[Memprof] Adds the option to collect AccessCountHistograms for memprof. (#94264)

Adds compile time flag -mllvm -memprof-histogram and runtime flag
histogram=true|false to turn Histogram collection on and off. The
-memprof-histogram flag relies on -memprof-use-callbacks=true to work.

Updates shadow mapping logic in histogram mode from having one 8 byte
counter for 64 bytes, to 1 byte for 8 bytes, capped at 255. Only
supports this granularity as of now.

Updates the RawMemprofReader and serializing MemoryInfoBlocks to binary
format, including changing to a new version of the raw binary format
from version 3 to version 4.

Updates creating MemoryInfoBlocks with and without Histograms. When two
MemoryInfoBlocks are merged, AccessCounts are summed up and the shorter
Histogram is removed.

Adds a memprof_histogram test case.

Initial commit for adding AccessCountHistograms up until RawProfile for
memprof

42 files changed, 878 insertions, 51 deletions

diff --git a/llvm/include/llvm/ProfileData/MIBEntryDef.inc b/llvm/include/llvm/ProfileData/MIBEntryDef.inc
index 794163a..58c1fc4 100644
--- a/llvm/include/llvm/ProfileData/MIBEntryDef.inc
+++ b/llvm/include/llvm/ProfileData/MIBEntryDef.inc
@@ -51,3 +51,5 @@ MIBEntryDef(MaxAccessDensity = 22, MaxAccessDensity, uint32_t)
 MIBEntryDef(TotalLifetimeAccessDensity = 23, TotalLifetimeAccessDensity, uint64_t)
 MIBEntryDef(MinLifetimeAccessDensity = 24, MinLifetimeAccessDensity, uint32_t)
 MIBEntryDef(MaxLifetimeAccessDensity = 25, MaxLifetimeAccessDensity, uint32_t)
+MIBEntryDef(AccessHistogramSize = 26, AccessHistogramSize, uint32_t)
+MIBEntryDef(AccessHistogram = 27, AccessHistogram, uintptr_t)
\ No newline at end of file
diff --git a/llvm/include/llvm/ProfileData/MemProf.h b/llvm/include/llvm/ProfileData/MemProf.h
index 5cd74be..cee8e5e 100644
--- a/llvm/include/llvm/ProfileData/MemProf.h
+++ b/llvm/include/llvm/ProfileData/MemProf.h
@@ -124,6 +124,13 @@ struct PortableMemInfoBlock {
   OS << "        " << #Name << ": " << Name << "\n";
 #include "llvm/ProfileData/MIBEntryDef.inc"
 #undef MIBEntryDef
+    if (AccessHistogramSize > 0) {
+      OS << "        " << "AccessHistogramValues" << ":";
+      for (uint32_t I = 0; I < AccessHistogramSize; ++I) {
+        OS << " " << ((uint64_t *)AccessHistogram)[I];
+      }
+      OS << "\n";
+    }
   }
 
   // Return the schema, only for unit tests.
diff --git a/llvm/include/llvm/ProfileData/MemProfData.inc b/llvm/include/llvm/ProfileData/MemProfData.inc
index b82a4ba..3f785bd 100644
--- a/llvm/include/llvm/ProfileData/MemProfData.inc
+++ b/llvm/include/llvm/ProfileData/MemProfData.inc
@@ -33,7 +33,13 @@
    (uint64_t)'o' << 24 | (uint64_t)'f' << 16 | (uint64_t)'r' << 8 | (uint64_t)129)
 
 // The version number of the raw binary format.
-#define MEMPROF_RAW_VERSION 3ULL
+#define MEMPROF_RAW_VERSION 4ULL
+
+// Currently supported versions.
+#define MEMPROF_RAW_SUPPORTED_VERSIONS                                         \
+  { 3ULL, 4ULL }
+
+#define MEMPROF_V3_MIB_SIZE 132ULL;
 
 #define MEMPROF_BUILDID_MAX_SIZE 32ULL
 
@@ -119,7 +125,8 @@ MemInfoBlock() {
 }
 
 MemInfoBlock(uint32_t Size, uint64_t AccessCount, uint32_t AllocTs,
-             uint32_t DeallocTs, uint32_t AllocCpu, uint32_t DeallocCpu)
+             uint32_t DeallocTs, uint32_t AllocCpu, uint32_t DeallocCpu,
+             uintptr_t Histogram, uint32_t HistogramSize)
     : MemInfoBlock() {
   AllocCount = 1U;
   TotalAccessCount = AccessCount;
@@ -149,6 +156,8 @@ MemInfoBlock(uint32_t Size, uint64_t AccessCount, uint32_t AllocTs,
   AllocCpuId = AllocCpu;
   DeallocCpuId = DeallocCpu;
   NumMigratedCpu = AllocCpuId != DeallocCpuId;
+  AccessHistogramSize = HistogramSize;
+  AccessHistogram = Histogram;
 }
 
 void Merge(const MemInfoBlock &newMIB) {
@@ -194,6 +203,24 @@ void Merge(const MemInfoBlock &newMIB) {
   NumSameDeallocCpu += DeallocCpuId == newMIB.DeallocCpuId;
   AllocCpuId = newMIB.AllocCpuId;
   DeallocCpuId = newMIB.DeallocCpuId;
+
+  // For merging histograms, we always keep the longer histogram, and add
+  // values of shorter histogram to larger one.
+  uintptr_t ShorterHistogram;
+  uint32_t ShorterHistogramSize;
+  if (newMIB.AccessHistogramSize > AccessHistogramSize) {
+    ShorterHistogram = AccessHistogram;
+    ShorterHistogramSize = AccessHistogramSize;
+    // Swap histogram of current to larger histogram
+    AccessHistogram = newMIB.AccessHistogram;
+    AccessHistogramSize = newMIB.AccessHistogramSize;
+  } else {
+    ShorterHistogram = newMIB.AccessHistogram;
+    ShorterHistogramSize = newMIB.AccessHistogramSize;
+  }
+  for (size_t i = 0; i < ShorterHistogramSize; ++i) {
+    ((uint64_t *)AccessHistogram)[i] += ((uint64_t *)ShorterHistogram)[i];
+  }
 }
 
 #ifdef _MSC_VER
diff --git a/llvm/include/llvm/ProfileData/MemProfReader.h b/llvm/include/llvm/ProfileData/MemProfReader.h
index fbba6483..da2f14b 100644
--- a/llvm/include/llvm/ProfileData/MemProfReader.h
+++ b/llvm/include/llvm/ProfileData/MemProfReader.h
@@ -137,7 +137,7 @@ class RawMemProfReader final : public MemProfReader {
 public:
   RawMemProfReader(const RawMemProfReader &) = delete;
   RawMemProfReader &operator=(const RawMemProfReader &) = delete;
-  ~RawMemProfReader() override = default;
+  virtual ~RawMemProfReader() override;
 
   // Prints the contents of the profile in YAML format.
   void printYAML(raw_ostream &OS);
@@ -205,8 +205,14 @@ private:
 
   object::SectionedAddress getModuleOffset(uint64_t VirtualAddress);
 
+  llvm::SmallVector<std::pair<uint64_t, MemInfoBlock>>
+  readMemInfoBlocks(const char *Ptr);
+
   // The profiled binary.
   object::OwningBinary<object::Binary> Binary;
+  // Version of raw memprof binary currently being read. Defaults to most up
+  // to date version.
+  uint64_t MemprofRawVersion = MEMPROF_RAW_VERSION;
   // The preferred load address of the executable segment.
   uint64_t PreferredTextSegmentAddress = 0;
   // The base address of the text segment in the process during profiling.
diff --git a/llvm/lib/ProfileData/MemProfReader.cpp b/llvm/lib/ProfileData/MemProfReader.cpp
index de58cb6..9112e19 100644
--- a/llvm/lib/ProfileData/MemProfReader.cpp
+++ b/llvm/lib/ProfileData/MemProfReader.cpp
@@ -41,7 +41,6 @@
 #include "llvm/Support/Path.h"
 
