Re-work bit/bits value resolving in tblgen

- This patch is inspired by the failure of the following code snippet
  which is used to convert enumerable values into encoding bits to
  improve the readability of td files.

  class S<int s> {
    bits<2> V = !if(!eq(s, 8),  {0, 0},
                !if(!eq(s, 16), {0, 1},
                !if(!eq(s, 32), {1, 0},
                !if(!eq(s, 64), {1, 1}, {?, ?}))));
  }

  Later, PR8330 is found to report not exactly the same bug relevant
  issue to bit/bits values.

- Instead of resolving bit/bits values separately through
  resolveBitReference(), this patch adds getBit() for all Inits and
  resolves bit value by resolving plus getting the specified bit. This
  unifies the resolving of bit with other values and removes redundant
  logic for resolving bit only. In addition,
  BitsInit::resolveReferences() is optimized to take advantage of this
  origanization by resolving VarBitInit's variable reference first and
  then getting bits from it.

- The type interference in '!if' operator is revised to support possible
  combinations of int and bits/bit in MHS and RHS.

- As there may be illegal assignments from integer value to bit, says
  assign 2 to a bit, but we only check this during instantiation in some
  cases, e.g.

  bit V = !if(!eq(x, 17), 0, 2);

  Verbose diagnostic message is generated when invalid value is
  resolveed to help locating the error.

- PR8330 is fixed as well.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163360 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 250 insertions, 201 deletions

diff --git a/include/llvm/TableGen/Record.h b/include/llvm/TableGen/Record.h
index 75ca88a1ed..c7baaeb9d9 100644
--- a/include/llvm/TableGen/Record.h
+++ b/include/llvm/TableGen/Record.h
@@ -509,6 +509,18 @@ public:
   virtual Init *resolveReferences(Record &R, const RecordVal *RV) const {
     return const_cast<Init *>(this);
   }
+
+  /// getBit - This method is used to return the initializer for the specified
+  /// bit.
+  virtual Init *getBit(unsigned Bit) const = 0;
+
+  /// getBitVar - This method is used to retrieve the initializer for bit
+  /// reference. For non-VarBitInit, it simply returns itself.
+  virtual Init *getBitVar() const { return const_cast<Init*>(this); }
+
+  /// getBitNum - This method is used to retrieve the bit number of a bit
+  /// reference. For non-VarBitInit, it simply returns 0.
+  virtual unsigned getBitNum() const { return 0; }
 };
 
 inline raw_ostream &operator<<(raw_ostream &OS, const Init &I) {
@@ -541,13 +553,6 @@ public:
   ///
   virtual RecTy *getFieldType(const std::string &FieldName) const;
 
-  /// resolveBitReference - This method is used to implement
-  /// VarBitInit::resolveReferences.  If the bit is able to be resolved, we
-  /// simply return the resolved value, otherwise we return null.
-  ///
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const = 0;
-
   /// resolveListElementReference - This method is used to implement
   /// VarListElementInit::resolveReferences.  If the list element is resolvable
   /// now, we return the resolved value, otherwise we return null.
@@ -571,6 +576,10 @@ public:
     return Ty->convertValue(const_cast<UnsetInit *>(this));
   }
 
+  virtual Init *getBit(unsigned Bit) const {
+    return const_cast<UnsetInit*>(this);
+  }
+
   virtual bool isComplete() const { return false; }
   virtual std::string getAsString() const { return "?"; }
 };
@@ -595,6 +604,11 @@ public:
     return Ty->convertValue(const_cast<BitInit *>(this));
   }
 
+  virtual Init *getBit(unsigned Bit) const {
+    assert(Bit < 1 && "Bit index out of range!");
+    return const_cast<BitInit*>(this);
+  }
+
   virtual std::string getAsString() const { return Value ? "1" : "0"; }
 };
 
@@ -616,11 +630,6 @@ public:
 
   unsigned getNumBits() const { return Bits.size(); }
 
-  Init *getBit(unsigned Bit) const {
-    assert(Bit < Bits.size() && "Bit index out of range!");
-    return Bits[Bit];
-  }
-
   virtual Init *convertInitializerTo(RecTy *Ty) const {
     return Ty->convertValue(const_cast<BitsInit *>(this));
   }
@@ -640,6 +649,11 @@ public:
   virtual std::string getAsString() const;
 
   virtual Init *resolveReferences(Record &R, const RecordVal *RV) const;
+
+  virtual Init *getBit(unsigned Bit) const {
+    assert(Bit < Bits.size() && "Bit index out of range!");
+    return Bits[Bit];
+  }
 };
 
