+// When CR bit registers are enabled, an extension of an i1 variable to a i32
+// or i64 value is lowered in terms of a SELECT_I[48] operation, and thus
+// involves constant materialization of a 0 or a 1 or both. If the result of
+// the extension is then operated upon by some operator that can be constant
+// folded with a constant 0 or 1, and that constant can be materialized using
+// only one instruction (like a zero or one), then we should fold in those
+// operations with the select.
+void PPCDAGToDAGISel::foldBoolExts(SDValue &Res, SDNode *&N) {
+ if (!PPCSubTarget->useCRBits())
+ return;
+
+ if (N->getOpcode() != ISD::ZERO_EXTEND &&
+ N->getOpcode() != ISD::SIGN_EXTEND &&
+ N->getOpcode() != ISD::ANY_EXTEND)
+ return;
+
+ if (N->getOperand(0).getValueType() != MVT::i1)
+ return;
+
+ if (!N->hasOneUse())
+ return;
+
+ SDLoc dl(N);
+ EVT VT = N->getValueType(0);
+ SDValue Cond = N->getOperand(0);
+ SDValue ConstTrue =
+ CurDAG->getConstant(N->getOpcode() == ISD::SIGN_EXTEND ? -1 : 1, dl, VT);
+ SDValue ConstFalse = CurDAG->getConstant(0, dl, VT);
+
+ do {
+ SDNode *User = *N->use_begin();
+ if (User->getNumOperands() != 2)
+ break;
+
+ auto TryFold = [this, N, User, dl](SDValue Val) {
+ SDValue UserO0 = User->getOperand(0), UserO1 = User->getOperand(1);
+ SDValue O0 = UserO0.getNode() == N ? Val : UserO0;
+ SDValue O1 = UserO1.getNode() == N ? Val : UserO1;
+
+ return CurDAG->FoldConstantArithmetic(User->getOpcode(), dl,
+ User->getValueType(0),
+ O0.getNode(), O1.getNode());
+ };
+
+ SDValue TrueRes = TryFold(ConstTrue);
+ if (!TrueRes)
+ break;
+ SDValue FalseRes = TryFold(ConstFalse);
+ if (!FalseRes)
+ break;
+
+ // For us to materialize these using one instruction, we must be able to
+ // represent them as signed 16-bit integers.
+ uint64_t True = cast<ConstantSDNode>(TrueRes)->getZExtValue(),
+ False = cast<ConstantSDNode>(FalseRes)->getZExtValue();
+ if (!isInt<16>(True) || !isInt<16>(False))
+ break;
+
+ // We can replace User with a new SELECT node, and try again to see if we
+ // can fold the select with its user.
+ Res = CurDAG->getSelect(dl, User->getValueType(0), Cond, TrueRes, FalseRes);
+ N = User;
+ ConstTrue = TrueRes;
+ ConstFalse = FalseRes;
+ } while (N->hasOneUse());
+}
+