 #define DEBUG_TYPE "memprof"
-
 namespace llvm {
 namespace memprof {
 namespace {
@@ -68,7 +67,14 @@ Error checkBuffer(const MemoryBuffer &Buffer) {
   const char *Next = Buffer.getBufferStart();
   while (Next < Buffer.getBufferEnd()) {
     const auto *H = reinterpret_cast<const Header *>(Next);
-    if (H->Version != MEMPROF_RAW_VERSION) {
+
+    // Check if the version in header is among the supported versions.
+    bool IsSupported = false;
+    for (auto SupportedVersion : MEMPROF_RAW_SUPPORTED_VERSIONS) {
+      if (H->Version == SupportedVersion)
+        IsSupported = true;
+    }
+    if (!IsSupported) {
       return make_error<InstrProfError>(instrprof_error::unsupported_version);
     }
 
@@ -96,19 +102,63 @@ llvm::SmallVector<SegmentEntry> readSegmentEntries(const char *Ptr) {
 }
 
 llvm::SmallVector<std::pair<uint64_t, MemInfoBlock>>
-readMemInfoBlocks(const char *Ptr) {
+readMemInfoBlocksV3(const char *Ptr) {
   using namespace support;
 
   const uint64_t NumItemsToRead =
-      endian::readNext<uint64_t, llvm::endianness::little>(Ptr);
+      endian::readNext<uint64_t, llvm::endianness::little, unaligned>(Ptr);
+
   llvm::SmallVector<std::pair<uint64_t, MemInfoBlock>> Items;
   for (uint64_t I = 0; I < NumItemsToRead; I++) {
     const uint64_t Id =
-        endian::readNext<uint64_t, llvm::endianness::little>(Ptr);
-    const MemInfoBlock MIB = *reinterpret_cast<const MemInfoBlock *>(Ptr);
+        endian::readNext<uint64_t, llvm::endianness::little, unaligned>(Ptr);
+
+    // We cheat a bit here and remove the const from cast to set the
+    // Histogram Pointer to newly allocated buffer. We also cheat, since V3 and
+    // V4 do not have the same fields. V3 is missing AccessHistogramSize and
+    // AccessHistogram. This means we read "dirty" data in here, but it should
+    // not segfault, since there will be callstack data placed after this in the
+    // binary format.
+    MemInfoBlock MIB = *reinterpret_cast<const MemInfoBlock *>(Ptr);
+    // Overwrite dirty data.
+    MIB.AccessHistogramSize = 0;
+    MIB.AccessHistogram = 0;
+
     Items.push_back({Id, MIB});
+    // Only increment by the size of MIB in V3.
+    Ptr += MEMPROF_V3_MIB_SIZE;
+  }
+  return Items;
+}
+
+llvm::SmallVector<std::pair<uint64_t, MemInfoBlock>>
+readMemInfoBlocksV4(const char *Ptr) {
+  using namespace support;
+
+  const uint64_t NumItemsToRead =
+      endian::readNext<uint64_t, llvm::endianness::little, unaligned>(Ptr);
+
+  llvm::SmallVector<std::pair<uint64_t, MemInfoBlock>> Items;
+  for (uint64_t I = 0; I < NumItemsToRead; I++) {
+    const uint64_t Id =
+        endian::readNext<uint64_t, llvm::endianness::little, unaligned>(Ptr);
+    // We cheat a bit here and remove the const from cast to set the
+    // Histogram Pointer to newly allocated buffer.
+    MemInfoBlock MIB = *reinterpret_cast<const MemInfoBlock *>(Ptr);
+
     // Only increment by size of MIB since readNext implicitly increments.
     Ptr += sizeof(MemInfoBlock);
+
+    if (MIB.AccessHistogramSize > 0) {
+      MIB.AccessHistogram =
+          (uintptr_t)malloc(MIB.AccessHistogramSize * sizeof(uint64_t));
+    }
+
+    for (uint64_t J = 0; J < MIB.AccessHistogramSize; J++) {
+      ((uint64_t *)MIB.AccessHistogram)[J] =
+          endian::readNext<uint64_t, llvm::endianness::little, unaligned>(Ptr);
+    }
+    Items.push_back({Id, MIB});
   }
   return Items;
 }
@@ -251,6 +301,16 @@ RawMemProfReader::create(std::unique_ptr<MemoryBuffer> Buffer,
   return std::move(Reader);
 }
 
+// We need to make sure that all leftover MIB histograms that have not been
+// freed by merge are freed here.
+RawMemProfReader::~RawMemProfReader() {
+  for (auto &[_, MIB] : CallstackProfileData) {
+    if (MemprofRawVersion >= 4ULL && MIB.AccessHistogramSize > 0) {
+      free((void *)MIB.AccessHistogram);
+    }
+  }
+}
+
 bool RawMemProfReader::hasFormat(const StringRef Path) {
   auto BufferOr = MemoryBuffer::getFileOrSTDIN(Path);
   if (!BufferOr)
@@ -281,7 +341,7 @@ void RawMemProfReader::printYAML(raw_ostream &OS) {
 
   OS << "MemprofProfile:\n";
   OS << "  Summary:\n";
-  OS << "    Version: " << MEMPROF_RAW_VERSION << "\n";
+  OS << "    Version: " << MemprofRawVersion << "\n";
   OS << "    NumSegments: " << SegmentInfo.size() << "\n";
   OS << "    NumMibInfo: " << NumMibInfo << "\n";
   OS << "    NumAllocFunctions: " << NumAllocFunctions << "\n";
@@ -610,6 +670,20 @@ RawMemProfReader::peekBuildIds(MemoryBuffer *DataBuffer) {
   return BuildIds.takeVector();
 }
 
+// FIXME: Add a schema for serializing similiar to IndexedMemprofReader. This
+// will help being able to deserialize different versions raw memprof versions
+// more easily.
+llvm::SmallVector<std::pair<uint64_t, MemInfoBlock>>
+RawMemProfReader::readMemInfoBlocks(const char *Ptr) {
+  if (MemprofRawVersion == 3ULL)
+    return readMemInfoBlocksV3(Ptr);
+  else if (MemprofRawVersion == 4ULL)
+    return readMemInfoBlocksV4(Ptr);
+  else
+    assert(false &&
+           "Panic: Unsupported version number when reading MemInfoBlocks");
+}
+
 Error RawMemProfReader::readRawProfile(
     std::unique_ptr<MemoryBuffer> DataBuffer) {
   const char *Next = DataBuffer->getBufferStart();
@@ -617,6 +691,10 @@ Error RawMemProfReader::readRawProfile(
   while (Next < DataBuffer->getBufferEnd()) {
     const auto *Header = reinterpret_cast<const memprof::Header *>(Next);
 
+    // Set Reader version to memprof raw version of profile. Checking if version
+    // is supported is checked before creating the reader.
+    MemprofRawVersion = Header->Version;
+
     // Read in the segment information, check whether its the same across all
     // profiles in this binary file.
     const llvm::SmallVector<SegmentEntry> Entries =
@@ -636,7 +714,21 @@ Error RawMemProfReader::readRawProfile(
     // stackdepot ids are the same.
     for (const auto &[Id, MIB] : readMemInfoBlocks(Next + Header->MIBOffset)) {
       if (CallstackProfileData.count(Id)) {
-        CallstackProfileData[Id].Merge(MIB);
+
+        if (MemprofRawVersion >= 4ULL &&
+            (CallstackProfileData[Id].AccessHistogramSize > 0 ||
+             MIB.AccessHistogramSize > 0)) {
+          uintptr_t ShorterHistogram;
+          if (CallstackProfileData[Id].AccessHistogramSize >
+              MIB.AccessHistogramSize)
+            ShorterHistogram = MIB.AccessHistogram;
+          else
+            ShorterHistogram = CallstackProfileData[Id].AccessHistogram;
+          CallstackProfileData[Id].Merge(MIB);
+          free((void *)ShorterHistogram);
+        } else {
+          CallstackProfileData[Id].Merge(MIB);
+        }
       } else {
         CallstackProfileData[Id] = MIB;
       }
diff --git a/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp b/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
index 8a12fa1..1880928 100644
--- a/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
@@ -77,6 +77,8 @@ constexpr char MemProfShadowMemoryDynamicAddress[] =
 
 constexpr char MemProfFilenameVar[] = "__memprof_profile_filename";
 
