {
+    if (!C.isExpression())
+      return;
+    unsigned ID = C.getExpressionID();
+    AdjustedExpressionIDs[ID] = 1;
+    mark(Expressions[ID].LHS);
+    mark(Expressions[ID].RHS);
+  }
+
+  void gatherUsed(Counter C) {
+    if (!C.isExpression() || !AdjustedExpressionIDs[C.getExpressionID()])
+      return;
+    AdjustedExpressionIDs[C.getExpressionID()] = UsedExpressions.size();
+    const auto &E = Expressions[C.getExpressionID()];
+    UsedExpressions.push_back(E);
+    gatherUsed(E.LHS);
+    gatherUsed(E.RHS);
+  }
+
+  CounterExpressionsMinimizer(ArrayRef<CounterExpression> Expressions,
+                              ArrayRef<CounterMappingRegion> MappingRegions)
+      : Expressions(Expressions) {
+    AdjustedExpressionIDs.resize(Expressions.size(), 0);
+    for (const auto &I : MappingRegions)
+      mark(I.Count);
+    for (const auto &I : MappingRegions)
+      gatherUsed(I.Count);
+  }
+
+  ArrayRef<CounterExpression> getExpressions() const { return UsedExpressions; }
+
+  /// \brief Adjust the given counter to correctly transition from the old
+  /// expression ids to the new expression ids.
+  Counter adjust(Counter C) const {
+    if (C.isExpression())
+      C = Counter::getExpression(AdjustedExpressionIDs[C.getExpressionID()]);
+    return C;
+  }
+};
+}
+
+static unsigned const EncodingCounterTagAndExpansionRegionTagBits =
+    Counter::EncodingTagBits + 1;
+
+/// \brief Return the number of regions that have the given FileID.
+static unsigned countFileIDs(ArrayRef<CounterMappingRegion> Regions,
+                             unsigned FileID) {
+  unsigned Result = 0;
+  for (const auto &I : Regions) {
+    if (I.FileID == FileID)
+      ++Result;
+    if (I.FileID > FileID)
+      break;
+  }
+  return Result;
+}
+
+/// \brief Encode the counter.
+///
+/// The encoding uses the following format:
+/// Low 2 bits - Tag:
+///   Counter::Zero(0) - A Counter with kind Counter::Zero
+///   Counter::CounterValueReference(1) - A counter with kind
+///     Counter::CounterValueReference
+///   Counter::Expression(2) + CounterExpression::Subtract(0) -
+///     A counter with kind Counter::Expression and an expression
+///     with kind CounterExpression::Subtract
+///   Counter::Expression(2) + CounterExpression::Add(1) -
+///     A counter with kind Counter::Expression and an expression
+///     with kind CounterExpression::Add
+/// Remaining bits - Counter/Expression ID.
+unsigned encodeCounter(ArrayRef<CounterExpression> Expressions, Counter C) {
+  unsigned Tag = unsigned(C.getKind());
+  if (C.isExpression())
+    Tag += Expressions[C.getExpressionID()].Kind;
+  unsigned ID = C.getCounterID();
+  assert(ID <=
+         (std::numeric_limits<unsigned>::max() >> Counter::EncodingTagBits));
+  return Tag | (ID << Counter::EncodingTagBits);
+}
+
+static void writeCounter(ArrayRef<CounterExpression> Expressions, Counter C,
+                         raw_ostream &OS) {
+  encodeULEB128(encodeCounter(Expressions, C), OS);
+}
+
+void CoverageMappingWriter::write(raw_ostream &OS) {
+  // Sort the regions in an ascending order by the file id and the starting
+  // location.
+  std::sort(MappingRegions.begin(), MappingRegions.end());
+
+  // Write out the fileid -> filename mapping.
+  encodeULEB128(VirtualFileMapping.size(), OS);
+  for (const auto &FileID : VirtualFileMapping)
+    encodeULEB128(FileID, OS);
+
+  // Write out the expressions.
+  CounterExpressionsMinimizer Minimizer(Expressions, MappingRegions);
+  auto MinExpressions = Minimizer.getExpressions();
+  encodeULEB128(MinExpressions.size(), OS);
+  for (const auto &E : MinExpressions) {
+    writeCounter(MinExpressions, Minimizer.adjust(E.LHS), OS);
+    writeCounter(MinExpressions, Minimizer.adjust(E.RHS), OS);
+  }
+
+  // Write out the mapping regions.
+  // Split the regions into subarrays where each region in a
+  // subarray has a fileID which is the index of that subarray.
+  unsigned PrevLineStart = 0;
+  unsigned CurrentFileID = MappingRegions.front().FileID;
+  assert(CurrentFileID == 0);
+  encodeULEB128(countFileIDs(MappingRegions, CurrentFileID), OS);
+  for (const auto &I : MappingRegions) {
+    if (I.FileID != CurrentFileID) {
+      // Ensure that all file ids have at least one mapping region.
+      assert(I.FileID == (CurrentFileID + 1));
+      // Start a new region sub-array.
+      CurrentFileID = I.FileID;
+      encodeULEB128(countFileIDs(MappingRegions, CurrentFileID), OS);
+      PrevLineStart = 0;
+    }
+    Counter Count = Minimizer.adjust(I.Count);
+    switch (I.Kind) {
+    case CounterMappingRegion::CodeRegion:
+      writeCounter(MinExpressions, Count, OS);
+      break;
+    case CounterMappingRegion::ExpansionRegion: {
+      assert(Count.isZero());
+      assert(I.ExpandedFileID <= (std::numeric_limits<unsigned>::max() >>
+                                  EncodingCounterTagAndExpansionRegionTagBits));
+      // Mark an expansion region with a set bit that follows the counter tag,
+      // and pack the expanded file id into the remaining bits.
+      unsigned EncodedTagExpandedFileID =
+          (1 << Counter::EncodingTagBits) |
+          (I.ExpandedFileID << EncodingCounterTagAndExpansionRegionTagBits);
+      encodeULEB128(EncodedTagExpandedFileID, OS);
+      break;
+    }
+    case CounterMappingRegion::EmptyRegion:
+      encodeULEB128(
+          unsigned(I.Kind) << EncodingCounterTagAndExpansionRegionTagBits, OS);
+      break;
+    case CounterMappingRegion::SkippedRegion:
+      assert(Count.isZero());
+      encodeULEB128(
+          unsigned(I.Kind) << EncodingCounterTagAndExpansionRegionTagBits, OS);
+      break;
+    }
+    assert(I.LineStart >= PrevLineStart);
+    encodeULEB128(I.LineStart - PrevLineStart, OS);
+    encodeULEB128(I.ColumnStart, OS);
+    assert(I.LineEnd >= I.LineStart);
+    encodeULEB128(I.LineEnd - I.LineStart, OS);
+    encodeULEB128(I.ColumnEnd, OS);
+    PrevLineStart = I.LineStart;
+  }
+  // Ensure that all file ids have at least one mapping region.
+  assert(CurrentFileID == (VirtualFileMapping.size() - 1));
+}

lib/ProfileData/LLVMBuild.txt

 type = Library
 name = ProfileData
 parent = Libraries
-required_libraries = Support
+required_libraries = Support Object