Add PTD version of getParticleCell (#3675)

The proposed changes:
- [ ] fix a bug or incorrect behavior in AMReX
- [x] add new capabilities to AMReX
- [ ] changes answers in the test suite to more than roundoff level
- [ ] are likely to significantly affect the results of downstream AMReX
users
- [ ] include documentation in the code and/or rst files, if appropriate

Author: atmyers

Src/Particle/AMReX_ParticleUtil.H

@@ -371,6 +371,26 @@ IntVect getParticleCell (P const& p,
     return iv;
 }
 
+template <typename PTD>
+AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+IntVect getParticleCell (PTD const& ptd, int i,
+                         amrex::GpuArray<amrex::Real,AMREX_SPACEDIM> const& plo,
+                         amrex::GpuArray<amrex::Real,AMREX_SPACEDIM> const& dxi,
+                         const Box& domain) noexcept
+{
+    if constexpr (PTD::ParticleType::is_soa_particle)
+    {
+        IntVect iv(
+                   AMREX_D_DECL(int(amrex::Math::floor((ptd.m_rdata[0][i]-plo[0])*dxi[0])),
+                                int(amrex::Math::floor((ptd.m_rdata[1][i]-plo[1])*dxi[1])),
+                                int(amrex::Math::floor((ptd.m_rdata[2][i]-plo[2])*dxi[2]))));
+        iv += domain.smallEnd();
+        return iv;
+    } else {
+        return getParticleCell(ptd.m_aos[i], plo, dxi, domain);;
+    }
+}
+
 struct DefaultAssignor
 {