+ if (LHSHi == RHSHi) {
+ // Comparing the low bits is enough.
+ NewLHS = Tmp1;
+ NewRHS = SDValue();
+ return;
+ }
+
+ // Lower with SETCCE if the target supports it.
+ // FIXME: Make all targets support this, then remove the other lowering.
+ if (TLI.getOperationAction(
+ ISD::SETCCE,
+ TLI.getTypeToExpandTo(*DAG.getContext(), LHSLo.getValueType())) ==
+ TargetLowering::Custom) {
+ // SETCCE can detect < and >= directly. For > and <=, flip operands and
+ // condition code.
+ bool FlipOperands = false;
+ switch (CCCode) {
+ case ISD::SETGT: CCCode = ISD::SETLT; FlipOperands = true; break;
+ case ISD::SETUGT: CCCode = ISD::SETULT; FlipOperands = true; break;
+ case ISD::SETLE: CCCode = ISD::SETGE; FlipOperands = true; break;
+ case ISD::SETULE: CCCode = ISD::SETUGE; FlipOperands = true; break;
+ default: break;
+ }
+ if (FlipOperands) {
+ std::swap(LHSLo, RHSLo);
+ std::swap(LHSHi, RHSHi);
+ }
+ // Perform a wide subtraction, feeding the carry from the low part into
+ // SETCCE. The SETCCE operation is essentially looking at the high part of
+ // the result of LHS - RHS. It is negative iff LHS < RHS. It is zero or
+ // positive iff LHS >= RHS.
+ SDVTList VTList = DAG.getVTList(LHSLo.getValueType(), MVT::Glue);
+ SDValue LowCmp = DAG.getNode(ISD::SUBC, dl, VTList, LHSLo, RHSLo);
+ SDValue Res =
+ DAG.getNode(ISD::SETCCE, dl, getSetCCResultType(LHSLo.getValueType()),
+ LHSHi, RHSHi, LowCmp.getValue(1), DAG.getCondCode(CCCode));
+ NewLHS = Res;
+ NewRHS = SDValue();
+ return;
+ }
+