Make codegen able to handle values of empty types. This is one way

to fix PR9900. I will keep it open until sable is able to comment on it.

llvm-svn: 131294

llvm/include/llvm/Type.h

@@ -273,6 +273,9 @@ public:
   /// @brief Determine if this type could be losslessly bitcast to Ty
   bool canLosslesslyBitCastTo(const Type *Ty) const;
 
+  /// isEmptyTy - Return true if this type is empty, that is, it has no
+  /// elements or all its elements are empty.
+  bool isEmptyTy() const;
 
   /// Here are some useful little methods to query what type derived types are
   /// Note that all other types can just compare to see if this == Type::xxxTy;

llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp

@@ -155,6 +155,10 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
          const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
       if (PN->use_empty()) continue;
 
+      // Skip empty types
+      if (PN->getType()->isEmptyTy())
+        continue;
+
       DebugLoc DL = PN->getDebugLoc();
       unsigned PHIReg = ValueMap[PN];
       assert(PHIReg && "PHI node does not have an assigned virtual register!");

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -1175,6 +1175,10 @@ void SelectionDAGBuilder::visitRet(const ReturnInst &I) {
 /// created for it, emit nodes to copy the value into the virtual
 /// registers.
 void SelectionDAGBuilder::CopyToExportRegsIfNeeded(const Value *V) {
+  // Skip empty types
+  if (V->getType()->isEmptyTy())
+    return;
+
   DenseMap<const Value *, unsigned>::iterator VMI = FuncInfo.ValueMap.find(V);
   if (VMI != FuncInfo.ValueMap.end()) {
     assert(!V->use_empty() && "Unused value assigned virtual registers!");
@@ -2810,16 +2814,18 @@ void SelectionDAGBuilder::visitInsertValue(const InsertValueInst &I) {
   SmallVector<SDValue, 4> Values(NumAggValues);
 
   SDValue Agg = getValue(Op0);
-  SDValue Val = getValue(Op1);
   unsigned i = 0;
   // Copy the beginning value(s) from the original aggregate.
   for (; i != LinearIndex; ++i)
     Values[i] = IntoUndef ? DAG.getUNDEF(AggValueVTs[i]) :
                 SDValue(Agg.getNode(), Agg.getResNo() + i);
   // Copy values from the inserted value(s).
-  for (; i != LinearIndex + NumValValues; ++i)
-    Values[i] = FromUndef ? DAG.getUNDEF(AggValueVTs[i]) :
-                SDValue(Val.getNode(), Val.getResNo() + i - LinearIndex);
+  if (NumValValues) {
+    SDValue Val = getValue(Op1);
+    for (; i != LinearIndex + NumValValues; ++i)
+      Values[i] = FromUndef ? DAG.getUNDEF(AggValueVTs[i]) :
+                  SDValue(Val.getNode(), Val.getResNo() + i - LinearIndex);
+  }
   // Copy remaining value(s) from the original aggregate.
   for (; i != NumAggValues; ++i)
     Values[i] = IntoUndef ? DAG.getUNDEF(AggValueVTs[i]) :
@@ -2842,6 +2848,13 @@ void SelectionDAGBuilder::visitExtractValue(const ExtractValueInst &I) {
   ComputeValueVTs(TLI, ValTy, ValValueVTs);
 
   unsigned NumValValues = ValValueVTs.size();
+
+  // Ignore a extractvalue that produces an empty object
+  if (!NumValValues) {
+    setValue(&I, DAG.getUNDEF(MVT(MVT::Other)));
+    return;
+  }
+
   SmallVector<SDValue, 4> Values(NumValValues);
 
   SDValue Agg = getValue(Op0);
@@ -4827,8 +4840,14 @@ void SelectionDAGBuilder::LowerCallTo(ImmutableCallSite CS, SDValue Callee,
 
   for (ImmutableCallSite::arg_iterator i = CS.arg_begin(), e = CS.arg_end();
        i != e; ++i) {
-    SDValue ArgNode = getValue(*i);
-    Entry.Node = ArgNode; Entry.Ty = (*i)->getType();
+    const Value *V = *i;
+
+    // Skip empty types
+    if (V->getType()->isEmptyTy())
+      continue;
+
+    SDValue ArgNode = getValue(V);
+    Entry.Node = ArgNode; Entry.Ty = V->getType();
 
     unsigned attrInd = i - CS.arg_begin() + 1;
     Entry.isSExt  = CS.paramHasAttr(attrInd, Attribute::SExt);
@@ -6498,6 +6517,10 @@ SelectionDAGBuilder::HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB) {
       // Ignore dead phi's.
       if (PN->use_empty()) continue;
 
