[PATCH] D10674: Value profiling - patchset 3

Justin Bogner via llvm-commits llvm-commits at lists.llvm.org
Tue Sep 8 14:35:32 PDT 2015


Betul Buyukkurt <betulb at codeaurora.org> writes:
> betulb updated this revision to Diff 33963.
> betulb added a comment.
>
> In this revision:
>
> - Turned the error to assert for "hash value not matching any known key"
> - Used rvalue-reference semantics when passing arguments into the
> InstrProfWriter's addRecord routine. String table usage caused the
> undesirable removal of const qualifier from addRecord's argument. Now
> the arguments to addRecord are clearly passed using std::move()
> - In combineInstrProfRecords, tried to account for when value
> profiling is not enabled for a given kind for Source vs enabled for
> Dest and vice versa.
> - Used std::vector's empty() instead of comparing size() against 0

This is starting to look pretty good. I have a few more comments, but
first, there was one suggestion I made in a previous mail that I'm not
entirely convinced by your answer to:

Betul Buyukkurt <betulb at codeaurora.org> writes:
>>> /// Profiling information for a single function.
>>> struct InstrProfRecord {
>>>    InstrProfRecord() {}
>>> InstrProfRecord(StringRef Name, uint64_t Hash, std::vector<uint64_t> Counts)
>>>        : Name(Name), Hash(Hash), Counts(std::move(Counts)) {}
>>>    StringRef Name;
>>>    uint64_t Hash;
>>>    std::vector<uint64_t> Counts;
>>> +  // Size of vector indicates the number of value sites for a value kind
>>> + std::vector<InstrProfValueSiteRecord> ValueSites[instrprof_value_kind::size];
>>
>> I don't think we're gaining much by having this be an array - I was
>> thinking it would be more like
>>
>>   std::vector<InstrProfValueSiteRecord> IndirectCalls;
>>
>> Then when we add more value types, they can have their own variables and
>> be accessed directly. Most of the code that works with these will have a
>> particular kind in mind, and since the value data is dependent on kind
>> looping over these isn't generally that useful. That is, the looping we
>> have now is only in the reader and writer, and I can't see the users of
>> the data ever doing that.
>
> I think, I'm leaning towards keeping an array of kinds here.

Why?

>> For the reader and writer, a switch statement over the kinds will allow
>> us to warn if someone doesn't update somewhere when they add a new
>> kind. For the users of profile data, Data->IndirectCalls reads a lot
>> better than Data->ValueSites[instrprof_value_kind::indirect_call_target].  
>
> I'll revisit my latest patch to allow for that.

Obviously, you didn't do this, since the comment above said you weren't
going to.

A few more things on the latest patch:

