[KnownBits] Add KnownBits::haveNoCommonBitsSet helper. NFCI.

Include exhaustive test coverage.

include/llvm/Support/KnownBits.h

@@ -285,6 +285,11 @@ public:
     return KnownBits(LHS.Zero & RHS.Zero, LHS.One & RHS.One);
   }
 
+  /// Return true if LHS and RHS have no common bits set.
+  static bool haveNoCommonBitsSet(const KnownBits &LHS, const KnownBits &RHS) {
+    return (LHS.Zero | RHS.Zero).isAllOnesValue();
+  }
+
   /// Compute known bits resulting from adding LHS, RHS and a 1-bit Carry.
   static KnownBits computeForAddCarry(
       const KnownBits &LHS, const KnownBits &RHS, const KnownBits &Carry);

lib/Analysis/ValueTracking.cpp

@@ -301,7 +301,7 @@ bool llvm::haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
   KnownBits RHSKnown(IT->getBitWidth());
   computeKnownBits(LHS, LHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
   computeKnownBits(RHS, RHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
-  return (LHSKnown.Zero | RHSKnown.Zero).isAllOnesValue();
+  return KnownBits::haveNoCommonBitsSet(LHSKnown, RHSKnown);
 }
 
 bool llvm::isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI) {

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -4351,7 +4351,8 @@ bool SelectionDAG::isEqualTo(SDValue A, SDValue B) const {
 bool SelectionDAG::haveNoCommonBitsSet(SDValue A, SDValue B) const {
   assert(A.getValueType() == B.getValueType() &&
          "Values must have the same type");
-  return (computeKnownBits(A).Zero | computeKnownBits(B).Zero).isAllOnesValue();
+  return KnownBits::haveNoCommonBitsSet(computeKnownBits(A),
+                                        computeKnownBits(B));
 }
 
 static SDValue FoldSTEP_VECTOR(const SDLoc &DL, EVT VT, SDValue Step,

unittests/Support/KnownBitsTest.cpp

@@ -463,4 +463,20 @@ TEST(KnownBitsTest, SExtInReg) {
   }
 }
 
+TEST(KnownBitsTest, CommonBitsSet) {
+  unsigned Bits = 4;
+  ForeachKnownBits(Bits, [&](const KnownBits &Known1) {
+    ForeachKnownBits(Bits, [&](const KnownBits &Known2) {
+      bool HasCommonBitsSet = false;
+      ForeachNumInKnownBits(Known1, [&](const APInt &N1) {
+        ForeachNumInKnownBits(Known2, [&](const APInt &N2) {
+          HasCommonBitsSet |= N1.intersects(N2);
+        });
+      });
+      EXPECT_EQ(!HasCommonBitsSet,
+                KnownBits::haveNoCommonBitsSet(Known1, Known2));
+    });
+  });
+}
+
 } // end anonymous namespace