[TableGen] Support non-def operators in !getdagop (#77531)

`!getdagop` expects the dag operator to be a def, and errors out if it's
not.

While that's true in most cases, when multiclasses are involved, the
late resolution of the dag operator can result in it not being a def
yet, but still have a proper type, wich is required to check against the
optional parameter Ty in `!getdagop<Ty>`.

e.g, in the following dag:
```
(!cast<TestInstruction>(TestInstructionAndPattern::NAME) foo)
```
the operator is a UnOpInit, but all we need here is to check its type.

This fixes a bug where !getdagop is used to query the dag operator that
is dependent on the multiclass, which is not yet resolved to a def. Once
the folding is performed, the field becomes a record that can be
queried.

1 files changed, 8 insertions, 7 deletions

diff --git a/llvm/lib/TableGen/Record.cpp b/llvm/lib/TableGen/Record.cpp
index aa981fd..2b3e8a0 100644
--- a/llvm/lib/TableGen/Record.cpp
+++ b/llvm/lib/TableGen/Record.cpp
@@ -923,15 +923,16 @@ Init *UnOpInit::Fold(Record *CurRec, bool IsFinal) const {
 
   case GETDAGOP:
     if (DagInit *Dag = dyn_cast<DagInit>(LHS)) {
-      DefInit *DI = DefInit::get(Dag->getOperatorAsDef({}));
-      if (!DI->getType()->typeIsA(getType())) {
+      // TI is not necessarily a def due to the late resolution in multiclasses,
+      // but has to be a TypedInit.
+      auto *TI = cast<TypedInit>(Dag->getOperator());
+      if (!TI->getType()->typeIsA(getType())) {
         PrintFatalError(CurRec->getLoc(),
-                        Twine("Expected type '") +
-                        getType()->getAsString() + "', got '" +
-                        DI->getType()->getAsString() + "' in: " +
-                        getAsString() + "\n");
+                        Twine("Expected type '") + getType()->getAsString() +
+                            "', got '" + TI->getType()->getAsString() +
+                            "' in: " + getAsString() + "\n");
       } else {
-        return DI;
+        return Dag->getOperator();
       }
     }
     break;