[llvm] [TableGen] Allow empty terminator in SequenceToOffsetTable (PR #119751)

[Rahul Joshi via llvm-commits]

================
@@ -97,25 +103,27 @@ class SequenceToOffsetTable {
   bool empty() const { return Seqs.empty(); }
 
   unsigned size() const {
-    assert((empty() || Entries) && "Call layout() before size()");
+    assert(IsLaidOut && "Call layout() before size()");
     return Entries;
   }
 
   /// layout - Computes the final table layout.
   void layout() {
-    assert(Entries == 0 && "Can only call layout() once");
+    assert(!IsLaidOut && "Can only call layout() once");
+    IsLaidOut = true;
+
     // Lay out the table in Seqs iteration order.
     for (typename SeqMap::iterator I = Seqs.begin(), E = Seqs.end(); I != E;
          ++I) {
       I->second = Entries;
       // Include space for a terminator.
-      Entries += I->first.size() + 1;
+      Entries += I->first.size() + Terminator.has_value();
----------------
jurahul wrote:

nit: Can we just do:

```
if (Terminator.has_value())
  Entries += Seqs.size();
```

after the loop?

https://github.com/llvm/llvm-project/pull/119751