[TableGen] Diagnose undefined fields when generating searchable tables

[foad]

Summary

Previously TableGen would crash trying to print the undefined value as
an integer.

Change-Id: I3900071ceaa07c26acafb33bc49966d7d7a02828

[foad]

Ping!

[nhaehnle]

Thanks, LGTM

llvm/test/TableGen/generic-tables.td

 // RUN: llvm-tblgen -gen-searchable-tables -I %p/../../include %s | FileCheck %s
+// RUN: not llvm-tblgen -gen-searchable-tables -I %p/../../include -DERROR1 %s 2>&1 | FileCheck --check-prefix=ERROR1 %s
 // XFAIL: vg_leak
 
 include "llvm/TableGen/SearchableTable.td"
 
 // CHECK-LABEL: GET_BValues_DECL
 // CHECK: enum BValues {
 // CHECK:   BAlice = 172,
 // CHECK:   BBob = 20,
def CTable : GenericTable {
   let PrimaryKeyName = "lookupCEntryByEncoding";
   let PrimaryKeyEarlyOut = 1;
 }
 
 def lookupCEntry : SearchIndex {
   let Table = CTable;
   let Key = ["Name", "Kind"];
 }
+
+#ifdef ERROR1
+
+class DEntry<string str, int val1> {
+  string Str = str;
+  bits<8> Val1 = val1;
+}
+
+def DFoo : DEntry<"foo", 1>;
+// ERROR1: [[@LINE+1]]:1: error: Record 'DBar' in table 'DTable' is missing field 'Val1'
+def DBar : DEntry<"bar", ?>;
+
+def DTable : GenericTable {
+  let FilterClass = "DEntry";
+  let Fields = ["Str", "Val1"];
+}
+
+#endif // ERROR1

llvm/utils/TableGen/SearchableTableEmitter.cpp

void SearchableTableEmitter::collectEnumEntries(
   }
 }
 
 void SearchableTableEmitter::collectTableEntries(
     GenericTable &Table, const std::vector<Record *> &Items) {
   for (auto EntryRec : Items) {
     for (auto &Field : Table.Fields) {
       auto TI = dyn_cast<TypedInit>(EntryRec->getValueInit(Field.Name));
-      if (!TI) {
+      if (!TI || !TI->isComplete()) {
         PrintFatalError(EntryRec->getLoc(),
                         Twine("Record '") + EntryRec->getName() +
                             "' in table '" + Table.Name +
                             "' is missing field '" + Field.Name + "'");
       }
       if (!Field.RecType) {
         Field.RecType = TI->getType();
       } else {