Revert "[DAGCombine] Fold redundant select"

This reverts commit bbdf243.

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -10956,73 +10956,6 @@ SDValue DAGCombiner::visitSELECT(SDNode *N) {
       }
     }
 
-    // If we have a chain of two selects, which share a true/false value and
-    // both are controlled from the two setcc nodes which cannot produce the
-    // same value, we can fold away N.
-    // select (setcc X), Y, (select (setcc X), Z, Y) -> select (setcc X), Z, Y
-    auto IsSelect = [](SDValue Op) {
-      return Op->getOpcode() == ISD::SELECT;
-    };
-    if ((IsSelect(N1) || IsSelect(N2)) && (N1.getOpcode() != N2.getOpcode())) {
-      auto AreSame = [](SDValue Op0, SDValue Op1) {
-        if (Op0 == Op1)
-          return true;
-        auto *C0 = dyn_cast<ConstantSDNode>(Op0);
-        auto *C1 = dyn_cast<ConstantSDNode>(Op1);
-        return C0 && C1 &&
-               APInt::isSameValue(C0->getAPIntValue(), C1->getAPIntValue());
-      };
-
-      SDValue OtherSelect;
-      bool SelectsShareOp = false;
-      if (IsSelect(N1)) {
-        OtherSelect = N1;
-        SelectsShareOp = AreSame(OtherSelect.getOperand(1), N2);
-      } else {
-        OtherSelect = N2;
-        SelectsShareOp = AreSame(OtherSelect.getOperand(2), N1);
-      }
-
-      auto CanNeverBeEqual = [](SDValue SetCC0, SDValue SetCC1) {
-        if (SetCC0->getOpcode() != ISD::SETCC ||
-            SetCC1->getOpcode() != ISD::SETCC ||
-            SetCC0->getOperand(0) != SetCC1->getOperand(0))
-          return false;
-
-        ISD::CondCode CC0 = cast<CondCodeSDNode>(SetCC0.getOperand(2))->get();
-        ISD::CondCode CC1 = cast<CondCodeSDNode>(SetCC1.getOperand(2))->get();
-        auto *C0 = dyn_cast<ConstantSDNode>(SetCC0.getOperand(1));
-        auto *C1 = dyn_cast<ConstantSDNode>(SetCC1.getOperand(1));
-        if (!C0 || !C1)
-          return false;
-
-        bool ConstantsAreSame =
-          APInt::isSameValue(C0->getAPIntValue(), C1->getAPIntValue());
-        auto IsEqual = [](ISD::CondCode CC) {
-          return CC == ISD::SETEQ;
-        };
-        auto IsNotEqual = [](ISD::CondCode CC) {
-          return CC == ISD::SETLT || CC == ISD::SETULT ||
-                 CC == ISD::SETGT || CC == ISD::SETUGT ||
-                 CC == ISD::SETNE;
-        };
-
-        if (ConstantsAreSame && IsNotEqual(CC0) && IsEqual(CC1))
-          return true;
-        if (ConstantsAreSame && IsNotEqual(CC1) && IsEqual(CC0))
-          return true;
-        if (!ConstantsAreSame && IsEqual(CC0) && IsEqual(CC1))
-          return true;
-
-        return false;
-      };
-
-      SDValue SetCC0 = N0;
-      SDValue SetCC1 = OtherSelect.getOperand(0);
-      if (SelectsShareOp && CanNeverBeEqual(SetCC0, SetCC1))
-        return OtherSelect;
-    }
-
     if (TLI.isOperationLegal(ISD::SELECT_CC, VT) ||
         (!LegalOperations &&
          TLI.isOperationLegalOrCustom(ISD::SELECT_CC, VT))) {