Add more tests and clarify the visibility

Author: wangpc-pp

llvm/docs/TableGen/ProgRef.rst

@@ -1842,6 +1842,9 @@ and non-0 as true.
     will be included. The format of *regex* is ERE (Extended POSIX Regular
     Expressions).
 
+    If ``!instances`` is in a class/multiclass/foreach, only these records of
+    *type* that have been instantiated will be considered.
+
 ``!interleave(``\ *list*\ ``,`` *delim*\ ``)``
     This operator concatenates the items in the *list*, interleaving the
     *delim* string between each pair, and produces the resulting string.

llvm/include/llvm/TableGen/Record.h

@@ -1217,7 +1217,7 @@ class InstancesOpInit final : public TypedInit, public FoldingSetNode {
 
   void Profile(FoldingSetNodeID &ID) const;
 
-  const Init *Fold() const;
+  const Init *Fold(const Record *CurRec, bool IsFinal = false) const;
 
   bool isComplete() const override { return false; }
 
@@ -2018,6 +2018,9 @@ class RecordKeeper {
     bool Ins = Defs.try_emplace(std::string(R->getName()), std::move(R)).second;
     (void)Ins;
     assert(Ins && "Record already exists");
+    // Clear cache
+    if (!Cache.empty())
+      Cache.clear();
   }
 
   void addExtraGlobal(StringRef Name, const Init *I) {

llvm/lib/TableGen/Record.cpp

@@ -2249,7 +2249,10 @@ void InstancesOpInit::Profile(FoldingSetNodeID &ID) const {
   ProfileInstancesOpInit(ID, Type, Regex);
 }
 
-const Init *InstancesOpInit::Fold() const {
+const Init *InstancesOpInit::Fold(const Record *CurRec, bool IsFinal) const {
+  if (CurRec && !IsFinal)
+    return this;
+
   const auto *RegexInit = dyn_cast<StringInit>(Regex);
   if (!RegexInit)
     return this;
@@ -2270,8 +2273,8 @@ const Init *InstancesOpInit::Fold() const {
 
 const Init *InstancesOpInit::resolveReferences(Resolver &R) const {
   const Init *NewRegex = Regex->resolveReferences(R);
-  if (Regex != NewRegex)
-    return get(Type, NewRegex)->Fold();
+  if (Regex != NewRegex || R.isFinal())
+    return get(Type, NewRegex)->Fold(R.getCurrentRecord(), R.isFinal());
   return this;
 }
 

llvm/lib/TableGen/TGParser.cpp

@@ -1495,7 +1495,7 @@ const Init *TGParser::ParseOperation(Record *CurRec, const RecTy *ItemType) {
       return nullptr;
     }
 
-    return InstancesOpInit::get(Type, Regex)->Fold();
+    return InstancesOpInit::get(Type, Regex)->Fold(CurRec);
   }
 
   case tgtok::XConcat: