[memprof] Make HeapProfileRecords optional (#155671)

memprof::AllMemProfData has become home to multiple types of memprof
data -- heap profile and static data profile.  When we write test
cases for static data profile in YAML, we do not want to include empty
heap profile.  That would just add visual clutter.

This patch makes HeapProfileRecords optional.

Author: kazutakahirata

llvm/include/llvm/ProfileData/DataAccessProf.h

@@ -185,6 +185,10 @@ class DataAccessProfData {
   ArrayRef<uint64_t> getKnownColdHashes() const {
     return KnownColdHashes.getArrayRef();
   }
+  [[nodiscard]] bool empty() const {
+    return Records.empty() && KnownColdSymbols.empty() &&
+           KnownColdHashes.empty();
+  }
 
 private:
   /// Serialize the symbol strings into the output stream.

llvm/include/llvm/ProfileData/MemProfYAML.h

@@ -263,7 +263,8 @@ template <> struct MappingTraits<memprof::YamlDataAccessProfData> {
 
 template <> struct MappingTraits<memprof::AllMemProfData> {
   static void mapping(IO &Io, memprof::AllMemProfData &Data) {
-    Io.mapRequired("HeapProfileRecords", Data.HeapProfileRecords);
+    if (!Io.outputting() || !Data.HeapProfileRecords.empty())
+      Io.mapOptional("HeapProfileRecords", Data.HeapProfileRecords);
     // Map data access profiles if reading input, or if writing output &&
     // the struct is populated.
     if (!Io.outputting() || !Data.YamlifiedDataAccessProfiles.isEmpty())

llvm/test/tools/llvm-profdata/memprof-yaml.test

@@ -18,6 +18,11 @@
 ; RUN: llvm-profdata show --memory %t/memprof-out.indexed > %t/memprof-out-no-dap.yaml
 ; RUN: diff -b %t/memprof-in-no-dap.yaml %t/memprof-out-no-dap.yaml
 
+; memprof-in-no-heap.yaml has empty heap access profiles.
+; RUN: llvm-profdata merge --memprof-version=4 %t/memprof-in-no-heap.yaml -o %t/memprof-out-no-heap.indexed
+; RUN: llvm-profdata show --memory %t/memprof-out-no-heap.indexed > %t/memprof-out-no-heap.yaml
+; RUN: diff -b %t/memprof-in-no-heap.yaml %t/memprof-out-no-heap.yaml
+
 ;--- memprof-in.yaml
 ---
 # MemProfSummary:
@@ -151,3 +156,32 @@ HeapProfileRecords:
         - { Function: 0x8888888888888888, LineOffset: 88, Column: 80, IsInlineFrame: false }
         CalleeGuids: [ 0x300 ]
 ...
+;--- memprof-in-no-heap.yaml
+---
+# MemProfSummary:
+#   Total contexts: 0
+#   Total cold contexts: 0
+#   Total hot contexts: 0
+#   Maximum cold context total size: 0
+#   Maximum warm context total size: 0
+#   Maximum hot context total size: 0
+---
+DataAccessProfiles:
+  SampledRecords:
+    - Symbol:          abcde
+      AccessCount:     100
+      Locations:
+      - FileName:      file2.h
+        Line:          123
+      - FileName:      file3.cpp
+        Line:          456
+    - Hash:            101010
+      AccessCount:     200
+      Locations:
+        - FileName:        file.cpp
+          Line:            233
+  KnownColdSymbols:
+    - foo
+    - bar
+  KnownColdStrHashes: [ 999, 1001 ]
+...

llvm/tools/llvm-profdata/llvm-profdata.cpp

@@ -760,7 +760,8 @@ loadInput(const WeightedFile &Input, SymbolRemapper *Remapper,
     auto DataAccessProfData = Reader->takeDataAccessProfData();
 
     // Check for the empty input in case the YAML file is invalid.
-    if (MemProfData.Records.empty()) {
+    if (MemProfData.Records.empty() &&
+        (!DataAccessProfData || DataAccessProfData->empty())) {
       WC->Errors.emplace_back(
           make_error<StringError>("The profile is empty.", std::error_code()),
           Filename);