+constexpr char MemProfHistogramFlagVar[] = "__memprof_histogram";
+
 // Command-line flags.
 
 static cl::opt<bool> ClInsertVersionCheck(
@@ -145,10 +147,14 @@ static cl::opt<int> ClDebugMax("memprof-debug-max", cl::desc("Debug max inst"),
 // override these hints anyway.
 static cl::opt<bool> ClMemProfMatchHotColdNew(
     "memprof-match-hot-cold-new",
-    cl::desc(
+ cl::desc(
         "Match allocation profiles onto existing hot/cold operator new calls"),
     cl::Hidden, cl::init(false));
 
+static cl::opt<bool> ClHistogram("memprof-histogram",
+                                 cl::desc("Collect access count histograms"),
+                                 cl::Hidden, cl::init(false));
+
 static cl::opt<bool>
     ClPrintMemProfMatchInfo("memprof-print-match-info",
                             cl::desc("Print matching stats for each allocation "
@@ -279,6 +285,11 @@ ModuleMemProfilerPass::ModuleMemProfilerPass() = default;
 
 PreservedAnalyses ModuleMemProfilerPass::run(Module &M,
                                              AnalysisManager<Module> &AM) {
+
+  assert((!ClHistogram || (ClHistogram && ClUseCalls)) &&
+         "Cannot use -memprof-histogram without Callbacks. Set "
+         "memprof-use-callbacks");
+
   ModuleMemProfiler Profiler(M);
   if (Profiler.instrumentModule(M))
     return PreservedAnalyses::none();
@@ -508,7 +519,24 @@ void createProfileFileNameVar(Module &M) {
   }
 }
 
+// Set MemprofHistogramFlag as a Global veriable in IR. This makes it accessible
+// to the runtime, changing shadow count behavior.
+void createMemprofHistogramFlagVar(Module &M) {
+  const StringRef VarName(MemProfHistogramFlagVar);
+  Type *IntTy1 = Type::getInt1Ty(M.getContext());
+  auto MemprofHistogramFlag = new GlobalVariable(
+      M, IntTy1, true, GlobalValue::WeakAnyLinkage,
+      Constant::getIntegerValue(IntTy1, APInt(1, ClHistogram)), VarName);
+  Triple TT(M.getTargetTriple());
+  if (TT.supportsCOMDAT()) {
+    MemprofHistogramFlag->setLinkage(GlobalValue::ExternalLinkage);
+    MemprofHistogramFlag->setComdat(M.getOrInsertComdat(VarName));
+  }
+  appendToCompilerUsed(M, MemprofHistogramFlag);
+}
+
 bool ModuleMemProfiler::instrumentModule(Module &M) {
+
   // Create a module constructor.
   std::string MemProfVersion = std::to_string(LLVM_MEM_PROFILER_VERSION);
   std::string VersionCheckName =
@@ -524,6 +552,8 @@ bool ModuleMemProfiler::instrumentModule(Module &M) {
 
   createProfileFileNameVar(M);
 
+  createMemprofHistogramFlagVar(M);
+
   return true;
 }
 
@@ -532,11 +562,12 @@ void MemProfiler::initializeCallbacks(Module &M) {
 
   for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
     const std::string TypeStr = AccessIsWrite ? "store" : "load";
+    const std::string HistPrefix = ClHistogram ? "hist_" : "";
 
     SmallVector<Type *, 2> Args1{1, IntptrTy};
-    MemProfMemoryAccessCallback[AccessIsWrite] =
-        M.getOrInsertFunction(ClMemoryAccessCallbackPrefix + TypeStr,
-                              FunctionType::get(IRB.getVoidTy(), Args1, false));
+    MemProfMemoryAccessCallback[AccessIsWrite] = M.getOrInsertFunction(
+        ClMemoryAccessCallbackPrefix + HistPrefix + TypeStr,
+        FunctionType::get(IRB.getVoidTy(), Args1, false));
   }
   MemProfMemmove = M.getOrInsertFunction(
       ClMemoryAccessCallbackPrefix + "memmove", PtrTy, PtrTy, PtrTy, IntptrTy);
@@ -1024,4 +1055,4 @@ PreservedAnalyses MemProfUsePass::run(Module &M, ModuleAnalysisManager &AM) {
   }
 
   return PreservedAnalyses::none();
-}
+}
\ No newline at end of file
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof.exe b/llvm/test/Transforms/PGOProfile/Inputs/memprof.exe
index b10c2f9..361354d 100755
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof.exe
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof.exe
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof.memprofraw b/llvm/test/Transforms/PGOProfile/Inputs/memprof.memprofraw
index 790249a..1ff4352 100644
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof.memprofraw
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof.memprofraw
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.exe b/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.exe
index 3000e2b..e9e6897 100755
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.exe
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.exe
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.memprofraw b/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.memprofraw
index c0db6d2..1ff4f1d 100644
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.memprofraw
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof.nocolinfo.memprofraw
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.exe b/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.exe
index 6e0eaaf..c9f81fc 100755
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.exe
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.exe
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.memprofraw b/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.memprofraw
index 43bd116..c496a13 100644
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.memprofraw
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof_internal_linkage.memprofraw
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.exe b/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.exe
index 6bb4279..d555a8c 100755
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.exe
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.exe
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.memprofraw b/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.memprofraw
index e74f966..923d309 100644
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.memprofraw
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof_loop_unroll.memprofraw
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.exe b/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.exe
index 212f8f8..1b4ca7f 100755
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.exe
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.exe
diff --git a/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.memprofraw b/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.memprofraw
index 3a06639..a2cfc3f 100644
--- a/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.memprofraw
+++ b/llvm/test/Transforms/PGOProfile/Inputs/memprof_missing_leaf.memprofraw
diff --git a/llvm/test/Transforms/PGOProfile/memprof_internal_linkage.ll b/llvm/test/Transforms/PGOProfile/memprof_internal_linkage.ll
index 3d4b93c..3c4138f 100644
--- a/llvm/test/Transforms/PGOProfile/memprof_internal_linkage.ll
+++ b/llvm/test/Transforms/PGOProfile/memprof_internal_linkage.ll
@@ -28,12 +28,12 @@ entry:
   store i32 0, ptr %retval, align 4
   store i32 %argc, ptr %argc.addr, align 4
   store ptr %argv, ptr %argv.addr, align 8
-  call void @_ZL3foov.__uniq.231888424933890731874095357293037629092() #4, !dbg !14
+  call void @_ZL3foov.__uniq.50354172613129440706982166615384819716() #4, !dbg !14
   ret i32 0, !dbg !15
 }
 