 
@@ -666,15 +680,6 @@ public:
 
   virtual std::string getAsString() const;
 
-  /// resolveBitReference - This method is used to implement
-  /// VarBitInit::resolveReferences.  If the bit is able to be resolved, we
-  /// simply return the resolved value, otherwise we return null.
-  ///
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const {
-    llvm_unreachable("Illegal bit reference off int");
-  }
-
   /// resolveListElementReference - This method is used to implement
   /// VarListElementInit::resolveReferences.  If the list element is resolvable
   /// now, we return the resolved value, otherwise we return null.
@@ -682,6 +687,10 @@ public:
                                             unsigned Elt) const {
     llvm_unreachable("Illegal element reference off int");
   }
+
+  virtual Init *getBit(unsigned Bit) const {
+    return BitInit::get((Value & (1 << Bit)) != 0);
+  }
 };
 
 
@@ -709,15 +718,6 @@ public:
   virtual std::string getAsString() const { return "\"" + Value + "\""; }
   virtual std::string getAsUnquotedString() const { return Value; }
 
-  /// resolveBitReference - This method is used to implement
-  /// VarBitInit::resolveReferences.  If the bit is able to be resolved, we
-  /// simply return the resolved value, otherwise we return null.
-  ///
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const {
-    llvm_unreachable("Illegal bit reference off string");
-  }
-
   /// resolveListElementReference - This method is used to implement
   /// VarListElementInit::resolveReferences.  If the list element is resolvable
   /// now, we return the resolved value, otherwise we return null.
@@ -725,6 +725,10 @@ public:
                                             unsigned Elt) const {
     llvm_unreachable("Illegal element reference off string");
   }
+
+  virtual Init *getBit(unsigned Bit) const {
+    llvm_unreachable("Illegal bit reference off string");
+  }
 };
 
 /// ListInit - [AL, AH, CL] - Represent a list of defs
@@ -777,20 +781,15 @@ public:
   inline size_t         size () const { return Values.size();  }
   inline bool           empty() const { return Values.empty(); }
 
-  /// resolveBitReference - This method is used to implement
-  /// VarBitInit::resolveReferences.  If the bit is able to be resolved, we
-  /// simply return the resolved value, otherwise we return null.
-  ///
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const {
-    llvm_unreachable("Illegal bit reference off list");
-  }
-
   /// resolveListElementReference - This method is used to implement
   /// VarListElementInit::resolveReferences.  If the list element is resolvable
   /// now, we return the resolved value, otherwise we return null.
   virtual Init *resolveListElementReference(Record &R, const RecordVal *RV,
                                             unsigned Elt) const;
+
+  virtual Init *getBit(unsigned Bit) const {
+    llvm_unreachable("Illegal bit reference off list");
+  }
 };
 
 
@@ -818,10 +817,10 @@ public:
     return Ty->convertValue(const_cast<OpInit *>(this));
   }
 
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const;
   virtual Init *resolveListElementReference(Record &R, const RecordVal *RV,
                                             unsigned Elt) const;
+
+  virtual Init *getBit(unsigned Bit) const;
 };
 
 
@@ -1003,8 +1002,6 @@ public:
     return getNameInit()->getAsUnquotedString();
   }
 
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const;
   virtual Init *resolveListElementReference(Record &R, const RecordVal *RV,
                                             unsigned Elt) const;
 
@@ -1019,6 +1016,8 @@ public:
   ///
   virtual Init *resolveReferences(Record &R, const RecordVal *RV) const;
 
+  virtual Init *getBit(unsigned Bit) const;
+
   virtual std::string getAsString() const { return getName(); }
 };
 
@@ -1030,8 +1029,10 @@ class VarBitInit : public Init {
   unsigned Bit;
 
   VarBitInit(TypedInit *T, unsigned B) : TI(T), Bit(B) {
-    assert(T->getType() && dynamic_cast<BitsRecTy*>(T->getType()) &&
-           ((BitsRecTy*)T->getType())->getNumBits() > B &&
+    assert(T->getType() &&
+           (dynamic_cast<IntRecTy*>(T->getType()) ||
+            (dynamic_cast<BitsRecTy*>(T->getType()) &&
+             dynamic_cast<BitsRecTy*>(T->getType())->getNumBits() > B)) &&
            "Illegal VarBitInit expression!");
   }
 
@@ -1045,11 +1046,16 @@ public:
     return Ty->convertValue(const_cast<VarBitInit *>(this));
   }
 
