Add Record::getValueAsOptionalDef().

Using `?` as an optional marker is very useful in Clang's AST-node
emitters because otherwise we need a separate class just to encode
the presence or absence of a base node reference.

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/TableGen/Record.cpp b/llvm/lib/TableGen/Record.cpp
index 835ef8c7141..2ab7b98ca03 100644
--- a/llvm/lib/TableGen/Record.cpp
+++ b/llvm/lib/TableGen/Record.cpp
@@ -2277,6 +2277,21 @@ Record *Record::getValueAsDef(StringRef FieldName) const {
     FieldName + "' does not have a def initializer!");
 }
 
+Record *Record::getValueAsOptionalDef(StringRef FieldName) const {
+  const RecordVal *R = getValue(FieldName);
+  if (!R || !R->getValue())
+    PrintFatalError(getLoc(), "Record `" + getName() +
+      "' does not have a field named `" + FieldName + "'!\n");
+
+  if (DefInit *DI = dyn_cast<DefInit>(R->getValue()))
+    return DI->getDef();
+  if (isa<UnsetInit>(R->getValue()))
+    return nullptr;
+  PrintFatalError(getLoc(), "Record `" + getName() + "', field `" +
+    FieldName + "' does not have either a def initializer or '?'!");
+}
+
+
 bool Record::getValueAsBit(StringRef FieldName) const {
   const RecordVal *R = getValue(FieldName);
   if (!R || !R->getValue())