[memprof] Accept Schema in the constructor of RecordWriterTrait (NFC) (llvm#89486)

The comment being deleted in this patch is not correct.  We already
construct an instance of RecordWriterTrait with Version.

This patch teaches the constructor of RecordWriterTrait to accept
Schema.  While I am at it, this patch makes Version a private
variable.

Author: kazutakahirata

llvm/include/llvm/ProfileData/MemProf.h

@@ -514,16 +514,17 @@ class RecordWriterTrait {
   using hash_value_type = uint64_t;
   using offset_type = uint64_t;
 
-  // Pointer to the memprof schema to use for the generator. Unlike the reader
-  // we must use a default constructor with no params for the writer trait so we
-  // have a public member which must be initialized by the user.
-  MemProfSchema *Schema = nullptr;
+private:
+  // Pointer to the memprof schema to use for the generator.
+  const MemProfSchema *Schema;
   // The MemProf version to use for the serialization.
   IndexedVersion Version;
 
+public:
   // We do not support the default constructor, which does not set Version.
   RecordWriterTrait() = delete;
-  RecordWriterTrait(IndexedVersion V) : Version(V) {}
+  RecordWriterTrait(const MemProfSchema *Schema, IndexedVersion V)
+      : Schema(Schema), Version(V) {}
 
   static hash_value_type ComputeHash(key_type_ref K) { return K; }
 

llvm/lib/ProfileData/InstrProfWriter.cpp

@@ -451,8 +451,7 @@ static uint64_t writeMemProfRecords(
     llvm::MapVector<GlobalValue::GUID, memprof::IndexedMemProfRecord>
         &MemProfRecordData,
     memprof::MemProfSchema *Schema, memprof::IndexedVersion Version) {
-  memprof::RecordWriterTrait RecordWriter(Version);
-  RecordWriter.Schema = Schema;
+  memprof::RecordWriterTrait RecordWriter(Schema, Version);
   OnDiskChainedHashTableGenerator<memprof::RecordWriterTrait>
       RecordTableGenerator;
   for (auto &[GUID, Record] : MemProfRecordData) {