-  TypedInit *getVariable() const { return TI; }
-  unsigned getBitNum() const { return Bit; }
+  virtual Init *getBitVar() const { return TI; }
+  virtual unsigned getBitNum() const { return Bit; }
 
   virtual std::string getAsString() const;
   virtual Init *resolveReferences(Record &R, const RecordVal *RV) const;
+
+  virtual Init *getBit(unsigned B) const {
+    assert(B < 1 && "Bit index out of range!");
+    return const_cast<VarBitInit*>(this);
+  }
 };
 
 /// VarListElementInit - List[4] - Represent access to one element of a var or
@@ -1080,9 +1086,6 @@ public:
   TypedInit *getVariable() const { return TI; }
   unsigned getElementNum() const { return Element; }
 
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const;
-
   /// resolveListElementReference - This method is used to implement
   /// VarListElementInit::resolveReferences.  If the list element is resolvable
   /// now, we return the resolved value, otherwise we return null.
@@ -1092,6 +1095,8 @@ public:
 
   virtual std::string getAsString() const;
   virtual Init *resolveReferences(Record &R, const RecordVal *RV) const;
+
+  virtual Init *getBit(unsigned Bit) const;
 };
 
 /// DefInit - AL - Represent a reference to a 'def' in the description
@@ -1122,12 +1127,7 @@ public:
 
   virtual std::string getAsString() const;
 
-  /// resolveBitReference - This method is used to implement
-  /// VarBitInit::resolveReferences.  If the bit is able to be resolved, we
-  /// simply return the resolved value, otherwise we return null.
-  ///
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const {
+  virtual Init *getBit(unsigned Bit) const {
     llvm_unreachable("Illegal bit reference off def");
   }
 
@@ -1163,8 +1163,8 @@ public:
     return Ty->convertValue(const_cast<FieldInit *>(this));
   }
 
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const;
+  virtual Init *getBit(unsigned Bit) const;
+
   virtual Init *resolveListElementReference(Record &R,
                                             const RecordVal *RV,
                                             unsigned Elt) const;
@@ -1243,8 +1243,7 @@ public:
   inline size_t              name_size () const { return ArgNames.size();  }
   inline bool                name_empty() const { return ArgNames.empty(); }
 
-  virtual Init *resolveBitReference(Record &R, const RecordVal *RV,
-                                    unsigned Bit) const {
+  virtual Init *getBit(unsigned Bit) const {
     llvm_unreachable("Illegal bit reference off dag");
   }
 
diff --git a/lib/TableGen/Record.cpp b/lib/TableGen/Record.cpp
index 3176b2af63..b2a7b628e4 100644
--- a/lib/TableGen/Record.cpp
+++ b/lib/TableGen/Record.cpp
@@ -112,7 +112,10 @@ Init *BitRecTy::convertValue(IntInit *II) {
 }
 
 Init *BitRecTy::convertValue(TypedInit *VI) {
-  if (dynamic_cast<BitRecTy*>(VI->getType()))
+  RecTy *Ty = VI->getType();
+  if (dynamic_cast<BitRecTy*>(Ty) ||
+      dynamic_cast<BitsRecTy*>(Ty) ||
+      dynamic_cast<IntRecTy*>(Ty))
     return VI;  // Accept variable if it is already of bit type!
   return 0;
 }
@@ -178,60 +181,15 @@ Init *BitsRecTy::convertValue(BitsInit *BI) {
 }
 
 Init *BitsRecTy::convertValue(TypedInit *VI) {
-  if (BitsRecTy *BRT = dynamic_cast<BitsRecTy*>(VI->getType()))
-    if (BRT->Size == Size) {
-      SmallVector<Init *, 16> NewBits(Size);
- 
-      for (unsigned i = 0; i != Size; ++i)
-        NewBits[i] = VarBitInit::get(VI, i);
-      return BitsInit::get(NewBits);
-    }
-
   if (Size == 1 && dynamic_cast<BitRecTy*>(VI->getType()))
     return BitsInit::get(VI);
 
