================
@@ -8900,6 +8900,83 @@ SDValue PPCTargetLowering::LowerINT_TO_FP(SDValue Op,
return FP;
}
+SDValue PPCTargetLowering::LowerSET_ROUNDING(SDValue Op,
+ SelectionDAG &DAG) const {
+ SDLoc Dl(Op);
+ MachineFunction &MF = DAG.getMachineFunction();
+ EVT PtrVT = getPointerTy(MF.getDataLayout());
+ SDValue Chain = Op.getOperand(0);
+
+ // If requested mode is constant, just use simpler mtfsb.
+ if (auto *CVal = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
+ uint64_t Mode = CVal->getZExtValue();
+ if (Mode >= 4)
+ llvm_unreachable("Unsupported rounding mode!");
+ unsigned InternalRnd = Mode ^ (~(Mode >> 1) & 1);
+ SDNode *SetHi = DAG.getMachineNode(
+ (InternalRnd & 2) ? PPC::MTFSB1 : PPC::MTFSB0, Dl, MVT::Other,
+ {DAG.getConstant(30, Dl, MVT::i32, true), Chain});
+ SDNode *SetLo = DAG.getMachineNode(
+ (InternalRnd & 1) ? PPC::MTFSB1 : PPC::MTFSB0, Dl, MVT::Other,
+ {DAG.getConstant(31, Dl, MVT::i32, true), SDValue(SetHi, 0)});
+ return SDValue(SetLo, 0);
+ }
+
+ // Use x ^ (~(x >> 1) & 1) to transform LLVM rounding mode to Power format.
+ SDValue One = DAG.getConstant(1, Dl, MVT::i32);
+ SDValue SrcFlag = DAG.getNode(ISD::AND, Dl, MVT::i32, Op.getOperand(1),
+ DAG.getConstant(3, Dl, MVT::i32));
+ SDValue DstFlag = DAG.getNode(
+ ISD::XOR, Dl, MVT::i32, SrcFlag,
+ DAG.getNode(ISD::AND, Dl, MVT::i32,
+ DAG.getNOT(Dl,
+ DAG.getNode(ISD::SRL, Dl, MVT::i32, SrcFlag, One),
+ MVT::i32),
+ One));
+ SDValue MFFS = DAG.getNode(PPCISD::MFFS, Dl, {MVT::f64, MVT::Other}, Chain);
+ Chain = MFFS.getValue(1);
+ SDValue NewFPSCR;
+ if (isTypeLegal(MVT::i64)) {
+ // Set the last two bits (rounding mode) of bitcasted FPSCR.
+ NewFPSCR = DAG.getNode(
+ ISD::OR, Dl, MVT::i64,
+ DAG.getNode(ISD::AND, Dl, MVT::i64,
+ DAG.getNode(ISD::BITCAST, Dl, MVT::i64, MFFS),
+ DAG.getNOT(Dl, DAG.getConstant(3, Dl, MVT::i64),
MVT::i64)),
+ DAG.getNode(ISD::ZERO_EXTEND, Dl, MVT::i64, DstFlag));
----------------
spavloff wrote:
Is there guarantee that the upper bits (63-2) of `DestFlag` are zeros?
https://github.com/llvm/llvm-project/pull/67302
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