 ; Function Attrs: mustprogress noinline optnone uwtable
-define internal void @_ZL3foov.__uniq.231888424933890731874095357293037629092() #1 !dbg !16 {
+define internal void @_ZL3foov.__uniq.50354172613129440706982166615384819716() #1 !dbg !16 {
 entry:
   %a = alloca ptr, align 8
   %call = call noalias noundef nonnull ptr @_Znam(i64 noundef 20) #5, !dbg !17
@@ -76,7 +76,7 @@ attributes #5 = { builtin allocsize(0) }
 !13 = !{}
 !14 = !DILocation(line: 8, column: 3, scope: !10)
 !15 = !DILocation(line: 9, column: 3, scope: !10)
-!16 = distinct !DISubprogram(name: "foo", linkageName: "_ZL3foov.__uniq.231888424933890731874095357293037629092", scope: !11, file: !11, line: 3, type: !12, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0)
+!16 = distinct !DISubprogram(name: "foo", linkageName: "_ZL3foov.__uniq.50354172613129440706982166615384819716", scope: !11, file: !11, line: 3, type: !12, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !0)
 !17 = !DILocation(line: 4, column: 12, scope: !16)
 !18 = !DILocation(line: 4, column: 8, scope: !16)
 !19 = !DILocation(line: 5, column: 10, scope: !16)
diff --git a/llvm/test/tools/llvm-profdata/Inputs/basic-histogram.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/basic-histogram.memprofexe
new file mode 100755
index 0000000..502472c
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/Inputs/basic-histogram.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/basic-histogram.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/basic-histogram.memprofraw
new file mode 100644
index 0000000..850da9e
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/Inputs/basic-histogram.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/basic.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/basic.memprofexe
index d03894b..32b52c8 100755
--- a/llvm/test/tools/llvm-profdata/Inputs/basic.memprofexe
+++ b/llvm/test/tools/llvm-profdata/Inputs/basic.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/basic.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/basic.memprofraw
index 62b7d29..dae9b4d 100644
--- a/llvm/test/tools/llvm-profdata/Inputs/basic.memprofraw
+++ b/llvm/test/tools/llvm-profdata/Inputs/basic.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/basic_v3.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/basic_v3.memprofexe
new file mode 100755
index 0000000..d03894b
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/Inputs/basic_v3.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/basic_v3.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/basic_v3.memprofraw
new file mode 100644
index 0000000..62b7d29
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/Inputs/basic_v3.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofexe
index 5687d06..3de26f6 100755
--- a/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofexe
+++ b/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofraw
index 43f9ca9..56926cb 100644
--- a/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofraw
+++ b/llvm/test/tools/llvm-profdata/Inputs/buildid.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/inline.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/inline.memprofexe
index 766d2c47..2953080 100755
--- a/llvm/test/tools/llvm-profdata/Inputs/inline.memprofexe
+++ b/llvm/test/tools/llvm-profdata/Inputs/inline.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/inline.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/inline.memprofraw
index 26254ae..453b059 100644
--- a/llvm/test/tools/llvm-profdata/Inputs/inline.memprofraw
+++ b/llvm/test/tools/llvm-profdata/Inputs/inline.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/multi.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/multi.memprofexe
index d5c3ec6..3ba9f8a 100755
--- a/llvm/test/tools/llvm-profdata/Inputs/multi.memprofexe
+++ b/llvm/test/tools/llvm-profdata/Inputs/multi.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/multi.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/multi.memprofraw
index a1018aa..792edb7 100644
--- a/llvm/test/tools/llvm-profdata/Inputs/multi.memprofraw
+++ b/llvm/test/tools/llvm-profdata/Inputs/multi.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/padding-histogram.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/padding-histogram.memprofexe
new file mode 100755
index 0000000..fad3fc1
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/Inputs/padding-histogram.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/padding-histogram.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/padding-histogram.memprofraw
new file mode 100644
index 0000000..0d540ca
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/Inputs/padding-histogram.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/pic.memprofexe b/llvm/test/tools/llvm-profdata/Inputs/pic.memprofexe
index d854186..b92ed10 100755
--- a/llvm/test/tools/llvm-profdata/Inputs/pic.memprofexe
+++ b/llvm/test/tools/llvm-profdata/Inputs/pic.memprofexe
diff --git a/llvm/test/tools/llvm-profdata/Inputs/pic.memprofraw b/llvm/test/tools/llvm-profdata/Inputs/pic.memprofraw
index 992022f..1994b49 100644
--- a/llvm/test/tools/llvm-profdata/Inputs/pic.memprofraw
+++ b/llvm/test/tools/llvm-profdata/Inputs/pic.memprofraw
diff --git a/llvm/test/tools/llvm-profdata/Inputs/update_memprof_inputs.sh b/llvm/test/tools/llvm-profdata/Inputs/update_memprof_inputs.sh
index 5365a0b..10c36a8 100755
--- a/llvm/test/tools/llvm-profdata/Inputs/update_memprof_inputs.sh
+++ b/llvm/test/tools/llvm-profdata/Inputs/update_memprof_inputs.sh
@@ -31,7 +31,7 @@ read -r -d '' INLINE << EOF
 
 __attribute__((always_inline))
 void qux(int x) {
-  char *ptr = malloc(x);
+  char *ptr = (char*) malloc(x);
   memset(ptr, 0, x);
   free(ptr);
 }
@@ -64,6 +64,190 @@ int main(int argc, char **argv) {
 }
 EOF
 
+read -r -d '' BASIC_HISTOGRAM << EOF
+struct A {
+  long int a;
+  long int b;
+  long int c;
+  long int d;
+  long int e;
+  long int f;
+  long int g;
+  long int h;
+  A() {};
+};
+
+void foo() {
+  long int acc = 0;
+  A *a = new A();
+  acc += a->a;
+  acc += a->b;
+  acc += a->c;
+  acc += a->d;
+  acc += a->e;
+  acc += a->f;
+  acc += a->g;
+  acc += a->h;
+  delete a;
+}
+void bar() {
+  long int acc = 0;
+  A *a = new A();
+  acc += a->a;
+  acc += a->a;
+  acc += a->a;
+  acc += a->a;
+  acc += a->a;
+  acc += a->a;
+  acc += a->a;
+  acc += a->a;
+  acc += a->b;
+  acc += a->b;
+  acc += a->b;
+  acc += a->b;
+  acc += a->b;
+  acc += a->b;
+  acc += a->b;
+  acc += a->c;
+  acc += a->c;
+  acc += a->c;
+  acc += a->c;
+  acc += a->c;
+  acc += a->c;
+  acc += a->d;
+  acc += a->d;
+  acc += a->d;
+  acc += a->d;
+  acc += a->d;
+  acc += a->e;
+  acc += a->e;
+  acc += a->e;
+  acc += a->e;
+  acc += a->f;
+  acc += a->f;
+  acc += a->f;
+  acc += a->g;
+  acc += a->g;
+  acc += a->h;
+
+  delete a;
+}
+
+int main(int argc, char **argv) {
+  long int acc = 0;
+  A *a = new A();
+  acc += a->a;
+  acc += a->b;
+  acc += a->c;
+  acc += a->d;
+  acc += a->e;
+  acc += a->f;
+  acc += a->g;
+  acc += a->h;
+
+  delete a;
+
+  A *b = new A();
+  acc += b->a;
+  acc += b->a;
+  acc += b->a;
+  acc += b->a;
+  acc += b->a;
+  acc += b->a;
+  acc += b->a;
+  acc += b->a;
+  acc += b->b;
+  acc += b->b;
+  acc += b->b;
+  acc += b->b;
+  acc += b->b;
+  acc += b->b;
+  acc += b->b;
+  acc += b->c;
+  acc += b->c;
+  acc += b->c;
+  acc += b->c;
+  acc += b->c;
+  acc += b->c;
+  acc += b->d;
+  acc += b->d;
+  acc += b->d;
+  acc += b->d;
+  acc += b->d;
+  acc += b->e;
+  acc += b->e;
+  acc += b->e;
+  acc += b->e;
+  acc += b->f;
+  acc += b->f;
+  acc += b->f;
+  acc += b->g;
+  acc += b->g;
+  acc += b->h;
+
+  delete b;
+
+  A *c = new A();
+  acc += c->a;
+
+  for (int i = 0; i < 21; ++i) {
+
+    foo();
+  }
+
+  for (int i = 0; i < 21; ++i) {
+
+    bar();
+  }
+
+  return 0;
+}
+EOF
+
+read -r -d '' PADDING_HISTOGRAM << EOF
+struct A {
+  char a;
+  char b;
+  long int c;
+  char d;
+  int e;
+  A() {};
+};
+
+struct B {
+  double x;
+  double y;
+  B() {};
+};
+
+struct C {
+  A a;
+  char z;
+  B b;
+  C() {};
+};
+
+int main(int argc, char **argv) {
+  long int acc = 0;
+
+  A *a = new A();
+  acc += a->a;
+  acc += a->b;
+  acc += a->c;
+  acc += a->d;
+  acc += a->e;
+
+  C *c = new C();
+  acc += c->a.a;
+  acc += c->a.a;
+  acc += c->b.x;
+  acc += c->b.y;
+
+  return 0;
+}
+EOF
+
+
 DEFAULT_MEMPROF_FLAGS="-fuse-ld=lld -Wl,--no-rosegment -gmlt -fdebug-info-for-profiling -fmemory-profile -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -m64 -Wl,-build-id -no-pie"
 