-  if (TernOpInit *Tern = dynamic_cast<TernOpInit*>(VI)) {
-    if (Tern->getOpcode() == TernOpInit::IF) {
-      Init *LHS = Tern->getLHS();
-      Init *MHS = Tern->getMHS();
-      Init *RHS = Tern->getRHS();
-
-      IntInit *MHSi = dynamic_cast<IntInit*>(MHS);
-      IntInit *RHSi = dynamic_cast<IntInit*>(RHS);
-
-      if (MHSi && RHSi) {
-        int64_t MHSVal = MHSi->getValue();
-        int64_t RHSVal = RHSi->getValue();
-
-        if (canFitInBitfield(MHSVal, Size) && canFitInBitfield(RHSVal, Size)) {
-          SmallVector<Init *, 16> NewBits(Size);
-
-          for (unsigned i = 0; i != Size; ++i)
-            NewBits[i] =
-              TernOpInit::get(TernOpInit::IF, LHS,
-                              IntInit::get((MHSVal & (1LL << i)) ? 1 : 0),
-                              IntInit::get((RHSVal & (1LL << i)) ? 1 : 0),
-                              VI->getType());
+  if (VI->getType()->typeIsConvertibleTo(this)) {
+    SmallVector<Init *, 16> NewBits(Size);
 
-          return BitsInit::get(NewBits);
-        }
-      } else {
-        BitsInit *MHSbs = dynamic_cast<BitsInit*>(MHS);
-        BitsInit *RHSbs = dynamic_cast<BitsInit*>(RHS);
-
-        if (MHSbs && RHSbs) {
-          SmallVector<Init *, 16> NewBits(Size);
-
-          for (unsigned i = 0; i != Size; ++i)
-            NewBits[i] = TernOpInit::get(TernOpInit::IF, LHS,
-                                         MHSbs->getBit(i),
-                                         RHSbs->getBit(i),
-                                         VI->getType());
-
-          return BitsInit::get(NewBits);
-        }
-      }
-    }
+    for (unsigned i = 0; i != Size; ++i)
+      NewBits[i] = VarBitInit::get(VI, i);
+    return BitsInit::get(NewBits);
   }
 
   return 0;
@@ -519,6 +477,15 @@ std::string BitsInit::getAsString() const {
   return Result + " }";
 }
 
+// Fix bit initializer to preserve the behavior that bit reference from a unset
+// bits initializer will resolve into VarBitInit to keep the field name and bit
+// number used in targets with fixed insn length.
+static Init *fixBitInit(const RecordVal *RV, Init *Before, Init *After) {
+  if (RV || After != UnsetInit::get())
+    return After;
+  return Before;
+}
+
 // resolveReferences - If there are any field references that refer to fields
 // that have been filled in, we can propagate the values now.
 //
@@ -526,16 +493,39 @@ Init *BitsInit::resolveReferences(Record &R, const RecordVal *RV) const {
   bool Changed = false;
   SmallVector<Init *, 16> NewBits(getNumBits());
 
-  for (unsigned i = 0, e = Bits.size(); i != e; ++i) {
-    Init *B;
-    Init *CurBit = getBit(i);
+  Init *CachedInit = 0;
+  Init *CachedBitVar = 0;
+  bool CachedBitVarChanged = false;
+
+  for (unsigned i = 0, e = getNumBits(); i != e; ++i) {
+    Init *CurBit = Bits[i];
+    Init *CurBitVar = CurBit->getBitVar();
 
-    do {
-      B = CurBit;
-      CurBit = CurBit->resolveReferences(R, RV);
-      Changed |= B != CurBit;
-    } while (B != CurBit);
     NewBits[i] = CurBit;
+
+    if (CurBitVar == CachedBitVar) {
+      if (CachedBitVarChanged) {
+        Init *Bit = CachedInit->getBit(CurBit->getBitNum());
+        NewBits[i] = fixBitInit(RV, CurBit, Bit);
+      }
+      continue;
+    }
+    CachedBitVar = CurBitVar;
+    CachedBitVarChanged = false;
+
+    Init *B;
+    do {
+      B = CurBitVar;
+      CurBitVar = CurBitVar->resolveReferences(R, RV);
+      CachedBitVarChanged |= B != CurBitVar;
+      Changed |= B != CurBitVar;
+    } while (B != CurBitVar);
+    CachedInit = CurBitVar;
+
+    if (CachedBitVarChanged) {
+      Init *Bit = CurBitVar->getBit(CurBit->getBitNum());
+      NewBits[i] = fixBitInit(RV, CurBit, Bit);
+    }
   }
 
   if (Changed)
@@ -682,20 +672,6 @@ std::string ListInit::getAsString() const {
   return Result + "]";
 }
 
-Init *OpInit::resolveBitReference(Record &R, const RecordVal *IRV,
-                                  unsigned Bit) const {
-  Init *Folded = Fold(&R, 0);
-
-  if (Folded != this) {
-    TypedInit *Typed = dynamic_cast<TypedInit *>(Folded);
-    if (Typed) {
-      return Typed->resolveBitReference(R, IRV, Bit);
-    }
-  }
-
-  return 0;
-}
-
 Init *OpInit::resolveListElementReference(Record &R, const RecordVal *IRV,
                                           unsigned Elt) const {
   Init *Resolved = resolveReferences(R, IRV);
@@ -718,6 +694,12 @@ Init *OpInit::resolveListElementReference(Record &R, const RecordVal *IRV,
   return 0;
 }
 
