improve support for uniontype and ConstantUnion, patch by Tim Northover!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98656 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -293,6 +293,8 @@ void BitcodeReaderValueList::ResolveConstantForwardRefs() {
       } else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) {
         NewC = ConstantStruct::get(Context, &NewOps[0], NewOps.size(),
                                          UserCS->getType()->isPacked());
+      } else if (ConstantUnion *UserCU = dyn_cast<ConstantUnion>(UserC)) {
+        NewC = ConstantUnion::get(UserCU->getType(), NewOps[0]);
       } else if (isa<ConstantVector>(UserC)) {
         NewC = ConstantVector::get(&NewOps[0], NewOps.size());
       } else {
@@ -1015,6 +1017,11 @@ bool BitcodeReader::ParseConstants() {
           Elts.push_back(ValueList.getConstantFwdRef(Record[i],
                                                      STy->getElementType(i)));
         V = ConstantStruct::get(STy, Elts);
+      } else if (const UnionType *UnTy = dyn_cast<UnionType>(CurTy)) {
+        uint64_t Index = Record[0];
+        Constant *Val = ValueList.getConstantFwdRef(Record[1],
+                                        UnTy->getElementType(Index));
+        V = ConstantUnion::get(UnTy, Val);
       } else if (const ArrayType *ATy = dyn_cast<ArrayType>(CurTy)) {
         const Type *EltTy = ATy->getElementType();
         for (unsigned i = 0; i != Size; ++i)

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -808,11 +808,25 @@ static void WriteConstants(unsigned FirstVal, unsigned LastVal,
       else if (isCStr7)
         AbbrevToUse = CString7Abbrev;
     } else if (isa<ConstantArray>(C) || isa<ConstantStruct>(V) ||
-               isa<ConstantUnion>(C) || isa<ConstantVector>(V)) {
+               isa<ConstantVector>(V)) {
       Code = bitc::CST_CODE_AGGREGATE;
       for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
         Record.push_back(VE.getValueID(C->getOperand(i)));
       AbbrevToUse = AggregateAbbrev;
+    } else if (isa<ConstantUnion>(C)) {
+      Code = bitc::CST_CODE_AGGREGATE;
+
+      // Unions only have one entry but we must send type along with it.
+      const Type *EntryKind = C->getOperand(0)->getType();
+
+      const UnionType *UnTy = cast<UnionType>(C->getType());
+      int UnionIndex = UnTy->getElementTypeIndex(EntryKind);
+      assert(UnionIndex != -1 && "Constant union contains invalid entry");
+
+      Record.push_back(UnionIndex);
+      Record.push_back(VE.getValueID(C->getOperand(0)));
+
+      AbbrevToUse = AggregateAbbrev;
     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
       switch (CE->getOpcode()) {
       default:

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1138,6 +1138,21 @@ static void EmitGlobalConstantStruct(const ConstantStruct *CS,
          "Layout of constant struct may be incorrect!");
 }
 
+static void EmitGlobalConstantUnion(const ConstantUnion *CU, 
+                                    unsigned AddrSpace, AsmPrinter &AP) {
+  const TargetData *TD = AP.TM.getTargetData();
+  unsigned Size = TD->getTypeAllocSize(CU->getType());
+
+  const Constant *Contents = CU->getOperand(0);
+  unsigned FilledSize = TD->getTypeAllocSize(Contents->getType());
+    
+  // Print the actually filled part
+  AP.EmitGlobalConstant(Contents, AddrSpace);
+
+  // And pad with enough zeroes
+  AP.OutStreamer.EmitZeros(Size-FilledSize, AddrSpace);
+}
+
 static void EmitGlobalConstantFP(const ConstantFP *CFP, unsigned AddrSpace,
                                  AsmPrinter &AP) {
   // FP Constants are printed as integer constants to avoid losing
@@ -1258,15 +1273,18 @@ void AsmPrinter::EmitGlobalConstant(const Constant *CV, unsigned AddrSpace) {
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV))
     return EmitGlobalConstantFP(CFP, AddrSpace, *this);
 