Betul Buyukkurt <betulb at codeaurora.org> writes:
> Index: unittests/ProfileData/InstrProfTest.cpp
> ===================================================================
> --- unittests/ProfileData/InstrProfTest.cpp
> +++ unittests/ProfileData/InstrProfTest.cpp
> @@ -50,7 +50,8 @@
>  }
>  
>  TEST_F(InstrProfTest, write_and_read_one_function) {
> -  Writer.addFunctionCounts("foo", 0x1234, {1, 2, 3, 4});
> +  InstrProfRecord Record("foo", 0x1234, {1, 2, 3, 4});
> +  Writer.addRecord(std::move(Record));
>    auto Profile = Writer.writeBuffer();
>    readProfile(std::move(Profile));
>  
> @@ -67,8 +68,10 @@
>  }
>  
>  TEST_F(InstrProfTest, get_function_counts) {
> -  Writer.addFunctionCounts("foo", 0x1234, {1, 2});
> -  Writer.addFunctionCounts("foo", 0x1235, {3, 4});
> +  InstrProfRecord Record1("foo", 0x1234, {1, 2});
> +  InstrProfRecord Record2("foo", 0x1235, {3, 4});
> +  Writer.addRecord(std::move(Record1));
> +  Writer.addRecord(std::move(Record2));
>    auto Profile = Writer.writeBuffer();
>    readProfile(std::move(Profile));
>  
> @@ -92,9 +95,12 @@
>  }
>  
>  TEST_F(InstrProfTest, get_max_function_count) {
> -  Writer.addFunctionCounts("foo", 0x1234, {1ULL << 31, 2});
> -  Writer.addFunctionCounts("bar", 0, {1ULL << 63});
> -  Writer.addFunctionCounts("baz", 0x5678, {0, 0, 0, 0});
> +  InstrProfRecord Record1("foo", 0x1234, {1ULL << 31, 2});
> +  InstrProfRecord Record2("bar", 0, {1ULL << 63});
> +  InstrProfRecord Record3("baz", 0x5678, {0, 0, 0, 0});
> +  Writer.addRecord(std::move(Record1));
> +  Writer.addRecord(std::move(Record2));
> +  Writer.addRecord(std::move(Record3));
>    auto Profile = Writer.writeBuffer();
>    readProfile(std::move(Profile));
>  
> Index: unittests/ProfileData/CoverageMappingTest.cpp
> ===================================================================
> --- unittests/ProfileData/CoverageMappingTest.cpp
> +++ unittests/ProfileData/CoverageMappingTest.cpp
> @@ -188,7 +188,8 @@
>  }
>  
>  TEST_F(CoverageMappingTest, basic_coverage_iteration) {
> -  ProfileWriter.addFunctionCounts("func", 0x1234, {30, 20, 10, 0});
> +  InstrProfRecord Record("func", 0x1234, {30, 20, 10, 0});
> +  ProfileWriter.addRecord(std::move(Record));
>    readProfCounts();
>  
>    addCMR(Counter::getCounter(0), "file1", 1, 1, 9, 9);
> @@ -238,7 +239,8 @@
>  }
>  
>  TEST_F(CoverageMappingTest, combine_regions) {
> -  ProfileWriter.addFunctionCounts("func", 0x1234, {10, 20, 30});
> +  InstrProfRecord Record("func", 0x1234, {10, 20, 30});
> +  ProfileWriter.addRecord(std::move(Record));
>    readProfCounts();
>  
>    addCMR(Counter::getCounter(0), "file1", 1, 1, 9, 9);
> @@ -256,7 +258,8 @@
>  }
>  
>  TEST_F(CoverageMappingTest, dont_combine_expansions) {
> -  ProfileWriter.addFunctionCounts("func", 0x1234, {10, 20});
> +  InstrProfRecord Record("func", 0x1234, {10, 20});
> +  ProfileWriter.addRecord(std::move(Record));
>    readProfCounts();
>  
>    addCMR(Counter::getCounter(0), "file1", 1, 1, 9, 9);
> @@ -275,7 +278,8 @@
>  }
>  
>  TEST_F(CoverageMappingTest, strip_filename_prefix) {
> -  ProfileWriter.addFunctionCounts("file1:func", 0x1234, {10});
> +  InstrProfRecord Record("file1:func", 0x1234, {10});
> +  ProfileWriter.addRecord(std::move(Record));
>    readProfCounts();
>  
>    addCMR(Counter::getCounter(0), "file1", 1, 1, 9, 9);
> Index: tools/llvm-profdata/llvm-profdata.cpp
> ===================================================================
> --- tools/llvm-profdata/llvm-profdata.cpp
> +++ tools/llvm-profdata/llvm-profdata.cpp
> @@ -58,9 +58,8 @@
>        exitWithError(ec.message(), Filename);
>  
>      auto Reader = std::move(ReaderOrErr.get());
> -    for (const auto &I : *Reader)
> -      if (std::error_code EC =
> -              Writer.addFunctionCounts(I.Name, I.Hash, I.Counts))
> +    for (auto &I : *Reader)
> +      if (std::error_code EC = Writer.addRecord(std::move(I)))
