https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102043
--- Comment #41 from Richard Biener <rguenth at gcc dot gnu.org> --- -- random ideas dumping below -- so reading about ISO_Fortran_binding.h it seems to be that a base of the object isn't readily available and making it available would require quite some computation. staying with the current scheme of simply piggy-backing on C [] operator semantics which is, when facing a pointer that is being indexed, equivalent to pointer arithmetic which _can_ advance to before the indexed pointer, looks reasonable. that rules out using ARRAY_REF for all accesses through a descriptor (unless all strides are positive - not sure if it's worth special casing that though). it might be helpful to have a tree code providing CFI_address in an expanded form with explicitely specified index, [low-bound,] stride per indexed dimension and with the guarantee of CFI that the dimensions are independent (non-overlapping elements). I'd call it ELEMENT_SELECT_EXPR here, it would not be a tcc_reference since it only computes an address that would need to be dereferenced with a MEM_REF. Since it would be variable-length it doesn't nicely map to GIMPLE. Lowering during gimplification would be possible. Note we already have a vehicle that should be usable for the 1-dimensional case, namely TARGET_MEM_REF which allows variable pointer offsetting with a scaled index. Of course it would be somewhat abusing this and dependence analysis doesn't play nicely with it either AFAIK. Going for selected ARRAY_REF -> POINTER_PLUS_EXPR + MEM_REF lowering sounds like the way of least resistance, but then that's probably backwards of what the OpenACC folks want to do.
