SDValue DAGCombiner::visitFSQRT(SDNode *N) {
if (DAG.getTarget().Options.UnsafeFPMath) {
- // Compute this as 1/(1/sqrt(X)): the reciprocal of the reciprocal sqrt.
+ // Compute this as X * (1/sqrt(X)) = X * (X ** -0.5)
if (SDValue RV = BuildRsqrtEstimate(N->getOperand(0))) {
AddToWorklist(RV.getNode());
- RV = BuildReciprocalEstimate(RV);
- if (RV.getNode()) {
- // Unfortunately, RV is now NaN if the input was exactly 0.
- // Select out this case and force the answer to 0.
- EVT VT = RV.getValueType();
-
- SDValue Zero = DAG.getConstantFP(0.0, VT);
- SDValue ZeroCmp =
- DAG.getSetCC(SDLoc(N), TLI.getSetCCResultType(*DAG.getContext(), VT),
- N->getOperand(0), Zero, ISD::SETEQ);
- AddToWorklist(ZeroCmp.getNode());
- AddToWorklist(RV.getNode());
+ EVT VT = RV.getValueType();
+ RV = DAG.getNode(ISD::FMUL, SDLoc(N), VT, N->getOperand(0), RV);
+ AddToWorklist(RV.getNode());
- RV = DAG.getNode(VT.isVector() ? ISD::VSELECT : ISD::SELECT,
- SDLoc(N), VT, ZeroCmp, Zero, RV);
- return RV;
- }
+ // Unfortunately, RV is now NaN if the input was exactly 0.
+ // Select out this case and force the answer to 0.
+ SDValue Zero = DAG.getConstantFP(0.0, VT);
+ SDValue ZeroCmp =
+ DAG.getSetCC(SDLoc(N), TLI.getSetCCResultType(*DAG.getContext(), VT),
+ N->getOperand(0), Zero, ISD::SETEQ);
+ AddToWorklist(ZeroCmp.getNode());
+ AddToWorklist(RV.getNode());
+
+ RV = DAG.getNode(VT.isVector() ? ISD::VSELECT : ISD::SELECT,
+ SDLoc(N), VT, ZeroCmp, Zero, RV);
+ return RV;
}
}
return SDValue();