 # Map each test to their source and any additional flags separated by ; 
@@ -81,3 +265,20 @@ for name in "${!INPUTS[@]}"; do
   env MEMPROF_OPTIONS=log_path=stdout ${OUTDIR}/${name}.memprofexe > ${OUTDIR}/${name}.memprofraw
   rm ${OUTDIR}/${name}.c
 done
+
+
+DEFAULT_HIST_FLAGS="${DEFAULT_MEMPROF_FLAGS} -mllvm -memprof-use-callbacks=true -mllvm -memprof-histogram"
+
+
+# Map each test to their source and any additional flags separated by ; 
+declare -A HISTOGRAM_INPUTS
+HISTOGRAM_INPUTS["basic-histogram"]="BASIC_HISTOGRAM"
+HISTOGRAM_INPUTS["padding-histogram"]="PADDING_HISTOGRAM"
+
+for name in "${!HISTOGRAM_INPUTS[@]}"; do
+  IFS=";" read -r src flags <<< "${HISTOGRAM_INPUTS[$name]}"
+  echo "${!src}" > ${OUTDIR}/${name}.c
+  ${CLANG} ${DEFAULT_HIST_FLAGS} ${flags} ${OUTDIR}/${name}.c -o ${OUTDIR}/${name}.memprofexe
+  env MEMPROF_OPTIONS=log_path=stdout ${OUTDIR}/${name}.memprofexe > ${OUTDIR}/${name}.memprofraw
+  rm ${OUTDIR}/${name}.c
+done
\ No newline at end of file
diff --git a/llvm/test/tools/llvm-profdata/memprof-basic-histogram.test b/llvm/test/tools/llvm-profdata/memprof-basic-histogram.test
new file mode 100644
index 0000000..3d30a62
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/memprof-basic-histogram.test
@@ -0,0 +1,244 @@
+REQUIRES: x86_64-linux
+
+To update the inputs used below run Inputs/update_memprof_inputs.sh /path/to/updated/clang
+RUN: llvm-profdata show --memory %p/Inputs/basic-histogram.memprofraw --profiled-binary %p/Inputs/basic-histogram.memprofexe -o - | FileCheck %s
+
+We expect 5 MIBs, each with different AccessHistogramValues.
+
+CHECK: MemprofProfile:
+CHECK-NEXT:   Summary:
+CHECK-NEXT:     Version: 4
+CHECK-NEXT:     NumSegments: {{[0-9]+}}
+CHECK-NEXT:     NumMibInfo: 5
+CHECK-NEXT:     NumAllocFunctions: 3
+CHECK-NEXT:     NumStackOffsets: 5
+CHECK-NEXT:   Segments:
+CHECK-NEXT:   -
+CHECK-NEXT:     BuildId: {{[[:xdigit:]]+}}
+CHECK-NEXT:     Start: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:     End: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:     Offset: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:   -
+
+CHECK:   Records:
+CHECK-NEXT:   -
+CHECK-NEXT:     FunctionGUID: {{[0-9]+}}
+CHECK-NEXT:     AllocSites:
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 2
+CHECK-NEXT:         Column: 10
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 1
+CHECK-NEXT:         TotalAccessCount: 8
+CHECK-NEXT:         MinAccessCount: 8
+CHECK-NEXT:         MaxAccessCount: 8
+CHECK-NEXT:         TotalSize: 64
+CHECK-NEXT:         MinSize: 64
+CHECK-NEXT:         MaxSize: 64
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 0
+CHECK-NEXT:         NumSameDeallocCpu: 0
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 12
+CHECK-NEXT:         MinAccessDensity: 12
+CHECK-NEXT:         MaxAccessDensity: 12
+CHECK-NEXT:         TotalLifetimeAccessDensity: 12000
+CHECK-NEXT:         MinLifetimeAccessDensity: 12000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 12000
+CHECK-NEXT:         AccessHistogramSize: 8
+CHECK-NEXT:         AccessHistogram: {{[0-9]+}}
+CHECK-NEXT:         AccessHistogramValues: 1 1 1 1 1 1 1 1
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 14
+CHECK-NEXT:         Column: 10
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 1
+CHECK-NEXT:         TotalAccessCount: 36
+CHECK-NEXT:         MinAccessCount: 36
+CHECK-NEXT:         MaxAccessCount: 36
+CHECK-NEXT:         TotalSize: 64
+CHECK-NEXT:         MinSize: 64
+CHECK-NEXT:         MaxSize: 64
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 0
+CHECK-NEXT:         NumSameDeallocCpu: 0
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 56
+CHECK-NEXT:         MinAccessDensity: 56
+CHECK-NEXT:         MaxAccessDensity: 56
+CHECK-NEXT:         TotalLifetimeAccessDensity: 56000
+CHECK-NEXT:         MinLifetimeAccessDensity: 56000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 56000
+CHECK-NEXT:         AccessHistogramSize: 8
+CHECK-NEXT:         AccessHistogram: {{[0-9]+}}
+CHECK-NEXT:         AccessHistogramValues: 8 7 6 5 4 3 2 1
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 54
+CHECK-NEXT:         Column: 10
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 1
+CHECK-NEXT:         TotalAccessCount: 1
+CHECK-NEXT:         MinAccessCount: 1
+CHECK-NEXT:         MaxAccessCount: 1
+CHECK-NEXT:         TotalSize: 64
+CHECK-NEXT:         MinSize: 64
+CHECK-NEXT:         MaxSize: 64
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 0
+CHECK-NEXT:         NumSameDeallocCpu: 0
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 1
+CHECK-NEXT:         MinAccessDensity: 1
+CHECK-NEXT:         MaxAccessDensity: 1
+CHECK-NEXT:         TotalLifetimeAccessDensity: 1000
+CHECK-NEXT:         MinLifetimeAccessDensity: 1000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 1000
+CHECK-NEXT:         AccessHistogramSize: 8
+CHECK-NEXT:         AccessHistogram: {{[0-9]+}}
+CHECK-NEXT:         AccessHistogramValues: 1 0 0 0 0 0 0 0
+CHECK-NEXT:     CallSites:
+CHECK-NEXT:     -
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 59
+CHECK-NEXT:         Column: 5
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:     -
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 64
+CHECK-NEXT:         Column: 5
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:   -
+CHECK-NEXT:     FunctionGUID: {{[0-9]+}}
+CHECK-NEXT:     AllocSites:
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: _Z3foov
+CHECK-NEXT:         LineOffset: 2
+CHECK-NEXT:         Column: 10
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 59
+CHECK-NEXT:         Column: 5
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 21
+CHECK-NEXT:         TotalAccessCount: 168
+CHECK-NEXT:         MinAccessCount: 8
+CHECK-NEXT:         MaxAccessCount: 8
+CHECK-NEXT:         TotalSize: 1344
+CHECK-NEXT:         MinSize: 64
+CHECK-NEXT:         MaxSize: 64
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 20
+CHECK-NEXT:         NumSameDeallocCpu: 20
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 252
+CHECK-NEXT:         MinAccessDensity: 12
+CHECK-NEXT:         MaxAccessDensity: 12
+CHECK-NEXT:         TotalLifetimeAccessDensity: 252000
+CHECK-NEXT:         MinLifetimeAccessDensity: 12000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 12000
+CHECK-NEXT:         AccessHistogramSize: 8
+CHECK-NEXT:         AccessHistogram: {{[0-9]+}}
+CHECK-NEXT:         AccessHistogramValues: 21 21 21 21 21 21 21 21
+CHECK-NEXT:   -
+CHECK-NEXT:     FunctionGUID: {{[0-9]+}}
+CHECK-NEXT:     AllocSites:
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: _Z3barv
+CHECK-NEXT:         LineOffset: 2
+CHECK-NEXT:         Column: 10
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 64
+CHECK-NEXT:         Column: 5
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 21
+CHECK-NEXT:         TotalAccessCount: 756
+CHECK-NEXT:         MinAccessCount: 36
+CHECK-NEXT:         MaxAccessCount: 36
+CHECK-NEXT:         TotalSize: 1344
+CHECK-NEXT:         MinSize: 64
+CHECK-NEXT:         MaxSize: 64
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 20
+CHECK-NEXT:         NumSameDeallocCpu: 20
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 1176
+CHECK-NEXT:         MinAccessDensity: 56
+CHECK-NEXT:         MaxAccessDensity: 56
+CHECK-NEXT:         TotalLifetimeAccessDensity: 1176000
+CHECK-NEXT:         MinLifetimeAccessDensity: 56000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 56000
+CHECK-NEXT:         AccessHistogramSize: 8
+CHECK-NEXT:         AccessHistogram: {{[0-9]+}}
+CHECK-NEXT:         AccessHistogramValues: 168 147 126 105 84 63 42 21
\ No newline at end of file
diff --git a/llvm/test/tools/llvm-profdata/memprof-basic.test b/llvm/test/tools/llvm-profdata/memprof-basic.test
index 8eaa2fa..e15df50 100644
--- a/llvm/test/tools/llvm-profdata/memprof-basic.test
+++ b/llvm/test/tools/llvm-profdata/memprof-basic.test
@@ -8,7 +8,7 @@ additional allocations which do not originate from the main binary are pruned.
 
