introduce a new ISDNODE POISON

Author: diggerlin

llvm/include/llvm/CodeGen/ISDOpcodes.h

@@ -217,6 +217,9 @@ enum NodeType {
   /// UNDEF - An undefined node.
   UNDEF,
 
+  /// POISON - A poison node.
+  POISON,
+
   /// FREEZE - FREEZE(VAL) returns an arbitrary value if VAL is UNDEF (or
   /// is evaluated to UNDEF), or returns VAL otherwise. Note that each
   /// read of UNDEF can yield different value, but FREEZE(UNDEF) cannot.

llvm/include/llvm/CodeGen/SelectionDAG.h

@@ -873,7 +873,7 @@ class SelectionDAG {
   /// for integers, a type wider than) VT's element type.
   SDValue getSplatBuildVector(EVT VT, const SDLoc &DL, SDValue Op) {
     // VerifySDNode (via InsertNode) checks BUILD_VECTOR later.
-    if (Op.getOpcode() == ISD::UNDEF) {
+    if (Op.isUndefOrPoison()) {
       assert((VT.getVectorElementType() == Op.getValueType() ||
               (VT.isInteger() &&
                VT.getVectorElementType().bitsLE(Op.getValueType()))) &&
@@ -889,7 +889,7 @@ class SelectionDAG {
   // Return a splat ISD::SPLAT_VECTOR node, consisting of Op splatted to all
   // elements.
   SDValue getSplatVector(EVT VT, const SDLoc &DL, SDValue Op) {
-    if (Op.getOpcode() == ISD::UNDEF) {
+    if (Op.isUndefOrPoison()) {
       assert((VT.getVectorElementType() == Op.getValueType() ||
               (VT.isInteger() &&
                VT.getVectorElementType().bitsLE(Op.getValueType()))) &&
@@ -1130,6 +1130,9 @@ class SelectionDAG {
     return getNode(ISD::UNDEF, SDLoc(), VT);
   }
 
+  /// Return an POISON node. POISON does not have a useful SDLoc.
+  SDValue getPoison(EVT VT) { return getNode(ISD::POISON, SDLoc(), VT); }
+
   /// Return a node that represents the runtime scaling 'MulImm * RuntimeVL'.
   SDValue getVScale(const SDLoc &DL, EVT VT, APInt MulImm,
                     bool ConstantFold = true);

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -213,6 +213,7 @@ class SDValue {
   inline bool isTargetOpcode() const;
   inline bool isMachineOpcode() const;
   inline bool isUndef() const;
+  inline bool isUndefOrPoison() const;
   inline unsigned getMachineOpcode() const;
   inline const DebugLoc &getDebugLoc() const;
   inline void dump() const;
@@ -693,6 +694,14 @@ END_TWO_BYTE_PACK()
   /// Return true if the type of the node type undefined.
   bool isUndef() const { return NodeType == ISD::UNDEF; }
 
+  /// Return true if the type of the node type poison.
+  bool isPoison() const { return NodeType == ISD::POISON; }
+
+  /// Return true if the type of the node type undefined or poison.
+  bool isUndefOrPoison() const {
+    return NodeType == ISD::UNDEF || NodeType == ISD::POISON;
+  }
+
   /// Test if this node is a memory intrinsic (with valid pointer information).
   bool isMemIntrinsic() const { return SDNodeBits.IsMemIntrinsic; }
 
@@ -1250,6 +1259,8 @@ inline bool SDValue::isUndef() const {
   return Node->isUndef();
 }
 
+inline bool SDValue::isUndefOrPoison() const { return Node->isUndefOrPoison(); }
+
 inline bool SDValue::use_empty() const {
   return !Node->hasAnyUseOfValue(ResNo);
 }