>          errs() << Filename << ": " << I.Name << ": " << EC.message() << "\n";
>      if (Reader->hasError())
>        exitWithError(Reader->getError().message(), Filename);
> @@ -134,8 +133,8 @@
>  }
>  
>  static int showInstrProfile(std::string Filename, bool ShowCounts,
> -                            bool ShowAllFunctions, std::string ShowFunction,
> -                            raw_fd_ostream &OS) {
> +                            bool ShowIndirectCallTargets, bool ShowAllFunctions,
> +                            std::string ShowFunction, raw_fd_ostream &OS) {
>    auto ReaderOrErr = InstrProfReader::create(Filename);
>    if (std::error_code EC = ReaderOrErr.getError())
>      exitWithError(EC.message(), Filename);
> @@ -162,6 +161,10 @@
>           << "    Hash: " << format("0x%016" PRIx64, Func.Hash) << "\n"
>           << "    Counters: " << Func.Counts.size() << "\n"
>           << "    Function count: " << Func.Counts[0] << "\n";
> +      if (ShowIndirectCallTargets)
> +        OS << "    Indirect Call Site Count: "
> +           << Func.ValueSites[instrprof_value_kind::indirect_call_target].size()
> +           << "\n";
>      }
>  
>      if (Show && ShowCounts)
> @@ -174,6 +177,17 @@
>      }
>      if (Show && ShowCounts)
>        OS << "]\n";
> +
> +    if (Show && ShowIndirectCallTargets) {
> +      OS << "    Indirect Target Results: \n";
> +      uint32_t ValueKind = instrprof_value_kind::indirect_call_target;
> +      for (size_t I = 0, E = Func.ValueSites[ValueKind].size(); I < E; ++I) {
> +        for (auto V : Func.ValueSites[ValueKind][I].ValueData) {
> +          OS << "\t[ " << I << ", ";
> +          OS << (const char *)V.first << ", " << V.second << " ]\n";
> +        }
> +      }
> +    }
>    }
>    if (Reader->hasError())
>      exitWithError(Reader->getError().message(), Filename);
> @@ -210,6 +224,8 @@
>  
>    cl::opt<bool> ShowCounts("counts", cl::init(false),
>                             cl::desc("Show counter values for shown functions"));
> +  cl::opt<bool> ShowIndirectCallTargets("ic-targets", cl::init(false),
> +      cl::desc("Show indirect call site target values for shown functions"));
>    cl::opt<bool> ShowAllFunctions("all-functions", cl::init(false),
>                                   cl::desc("Details for every function"));
>    cl::opt<std::string> ShowFunction("function",
> @@ -238,8 +254,8 @@
>      errs() << "warning: -function argument ignored: showing all functions\n";
>  
>    if (ProfileKind == instr)
> -    return showInstrProfile(Filename, ShowCounts, ShowAllFunctions,
> -                            ShowFunction, OS);
> +    return showInstrProfile(Filename, ShowCounts, ShowIndirectCallTargets,
> +                            ShowAllFunctions, ShowFunction, OS);
>    else
>      return showSampleProfile(Filename, ShowCounts, ShowAllFunctions,
>                               ShowFunction, OS);
> Index: lib/ProfileData/InstrProfWriter.cpp
> ===================================================================
> --- lib/ProfileData/InstrProfWriter.cpp
> +++ lib/ProfileData/InstrProfWriter.cpp
> @@ -26,8 +26,8 @@
>    typedef StringRef key_type;
>    typedef StringRef key_type_ref;
>  
> -  typedef const InstrProfWriter::CounterData *const data_type;
> -  typedef const InstrProfWriter::CounterData *const data_type_ref;
> +  typedef const InstrProfWriter::ProfilingData *const data_type;
> +  typedef const InstrProfWriter::ProfilingData *const data_type_ref;
>  
>    typedef uint64_t hash_value_type;
>    typedef uint64_t offset_type;
> @@ -45,8 +45,30 @@
>      LE.write<offset_type>(N);
>  
>      offset_type M = 0;
> -    for (const auto &Counts : *V)
> -      M += (2 + Counts.second.size()) * sizeof(uint64_t);
> +    for (const auto &ProfileData : *V) {
> +      M += sizeof(uint64_t); // size of function hash
> +      M += sizeof(uint64_t); // size of ProfileData.second.Counts.size()