+Init *OpInit::getBit(unsigned Bit) const {
+  if (getType() == BitRecTy::get())
+    return const_cast<OpInit*>(this);
+  return VarBitInit::get(const_cast<OpInit*>(this), Bit);
+}
+
 UnOpInit *UnOpInit::get(UnaryOp opc, Init *lhs, RecTy *Type) {
   typedef std::pair<std::pair<unsigned, Init *>, RecTy *> Key;
 
@@ -922,9 +904,9 @@ Init *BinOpInit::Fold(Record *CurRec, MultiClass *CurMultiClass) const {
   case EQ: {
     // try to fold eq comparison for 'bit' and 'int', otherwise fallback
     // to string objects.
-    IntInit* L =
+    IntInit *L =
       dynamic_cast<IntInit*>(LHS->convertInitializerTo(IntRecTy::get()));
-    IntInit* R =
+    IntInit *R =
       dynamic_cast<IntInit*>(RHS->convertInitializerTo(IntRecTy::get()));
 
     if (L && R)
@@ -1324,25 +1306,10 @@ const std::string &VarInit::getName() const {
   return NameString->getValue();
 }
 
-Init *VarInit::resolveBitReference(Record &R, const RecordVal *IRV,
-                                   unsigned Bit) const {
-  if (R.isTemplateArg(getNameInit())) return 0;
-  if (IRV && IRV->getNameInit() != getNameInit()) return 0;
-
-  RecordVal *RV = R.getValue(getNameInit());
-  assert(RV && "Reference to a non-existent variable?");
-  assert(dynamic_cast<BitsInit*>(RV->getValue()));
-  BitsInit *BI = (BitsInit*)RV->getValue();
-
-  assert(Bit < BI->getNumBits() && "Bit reference out of range!");
-  Init *B = BI->getBit(Bit);
-
-  // If the bit is set to some value, or if we are resolving a reference to a
-  // specific variable and that variable is explicitly unset, then replace the
-  // VarBitInit with it.
-  if (IRV || !dynamic_cast<UnsetInit*>(B))
-    return B;
-  return 0;
+Init *VarInit::getBit(unsigned Bit) const {
+  if (getType() == BitRecTy::get())
+    return const_cast<VarInit*>(this);
+  return VarBitInit::get(const_cast<VarInit*>(this), Bit);
 }
 
 Init *VarInit::resolveListElementReference(Record &R,
@@ -1425,9 +1392,11 @@ std::string VarBitInit::getAsString() const {
 }
 
 Init *VarBitInit::resolveReferences(Record &R, const RecordVal *RV) const {
-  if (Init *I = getVariable()->resolveBitReference(R, RV, getBitNum()))
-    return I;
-  return const_cast<VarBitInit *>(this);
+  Init *I = TI->resolveReferences(R, RV);
+  if (TI != I)
+    return I->getBit(getBitNum());
+
+  return const_cast<VarBitInit*>(this);
 }
 
 VarListElementInit *VarListElementInit::get(TypedInit *T,
@@ -1456,11 +1425,10 @@ VarListElementInit::resolveReferences(Record &R, const RecordVal *RV) const {
   return const_cast<VarListElementInit *>(this);
 }
 
-Init *VarListElementInit::resolveBitReference(Record &R, const RecordVal *RV,
-                                              unsigned Bit) const {
-  // FIXME: This should be implemented, to support references like:
-  // bit B = AA[0]{1};
-  return 0;
+Init *VarListElementInit::getBit(unsigned Bit) const {
+  if (getType() == BitRecTy::get())
+    return const_cast<VarListElementInit*>(this);
+  return VarBitInit::get(const_cast<VarListElementInit*>(this), Bit);
 }
 
 Init *VarListElementInit:: resolveListElementReference(Record &R,
@@ -1513,17 +1481,10 @@ FieldInit *FieldInit::get(Init *R, const std::string &FN) {
   return I;
 }
 
-Init *FieldInit::resolveBitReference(Record &R, const RecordVal *RV,
-                                     unsigned Bit) const {
-  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);
-
-      if (dynamic_cast<BitInit*>(B))  // If the bit is set.
-        return B;                     // Replace the VarBitInit with it.
-    }
-  return 0;
+Init *FieldInit::getBit(unsigned Bit) const {
+  if (getType() == BitRecTy::get())
+    return const_cast<FieldInit*>(this);
+  return VarBitInit::get(const_cast<FieldInit*>(this), Bit);
 }
 
