[DAG] SDPatternMatch m_Zero/m_One/m_AllOnes have inconsistent undef handling

Author: woruyu

llvm/include/llvm/CodeGen/SDPatternMatch.h

@@ -1100,19 +1100,46 @@ inline SpecificInt_match m_SpecificInt(uint64_t V) {
   return SpecificInt_match(APInt(64, V));
 }
 
-inline SpecificInt_match m_Zero() { return m_SpecificInt(0U); }
-inline SpecificInt_match m_One() { return m_SpecificInt(1U); }
+struct Zero_match {
+  bool AllowUndefs;
+
+  explicit Zero_match(bool AllowUndefs) : AllowUndefs(AllowUndefs) {}
+
+  template <typename MatchContext>
+  bool match(const MatchContext &, SDValue N) const {
+    return isZeroOrZeroSplat(N, AllowUndefs);
+  }
+};
+
+struct Ones_match {
+  bool AllowUndefs;
+
+  Ones_match(bool AllowUndefs) : AllowUndefs(AllowUndefs) {}
+
+  template <typename MatchContext> bool match(const MatchContext &, SDValue N) {
+    return isOnesOrOnesSplat(N, AllowUndefs);
+  }
+};
 
 struct AllOnes_match {
+  bool AllowUndefs;
 
-  AllOnes_match() = default;
+  AllOnes_match(bool AllowUndefs) : AllowUndefs(AllowUndefs) {}
 
   template <typename MatchContext> bool match(const MatchContext &, SDValue N) {
-    return isAllOnesOrAllOnesSplat(N);
+    return isAllOnesOrAllOnesSplat(N, AllowUndefs);
   }
 };
 
-inline AllOnes_match m_AllOnes() { return AllOnes_match(); }
+inline Ones_match m_One(bool AllowUndefs = false) {
+  return Ones_match(AllowUndefs);
+}
+inline Zero_match m_Zero(bool AllowUndefs = false) {
+  return Zero_match(AllowUndefs);
+}
+inline AllOnes_match m_AllOnes(bool AllowUndefs = false) {
+  return AllOnes_match(AllowUndefs);
+}
 
 /// Match true boolean value based on the information provided by
 /// TargetLowering.
@@ -1189,7 +1216,7 @@ inline CondCode_match m_SpecificCondCode(ISD::CondCode CC) {
 
 /// Match a negate as a sub(0, v)
 template <typename ValTy>
-inline BinaryOpc_match<SpecificInt_match, ValTy> m_Neg(const ValTy &V) {
+inline BinaryOpc_match<Zero_match, ValTy, false> m_Neg(const ValTy &V) {
   return m_Sub(m_Zero(), V);
 }
 

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -1937,6 +1937,10 @@ LLVM_ABI bool isOneOrOneSplat(SDValue V, bool AllowUndefs = false);
 /// Does not permit build vector implicit truncation.
 LLVM_ABI bool isAllOnesOrAllOnesSplat(SDValue V, bool AllowUndefs = false);
 
+LLVM_ABI bool isOnesOrOnesSplat(SDValue N, bool AllowUndefs = false);
+
+LLVM_ABI bool isZeroOrZeroSplat(SDValue N, bool AllowUndefs = false);
+
 /// Return true if \p V is either a integer or FP constant.
 inline bool isIntOrFPConstant(SDValue V) {
   return isa<ConstantSDNode>(V) || isa<ConstantFPSDNode>(V);

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -4281,7 +4281,7 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
     return V;
 
   // (A - B) - 1  ->  add (xor B, -1), A
-  if (sd_match(N, m_Sub(m_OneUse(m_Sub(m_Value(A), m_Value(B))), m_One())))
+  if (sd_match(N, m_Sub(m_OneUse(m_Sub(m_Value(A), m_Value(B))), m_One(true))))
     return DAG.getNode(ISD::ADD, DL, VT, A, DAG.getNOT(DL, B, VT));
 
   // Look for:

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -12569,6 +12569,18 @@ bool llvm::isAllOnesOrAllOnesSplat(SDValue N, bool AllowUndefs) {
   return C && C->isAllOnes() && C->getValueSizeInBits(0) == BitWidth;
 }
 
+bool llvm::isOnesOrOnesSplat(SDValue N, bool AllowUndefs) {
+  N = peekThroughBitcasts(N);
+  ConstantSDNode *C = isConstOrConstSplat(N, AllowUndefs);
+  return C && C->getAPIntValue() == 1;
+}
+
+bool llvm::isZeroOrZeroSplat(SDValue N, bool AllowUndefs) {
+  N = peekThroughBitcasts(N);
+  ConstantSDNode *C = isConstOrConstSplat(N, AllowUndefs, true);
+  return C && C->isZero();
+}
+
 HandleSDNode::~HandleSDNode() {
   DropOperands();
 }

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -57925,22 +57925,20 @@ static SDValue combineAdd(SDNode *N, SelectionDAG &DAG,
     }
   }
 
+  SDValue X, Y;
+
   // add(psadbw(X,0),psadbw(Y,0)) -> psadbw(add(X,Y),0)
   // iff X and Y won't overflow.
-  if (Op0.getOpcode() == X86ISD::PSADBW && Op1.getOpcode() == X86ISD::PSADBW &&
-      ISD::isBuildVectorAllZeros(Op0.getOperand(1).getNode()) &&
-      ISD::isBuildVectorAllZeros(Op1.getOperand(1).getNode())) {
-    if (DAG.willNotOverflowAdd(false, Op0.getOperand(0), Op1.getOperand(0))) {
-      MVT OpVT = Op0.getOperand(1).getSimpleValueType();
-      SDValue Sum =
-          DAG.getNode(ISD::ADD, DL, OpVT, Op0.getOperand(0), Op1.getOperand(0));
-      return DAG.getNode(X86ISD::PSADBW, DL, VT, Sum,
-                         getZeroVector(OpVT, Subtarget, DAG, DL));
-    }
+  if (sd_match(Op0, m_c_BinOp(X86ISD::PSADBW, m_Value(X), m_Zero())) &&
+      sd_match(Op1, m_c_BinOp(X86ISD::PSADBW, m_Value(Y), m_Zero())) &&
+      DAG.willNotOverflowAdd(/*IsSigned=*/false, X, Y)) {
+    MVT OpVT = X.getSimpleValueType();
+    SDValue Sum = DAG.getNode(ISD::ADD, DL, OpVT, X, Y);
+    return DAG.getNode(X86ISD::PSADBW, DL, VT, Sum,
+                       getZeroVector(OpVT, Subtarget, DAG, DL));
   }
 
   if (VT.isVector()) {
-    SDValue X, Y;
     EVT BoolVT = EVT::getVectorVT(*DAG.getContext(), MVT::i1,
                                   VT.getVectorElementCount());