bool DAGCombiner::SimplifyDemandedBits(SDValue Op, const APInt &Demanded) {
TargetLowering::TargetLoweringOpt TLO(DAG, LegalTypes, LegalOperations);
APInt KnownZero, KnownOne;
+
+ // XXX-disabled:
+ auto Opcode = Op.getOpcode();
+ if (Opcode == ISD::AND || Opcode == ISD::OR) {
+ auto* Op1 = Op.getOperand(0).getNode();
+ auto* Op2 = Op.getOperand(1).getNode();
+ auto* Op1C = dyn_cast<ConstantSDNode>(Op1);
+ auto* Op2C = dyn_cast<ConstantSDNode>(Op2);
+
+ // and X, 0
+ if (Opcode == ISD::AND && !Op1C && Op2C && Op2C->isNullValue()) {
+ return false;
+ }
+
+ // or (and X, 0), Y
+ if (Opcode == ISD::OR) {
+ if (Op1->getOpcode() == ISD::AND) {
+ auto* Op11 = Op1->getOperand(0).getNode();
+ auto* Op12 = Op1->getOperand(1).getNode();
+ auto* Op11C = dyn_cast<ConstantSDNode>(Op11);
+ auto* Op12C = dyn_cast<ConstantSDNode>(Op12);
+ if (!Op11C && Op12C && Op12C->isNullValue()) {
+ return false;
+ }
+ }
+ if (Op1->getOpcode() == ISD::TRUNCATE) {
+ // or (trunc (and %0, 0)), Y
+ auto* Op11 = Op1->getOperand(0).getNode();
+ if (Op11->getOpcode() == ISD::AND) {
+ auto* Op111 = Op11->getOperand(0).getNode();
+ auto* Op112 = Op11->getOperand(1).getNode();
+ auto* Op111C = dyn_cast<ConstantSDNode>(Op111);
+ auto* Op112C = dyn_cast<ConstantSDNode>(Op112);
+ if (!Op111C && Op112C && Op112C->isNullValue()) {
+ // or (and X, 0), Y
+ return false;
+ }
+ }
+ }
+ }
+ }
+
+ // trunc (and X, 0)
+ if (Opcode == ISD::TRUNCATE) {
+ auto* Op1 = Op.getOperand(0).getNode();
+ if (Op1->getOpcode() == ISD::AND) {
+ auto* Op11 = Op1->getOperand(0).getNode();
+ auto* Op12 = Op1->getOperand(1).getNode();
+ auto* Op11C = dyn_cast<ConstantSDNode>(Op11);
+ auto* Op12C = dyn_cast<ConstantSDNode>(Op12);
+ if (!Op11C && Op12C && Op12C->isNullValue()) {
+ return false;
+ }
+ }
+ }
+
if (!TLI.SimplifyDemandedBits(Op, Demanded, KnownZero, KnownOne, TLO))
return false;
// fold (and c1, c2) -> c1&c2
ConstantSDNode *N0C = getAsNonOpaqueConstant(N0);
ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
+
+ // XXX-disabled: (and x, 0) should not be folded.
+ if (!N0C && N1C->isNullValue()) {
+ return SDValue();
+ }
+
if (N0C && N1C && !N1C->isOpaque())
return DAG.FoldConstantArithmetic(ISD::AND, SDLoc(N), VT, N0C, N1C);
// canonicalize constant to RHS