[DAG] SDPatternMatch m_Zero/m_One/m_AllOnes have inconsistent undef h… (#147044)

### Summary
This PR resolves https://github.com/llvm/llvm-project/issues/146871 
This PR resolves https://github.com/llvm/llvm-project/issues/140745

Refactor m_Zero/m_One/m_AllOnes all use struct template function to
match and AllowUndefs=false as default.

5 files changed, 143 insertions, 7 deletions

diff --git a/llvm/include/llvm/CodeGen/SDPatternMatch.h b/llvm/include/llvm/CodeGen/SDPatternMatch.h
index 35322c3..7c5cdbb 100644
--- a/llvm/include/llvm/CodeGen/SDPatternMatch.h
+++ b/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);
 }
 
diff --git a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
index a3675ee..5d9937f 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -1937,6 +1937,16 @@ 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);
 
+/// Return true if the value is a constant 1 integer or a splatted vector of a
+/// constant 1 integer (with no undefs).
+/// Does not permit build vector implicit truncation.
+LLVM_ABI bool isOnesOrOnesSplat(SDValue N, bool AllowUndefs = false);
+
+/// Return true if the value is a constant 0 integer or a splatted vector of a
+/// constant 0 integer (with no undefs).
+/// Does not permit build vector implicit truncation.
+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);
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a10f9af..e7f1fdf 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4280,7 +4280,8 @@ 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(/*AllowUndefs=*/true))))
     return DAG.getNode(ISD::ADD, DL, VT, A, DAG.getNOT(DL, B, VT));
 
   // Look for:
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index a0f4c49..2a8bda5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -12644,6 +12644,18 @@ bool llvm::isAllOnesOrAllOnesSplat(SDValue N, bool AllowUndefs) {
   return C && C->isAllOnes() && C->getValueSizeInBits(0) == BitWidth;
 }
 