 CHECK:  MemprofProfile:
 CHECK-NEXT:   Summary:
-CHECK-NEXT:     Version: 3
+CHECK-NEXT:     Version: 4
 CHECK-NEXT:     NumSegments: {{[0-9]+}}
 CHECK-NEXT:     NumMibInfo: 2
 CHECK-NEXT:     NumAllocFunctions: 1
@@ -59,6 +59,8 @@ CHECK-NEXT:         MaxAccessDensity: 20
 CHECK-NEXT:         TotalLifetimeAccessDensity: 20000
 CHECK-NEXT:         MinLifetimeAccessDensity: 20000
 CHECK-NEXT:         MaxLifetimeAccessDensity: 20000
+CHECK-NEXT:         AccessHistogramSize: 0
+CHECK-NEXT:         AccessHistogram: 0
 CHECK-NEXT:     -
 CHECK-NEXT:       Callstack:
 CHECK-NEXT:       -
@@ -93,3 +95,5 @@ CHECK-NEXT:         MaxAccessDensity: 20
 CHECK-NEXT:         TotalLifetimeAccessDensity: 20000
 CHECK-NEXT:         MinLifetimeAccessDensity: 20000
 CHECK-NEXT:         MaxLifetimeAccessDensity: 20000
+CHECK-NEXT:         AccessHistogramSize: 0
+CHECK-NEXT:         AccessHistogram: 0
\ No newline at end of file
diff --git a/llvm/test/tools/llvm-profdata/memprof-basic_v3.test b/llvm/test/tools/llvm-profdata/memprof-basic_v3.test
new file mode 100644
index 0000000..3c10c57
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/memprof-basic_v3.test
@@ -0,0 +1,102 @@
+REQUIRES: x86_64-linux
+
+This is a copy of memprof-basic.test with slight changes to check that we can still read v3 of memprofraw.
+
+Inputs cannot and should not be updated.
+
+RUN: llvm-profdata show --memory %p/Inputs/basic_v3.memprofraw --profiled-binary %p/Inputs/basic_v3.memprofexe -o - | FileCheck %s
+
+We expect 2 MIB entries, 1 each for the malloc calls in the program. Any
+additional allocations which do not originate from the main binary are pruned.
+
+CHECK:  MemprofProfile:
+CHECK-NEXT:   Summary:
+CHECK-NEXT:     Version: 3
+CHECK-NEXT:     NumSegments: {{[0-9]+}}
+CHECK-NEXT:     NumMibInfo: 2
+CHECK-NEXT:     NumAllocFunctions: 1
+CHECK-NEXT:     NumStackOffsets: 2
+CHECK-NEXT:   Segments:
+CHECK-NEXT:   -
+CHECK-NEXT:     BuildId: {{[[:xdigit:]]+}}
+CHECK-NEXT:     Start: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:     End: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:     Offset: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:   -
+
+CHECK:   Records:
+CHECK-NEXT:   -
+CHECK-NEXT:     FunctionGUID: {{[0-9]+}}
+CHECK-NEXT:     AllocSites:
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 1
+CHECK-NEXT:         Column: 21
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 1
+CHECK-NEXT:         TotalAccessCount: 2
+CHECK-NEXT:         MinAccessCount: 2
+CHECK-NEXT:         MaxAccessCount: 2
+CHECK-NEXT:         TotalSize: 10
+CHECK-NEXT:         MinSize: 10
+CHECK-NEXT:         MaxSize: 10
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 0
+CHECK-NEXT:         NumSameDeallocCpu: 0
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 20
+CHECK-NEXT:         MinAccessDensity: 20
+CHECK-NEXT:         MaxAccessDensity: 20
+CHECK-NEXT:         TotalLifetimeAccessDensity: 20000
+CHECK-NEXT:         MinLifetimeAccessDensity: 20000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 20000
+CHECK-NEXT:         AccessHistogramSize: 0
+CHECK-NEXT:         AccessHistogram: 0
+CHECK-NEXT:     -
+CHECK-NEXT:       Callstack:
+CHECK-NEXT:       -
+CHECK-NEXT:         Function: {{[0-9]+}}
+CHECK-NEXT:         SymbolName: main
+CHECK-NEXT:         LineOffset: 4
+CHECK-NEXT:         Column: 15
+CHECK-NEXT:         Inline: 0
+CHECK-NEXT:       MemInfoBlock:
+CHECK-NEXT:         AllocCount: 1
+CHECK-NEXT:         TotalAccessCount: 2
+CHECK-NEXT:         MinAccessCount: 2
+CHECK-NEXT:         MaxAccessCount: 2
+CHECK-NEXT:         TotalSize: 10
+CHECK-NEXT:         MinSize: 10
+CHECK-NEXT:         MaxSize: 10
+CHECK-NEXT:         AllocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         DeallocTimestamp: {{[0-9]+}}
+CHECK-NEXT:         TotalLifetime: 0
+CHECK-NEXT:         MinLifetime: 0
+CHECK-NEXT:         MaxLifetime: 0
+CHECK-NEXT:         AllocCpuId: {{[0-9]+}}
+CHECK-NEXT:         DeallocCpuId: {{[0-9]+}}
+CHECK-NEXT:         NumMigratedCpu: 0
+CHECK-NEXT:         NumLifetimeOverlaps: 0
+CHECK-NEXT:         NumSameAllocCpu: 0
+CHECK-NEXT:         NumSameDeallocCpu: 0
+CHECK-NEXT:         DataTypeId: {{[0-9]+}}
+CHECK-NEXT:         TotalAccessDensity: 20
+CHECK-NEXT:         MinAccessDensity: 20
+CHECK-NEXT:         MaxAccessDensity: 20
+CHECK-NEXT:         TotalLifetimeAccessDensity: 20000
+CHECK-NEXT:         MinLifetimeAccessDensity: 20000
+CHECK-NEXT:         MaxLifetimeAccessDensity: 20000
+CHECK-NEXT:         AccessHistogramSize: 0
+CHECK-NEXT:         AccessHistogram: 0
\ No newline at end of file
diff --git a/llvm/test/tools/llvm-profdata/memprof-inline.test b/llvm/test/tools/llvm-profdata/memprof-inline.test
index dd842c0..79ce2ad 100644
--- a/llvm/test/tools/llvm-profdata/memprof-inline.test
+++ b/llvm/test/tools/llvm-profdata/memprof-inline.test
@@ -5,7 +5,7 @@ RUN: llvm-profdata show --memory %p/Inputs/inline.memprofraw --profiled-binary %
 
 CHECK:  MemprofProfile:
 CHECK-NEXT:  Summary:
-CHECK-NEXT:    Version: 3
+CHECK-NEXT:    Version: 4
 CHECK-NEXT:    NumSegments: {{[0-9]+}}
 CHECK-NEXT:    NumMibInfo: 2
 CHECK-NEXT:    NumAllocFunctions: 2
@@ -20,25 +20,25 @@ CHECK-NEXT:  -
 
 CHECK:  Records:
 CHECK-NEXT:  -
-CHECK-NEXT:    FunctionGUID: 15505678318020221912
+CHECK-NEXT:    FunctionGUID: 3873612792189045660
 CHECK-NEXT:    AllocSites:
 CHECK-NEXT:    -
 CHECK-NEXT:      Callstack:
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 15505678318020221912
-CHECK-NEXT:        SymbolName: qux
+CHECK-NEXT:        Function: 3873612792189045660
+CHECK-NEXT:        SymbolName: _Z3quxi
 CHECK-NEXT:        LineOffset: 1
-CHECK-NEXT:        Column: 15
+CHECK-NEXT:        Column: 23
 CHECK-NEXT:        Inline: 1
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 6699318081062747564
-CHECK-NEXT:        SymbolName: foo
+CHECK-NEXT:        Function: 1228452328526475178
+CHECK-NEXT:        SymbolName: _Z3fooi
 CHECK-NEXT:        LineOffset: 0
 CHECK-NEXT:        Column: 18
 CHECK-NEXT:        Inline: 0
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 16434608426314478903
-CHECK-NEXT:        SymbolName: bar
+CHECK-NEXT:        Function: 3727899762981752933
+CHECK-NEXT:        SymbolName: _Z3bari
 CHECK-NEXT:        LineOffset: 0
 CHECK-NEXT:        Column: 19
 CHECK-NEXT:        Inline: 0
@@ -74,26 +74,30 @@ CHECK-NEXT:        MaxAccessDensity: 100
 CHECK-NEXT:        TotalLifetimeAccessDensity: 100000
 CHECK-NEXT:        MinLifetimeAccessDensity: 100000
 CHECK-NEXT:        MaxLifetimeAccessDensity: 100000
+CHECK-NEXT:        AccessHistogramSize: 0
+CHECK-NEXT:        AccessHistogram: 0
+
+
 CHECK-NEXT:  -
-CHECK-NEXT:    FunctionGUID: 6699318081062747564
+CHECK-NEXT:    FunctionGUID: 1228452328526475178
 CHECK-NEXT:    AllocSites:
 CHECK-NEXT:    -
 CHECK-NEXT:      Callstack:
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 15505678318020221912
-CHECK-NEXT:        SymbolName: qux
+CHECK-NEXT:        Function: 3873612792189045660
+CHECK-NEXT:        SymbolName: _Z3quxi
 CHECK-NEXT:        LineOffset: 1
-CHECK-NEXT:        Column: 15
+CHECK-NEXT:        Column: 23
 CHECK-NEXT:        Inline: 1
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 6699318081062747564
-CHECK-NEXT:        SymbolName: foo
+CHECK-NEXT:        Function: 1228452328526475178
+CHECK-NEXT:        SymbolName: _Z3fooi
 CHECK-NEXT:        LineOffset: 0
 CHECK-NEXT:        Column: 18
 CHECK-NEXT:        Inline: 0
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 16434608426314478903
-CHECK-NEXT:        SymbolName: bar
+CHECK-NEXT:        Function: 3727899762981752933
+CHECK-NEXT:        SymbolName: _Z3bari
 CHECK-NEXT:        LineOffset: 0
 CHECK-NEXT:        Column: 19
 CHECK-NEXT:        Inline: 0
@@ -129,28 +133,31 @@ CHECK-NEXT:        MaxAccessDensity: 100
 CHECK-NEXT:        TotalLifetimeAccessDensity: 100000
 CHECK-NEXT:        MinLifetimeAccessDensity: 100000
 CHECK-NEXT:        MaxLifetimeAccessDensity: 100000
+CHECK-NEXT:        AccessHistogramSize: 0
+CHECK-NEXT:        AccessHistogram: 0
+
 CHECK-NEXT:    CallSites:
 CHECK-NEXT:    -
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 15505678318020221912
-CHECK-NEXT:        SymbolName: qux
+CHECK-NEXT:        Function: 3873612792189045660
+CHECK-NEXT:        SymbolName: _Z3quxi
 CHECK-NEXT:        LineOffset: 1
-CHECK-NEXT:        Column: 15
+CHECK-NEXT:        Column: 23
 CHECK-NEXT:        Inline: 1
 CHECK-NEXT:    -
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 6699318081062747564
-CHECK-NEXT:        SymbolName: foo
+CHECK-NEXT:        Function: 1228452328526475178
+CHECK-NEXT:        SymbolName: _Z3fooi
 CHECK-NEXT:        LineOffset: 0
 CHECK-NEXT:        Column: 18
 CHECK-NEXT:        Inline: 0
 CHECK-NEXT:  -
-CHECK-NEXT:    FunctionGUID: 16434608426314478903
+CHECK-NEXT:    FunctionGUID: 3727899762981752933
 CHECK-NEXT:    CallSites:
 CHECK-NEXT:    -
 CHECK-NEXT:      -
-CHECK-NEXT:        Function: 16434608426314478903
-CHECK-NEXT:        SymbolName: bar
+CHECK-NEXT:        Function: 3727899762981752933
+CHECK-NEXT:        SymbolName: _Z3bari
 CHECK-NEXT:        LineOffset: 0
 CHECK-NEXT:        Column: 19
 CHECK-NEXT:        Inline: 0
diff --git a/llvm/test/tools/llvm-profdata/memprof-multi.test b/llvm/test/tools/llvm-profdata/memprof-multi.test
index f3cdbd1..6243982 100644
--- a/llvm/test/tools/llvm-profdata/memprof-multi.test
+++ b/llvm/test/tools/llvm-profdata/memprof-multi.test
@@ -7,7 +7,7 @@ We expect 2 MIB entries, 1 each for the malloc calls in the program.
 
