diff --git a/compiler-rt/include/profile/InstrProfData.inc b/compiler-rt/include/profile/InstrProfData.inc
--- a/compiler-rt/include/profile/InstrProfData.inc
+++ b/compiler-rt/include/profile/InstrProfData.inc
@@ -128,11 +128,9 @@
 INSTR_PROF_RAW_HEADER(uint64_t, Magic, __llvm_profile_get_magic())
 INSTR_PROF_RAW_HEADER(uint64_t, Version, __llvm_profile_get_version())
 INSTR_PROF_RAW_HEADER(uint64_t, BinaryIdsSize, __llvm_write_binary_ids(NULL))
-/* FIXME: A more accurate name is NumData */
-INSTR_PROF_RAW_HEADER(uint64_t, DataSize, DataSize)
+INSTR_PROF_RAW_HEADER(uint64_t, NumData, NumData)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesBeforeCounters, PaddingBytesBeforeCounters)
-/* FIXME: A more accurate name is NumCounters */
-INSTR_PROF_RAW_HEADER(uint64_t, CountersSize, CountersSize)
+INSTR_PROF_RAW_HEADER(uint64_t, NumCounters, NumCounters)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesAfterCounters, PaddingBytesAfterCounters)
 INSTR_PROF_RAW_HEADER(uint64_t, NamesSize,  NamesSize)
 INSTR_PROF_RAW_HEADER(uint64_t, CountersDelta,
diff --git a/compiler-rt/lib/profile/InstrProfilingMerge.c b/compiler-rt/lib/profile/InstrProfilingMerge.c
--- a/compiler-rt/lib/profile/InstrProfilingMerge.c
+++ b/compiler-rt/lib/profile/InstrProfilingMerge.c
@@ -52,7 +52,7 @@
   SrcDataStart =
       (__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
                               Header->BinaryIdsSize);
-  SrcDataEnd = SrcDataStart + Header->DataSize;
+  SrcDataEnd = SrcDataStart + Header->NumData;
 
   if (ProfileSize < sizeof(__llvm_profile_header))
     return 1;
@@ -60,10 +60,10 @@
   /* Check the header first.  */
   if (Header->Magic != __llvm_profile_get_magic() ||
       Header->Version != __llvm_profile_get_version() ||
-      Header->DataSize !=
+      Header->NumData !=
           __llvm_profile_get_num_data(__llvm_profile_begin_data(),
                                       __llvm_profile_end_data()) ||
-      Header->CountersSize !=
+      Header->NumCounters !=
           __llvm_profile_get_num_counters(__llvm_profile_begin_counters(),
                                           __llvm_profile_end_counters()) ||
       Header->NamesSize != (uint64_t)(__llvm_profile_end_names() -
@@ -73,8 +73,8 @@
 
   if (ProfileSize <
       sizeof(__llvm_profile_header) + Header->BinaryIdsSize +
-          Header->DataSize * sizeof(__llvm_profile_data) + Header->NamesSize +
-          Header->CountersSize * __llvm_profile_counter_entry_size())
+          Header->NumData * sizeof(__llvm_profile_data) + Header->NamesSize +
+          Header->NumCounters * __llvm_profile_counter_entry_size())
     return 1;
 
   for (SrcData = SrcDataStart,
@@ -119,10 +119,10 @@
   SrcDataStart =
       (__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
                               Header->BinaryIdsSize);
-  SrcDataEnd = SrcDataStart + Header->DataSize;
+  SrcDataEnd = SrcDataStart + Header->NumData;
   SrcCountersStart = (char *)SrcDataEnd;
   SrcCountersEnd = SrcCountersStart +
-                 Header->CountersSize * __llvm_profile_counter_entry_size(); 
+                   Header->NumCounters * __llvm_profile_counter_entry_size();
   SrcNameStart = SrcCountersEnd;
   SrcValueProfDataStart =
       SrcNameStart + Header->NamesSize +
@@ -132,7 +132,7 @@
 
   // Merge counters when there is no data section and debug info correlation is
   // enabled.
-  if (Header->DataSize == 0) {
+  if (Header->NumData == 0) {
     if (!(__llvm_profile_get_version() & VARIANT_MASK_DBG_CORRELATE)) {
       PROF_ERR("%s\n", "Missing profile data section.");
       return 1;
diff --git a/compiler-rt/lib/profile/InstrProfilingWriter.c b/compiler-rt/lib/profile/InstrProfilingWriter.c
--- a/compiler-rt/lib/profile/InstrProfilingWriter.c
+++ b/compiler-rt/lib/profile/InstrProfilingWriter.c
@@ -286,11 +286,6 @@
       &PaddingBytesAfterNames);
 
   {
-    // TODO: Unfortunately the header's fields are named DataSize and
-    // CountersSize when they should be named NumData and NumCounters,
-    // respectively.
-    const uint64_t CountersSize = NumCounters;
-    const uint64_t DataSize = NumData;
 /* Initialize header structure.  */
 #define INSTR_PROF_RAW_HEADER(Type, Name, Init) Header.Name = Init;
 #include "profile/InstrProfData.inc"
diff --git a/llvm/include/llvm/ProfileData/InstrProfData.inc b/llvm/include/llvm/ProfileData/InstrProfData.inc
--- a/llvm/include/llvm/ProfileData/InstrProfData.inc
+++ b/llvm/include/llvm/ProfileData/InstrProfData.inc
@@ -128,11 +128,9 @@
 INSTR_PROF_RAW_HEADER(uint64_t, Magic, __llvm_profile_get_magic())
 INSTR_PROF_RAW_HEADER(uint64_t, Version, __llvm_profile_get_version())
 INSTR_PROF_RAW_HEADER(uint64_t, BinaryIdsSize, __llvm_write_binary_ids(NULL))
-/* FIXME: A more accurate name is NumData */
-INSTR_PROF_RAW_HEADER(uint64_t, DataSize, DataSize)
+INSTR_PROF_RAW_HEADER(uint64_t, NumData, NumData)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesBeforeCounters, PaddingBytesBeforeCounters)
-/* FIXME: A more accurate name is NumCounters */
-INSTR_PROF_RAW_HEADER(uint64_t, CountersSize, CountersSize)
+INSTR_PROF_RAW_HEADER(uint64_t, NumCounters, NumCounters)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesAfterCounters, PaddingBytesAfterCounters)
 INSTR_PROF_RAW_HEADER(uint64_t, NamesSize,  NamesSize)
 INSTR_PROF_RAW_HEADER(uint64_t, CountersDelta,
diff --git a/llvm/lib/ProfileData/InstrProfReader.cpp b/llvm/lib/ProfileData/InstrProfReader.cpp
--- a/llvm/lib/ProfileData/InstrProfReader.cpp
+++ b/llvm/lib/ProfileData/InstrProfReader.cpp
@@ -550,9 +550,9 @@
 
   CountersDelta = swap(Header.CountersDelta);
   NamesDelta = swap(Header.NamesDelta);
-  auto NumData = swap(Header.DataSize);
+  auto NumData = swap(Header.NumData);
   auto PaddingBytesBeforeCounters = swap(Header.PaddingBytesBeforeCounters);
-  auto CountersSize = swap(Header.CountersSize) * getCounterTypeSize();
+  auto CountersSize = swap(Header.NumCounters) * getCounterTypeSize();
   auto PaddingBytesAfterCounters = swap(Header.PaddingBytesAfterCounters);
   auto NamesSize = swap(Header.NamesSize);
   ValueKindLast = swap(Header.ValueKindLast);