Fix evil TableGen bug in template parameters with defaults.

If a TableGen class has an initializer expression containing an X.Y subexpression,
AND X depends on template parameters,
AND those template parameters have defaults,
AND some parameters with defaults are beyond position 1,
THEN parts of the initializer expression are evaluated prematurely with the default values when the first explicit template parameter is substituted, before the remaining explicit template parameters have been substituted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99492 91177308-0d34-0410-b5e6-96231b3b80d8

test/TableGen/2010-03-24-PrematureDefaults.td

@@ -0,0 +1,43 @@
+// RUN: tblgen %s | FileCheck %s
+
+class A<int k, bits<2> x = 1> {
+  int K = k;
+  bits<2> Bits = x;
+}
+
+// CHECK: def a1
+// CHECK: Bits = { 0, 1 }
+def a1 : A<12>;
+
+// CHECK: def a2
+// CHECK: Bits = { 1, 0 }
+def a2 : A<13, 2>;
+
+// Here was the bug: X.Bits would get resolved to the default a1.Bits while
+// resolving the first template argument. When the second template argument
+// was processed, X would be set correctly, but Bits retained the default
+// value.
+class B<int k, A x = a1> {
+  A X = x;
+  bits<2> Bits = X.Bits;
+}
+
+// CHECK: def b1
+// CHECK: Bits = { 0, 1 }
+def b1 : B<27>;
+
+// CHECK: def b2
+// CHECK: Bits = { 1, 0 }
+def b2 : B<28, a2>;
+
+class C<A x = a1> {
+  bits<2> Bits = x.Bits;
+}
+
+// CHECK: def c1
+// CHECK: Bits = { 0, 1 }
+def c1 : C;
+
+// CHECK: def c2
+// CHECK: Bits = { 1, 0 }
+def c2 : C<a2>;

utils/TableGen/Record.cpp

@@ -1108,12 +1108,15 @@ RecTy *VarInit::getFieldType(const std::string &FieldName) const {
   return 0;
 }
 
-Init *VarInit::getFieldInit(Record &R, const std::string &FieldName) const {
+Init *VarInit::getFieldInit(Record &R, const RecordVal *RV,
+                            const std::string &FieldName) const {
   if (dynamic_cast<RecordRecTy*>(getType()))
-    if (const RecordVal *RV = R.getValue(VarName)) {
+    if (const RecordVal *Val = R.getValue(VarName)) {
-      Init *TheInit = RV->getValue();
+      if (RV != Val && (RV || dynamic_cast<UnsetInit*>(Val->getValue())))
+        return 0;
+      Init *TheInit = Val->getValue();
       assert(TheInit != this && "Infinite loop detected!");
-      if (Init *I = TheInit->getFieldInit(R, FieldName))
+      if (Init *I = TheInit->getFieldInit(R, RV, FieldName))
         return I;
       else
         return 0;
@@ -1174,7 +1177,8 @@ RecTy *DefInit::getFieldType(const std::string &FieldName) const {
   return 0;
 }
 
-Init *DefInit::getFieldInit(Record &R, const std::string &FieldName) const {
+Init *DefInit::getFieldInit(Record &R, const RecordVal *RV,
+                            const std::string &FieldName) const {
   return Def->getValue(FieldName)->getValue();
 }
 
@@ -1185,7 +1189,7 @@ std::string DefInit::getAsString() const {
 
 Init *FieldInit::resolveBitReference(Record &R, const RecordVal *RV,
                                      unsigned Bit) {
-  if (Init *BitsVal = Rec->getFieldInit(R, FieldName))
+  if (Init *BitsVal = Rec->getFieldInit(R, RV, FieldName))
     if (BitsInit *BI = dynamic_cast<BitsInit*>(BitsVal)) {
       assert(Bit < BI->getNumBits() && "Bit reference out of range!");
       Init *B = BI->getBit(Bit);
@@ -1198,7 +1202,7 @@ Init *FieldInit::resolveBitReference(Record &R, const RecordVal *RV,
 
 Init *FieldInit::resolveListElementReference(Record &R, const RecordVal *RV,
                                              unsigned Elt) {
-  if (Init *ListVal = Rec->getFieldInit(R, FieldName))
+  if (Init *ListVal = Rec->getFieldInit(R, RV, FieldName))
     if (ListInit *LI = dynamic_cast<ListInit*>(ListVal)) {
       if (Elt >= LI->getSize()) return 0;
       Init *E = LI->getElement(Elt);
@@ -1215,7 +1219,7 @@ Init *FieldInit::resolveListElementReference(Record &R, const RecordVal *RV,
 Init *FieldInit::resolveReferences(Record &R, const RecordVal *RV) {
   Init *NewRec = RV ? Rec->resolveReferences(R, RV) : Rec;
 
-  Init *BitsVal = NewRec->getFieldInit(R, FieldName);
+  Init *BitsVal = NewRec->getFieldInit(R, RV, FieldName);
   if (BitsVal) {
     Init *BVR = BitsVal->resolveReferences(R, RV);
     return BVR->isComplete() ? BVR : this;

utils/TableGen/Record.h

@@ -503,7 +503,8 @@ struct Init {
   /// initializer for the specified field.  If getFieldType returns non-null
   /// this method should return non-null, otherwise it returns null.
   ///
-  virtual Init *getFieldInit(Record &R, const std::string &FieldName) const {
+  virtual Init *getFieldInit(Record &R, const RecordVal *RV,
+                             const std::string &FieldName) const {
     return 0;
   }
 
@@ -950,7 +951,8 @@ public:
                                             unsigned Elt);
 
   virtual RecTy *getFieldType(const std::string &FieldName) const;
-  virtual Init *getFieldInit(Record &R, const std::string &FieldName) const;
+  virtual Init *getFieldInit(Record &R, const RecordVal *RV,
+                             const std::string &FieldName) const;
 
   /// resolveReferences - This method is used by classes that refer to other
   /// variables which may not be defined at the time they expression is formed.
@@ -1035,7 +1037,8 @@ public:
   //virtual Init *convertInitializerBitRange(const std::vector<unsigned> &Bits);
 
   virtual RecTy *getFieldType(const std::string &FieldName) const;
-  virtual Init *getFieldInit(Record &R, const std::string &FieldName) const;
+  virtual Init *getFieldInit(Record &R, const RecordVal *RV,
+                             const std::string &FieldName) const;
 
   virtual std::string getAsString() const;