I'd write this as "The function hash", and "The number of profile counts".

> +      M += ProfileData.second.Counts.size() * sizeof(uint64_t);
> +
> +      // Value data
> +      M += sizeof(uint64_t); // Number of value kinds with value sites.
> +      for (uint32_t Kind = instrprof_value_kind::first;
> +           Kind < instrprof_value_kind::size; ++Kind) {
> +        if (ProfileData.second.ValueSites[Kind].empty())
> +          continue;
> +        M += sizeof(uint64_t); // Value kind
> +        // Number of value sites for current value kind
> +        M += sizeof(uint64_t); // ProfileData.second.ValuesSites[Kind].size()

"The number of value kinds"

> +        for (InstrProfValueSiteRecord I : ProfileData.second.ValueSites[Kind]) {
> +          // Number of value data pairs at a value site
> +          M += sizeof(uint64_t); // I.ValueData.size()
> +          for (auto V : I.ValueData) {
> +            M += sizeof(uint64_t); // size of TargetValue
> +            M += sizeof(uint64_t); // size of NumTaken
> +          }

Either way's fine, but would it read better to do

  M += 2 * sizeof(uint64_t) * I.ValueData.size();

?

> +        }
> +      }
> +    }
>      LE.write<offset_type>(M);
>  
>      return std::make_pair(N, M);
> @@ -60,52 +82,106 @@
>                         offset_type) {
>      using namespace llvm::support;
>      endian::Writer<little> LE(Out);
> -
> -    for (const auto &Counts : *V) {
> -      LE.write<uint64_t>(Counts.first);
> -      LE.write<uint64_t>(Counts.second.size());
> -      for (uint64_t I : Counts.second)
> +    for (const auto &ProfileData : *V) {
> +      LE.write<uint64_t>(ProfileData.first); // Function hash
> +      LE.write<uint64_t>(ProfileData.second.Counts.size());
> +      for (uint64_t I : ProfileData.second.Counts)
>          LE.write<uint64_t>(I);
> +
> +      // Compute the number of value kinds with value sites.
> +      uint64_t NumValueKinds = 0;
> +      for (uint32_t Kind = instrprof_value_kind::first;
> +           Kind < instrprof_value_kind::size; ++Kind)
> +        NumValueKinds += !(ProfileData.second.ValueSites[Kind].empty());
> +      LE.write<uint64_t>(NumValueKinds);
> +
> +      // Write value data
> +      for (uint32_t Kind = instrprof_value_kind::first;
> +           Kind < instrprof_value_kind::size; ++Kind) {
> +        if (ProfileData.second.ValueSites[Kind].empty())
> +          continue;
> +        LE.write<uint64_t>(Kind); // Write value kind
> +        // Write number of value sites for current value kind
> +        LE.write<uint64_t>(ProfileData.second.ValueSites[Kind].size());
> +        for (InstrProfValueSiteRecord I : ProfileData.second.ValueSites[Kind]) {
> +          // Write number of value data pairs at this value site
> +          LE.write<uint64_t>(I.ValueData.size());
> +          for (auto V : I.ValueData) {
> +            if (Kind == instrprof_value_kind::indirect_call_target)
> +              LE.write<uint64_t>(ComputeHash((const char *)V.first));
> +            else
> +              LE.write<uint64_t>(V.first);

This should just assert(Kind == instrprof_value_kind::indirect_call_target).
We don't want to be writing out data we don't understand. That said, if
you get rid of the array that doesn't come up.

> +            LE.write<uint64_t>(V.second);
> +          }
> +        }
> +      }
>      }
>    }
>  };
>  }
>  
> -std::error_code
> -InstrProfWriter::addFunctionCounts(StringRef FunctionName,
> -                                   uint64_t FunctionHash,
> -                                   ArrayRef<uint64_t> Counters) {
> -  auto &CounterData = FunctionData[FunctionName];
> -
> -  auto Where = CounterData.find(FunctionHash);
> -  if (Where == CounterData.end()) {
> -    // We've never seen a function with this name and hash, add it.
> -    CounterData[FunctionHash] = Counters;
> -    // We keep track of the max function count as we go for simplicity.
> -    if (Counters[0] > MaxFunctionCount)
> -      MaxFunctionCount = Counters[0];
> -    return instrprof_error::success;
> -  }
> -
> -  // We're updating a function we've seen before.
> -  auto &FoundCounters = Where->second;
> -  // If the number of counters doesn't match we either have bad data or a hash
> -  // collision.
> -  if (FoundCounters.size() != Counters.size())
> +static std::error_code combineInstrProfRecords(InstrProfRecord &Dest,
> +                                               InstrProfRecord &Source,
> +                                               uint64_t &MaxFunctionCount) {
> +  // If the number of counters doesn't match we either have bad data
> +  // or a hash collision.
> +  if (Dest.Counts.size() != Source.Counts.size())
>      return instrprof_error::count_mismatch;
>  
> -  for (size_t I = 0, E = Counters.size(); I < E; ++I) {
> -    if (FoundCounters[I] + Counters[I] < FoundCounters[I])
> +  for (size_t I = 0, E = Source.Counts.size(); I < E; ++I) {
> +    if (Dest.Counts[I] + Source.Counts[I] < Dest.Counts[I])
>        return instrprof_error::counter_overflow;
> -    FoundCounters[I] += Counters[I];
> +    Dest.Counts[I] += Source.Counts[I];
> +  }
> +
> +  for (uint32_t Kind = instrprof_value_kind::first;
> +       Kind < instrprof_value_kind::size; ++Kind) {
> +    if (Source.ValueSites[Kind].empty())
> +      continue;
> +    if (Dest.ValueSites[Kind].empty()) {
> +      Dest.ValueSites[Kind].swap(Source.ValueSites[Kind]);
> +      continue;
> +    }

Why do we allow combining data that has no value sites with data that
does? Does that actually make sense?

> +    if (Dest.ValueSites[Kind].size() != Source.ValueSites[Kind].size())
> +      return instrprof_error::value_site_count_mismatch;
> +    for (size_t I = 0, E = Source.ValueSites[Kind].size(); I < E; ++I)
> +      Dest.ValueSites[Kind][I].mergeValueData(Source.ValueSites[Kind][I]);
>    }
> +
>    // We keep track of the max function count as we go for simplicity.
> -  if (FoundCounters[0] > MaxFunctionCount)
> -    MaxFunctionCount = FoundCounters[0];
> +  if (Dest.Counts[0] > MaxFunctionCount)
> +    MaxFunctionCount = Dest.Counts[0];
>  
>    return instrprof_error::success;
>  }
>  
> +void InstrProfWriter::updateStringTableReferences(InstrProfRecord &I) {
> +  I.Name = StringTable.insertString(I.Name);
> +  for (auto& VSite : I.ValueSites[instrprof_value_kind::indirect_call_target])
> +    for (auto& VData : VSite.ValueData)
> +      VData.first =
> +          (uint64_t)StringTable.insertString((const char *)VData.first);

I'm a little uncomfortable that we need to modify the Name in the
iterators here. Can't the data structure backing the string table just
work in StringRefs instead?

> +}
> +
> +std::error_code InstrProfWriter::addRecord(InstrProfRecord &&I) {
> +  updateStringTableReferences(I);
> +  auto &ProfileDataMap = FunctionData[I.Name];
> +
> +  auto Where = ProfileDataMap.find(I.Hash);
> +  if (Where == ProfileDataMap.end()) {
> +    // We've never seen a function with this name and hash, add it.
> +    ProfileDataMap[I.Hash] = I;
> +
> +    // We keep track of the max function count as we go for simplicity.
> +    if (I.Counts[0] > MaxFunctionCount)
> +      MaxFunctionCount = I.Counts[0];
> +    return instrprof_error::success;
> +  }
> +
> +  // We're updating a function we've seen before.
> +  return combineInstrProfRecords(Where->second, I, MaxFunctionCount);
> +}
> +
>  std::pair<uint64_t, uint64_t> InstrProfWriter::writeImpl(raw_ostream &OS) {
>    OnDiskChainedHashTableGenerator<InstrProfRecordTrait> Generator;
>  
> Index: lib/ProfileData/InstrProfReader.cpp
> ===================================================================
> --- lib/ProfileData/InstrProfReader.cpp
> +++ lib/ProfileData/InstrProfReader.cpp
> @@ -15,8 +15,12 @@
>  #include "llvm/ProfileData/InstrProfReader.h"
>  #include "InstrProfIndexed.h"
>  #include "llvm/ADT/STLExtras.h"
> +#include "llvm/Support/Debug.h"
> +#include "llvm/Support/raw_ostream.h"
>  #include <cassert>
>  
> +#define DEBUG_TYPE "InstrProfReader"
> +
>  using namespace llvm;
>  
>  static ErrorOr<std::unique_ptr<MemoryBuffer>>
> @@ -302,42 +306,94 @@
>  typedef InstrProfLookupTrait::data_type data_type;
>  typedef InstrProfLookupTrait::offset_type offset_type;
>  
> +bool InstrProfLookupTrait::ReadValueProfilingData(
> +    const unsigned char *&D, const unsigned char *const End) {
> +
> +  using namespace support;
> +  // Read number of value kinds with value sites.
> +  if (D + sizeof(uint64_t) > End)
> +    return false;
> +  uint64_t ValueKindCount = endian::readNext<uint64_t, little, unaligned>(D);
> +
> +  for (uint32_t Kind = 0; Kind < ValueKindCount; ++Kind) {
> +
> +    // Read value kind and number of value sites for kind.
> +    if (D + 2*sizeof(uint64_t) > End)
> +      return false;
> +    uint64_t ValueKind = endian::readNext<uint64_t, little, unaligned>(D);
> +    uint64_t ValueSiteCount = endian::readNext<uint64_t, little, unaligned>(D);
> +
> +    DataBuffer.back().ValueSites[ValueKind].reserve(ValueSiteCount);
> +    for (uint64_t VSite = 0; VSite < ValueSiteCount; ++VSite) {
> +      // Read number of value data pairs at value site.
> +      if (D + sizeof(uint64_t) > End)
> +        return false;
> +      uint64_t ValueDataCount =
> +          endian::readNext<uint64_t, little, unaligned>(D);
> +
> +      // Check if there are as many ValueDataPairs as ValueDataCount in memory.
> +      if (D + (ValueDataCount<<1)*sizeof(uint64_t) > End)
> +        return false;
> +
> +      InstrProfValueSiteRecord VSiteRecord;
> +      for (uint64_t VCount = 0; VCount < ValueDataCount; ++VCount) {
> +        uint64_t Value = endian::readNext<uint64_t, little, unaligned>(D);
> +        uint64_t NumTaken = endian::readNext<uint64_t, little, unaligned>(D);
> +        if (ValueKind == instrprof_value_kind::indirect_call_target) {

If we see anything other than indirect_call_target we should return
false - we don't know how to interpret that data.

