AMDGPU: Don't promote arcp to unsafe math flag

[arsenm]

Summary

If only arcp was allowed, this was enabling unsafe math on the
resulting nodes. Preserve the original unsafe math flags.

lib/Target/AMDGPU/SIISelLowering.cpp

if (Unsafe || (VT == MVT::f32 && !Subtarget->hasFP32Denormals()) ||
         // -1.0 / x -> rcp (fneg x)
         SDValue FNegRHS = DAG.getNode(ISD::FNEG, SL, VT, RHS);
         return DAG.getNode(AMDGPUISD::RCP, SL, VT, FNegRHS);
       }
     }
   }
 
   const SDNodeFlags *Flags = Op->getFlags();
-
   if (Unsafe || Flags->hasAllowReciprocal()) {
     // Turn into multiply by the reciprocal.
     // x / y -> x * (1.0 / y)
-    SDNodeFlags Flags;
-    Flags.setUnsafeAlgebra(true);
     SDValue Recip = DAG.getNode(AMDGPUISD::RCP, SL, VT, RHS);
-    return DAG.getNode(ISD::FMUL, SL, VT, LHS, Recip, &Flags);
+    return DAG.getNode(ISD::FMUL, SL, VT, LHS, Recip, Flags);
   }
 
   return SDValue();
 }
 
 static SDValue getFPBinOp(SelectionDAG &DAG, unsigned Opcode, const SDLoc &SL,
                           EVT VT, SDValue A, SDValue B, SDValue GlueChain) {
   if (GlueChain->getNumValues() <= 1) {