 Init *FieldInit::resolveListElementReference(Record &R, const RecordVal *RV,
@@ -1751,7 +1712,15 @@ void Record::resolveReferencesTo(const RecordVal *RV) {
     if (RV == &Values[i]) // Skip resolve the same field as the given one
       continue;
     if (Init *V = Values[i].getValue())
-      Values[i].setValue(V->resolveReferences(*this, RV));
+      if (Values[i].setValue(V->resolveReferences(*this, RV)))
+        throw TGError(getLoc(), "Invalid value is found when setting '"
+                      + Values[i].getNameInitAsString()
+                      + "' after resolving references"
+                      + (RV ? " against '" + RV->getNameInitAsString()
+                              + "' of ("
+                              + RV->getValue()->getAsUnquotedString() + ")"
+                            : "")
+                      + "\n");
   }
   Init *OldName = getNameInit();
   Init *NewName = Name->resolveReferences(*this, RV);
diff --git a/lib/TableGen/TGParser.cpp b/lib/TableGen/TGParser.cpp
index 5e2b66ed69..aee93e7696 100644
--- a/lib/TableGen/TGParser.cpp
+++ b/lib/TableGen/TGParser.cpp
@@ -1044,35 +1044,28 @@ Init *TGParser::ParseOperation(Record *CurRec) {
     switch (LexCode) {
     default: llvm_unreachable("Unhandled code!");
     case tgtok::XIf: {
-      // FIXME: The `!if' operator doesn't handle non-TypedInit well at
-      // all. This can be made much more robust.
-      TypedInit *MHSt = dynamic_cast<TypedInit*>(MHS);
-      TypedInit *RHSt = dynamic_cast<TypedInit*>(RHS);
-
       RecTy *MHSTy = 0;
       RecTy *RHSTy = 0;
 
-      if (MHSt == 0 && RHSt == 0) {
-        BitsInit *MHSbits = dynamic_cast<BitsInit*>(MHS);
-        BitsInit *RHSbits = dynamic_cast<BitsInit*>(RHS);
-
-        if (MHSbits && RHSbits &&
-            MHSbits->getNumBits() == RHSbits->getNumBits()) {
-          Type = BitRecTy::get();
-          break;
-        } else {
-          BitInit *MHSbit = dynamic_cast<BitInit*>(MHS);
-          BitInit *RHSbit = dynamic_cast<BitInit*>(RHS);
-
-          if (MHSbit && RHSbit) {
-            Type = BitRecTy::get();
-            break;
-          }
-        }
-      } else if (MHSt != 0 && RHSt != 0) {
+      if (TypedInit *MHSt = dynamic_cast<TypedInit*>(MHS))
         MHSTy = MHSt->getType();
+      if (BitsInit *MHSbits = dynamic_cast<BitsInit*>(MHS))
+        MHSTy = BitsRecTy::get(MHSbits->getNumBits());
+      if (dynamic_cast<BitInit*>(MHS))
+        MHSTy = BitRecTy::get();
+
+      if (TypedInit *RHSt = dynamic_cast<TypedInit*>(RHS))
         RHSTy = RHSt->getType();
-      }
+      if (BitsInit *RHSbits = dynamic_cast<BitsInit*>(RHS))
+        RHSTy = BitsRecTy::get(RHSbits->getNumBits());
+      if (dynamic_cast<BitInit*>(RHS))
+        RHSTy = BitRecTy::get();
+
+      // For UnsetInit, it's typed from the other hand.
+      if (dynamic_cast<UnsetInit*>(MHS))
+        MHSTy = RHSTy;
+      if (dynamic_cast<UnsetInit*>(RHS))
+        RHSTy = MHSTy;
 
       if (!MHSTy || !RHSTy) {
         TokError("could not get type for !if");
diff --git a/test/TableGen/if.td b/test/TableGen/if.td
index 18de368af9..1d8d62329a 100644
--- a/test/TableGen/if.td
+++ b/test/TableGen/if.td
@@ -3,15 +3,59 @@
 
