add remaining handling of padding

src/ParallelKernel/parallel.jl

@@ -170,6 +170,7 @@ end
 function parallel_kernel(caller::Module, package::Symbol, numbertype::DataType, inbounds::Bool, indices::Union{Symbol,Expr}, kernel::Expr)
     if (!isa(indices,Symbol) && !isa(indices.head,Symbol)) @ArgumentError("@parallel_indices: argument 'indices' must be a tuple of indices or a single index (e.g. (ix, iy, iz) or (ix, iy) or ix ).") end
     indices = extract_tuple(indices)
+    padding = get_padding(caller)
     body = get_body(kernel)
     body = remove_return(body)
     body = macroexpand(caller, body)
@@ -183,7 +184,7 @@ function parallel_kernel(caller::Module, package::Symbol, numbertype::DataType,
     end
     if isgpu(package) kernel = insert_device_types(caller, kernel) end
     kernel = adjust_signatures(kernel, package)
-    body   = handle_padding(body, get_padding(caller)) # TODO: padding can later be made configurable per kernel (to enable working with arrays as before).
+    body   = handle_padding(body, padding) # TODO: padding can later be made configurable per kernel (to enable working with arrays as before).
     body   = handle_indices_and_literals(body, indices, package, numbertype)
     if (inbounds) body = add_inbounds(body) end
     body = add_return(body)
@@ -365,13 +366,47 @@ function adjust_signatures(kernel::Expr, package::Symbol)
 end
 
 function handle_padding(body::Expr, padding::Bool)
+    body = substitute_indices_inn(body, padding)
+    if padding
+        body = substitute_firstlastindex(body)
+        body = substitute_view_accesses(body, INDICES)
+    end
+    return body
+end
+
+function substitute_indices_inn(body::Expr, padding::Bool)
     for i=1:length(INDICES_INN)
         index_inn = (padding) ? INDICES[i] : :($(INDICES[i]) + 1) # NOTE: expression of ixi with ix, etc.: if padding is not used, they must be shifted by 1.
         body = substitute(body, INDICES_INN[i], index_inn)
     end
     return body
 end
 
+function substitute_firstlastindex(body::Expr)
+    padding = true
+    return postwalk(body) do ex
+        if @capture(ex, f_(args__)) 
+            if     (f == :firstindex) return :(ParallelStencil.ParallelKernel.@firstindex($(args...), $padding))
+            elseif (f == :lastindex)  return :(ParallelStencil.ParallelKernel.@lastindex($(args...), $padding))
+            else return ex
+            end
+        else
+            return ex
+        end
+    end
+end
+
+function substitute_view_accesses(expr::Expr, indices::NTuple{N,<:Union{Symbol,Expr}} where N)
+    return postwalk(expr) do ex
+        if is_access(ex, indices...)
+            @capture(ex, A_[indices_expr__]) || @ModuleInternalError("a stencil access could not be pattern matched.")
+            return :($A.parent[$(indices_expr...)])
+        else
+            return ex
+        end
+    end
+end
+
 function handle_indices_and_literals(body::Expr, indices::Array, package::Symbol, numbertype::DataType)
     int_type = kernel_int_type(package)
     ranges = [:($RANGES_VARNAME[1]), :($RANGES_VARNAME[2]), :($RANGES_VARNAME[3])]