-  if (const ConstantVector *V = dyn_cast<ConstantVector>(CV))
-    return EmitGlobalConstantVector(V, AddrSpace, *this);
-
   if (isa<ConstantPointerNull>(CV)) {
     unsigned Size = TM.getTargetData()->getTypeAllocSize(CV->getType());
     OutStreamer.EmitIntValue(0, Size, AddrSpace);
     return;
   }
   
+  if (const ConstantUnion *CVU = dyn_cast<ConstantUnion>(CV))
+    return EmitGlobalConstantUnion(CVU, AddrSpace, *this);
+  
+  if (const ConstantVector *V = dyn_cast<ConstantVector>(CV))
+    return EmitGlobalConstantVector(V, AddrSpace, *this);
+  
   // Otherwise, it must be a ConstantExpr.  Lower it to an MCExpr, then emit it
   // thread the streamer with EmitValue.
   OutStreamer.EmitValue(LowerConstant(CV, *this),

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -2592,6 +2592,11 @@ void SelectionDAGBuilder::visitGetElementPtr(User &I) {
       }
 
       Ty = StTy->getElementType(Field);
+    } else if (const UnionType *UnTy = dyn_cast<UnionType>(Ty)) {
+      unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
+      
+      // Offset canonically 0 for unions, but type changes
+      Ty = UnTy->getElementType(Field);
     } else {
       Ty = cast<SequentialType>(Ty)->getElementType();
 

lib/Target/TargetData.cpp

@@ -460,6 +460,15 @@ uint64_t TargetData::getTypeSizeInBits(const Type *Ty) const {
   case Type::StructTyID:
     // Get the layout annotation... which is lazily created on demand.
     return getStructLayout(cast<StructType>(Ty))->getSizeInBits();
+  case Type::UnionTyID: {
+    const UnionType *UnTy = cast<UnionType>(Ty);
+    uint64_t Size = 0;
+    for (UnionType::element_iterator i = UnTy->element_begin(),
+             e = UnTy->element_end(); i != e; ++i) {
+      Size = std::max(Size, getTypeSizeInBits(*i));
+    }
+    return Size;
+  }
   case Type::IntegerTyID:
     return cast<IntegerType>(Ty)->getBitWidth();
   case Type::VoidTyID:
@@ -516,6 +525,17 @@ unsigned char TargetData::getAlignment(const Type *Ty, bool abi_or_pref) const {
     unsigned Align = getAlignmentInfo(AGGREGATE_ALIGN, 0, abi_or_pref, Ty);
     return std::max(Align, (unsigned)Layout->getAlignment());
   }
+  case Type::UnionTyID: {
+    const UnionType *UnTy = cast<UnionType>(Ty);
+    unsigned Align = 1;
+
+    // Unions need the maximum alignment of all their entries
+    for (UnionType::element_iterator i = UnTy->element_begin(), 
+             e = UnTy->element_end(); i != e; ++i) {
+      Align = std::max(Align, (unsigned)getAlignment(*i, abi_or_pref));
+    }
+    return Align;
+  }
   case Type::IntegerTyID:
   case Type::VoidTyID:
     AlignType = INTEGER_ALIGN;
@@ -600,6 +620,11 @@ uint64_t TargetData::getIndexedOffset(const Type *ptrTy, Value* const* Indices,
 
       // Update Ty to refer to current element
       Ty = STy->getElementType(FieldNo);
+    } else if (const UnionType *UnTy = dyn_cast<UnionType>(*TI)) {
+        unsigned FieldNo = cast<ConstantInt>(Indices[CurIDX])->getZExtValue();
+
+        // Offset into union is canonically 0, but type changes
+        Ty = UnTy->getElementType(FieldNo);
     } else {
       // Update Ty to refer to current element
       Ty = cast<SequentialType>(Ty)->getElementType();