 // Support for an `!if' operator as part of a `let' statement.
 // CHECK:      class C
-// CHECK-NEXT: bits<16> n = { ?, ?, ?, ?, ?, ?, ?, !if({ C:x{2} }, 0, 1), !if({ C:x{2} }, 1, 1), !if({ C:x{2} }, 0, 0), !if({ C:x{1} }, C:y{3}, 0), !if({ C:x{1} }, C:y{2}, 1), !if({ C:x{0} }, C:y{3}, C:z), !if({ C:x{0} }, C:y{2}, C:y{2}), !if({ C:x{0} }, C:y{1}, C:y{1}), !if({ C:x{0} }, C:y{0}, C:y{0}) };
+// CHECK-NEXT: bits<16> n = { ?, ?, ?, ?, !if({ C:y{3} }, 1, !if({ C:y{2} }, { C:x{0} }, !if({ C:y{1} }, { C:x{1} }, !if({ C:y{0} }, { C:x{2} }, ?)))){0}, !if({ C:x{2} }, { C:y{3}, C:y{2} }, !if({ C:x{1} }, { C:y{2}, C:y{1} }, !if({ C:x{0} }, { C:y{1}, C:y{0} }, ?))){1}, !if({ C:x{2} }, { C:y{3}, C:y{2} }, !if({ C:x{1} }, { C:y{2}, C:y{1} }, !if({ C:x{0} }, { C:y{1}, C:y{0} }, ?))){0}, !if({ C:x{2} }, 2, 6){2}, !if({ C:x{2} }, 2, 6){1}, !if({ C:x{2} }, 2, 6){0}, !if({ C:x{1} }, { C:y{3}, C:y{2} }, { 0, 1 }){1}, !if({ C:x{1} }, { C:y{3}, C:y{2} }, { 0, 1 }){0}, !if({ C:x{0} }, { C:y{3}, C:y{2}, C:y{1}, C:y{0} }, { C:z, C:y{2}, C:y{1}, C:y{0} }){3}, !if({ C:x{0} }, { C:y{3}, C:y{2}, C:y{1}, C:y{0} }, { C:z, C:y{2}, C:y{1}, C:y{0} }){2}, !if({ C:x{0} }, { C:y{3}, C:y{2}, C:y{1}, C:y{0} }, { C:z, C:y{2}, C:y{1}, C:y{0} }){1}, !if({ C:x{0} }, { C:y{3}, C:y{2}, C:y{1}, C:y{0} }, { C:z, C:y{2}, C:y{1}, C:y{0} }){0} };
 class C<bits<3> x, bits<4> y, bit z> {
   bits<16> n;
 
+  let n{11}  = !if(y{3}, 1,
+               !if(y{2}, x{0},
+               !if(y{1}, x{1},
+               !if(y{0}, x{2}, ?))));
+  let n{10-9}= !if(x{2}, y{3-2},
+               !if(x{1}, y{2-1},
+               !if(x{0}, y{1-0}, ?)));
   let n{8-6} = !if(x{2}, 0b010, 0b110);
   let n{5-4} = !if(x{1}, y{3-2}, {0, 1});
   let n{3-0} = !if(x{0}, y{3-0}, {z, y{2}, y{1}, y{0}});
 }
 
