TableGen: Explicitly forbid self-references to field members

Summary:
Otherwise, patterns like in the test case produce cryptic error
messages about fields being resolved incompletely.

Change-Id: I713c0191f00fe140ad698675803ab1f8823dc5bd

Reviewers: arsenm, craig.topper, tra, MartinO

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D44476

llvm-svn: 327850

2 files changed, 10 insertions, 4 deletions

diff --git a/llvm/lib/TableGen/Record.cpp b/llvm/lib/TableGen/Record.cpp
index 333f45b7be9..866cda3152f 100644
--- a/llvm/lib/TableGen/Record.cpp
+++ b/llvm/lib/TableGen/Record.cpp
@@ -1684,13 +1684,19 @@ Init *FieldInit::getBit(unsigned Bit) const {
 Init *FieldInit::resolveReferences(Resolver &R) const {
   Init *NewRec = Rec->resolveReferences(R);
   if (NewRec != Rec)
-    return FieldInit::get(NewRec, FieldName)->Fold();
+    return FieldInit::get(NewRec, FieldName)->Fold(R.getCurrentRecord());
   return const_cast<FieldInit *>(this);
 }
 
-Init *FieldInit::Fold() const {
+Init *FieldInit::Fold(Record *CurRec) const {
   if (DefInit *DI = dyn_cast<DefInit>(Rec)) {
-    Init *FieldVal = DI->getDef()->getValue(FieldName)->getValue();
+    Record *Def = DI->getDef();
+    if (Def == CurRec)
+      PrintFatalError(CurRec->getLoc(),
+                      Twine("Attempting to access field '") +
+                      FieldName->getAsUnquotedString() + "' of '" +
+                      Rec->getAsString() + "' is a forbidden self-reference");
+    Init *FieldVal = Def->getValue(FieldName)->getValue();
     if (FieldVal->isComplete())
       return FieldVal;
   }
diff --git a/llvm/lib/TableGen/TGParser.cpp b/llvm/lib/TableGen/TGParser.cpp
index 0c92cf74965..0eb75424db5 100644
--- a/llvm/lib/TableGen/TGParser.cpp
+++ b/llvm/lib/TableGen/TGParser.cpp
@@ -1943,7 +1943,7 @@ Init *TGParser::ParseValue(Record *CurRec, RecTy *ItemType, IDParseMode Mode) {
                  Result->getAsString() + "'");
         return nullptr;
       }
-      Result = FieldInit::get(Result, FieldName)->Fold();
+      Result = FieldInit::get(Result, FieldName)->Fold(CurRec);
       Lex.Lex();  // eat field name
       break;
     }