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diff --git a/contrib/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp b/contrib/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
new file mode 100644
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+++ b/contrib/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
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+//=-- 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/Coverage/CoverageMappingWriter.h"
+#include "llvm/Support/LEB128.h"
+
+using namespace llvm;
+using namespace coverage;
+
+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;
+  }
+};
+}
+
+/// \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.
+static 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::stable_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 = ~0U;
+  for (auto I = MappingRegions.begin(), E = MappingRegions.end(); I != E; ++I) {
+    if (I->FileID != CurrentFileID) {
+      // Ensure that all file ids have at least one mapping region.
+      assert(I->FileID == (CurrentFileID + 1));
+      // Find the number of regions with this file id.
+      unsigned RegionCount = 1;
+      for (auto J = I + 1; J != E && I->FileID == J->FileID; ++J)
+        ++RegionCount;
+      // Start a new region sub-array.
+      encodeULEB128(RegionCount, OS);
+
+      CurrentFileID = I->FileID;
+      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() >>
+              Counter::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
+           << Counter::EncodingCounterTagAndExpansionRegionTagBits);
+      encodeULEB128(EncodedTagExpandedFileID, OS);
+      break;
+    }
+    case CounterMappingRegion::SkippedRegion:
+      assert(Count.isZero());
+      encodeULEB128(unsigned(I->Kind)
+                        << Counter::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));
+}