[llvm] [NFC][TableGen] Remove small heap allocations in SearchableTableEmitter (PR #147845)

[Rahul Joshi via llvm-commits]

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@@ -625,30 +638,29 @@ std::unique_ptr<SearchIndex> SearchableTableEmitter::parseSearchIndex(
 void SearchableTableEmitter::collectEnumEntries(
     GenericEnum &Enum, StringRef NameField, StringRef ValueField,
     ArrayRef<const Record *> Items) {
+  Enum.Entries.reserve(Items.size());
   for (const Record *EntryRec : Items) {
-    StringRef Name;
-    if (NameField.empty())
-      Name = EntryRec->getName();
-    else
-      Name = EntryRec->getValueAsString(NameField);
-
-    int64_t Value = 0;
-    if (!ValueField.empty())
-      Value = getInt(EntryRec, ValueField);
-
-    Enum.Entries.push_back(std::make_unique<GenericEnum::Entry>(Name, Value));
-    Enum.EntryMap.try_emplace(EntryRec, Enum.Entries.back().get());
+    StringRef Name = NameField.empty() ? EntryRec->getName()
+                                       : EntryRec->getValueAsString(NameField);
+    int64_t Value = ValueField.empty() ? 0 : getInt(EntryRec, ValueField);
+    Enum.Entries.try_emplace(EntryRec, Name, Value);
   }
 
+  // If no values are provided for enums, assign values in the order of sorted
+  // enum names.
   if (ValueField.empty()) {
-    llvm::stable_sort(Enum.Entries,
-                      [](const std::unique_ptr<GenericEnum::Entry> &LHS,
-                         const std::unique_ptr<GenericEnum::Entry> &RHS) {
-                        return LHS->first < RHS->first;
-                      });
-
-    for (size_t i = 0; i < Enum.Entries.size(); ++i)
-      Enum.Entries[i]->second = i;
+    // Copy the map entries for sorting and clear the map.
+    auto SavedEntries = Enum.Entries.takeVector();
+    llvm::stable_sort(
+        SavedEntries,
+        [](const std::pair<const Record *, GenericEnum::Entry> &LHS,
+           const std::pair<const Record *, GenericEnum::Entry> &RHS) {
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jurahul wrote:

Agreed, I'll revert back to explicit type here.

https://github.com/llvm/llvm-project/pull/147845