> +          auto Result = HashKeyMap.find(Value);
> +          assert(Result != HashKeyMap.end() &&
> +                 "Hash does not match any known keys\n");
> +          Value = (uint64_t)Result->second;
> +        }
> +        VSiteRecord.ValueData.push_back(std::make_pair(Value, NumTaken));
> +      }
> +      DataBuffer.back().ValueSites[ValueKind].push_back(std::move(VSiteRecord));
> +    }
> +  }
> +  return true;
> +}
> +
>  data_type InstrProfLookupTrait::ReadData(StringRef K, const unsigned char *D,
>                                           offset_type N) {
> -
>    // Check if the data is corrupt. If so, don't try to read it.
>    if (N % sizeof(uint64_t))
>      return data_type();
>  
>    DataBuffer.clear();
> -  uint64_t NumCounts;
> -  uint64_t NumEntries = N / sizeof(uint64_t);
>    std::vector<uint64_t> CounterBuffer;
> -  for (uint64_t I = 0; I < NumEntries; I += NumCounts) {
> -    using namespace support;
> -    // The function hash comes first.
> -    uint64_t Hash = endian::readNext<uint64_t, little, unaligned>(D);
>  
> -    if (++I >= NumEntries)
> +  using namespace support;
> +  const unsigned char *End = D + N;
> +  while (D < End) {
> +    // Read hash
> +    if (D + sizeof(uint64_t) >= End)
>        return data_type();
> +    uint64_t Hash = endian::readNext<uint64_t, little, unaligned>(D);
>  
> -    // In v1, we have at least one count.
> -    // Later, we have the number of counts.
> -    NumCounts = (1 == FormatVersion)
> -                    ? NumEntries - I
> -                    : endian::readNext<uint64_t, little, unaligned>(D);
> -    if (1 != FormatVersion)
> -      ++I;
> -
> -    // If we have more counts than data, this is bogus.
> -    if (I + NumCounts > NumEntries)
> +    // Initialize number of counters for FormatVersion == 1
> +    uint64_t CountsSize = N / sizeof(uint64_t) - 1;
> +    // If format version is different then read number of counters
> +    if (FormatVersion != 1) {
> +      if (D + sizeof(uint64_t) > End)
> +        return data_type();
> +      CountsSize = endian::readNext<uint64_t, little, unaligned>(D);
> +    }
> +    // Read counter values
> +    if (D + CountsSize * sizeof(uint64_t) > End)
>        return data_type();
>  
>      CounterBuffer.clear();
> -    for (unsigned J = 0; J < NumCounts; ++J)
> +    CounterBuffer.reserve(CountsSize);
> +    for (uint64_t J = 0; J < CountsSize; ++J)
>        CounterBuffer.push_back(endian::readNext<uint64_t, little, unaligned>(D));
>  
>      DataBuffer.push_back(InstrProfRecord(K, Hash, std::move(CounterBuffer)));
> +
> +    // Read value profiling data
> +    if (FormatVersion == 3 && !ReadValueProfilingData(D, End)) {

This should be "FormatVersion > 2".

> +      DataBuffer.clear();
> +      return data_type();
> +    }
>    }
>    return DataBuffer;
>  }
> @@ -383,7 +439,19 @@
>    // The rest of the file is an on disk hash table.
>    Index.reset(InstrProfReaderIndex::Create(
>        Start + HashOffset, Cur, Start,
> -      InstrProfLookupTrait(HashType, FormatVersion)));
> +      InstrProfLookupTrait(HashType, FormatVersion, HashKeyMap)));
> +  for (auto Key : Index->keys()) {
> +    const char *KeyTableRef = StringTable.insertString(Key);
> +    auto Result = HashKeyMap.insert(std::make_pair(ComputeHash(HashType, Key),
> +                                                   KeyTableRef));

The way the HashKeyMap works here seems a little off. Why does the
Reader own it? Only the trait uses it. Also, since it follows a strict
"fill then query" pattern, it's probably better to just use a vector
that we sort after filling and then binary search later.

> +    // Emit warning if a hash collision is detected.
> +    if (Result.second == false)
> +      DEBUG(dbgs() << "IndexedInstrProfReader: hash collision detected: \n"
> +                   << "\t Map Entry(Hash, Key): " << Result.first->first
> +                   << ", " << Result.first->second << "\n"
> +                   << "\t New Entry(Hash, Key): " << ComputeHash(HashType, Key)
> +                   << ", " << Key << "\n");

This is not "emitting a warning". This will only be printed if the host
compiler is built in debug mode, so it seems pretty pointless. Actually
emitting a proper warning from this point in the compiler might be kind
of tricky though.