+def C1 : C<{1, 0, 1}, {0, 1, 0, 1}, 0>;
+def C2 : C<{0, 1, 0}, {1, 0, 1, 0}, 1>;
+def C3 : C<{0, 0, 0}, {1, 0, 1, 0}, 0>;
+def C4 : C<{0, 0, 0}, {0, 0, 0, 0}, 0>;
+
+// CHECK: def C1
+// CHECK-NEXT: bits<16> n = { ?, ?, ?, ?, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 1 };
+// CHECK: def C2
+// CHECK-NEXT: bits<16> n = { ?, ?, ?, ?, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0 };
+// CHECK: def C3
+// CHECK-NEXT: bits<16> n = { ?, ?, ?, ?, 1, ?, ?, 1, 1, 0, 0, 1, 0, 0, 1, 0 };
+// CHECK: def C4
+// CHECK-NEXT: bits<16> n = { ?, ?, ?, ?, ?, ?, ?, 1, 1, 0, 0, 1, 0, 0, 0, 0 };
+
+class S<int s> {
+  bits<2> val = !if(!eq(s, 8),  {0, 0},
+                !if(!eq(s, 16), 0b01,
+                !if(!eq(s, 32), 2,
+                !if(!eq(s, 64), {1, 1}, ?))));
+}
+
+def D8  : S<8>;
+def D16 : S<16>;
+def D32 : S<32>;
+def D64 : S<64>;
+def D128: S<128>;
+// CHECK: def D128
+// CHECK-NEXT: bits<2> val = { ?, ? };
+// CHECK: def D16
+// CHECK-NEXT: bits<2> val = { 0, 1 };
+// CHECK: def D32
+// CHECK-NEXT: bits<2> val = { 1, 0 };
+// CHECK: def D64
+// CHECK-NEXT: bits<2> val = { 1, 1 };
+// CHECK: def D8
+// CHECK-NEXT: bits<2> val = { 0, 0 };
+
 // CHECK:      def One
 // CHECK-NEXT: list<int> first = [1, 2, 3];
 // CHECK-NEXT: list<int> rest = [1, 2, 3];
diff --git a/test/TableGen/list-element-bitref.td b/test/TableGen/list-element-bitref.td
new file mode 100644
index 0000000000..5f3e3dabf4
--- /dev/null
+++ b/test/TableGen/list-element-bitref.td
@@ -0,0 +1,15 @@
+// RUN: llvm-tblgen %s | FileCheck %s
+// XFAIL: vg_leak
+
+class C<list<bits<8>> L> {
+  bits<2> V0 = L[0]{1-0};
+  bits<2> V1 = L[1]{3-2};
+  string V2 = !if(L[0]{0}, "Odd", "Even");
+}
+
+def c0 : C<[0b0101, 0b1010]>;
+
+// CHECK: def c0
+// CHECk-NEXT: bits<2> V0 = { 0, 1 };
+// CHECk-NEXT: bits<2> V1 = { 1, 0 };
+// CHECk-NEXT: string V2 = "Odd";
diff --git a/test/TableGen/pr8330.td b/test/TableGen/pr8330.td
new file mode 100644
index 0000000000..7779b635e3
--- /dev/null
+++ b/test/TableGen/pr8330.td
@@ -0,0 +1,29 @@
+// RUN: llvm-tblgen %s | FileCheck %s
+// XFAIL: vg_leak
+
+class Or4<bits<8> Val> {
+  bits<8> V = {Val{7}, Val{6}, Val{5}, Val{4}, Val{3}, 1, Val{1}, Val{0} };
+}
+
+class Whatev<bits<8> x>;
+
+class Whatever<bits<8> x> {
+  bits<8> W = {x{0}, x{1}, x{2}, x{3}, x{4}, x{5}, x{6}, x{7} };
+}
+
+multiclass X<bits<8> BaseOpc> {
+ def bar : Whatev<Or4<BaseOpc>.V >;
+}
+
+multiclass Y<bits<8> BaseOpc> {
+ def foo : Whatever<Or4<BaseOpc>.V >;
+}
+
+defm a : X<4>;
+
+// CHECK: def abar
+
+defm b : Y<8>;
+
+// CHECK: def bfoo
+// CHECK-NEXT: bits<8> W = { 0, 0, 1, 1, 0, 0, 0, 0 };
diff --git a/utils/TableGen/CodeEmitterGen.cpp b/utils/TableGen/CodeEmitterGen.cpp
index 31a39b1f04..9c8ad67b42 100644
--- a/utils/TableGen/CodeEmitterGen.cpp
+++ b/utils/TableGen/CodeEmitterGen.cpp
@@ -92,7 +92,7 @@ void CodeEmitterGen::reverseBits(std::vector<Record*> &Insts) {
 int CodeEmitterGen::getVariableBit(const std::string &VarName,
                                    BitsInit *BI, int bit) {
   if (VarBitInit *VBI = dynamic_cast<VarBitInit*>(BI->getBit(bit))) {
-    if (VarInit *VI = dynamic_cast<VarInit*>(VBI->getVariable()))
+    if (VarInit *VI = dynamic_cast<VarInit*>(VBI->getBitVar()))
       if (VI->getName() == VarName)
         return VBI->getBitNum();
   } else if (VarInit *VI = dynamic_cast<VarInit*>(BI->getBit(bit))) {
diff --git a/utils/TableGen/FixedLenDecoderEmitter.cpp b/utils/TableGen/FixedLenDecoderEmitter.cpp
index e89c393b6a..aa6d7962a0 100644
--- a/utils/TableGen/FixedLenDecoderEmitter.cpp
+++ b/utils/TableGen/FixedLenDecoderEmitter.cpp
@@ -1783,7 +1783,7 @@ static bool populateInstruction(const CodeGenInstruction &CGI, unsigned Opc,
       VarInit *Var = 0;
       VarBitInit *BI = dynamic_cast<VarBitInit*>(Bits.getBit(bi));
       if (BI)
-        Var = dynamic_cast<VarInit*>(BI->getVariable());
+        Var = dynamic_cast<VarInit*>(BI->getBitVar());
       else
         Var = dynamic_cast<VarInit*>(Bits.getBit(bi));