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
@@ -128,9 +128,11 @@
 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))
-INSTR_PROF_RAW_HEADER(uint64_t, NumData, NumData)
+/* FIXME: A more accurate name is NumData */
+INSTR_PROF_RAW_HEADER(uint64_t, DataSize, DataSize)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesBeforeCounters, PaddingBytesBeforeCounters)
-INSTR_PROF_RAW_HEADER(uint64_t, NumCounters, NumCounters)
+/* FIXME: A more accurate name is NumCounters */
+INSTR_PROF_RAW_HEADER(uint64_t, CountersSize, CountersSize)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesAfterCounters, PaddingBytesAfterCounters)
 INSTR_PROF_RAW_HEADER(uint64_t, NamesSize,  NamesSize)
 INSTR_PROF_RAW_HEADER(uint64_t, CountersDelta,
@@ -644,6 +646,7 @@
        (uint64_t)'p' << 40 | (uint64_t)'r' << 32 | (uint64_t)'o' << 24 |  \
         (uint64_t)'f' << 16 | (uint64_t)'R' << 8 | (uint64_t)129
 
+/* FIXME: Please remedy the fixme in the header before bumping the version.
 /* Raw profile format version (start from 1). */
 #define INSTR_PROF_RAW_VERSION 8
 /* Indexed profile format version (start from 1). */
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
@@ -48,7 +48,7 @@
   SrcDataStart =
       (__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
                               Header->BinaryIdsSize);
-  SrcDataEnd = SrcDataStart + Header->NumData;
+  SrcDataEnd = SrcDataStart + Header->DataSize;
 
   if (ProfileSize < sizeof(__llvm_profile_header))
     return 1;
@@ -56,10 +56,10 @@
   /* Check the header first.  */
   if (Header->Magic != __llvm_profile_get_magic() ||
       Header->Version != __llvm_profile_get_version() ||
-      Header->NumData !=
+      Header->DataSize !=
           __llvm_profile_get_num_data(__llvm_profile_begin_data(),
                                       __llvm_profile_end_data()) ||
-      Header->NumCounters !=
+      Header->CountersSize !=
           __llvm_profile_get_num_counters(__llvm_profile_begin_counters(),
                                           __llvm_profile_end_counters()) ||
       Header->NamesSize != (uint64_t)(__llvm_profile_end_names() -
@@ -69,8 +69,8 @@
 
   if (ProfileSize <
       sizeof(__llvm_profile_header) + Header->BinaryIdsSize +
-          Header->NumData * sizeof(__llvm_profile_data) + Header->NamesSize +
-          Header->NumCounters * __llvm_profile_counter_entry_size())
+          Header->DataSize * sizeof(__llvm_profile_data) + Header->NamesSize +
+          Header->CountersSize * __llvm_profile_counter_entry_size())
     return 1;
 
   for (SrcData = SrcDataStart,
@@ -115,10 +115,10 @@
   SrcDataStart =
       (__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
                               Header->BinaryIdsSize);
-  SrcDataEnd = SrcDataStart + Header->NumData;
+  SrcDataEnd = SrcDataStart + Header->DataSize;
   SrcCountersStart = (char *)SrcDataEnd;
   SrcNameStart = SrcCountersStart +
-                 Header->NumCounters * __llvm_profile_counter_entry_size();
+                 Header->CountersSize * __llvm_profile_counter_entry_size();
   SrcValueProfDataStart =
       SrcNameStart + Header->NamesSize +
       __llvm_profile_get_num_padding_bytes(Header->NamesSize);
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
@@ -287,9 +287,16 @@
       DataSize, CountersSize, NamesSize, &PaddingBytesBeforeCounters,
       &PaddingBytesAfterCounters, &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"
+  }
 
   /* On WIN64, label differences are truncated 32-bit values. Truncate
    * CountersDelta to match. */
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
@@ -128,9 +128,11 @@
 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))
-INSTR_PROF_RAW_HEADER(uint64_t, NumData, NumData)
+/* FIXME: A more accurate name is NumData */
+INSTR_PROF_RAW_HEADER(uint64_t, DataSize, DataSize)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesBeforeCounters, PaddingBytesBeforeCounters)
-INSTR_PROF_RAW_HEADER(uint64_t, NumCounters, NumCounters)
+/* FIXME: A more accurate name is NumCounters */
+INSTR_PROF_RAW_HEADER(uint64_t, CountersSize, CountersSize)
 INSTR_PROF_RAW_HEADER(uint64_t, PaddingBytesAfterCounters, PaddingBytesAfterCounters)
 INSTR_PROF_RAW_HEADER(uint64_t, NamesSize,  NamesSize)
 INSTR_PROF_RAW_HEADER(uint64_t, CountersDelta,
@@ -644,6 +646,7 @@
        (uint64_t)'p' << 40 | (uint64_t)'r' << 32 | (uint64_t)'o' << 24 |  \
         (uint64_t)'f' << 16 | (uint64_t)'R' << 8 | (uint64_t)129
 
+/* FIXME: Please remedy the fixme in the header before bumping the version.
 /* Raw profile format version (start from 1). */
 #define INSTR_PROF_RAW_VERSION 8
 /* Indexed profile format version (start from 1). */
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
@@ -383,9 +383,9 @@
 
   CountersDelta = swap(Header.CountersDelta);
   NamesDelta = swap(Header.NamesDelta);
-  auto NumData = swap(Header.NumData);
+  auto NumData = swap(Header.DataSize);
   auto PaddingBytesBeforeCounters = swap(Header.PaddingBytesBeforeCounters);
-  auto CountersSize = swap(Header.NumCounters) * getCounterTypeSize();
+  auto CountersSize = swap(Header.CountersSize) * getCounterTypeSize();
   auto PaddingBytesAfterCounters = swap(Header.PaddingBytesAfterCounters);
   auto NamesSize = swap(Header.NamesSize);
   ValueKindLast = swap(Header.ValueKindLast);