 CHECK:  MemprofProfile:
 CHECK-NEXT:  Summary:
-CHECK-NEXT:    Version: 3
+CHECK-NEXT:    Version: 4
 CHECK-NEXT:    NumSegments: {{[0-9]+}}
 CHECK-NEXT:    NumMibInfo: 2
 CHECK-NEXT:    NumAllocFunctions: 1
diff --git a/llvm/test/tools/llvm-profdata/memprof-padding-histogram.test b/llvm/test/tools/llvm-profdata/memprof-padding-histogram.test
new file mode 100644
index 0000000..4ba58e3
--- /dev/null
+++ b/llvm/test/tools/llvm-profdata/memprof-padding-histogram.test
@@ -0,0 +1,99 @@
+REQUIRES: x86_64-linux
+
+To update the inputs used below run Inputs/update_memprof_inputs.sh /path/to/updated/clang
+RUN: llvm-profdata show --memory %p/Inputs/padding-histogram.memprofraw --profiled-binary %p/Inputs/padding-histogram.memprofexe -o - | FileCheck %s
+
+We expect 2 different MIBs with histogram values. This test is to make sure we properly deal with padding.
+
+CHECK: MemprofProfile:
+CHECK-NEXT:   Summary:
+CHECK-NEXT:     Version: 4
+CHECK-NEXT:     NumSegments: {{[0-9]+}}
+CHECK-NEXT:     NumMibInfo: 2
+CHECK-NEXT:     NumAllocFunctions: 1
+CHECK-NEXT:     NumStackOffsets: 2
+CHECK-NEXT:   Segments:
+CHECK-NEXT:   -
+CHECK-NEXT:     BuildId: {{[[:xdigit:]]+}}
+CHECK-NEXT:     Start: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:     End: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:     Offset: 0x{{[[:xdigit:]]+}}
+CHECK-NEXT:   -
+
+CHECK:   Records:
+CHEC-NEXT    FunctionGUID: {{[0-9]+}}
+CHEC-NEXT    AllocSites:
+CHEC-NEXT    -
+CHEC-NEXT      Callstack:
+CHEC-NEXT      -
+CHEC-NEXT        Function: {{[0-9]+}}
+CHEC-NEXT        SymbolName: main
+CHEC-NEXT        LineOffset: 3
+CHEC-NEXT        Column: 10
+CHEC-NEXT        Inline: 0
+CHEC-NEXT      MemInfoBlock:
+CHEC-NEXT        AllocCount: 1
+CHEC-NEXT        TotalAccessCount: 5
+CHEC-NEXT        MinAccessCount: 5
+CHEC-NEXT        MaxAccessCount: 5
+CHEC-NEXT        TotalSize: 24
+CHEC-NEXT        MinSize: 24
+CHEC-NEXT        MaxSize: 24
+CHEC-NEXT        AllocTimestamp: {{[0-9]+}}
+CHEC-NEXT        DeallocTimestamp: {{[0-9]+}}
+CHEC-NEXT        TotalLifetime: 0
+CHEC-NEXT        MinLifetime: 0
+CHEC-NEXT        MaxLifetime: 0
+CHEC-NEXT        AllocCpuId: 11
+CHEC-NEXT        DeallocCpuId: 11
+CHEC-NEXT        NumMigratedCpu: 0
+CHEC-NEXT        NumLifetimeOverlaps: 0
+CHEC-NEXT        NumSameAllocCpu: 0
+CHEC-NEXT        NumSameDeallocCpu: 0
+CHEC-NEXT        DataTypeId: 0
+CHEC-NEXT        TotalAccessDensity: 20
+CHEC-NEXT        MinAccessDensity: 20
+CHEC-NEXT        MaxAccessDensity: 20
+CHEC-NEXT        TotalLifetimeAccessDensity: 20000
+CHEC-NEXT        MinLifetimeAccessDensity: 20000
+CHEC-NEXT        MaxLifetimeAccessDensity: 20000
+CHEC-NEXT        AccessHistogramSize: 3
+CHEC-NEXT        AccessHistogram: {{[0-9]+}}
+CHEC-NEXT        AccessHistogramValues: -2 -1 -2
+CHEC-NEXT    -
+CHEC-NEXT      Callstack:
+CHEC-NEXT      -
+CHEC-NEXT        Function: {{[0-9]+}}
+CHEC-NEXT        SymbolName: main
+CHEC-NEXT        LineOffset: 10
+CHEC-NEXT        Column: 10
+CHEC-NEXT        Inline: 0
+CHEC-NEXT      MemInfoBlock:
+CHEC-NEXT        AllocCount: 1
+CHEC-NEXT        TotalAccessCount: 4
+CHEC-NEXT        MinAccessCount: 4
+CHEC-NEXT        MaxAccessCount: 4
+CHEC-NEXT        TotalSize: 48
+CHEC-NEXT        MinSize: 48
+CHEC-NEXT        MaxSize: 48
+CHEC-NEXT        AllocTimestamp: {{[0-9]+}}
+CHEC-NEXT        DeallocTimestamp: {{[0-9]+}}
+CHEC-NEXT        TotalLifetime: 0
+CHEC-NEXT        MinLifetime: 0
+CHEC-NEXT        MaxLifetime: 0
+CHEC-NEXT        AllocCpuId: 11
+CHEC-NEXT        DeallocCpuId: 11
+CHEC-NEXT        NumMigratedCpu: 0
+CHEC-NEXT        NumLifetimeOverlaps: 0
+CHEC-NEXT        NumSameAllocCpu: 0
+CHEC-NEXT        NumSameDeallocCpu: 0
+CHEC-NEXT        DataTypeId: 0
+CHEC-NEXT        TotalAccessDensity: 8
+CHEC-NEXT        MinAccessDensity: 8
+CHEC-NEXT        MaxAccessDensity: 8
+CHEC-NEXT        TotalLifetimeAccessDensity: 8000
+CHEC-NEXT        MinLifetimeAccessDensity: 8000
+CHEC-NEXT        MaxLifetimeAccessDensity: 8000
+CHEC-NEXT        AccessHistogramSize: 6
+CHEC-NEXT        AccessHistogram: {{[0-9]+}}
+CHEC-NEXT        AccessHistogramValues: -2 -0 -0 -0 -1 -1
\ No newline at end of file
diff --git a/llvm/test/tools/llvm-profdata/memprof-pic.test b/llvm/test/tools/llvm-profdata/memprof-pic.test
index 03c98ed9..78d2c5c 100644
--- a/llvm/test/tools/llvm-profdata/memprof-pic.test
+++ b/llvm/test/tools/llvm-profdata/memprof-pic.test
@@ -11,7 +11,7 @@ RUN: llvm-profdata show --memory %p/Inputs/pic.memprofraw --profiled-binary %p/I
 
 CHECK:  MemprofProfile:
 CHECK-NEXT:   Summary:
-CHECK-NEXT:     Version: 3
+CHECK-NEXT:     Version: 4
 CHECK-NEXT:     NumSegments: {{[0-9]+}}
 CHECK-NEXT:     NumMibInfo: 2
 CHECK-NEXT:     NumAllocFunctions: 1
@@ -62,6 +62,9 @@ CHECK-NEXT:         MaxAccessDensity: 20
 CHECK-NEXT:         TotalLifetimeAccessDensity: 20000
 CHECK-NEXT:         MinLifetimeAccessDensity: 20000
 CHECK-NEXT:         MaxLifetimeAccessDensity: 20000
+CHECK-NEXT:         AccessHistogramSize: 0
+CHECK-NEXT:         AccessHistogram: 0
+
 CHECK-NEXT:     -
 CHECK-NEXT:       Callstack:
 CHECK-NEXT:       -
@@ -96,3 +99,5 @@ CHECK-NEXT:         MaxAccessDensity: 20
 CHECK-NEXT:         TotalLifetimeAccessDensity: 20000
 CHECK-NEXT:         MinLifetimeAccessDensity: 20000
 CHECK-NEXT:         MaxLifetimeAccessDensity: 20000
+CHECK-NEXT:         AccessHistogramSize: 0
+CHECK-NEXT:         AccessHistogram: 0
\ No newline at end of file
diff --git a/llvm/unittests/ProfileData/MemProfTest.cpp b/llvm/unittests/ProfileData/MemProfTest.cpp
index 15eb59e..14623e18 100644
--- a/llvm/unittests/ProfileData/MemProfTest.cpp
+++ b/llvm/unittests/ProfileData/MemProfTest.cpp
@@ -247,7 +247,7 @@ TEST(MemProf, FillsValue) {
 TEST(MemProf, PortableWrapper) {
   MemInfoBlock Info(/*size=*/16, /*access_count=*/7, /*alloc_timestamp=*/1000,
                     /*dealloc_timestamp=*/2000, /*alloc_cpu=*/3,
-                    /*dealloc_cpu=*/4);
+                    /*dealloc_cpu=*/4, /*Histogram=*/0, /*HistogramSize=*/0);
 
   const auto Schema = llvm::memprof::getFullSchema();
   PortableMemInfoBlock WriteBlock(Info, Schema);
@@ -276,7 +276,7 @@ TEST(MemProf, RecordSerializationRoundTripVersion0And1) {
 
   MemInfoBlock Info(/*size=*/16, /*access_count=*/7, /*alloc_timestamp=*/1000,
                     /*dealloc_timestamp=*/2000, /*alloc_cpu=*/3,
-                    /*dealloc_cpu=*/4);
+                    /*dealloc_cpu=*/4, /*Histogram=*/0, /*HistogramSize=*/0);
 
   llvm::SmallVector<llvm::SmallVector<FrameId>> AllocCallStacks = {
       {0x123, 0x345}, {0x123, 0x567}};
@@ -310,7 +310,7 @@ TEST(MemProf, RecordSerializationRoundTripVerion2) {
 
   MemInfoBlock Info(/*size=*/16, /*access_count=*/7, /*alloc_timestamp=*/1000,
                     /*dealloc_timestamp=*/2000, /*alloc_cpu=*/3,
-                    /*dealloc_cpu=*/4);
+                    /*dealloc_cpu=*/4, /*Histogram=*/0, /*HistogramSize=*/0);
 
   llvm::SmallVector<llvm::memprof::CallStackId> CallStackIds = {0x123, 0x456};