+bool llvm::isOnesOrOnesSplat(SDValue N, bool AllowUndefs) {
+  ConstantSDNode *C = isConstOrConstSplat(N, AllowUndefs);
+  return C && APInt::isSameValue(C->getAPIntValue(),
+                                 APInt(C->getAPIntValue().getBitWidth(), 1));
+}
+
+bool llvm::isZeroOrZeroSplat(SDValue N, bool AllowUndefs) {
+  N = peekThroughBitcasts(N);
+  ConstantSDNode *C = isConstOrConstSplat(N, AllowUndefs, true);
+  return C && C->isZero();
+}
+
 HandleSDNode::~HandleSDNode() {
   DropOperands();
 }
diff --git a/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp b/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
index baee286..dc531e6 100644
--- a/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
+++ b/llvm/unittests/CodeGen/SelectionDAGPatternMatchTest.cpp
@@ -825,3 +825,89 @@ TEST_F(SelectionDAGPatternMatchTest, matchReassociatableOp) {
   EXPECT_FALSE(sd_match(
       ORS0123, m_ReassociatableOr(m_Value(), m_Value(), m_Value(), m_Value())));
 }
+
+TEST_F(SelectionDAGPatternMatchTest, MatchZeroOneAllOnes) {
+  using namespace SDPatternMatch;
+
+  SDLoc DL;
+  EVT VT = EVT::getIntegerVT(Context, 32);
+
+  // Scalar constant 0
+  SDValue Zero = DAG->getConstant(0, DL, VT);
+  EXPECT_TRUE(sd_match(Zero, DAG.get(), llvm::SDPatternMatch::m_Zero()));
+  EXPECT_FALSE(sd_match(Zero, DAG.get(), m_One()));
+  EXPECT_FALSE(sd_match(Zero, DAG.get(), m_AllOnes()));
+
+  // Scalar constant 1
+  SDValue One = DAG->getConstant(1, DL, VT);
+  EXPECT_FALSE(sd_match(One, DAG.get(), m_Zero()));
+  EXPECT_TRUE(sd_match(One, DAG.get(), m_One()));
+  EXPECT_FALSE(sd_match(One, DAG.get(), m_AllOnes()));
+
+  // Scalar constant -1
+  SDValue AllOnes =
+      DAG->getConstant(APInt::getAllOnes(VT.getSizeInBits()), DL, VT);
+  EXPECT_FALSE(sd_match(AllOnes, DAG.get(), m_Zero()));
+  EXPECT_FALSE(sd_match(AllOnes, DAG.get(), m_One()));
+  EXPECT_TRUE(sd_match(AllOnes, DAG.get(), m_AllOnes()));
+
+  EVT VecF32 = EVT::getVectorVT(Context, MVT::f32, 4);
+  EVT VecVT = EVT::getVectorVT(Context, MVT::i32, 4);
+
+  // m_Zero: splat vector of 0 → bitcast
+  {
+    SDValue SplatVal = DAG->getConstant(0, DL, MVT::i32);
+    SDValue VecSplat = DAG->getSplatBuildVector(VecVT, DL, SplatVal);
+    SDValue Bitcasted = DAG->getNode(ISD::BITCAST, DL, VecF32, VecSplat);
+    EXPECT_TRUE(sd_match(Bitcasted, DAG.get(), m_Zero()));
+  }
+
+  // m_One: splat vector of 1 → bitcast
+  {
+    SDValue SplatVal = DAG->getConstant(1, DL, MVT::i32);
+    SDValue VecSplat = DAG->getSplatBuildVector(VecVT, DL, SplatVal);
+    SDValue Bitcasted = DAG->getNode(ISD::BITCAST, DL, VecF32, VecSplat);
+    EXPECT_FALSE(sd_match(Bitcasted, DAG.get(), m_One()));
+  }
+
+  // m_AllOnes: splat vector of -1 → bitcast
+  {
+    SDValue SplatVal = DAG->getConstant(APInt::getAllOnes(32), DL, MVT::i32);
+    SDValue VecSplat = DAG->getSplatBuildVector(VecVT, DL, SplatVal);
+    SDValue Bitcasted = DAG->getNode(ISD::BITCAST, DL, VecF32, VecSplat);
+    EXPECT_TRUE(sd_match(Bitcasted, DAG.get(), m_AllOnes()));
+  }
+
+  // splat vector with one undef → default should NOT match
+  SDValue Undef = DAG->getUNDEF(MVT::i32);
+
+  {
+    // m_Zero: Undef + constant 0
+    SDValue Zero = DAG->getConstant(0, DL, MVT::i32);
+    SmallVector<SDValue, 4> Ops(4, Zero);
+    Ops[2] = Undef;
+    SDValue Vec = DAG->getBuildVector(VecVT, DL, Ops);
+    EXPECT_FALSE(sd_match(Vec, DAG.get(), m_Zero()));
+    EXPECT_TRUE(sd_match(Vec, DAG.get(), m_Zero(true)));
+  }
+
+  {
+    // m_One: Undef + constant 1
+    SDValue One = DAG->getConstant(1, DL, MVT::i32);
+    SmallVector<SDValue, 4> Ops(4, One);
+    Ops[1] = Undef;
+    SDValue Vec = DAG->getBuildVector(VecVT, DL, Ops);
+    EXPECT_FALSE(sd_match(Vec, DAG.get(), m_One()));
+    EXPECT_TRUE(sd_match(Vec, DAG.get(), m_One(true)));
+  }
+
+  {
+    // m_AllOnes: Undef + constant -1
+    SDValue AllOnes = DAG->getConstant(APInt::getAllOnes(32), DL, MVT::i32);
+    SmallVector<SDValue, 4> Ops(4, AllOnes);
+    Ops[0] = Undef;
+    SDValue Vec = DAG->getBuildVector(VecVT, DL, Ops);
+    EXPECT_FALSE(sd_match(Vec, DAG.get(), m_AllOnes()));
+    EXPECT_TRUE(sd_match(Vec, DAG.get(), m_AllOnes(true)));
+  }
+}