> +  }
>    // Set up our iterator for readNextRecord.
>    RecordIterator = Index->data_begin();
>  
> Index: lib/ProfileData/InstrProfIndexed.h
> ===================================================================
> --- lib/ProfileData/InstrProfIndexed.h
> +++ lib/ProfileData/InstrProfIndexed.h
> @@ -47,7 +47,7 @@
>  }
>  
>  const uint64_t Magic = 0x8169666f72706cff; // "\xfflprofi\x81"
> -const uint64_t Version = 2;
> +const uint64_t Version = 3;
>  const HashT HashType = HashT::MD5;
>  }
>  
> Index: lib/ProfileData/InstrProf.cpp
> ===================================================================
> --- lib/ProfileData/InstrProf.cpp
> +++ lib/ProfileData/InstrProf.cpp
> @@ -50,6 +50,8 @@
>        return "Function count mismatch";
>      case instrprof_error::counter_overflow:
>        return "Counter overflow";
> +    case instrprof_error::value_site_count_mismatch:
> +      return "Function's value site counts mismatch";
>      }
>      llvm_unreachable("A value of instrprof_error has no message.");
>    }
> Index: include/llvm/ProfileData/InstrProfWriter.h
> ===================================================================
> --- include/llvm/ProfileData/InstrProfWriter.h
> +++ include/llvm/ProfileData/InstrProfWriter.h
> @@ -15,33 +15,32 @@
>  #ifndef LLVM_PROFILEDATA_INSTRPROFWRITER_H
>  #define LLVM_PROFILEDATA_INSTRPROFWRITER_H
>  
> -#include "llvm/ADT/ArrayRef.h"
>  #include "llvm/ADT/DenseMap.h"
> -#include "llvm/ADT/StringMap.h"
>  #include "llvm/ProfileData/InstrProf.h"
>  #include "llvm/Support/DataTypes.h"
>  #include "llvm/Support/MemoryBuffer.h"
>  #include "llvm/Support/raw_ostream.h"
> -#include <vector>
>  
>  namespace llvm {
>  
>  /// Writer for instrumentation based profile data.
>  class InstrProfWriter {
>  public:
> -  typedef SmallDenseMap<uint64_t, std::vector<uint64_t>, 1> CounterData;
> +  typedef SmallDenseMap<uint64_t, InstrProfRecord, 1> ProfilingData;
> +
>  private:
> -  StringMap<CounterData> FunctionData;
> +  InstrProfStringTable StringTable;
> +  StringMap<ProfilingData> FunctionData;
>    uint64_t MaxFunctionCount;
>  public:
>    InstrProfWriter() : MaxFunctionCount(0) {}
>  
> +  /// Update string entries in profile data with references to StringTable.
> +  void updateStringTableReferences(InstrProfRecord &I);
>    /// Add function counts for the given function. If there are already counts
>    /// for this function and the hash and number of counts match, each counter is
>    /// summed.
> -  std::error_code addFunctionCounts(StringRef FunctionName,
> -                                    uint64_t FunctionHash,
> -                                    ArrayRef<uint64_t> Counters);
> +  std::error_code addRecord(InstrProfRecord &&I);
>    /// Write the profile to \c OS
>    void write(raw_fd_ostream &OS);
>    /// Write the profile, returning the raw data. For testing.
> Index: include/llvm/ProfileData/InstrProfReader.h
> ===================================================================
> --- include/llvm/ProfileData/InstrProfReader.h
> +++ include/llvm/ProfileData/InstrProfReader.h
> @@ -24,6 +24,7 @@
>  #include "llvm/Support/MemoryBuffer.h"
>  #include "llvm/Support/OnDiskHashTable.h"
>  #include <iterator>
> +#include <map>
>  
>  namespace llvm {
>  
> @@ -65,6 +66,9 @@
>    InstrProfIterator end() { return InstrProfIterator(); }
>  
>  protected:
> +  /// String table for holding a unique copy of all the strings in the profile.
> +  InstrProfStringTable StringTable;
> +
>    /// Set the current std::error_code and return same.
>    std::error_code error(std::error_code EC) {
>      LastError = EC;
> @@ -195,10 +199,13 @@
>    std::vector<InstrProfRecord> DataBuffer;
>    IndexedInstrProf::HashT HashType;
>    unsigned FormatVersion;
> +  const std::map<uint64_t, const char *> &HashKeyMap;
>  
>  public:
> -  InstrProfLookupTrait(IndexedInstrProf::HashT HashType, unsigned FormatVersion)
> -      : HashType(HashType), FormatVersion(FormatVersion) {}
> +  InstrProfLookupTrait(IndexedInstrProf::HashT HashType, unsigned FormatVersion,
> +                       std::map<uint64_t, const char *> &HashKeyMap)
> +      : HashType(HashType), FormatVersion(FormatVersion),
> +        HashKeyMap(HashKeyMap) {}
>  
>    typedef ArrayRef<InstrProfRecord> data_type;
>  
> @@ -209,6 +216,7 @@
>  
>    static bool EqualKey(StringRef A, StringRef B) { return A == B; }
>    static StringRef GetInternalKey(StringRef K) { return K; }
> +  static StringRef GetExternalKey(StringRef K) { return K; }

What do you need GetExternalKey for?