+      // Skip empty types
+      if (PN->getType()->isEmptyTy())
+        continue;
+
       unsigned Reg;
       const Value *PHIOp = PN->getIncomingValueForBlock(LLVMBB);
 

llvm/lib/VMCore/Type.cpp

@@ -197,6 +197,25 @@ bool Type::canLosslesslyBitCastTo(const Type *Ty) const {
   return false;  // Other types have no identity values
 }
 
+bool Type::isEmptyTy() const {
+  const ArrayType *ATy = dyn_cast<ArrayType>(this);
+  if (ATy) {
+    unsigned NumElements = ATy->getNumElements();
+    return NumElements == 0 || ATy->getElementType()->isEmptyTy();
+  }
+
+  const StructType *STy = dyn_cast<StructType>(this);
+  if (STy) {
+    unsigned NumElements = STy->getNumElements();
+    for (unsigned i = 0; i < NumElements; ++i)
+      if (!STy->getElementType(i)->isEmptyTy())
+        return false;
+    return true;
+  }
+
+  return false;
+}
+
 unsigned Type::getPrimitiveSizeInBits() const {
   switch (getTypeID()) {
   case Type::FloatTyID: return 32;

llvm/test/CodeGen/Generic/zero-sized-array.ll

@@ -0,0 +1,81 @@
+; RUN: llc < %s
+; PR9900
+
+%zero = type [0 x i8]
+%foobar = type { i32, %zero }
+
+define void @f(%foobar %arg) {
+  %arg1 = extractvalue %foobar %arg, 0
+  %arg2 = extractvalue %foobar %arg, 1
+  call i32 @f2(%zero %arg2, i32 5, i32 42)
+  ret void
+}
+
+define i32 @f2(%zero %x, i32 %y, i32 %z) {
+  ret i32 %y
+}
+
+define void @f3(%zero %x, i32 %y) {
+  call i32 @f2(%zero %x, i32 5, i32 %y)
+  ret void
+}
+
+define void @f4(%zero %z) {
+  insertvalue %foobar undef, %zero %z, 1
+  ret void
+}
+
+define void @f5(%foobar %x) {
+allocas:
+  %y = extractvalue %foobar %x, 1
+  br  label %b1
+
+b1:
+  %insert120 = insertvalue %foobar undef, %zero %y, 1
+  ret void
+}
+
+define void @f6(%zero %x, %zero %y) {
+b1:
+  br i1 undef, label %end, label %b2
+
+b2:
+  br label %end
+
+end:
+  %z = phi %zero [ %y, %b1 ], [ %x, %b2 ]
+  call void @f4(%zero %z)
+  ret void
+}
+
+%zero2 = type {}
+
+define i32 @g1(%zero2 %x, i32 %y, i32 %z) {
+  ret i32 %y
+}
+
+define void @g2(%zero2 %x, i32 %y) {
+  call i32 @g1(%zero2 %x, i32 5, i32 %y)
+  ret void
+}
+
+%zero2r = type {%zero2}
+
+define i32 @h1(%zero2r %x, i32 %y, i32 %z) {
+  ret i32 %y
+}
+
+define void @h2(%zero2r %x, i32 %y) {
+  call i32 @h1(%zero2r %x, i32 5, i32 %y)
+  ret void
+}
+
+%foobar2 = type { i32, %zero2r }
+
+define void @h3(%foobar2 %arg) {
+  %arg1 = extractvalue %foobar2 %arg, 0
+  %arg2 = extractvalue %foobar2 %arg, 1
+  %arg21 = extractvalue %zero2r %arg2, 0
+  call void @g2(%zero2 %arg21, i32 5)
+  ret void
+}