TableGen: Only fold when some operand made resolve progress

Summary:
Make sure that we always fold immediately, so there's no point in
attempting to re-fold when nothing changes.

Change-Id: I069e1989455b6f2ca8606152f6adc1a5e817f1c8

Reviewers: arsenm, craig.topper, tra, MartinO

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D44198

llvm-svn: 327847

llvm/lib/TableGen/Record.cpp

@@ -765,7 +765,7 @@ Init *UnOpInit::resolveReferences(Resolver &R) const {
   if (LHS != lhs)
     return (UnOpInit::get(getOpcode(), lhs, getType()))
         ->Fold(R.getCurrentRecord());
-  return Fold(R.getCurrentRecord());
+  return const_cast<UnOpInit *>(this);
 }
 
 std::string UnOpInit::getAsString() const {
@@ -948,7 +948,7 @@ Init *BinOpInit::resolveReferences(Resolver &R) const {
   if (LHS != lhs || RHS != rhs)
     return (BinOpInit::get(getOpcode(), lhs, rhs, getType()))
         ->Fold(R.getCurrentRecord());
-  return Fold(R.getCurrentRecord());
+  return const_cast<BinOpInit *>(this);
 }
 
 std::string BinOpInit::getAsString() const {
@@ -1173,7 +1173,7 @@ Init *TernOpInit::resolveReferences(Resolver &R) const {
   if (LHS != lhs || MHS != mhs || RHS != rhs)
     return (TernOpInit::get(getOpcode(), lhs, mhs, rhs, getType()))
         ->Fold(R.getCurrentRecord());
-  return Fold(R.getCurrentRecord());
+  return const_cast<TernOpInit *>(this);
 }
 
 std::string TernOpInit::getAsString() const {

llvm/lib/TableGen/TGParser.cpp

@@ -1961,7 +1961,14 @@ Init *TGParser::ParseValue(Record *CurRec, RecTy *ItemType, IDParseMode Mode) {
       }
 
       if (LHS->getType() != StringRecTy::get()) {
-        LHS = UnOpInit::get(UnOpInit::CAST, LHS, StringRecTy::get());
+        LHS = dyn_cast<TypedInit>(
+            UnOpInit::get(UnOpInit::CAST, LHS, StringRecTy::get())
+                ->Fold(CurRec));
+        if (!LHS) {
+          Error(PasteLoc, Twine("can't cast '") + LHS->getAsString() +
+                              "' to string");
+          return nullptr;
+        }
       }
 
       TypedInit *RHS = nullptr;
@@ -1988,7 +1995,14 @@ Init *TGParser::ParseValue(Record *CurRec, RecTy *ItemType, IDParseMode Mode) {
         }
 
         if (RHS->getType() != StringRecTy::get()) {
-          RHS = UnOpInit::get(UnOpInit::CAST, RHS, StringRecTy::get());
+          RHS = dyn_cast<TypedInit>(
+              UnOpInit::get(UnOpInit::CAST, RHS, StringRecTy::get())
+                  ->Fold(CurRec));
+          if (!RHS) {
+            Error(PasteLoc, Twine("can't cast '") + RHS->getAsString() +
+                                "' to string");
+            return nullptr;
+          }
         }
 
         break;