>  
>    hash_value_type ComputeHash(StringRef K);
>  
> @@ -224,6 +232,8 @@
>      return StringRef((const char *)D, N);
>    }
>  
> +  bool ReadValueProfilingData(const unsigned char *&D,
> +                              const unsigned char *const End);
>    data_type ReadData(StringRef K, const unsigned char *D, offset_type N);
>  };
>  
> @@ -243,6 +253,8 @@
>    uint64_t FormatVersion;
>    /// The maximal execution count among all functions.
>    uint64_t MaxFunctionCount;
> +  /// Map of hash values to const char* keys in profiling data.
> +  std::map<uint64_t, const char *> HashKeyMap;
>  
>    IndexedInstrProfReader(const IndexedInstrProfReader &) = delete;
>    IndexedInstrProfReader &operator=(const IndexedInstrProfReader &) = delete;
> Index: include/llvm/ProfileData/InstrProf.h
> ===================================================================
> --- include/llvm/ProfileData/InstrProf.h
> +++ include/llvm/ProfileData/InstrProf.h
> @@ -16,42 +16,102 @@
>  #ifndef LLVM_PROFILEDATA_INSTRPROF_H_
>  #define LLVM_PROFILEDATA_INSTRPROF_H_
>  
> -#include "llvm/ADT/StringRef.h"
> +#include "llvm/ADT/StringSet.h"
>  #include <cstdint>
> +#include <list>
>  #include <system_error>
>  #include <vector>
>  
>  namespace llvm {
>  const std::error_category &instrprof_category();
>  
>  enum class instrprof_error {
> -    success = 0,
> -    eof,
> -    bad_magic,
> -    bad_header,
> -    unsupported_version,
> -    unsupported_hash_type,
> -    too_large,
> -    truncated,
> -    malformed,
> -    unknown_function,
> -    hash_mismatch,
> -    count_mismatch,
> -    counter_overflow
> +  success = 0,
> +  eof,
> +  bad_magic,
> +  bad_header,
> +  unsupported_version,
> +  unsupported_hash_type,
> +  too_large,
> +  truncated,
> +  malformed,
> +  unknown_function,
> +  hash_mismatch,
> +  count_mismatch,
> +  counter_overflow,
> +  value_site_count_mismatch
>  };
>  
>  inline std::error_code make_error_code(instrprof_error E) {
>    return std::error_code(static_cast<int>(E), instrprof_category());
>  }
>  
> +enum instrprof_value_kind : uint32_t {
> +  first = 0,
> +  indirect_call_target = 0,
> +  size = 1
> +};
> +
> +struct InstrProfStringTable {
> +  // Set of string values in profiling data.
> +  StringSet<> StringValueSet;
> +  InstrProfStringTable() { StringValueSet.clear(); }
> +  // Get a pointer to internal storage of a string in set
> +  const char *getStringData(StringRef Str) {
> +    auto Result = StringValueSet.find(Str);
> +    return (Result == StringValueSet.end()) ? nullptr : Result->first().data();
> +  }
> +  // Insert a string to StringTable
> +  const char *insertString(StringRef Str) {
> +    auto Result = StringValueSet.insert(Str);
> +    return Result.first->first().data();
> +  }
> +};
> +
> +struct InstrProfValueSiteRecord {
> +  // Typedef for a single TargetValue-NumTaken pair.
> +  typedef std::pair<uint64_t, uint64_t> ValueDataPair;
> +  // Value profiling data pairs at a given value site.
> +  std::list<ValueDataPair> ValueData;
> +
> +  InstrProfValueSiteRecord() { ValueData.clear(); }
> +
> +  // Sort ValueData ascending by TargetValue
> +  void sortByTargetValues() {
> +    ValueData.sort([](const ValueDataPair &left, const ValueDataPair &right) {
> +      return left.first < right.first;
> +    });
> +  }
> +  // Merge data from another InstrProfValueSiteRecord
> +  void mergeValueData(InstrProfValueSiteRecord &Input) {
> +    this->sortByTargetValues();
> +    Input.sortByTargetValues();
> +    auto I = ValueData.begin();
> +    auto IE = ValueData.end();
> +    for (auto J = Input.ValueData.begin(), JE = Input.ValueData.end(); J != JE;
> +         ++J) {
> +      while (I != IE && I->first < J->first)
> +        ++I;
> +      if (I != IE && I->first == J->first) {
> +        I->second += J->second;
> +        ++I;
> +        continue;
> +      }
> +      ValueData.insert(I, *J);
> +    }
> +  }
> +};
> +
>  /// Profiling information for a single function.
>  struct InstrProfRecord {
>    InstrProfRecord() {}
>    InstrProfRecord(StringRef Name, uint64_t Hash, std::vector<uint64_t> Counts)
>        : Name(Name), Hash(Hash), Counts(std::move(Counts)) {}
>    StringRef Name;
>    uint64_t Hash;
>    std::vector<uint64_t> Counts;
> +  // Size of vector indicates the number of value sites for a value kind
> +  std::vector<InstrProfValueSiteRecord> ValueSites[instrprof_value_kind::size];
>  };
>  
>  } // end namespace llvm



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