On Fri, Feb 1, 2013 at 5:03 AM, Matt Davis <mattdav...@gmail.com> wrote:
> Hello,
> I have a routine that creates a local array containing pointers to
> global data. At runtime, when this array is passed to a function, I
> do not see the pointers to the global objects. The GIMPLE does show
> that the array is declared with the addresses of the globals as the
> elements to the array, and that looks fine to me. But at runtime,
> when this array is passed to a callee function, the callee receives
> the array, but its contents are not the addresses of the globals.
>
> After looking at the corresponding assembly, this makes sense, as I do
> not see the assembly building the array before it passes the array to
> the callee. I do not see the asm code assigning the elements of the
> array to be that of the global pointers. I suppose there is a flag I
> need to set? If not, I suppose I can always build the array as a
> series of assignments.
>
> Here is how I build the local array. Note, if I build this array as a
> global with static-linkage, then everything works fine:
>
> tree create_array(const region_t reg, gimple stmt)
> {
> unsigned i, n_elts;
> const type_info_t *ti;
> tree type, unique, decl;
> VEC(constructor_elt,gc) *entries = NULL;
>
> n_elts = VEC_length(tree, reg->unique_types);
> type = build_array_type_nelts(ptr_type_node, n_elts);
>
> FOR_EACH_VEC_ELT(tree, reg->unique_types, i, unique)
> {
> ti = get_type_info(reg, unique);
> CONSTRUCTOR_APPEND_ELT(
> entries, NULL, build1(ADDR_EXPR, ptr_type_node, ti->decl));
> }
>
> decl = create_tmp_var(type, "testarray");
> DECL_INITIAL(decl) = build_constructor(type, entries);
>
> return decl;
> }
>
> Do I have to explicitly create assignment statements for each element,
> since my array is local? As I mention above, if I make my array
> global, everything is fine.
Locals with DECL_INITIAL need to be lowered in GIMPLE to make the
initialization explicit. What you can do is output the constructor as
constant (supposed all elements are constant) using tree_output_constant_def.
See how gimplification handles initializers of locals.
Richard.
> -Matt
