(I'm copying this thread back to the main GCC list, to
document the problem that we ran into, RG's suggestion
and the fix that we made.)
While merging our GCC/UPC implementation with
the GCC trunk, we ran into a situation where
some tests failed on the check shown below in
verify_gimple_assign_single(). This failed because
our representation of a UPC pointer-to-shared has an
internal struct representation but in other respects
is a pointer type (and appears to be register type).
For some temps that UPC creates, they have to be
marked as addressable, which causes them to no longer
qualify as is_gimple_reg(), but the type still asserts
is_gimple_reg_type().
The trees that were being created failed on this test:
if (!is_gimple_reg (lhs)
&& is_gimple_reg_type (TREE_TYPE (lhs)))
{
error ("invalid rhs for gimple memory store");
debug_generic_stmt (lhs);
debug_generic_stmt (rhs1);
return true;
}
At first, I wondered if the checks above might be overly
inclusive?
On 01/11/10 11:03:46, Richard Guenther wrote:
> You need a temporary for register type but non-register copy. Thus
> it needs to be
>
> tmp_2 = A;
> B = tmp_2;
>
> with tmp_2 being an SSA name, not
>
> B = A;
Looking at some of the code in gimplify.c, we determined
that calling prepare_gimple_addressable() is all that is needed:
if (!is_gimple_addressable (src)
|| is_gimple_non_addressable (src))
{
/* We can't address the object - we have to copy
to a local (non-shared) temporary. */
- src = get_initialized_tmp_var (src, pre_p, NULL);
+ prepare_gimple_addressable (&src, pre_p);
mark_addressable (src);
is_shared_copy = 0;
is_src_shared = 0;
}
}
To make this work, prepare_gimple_addressable() needed to be changed
so that it is exported from gimplify.c:
-static void
+void
prepare_gimple_addressable (tree *expr_p, gimple_seq *seq_p)
{
while (handled_component_p (*expr_p))
expr_p = &TREE_OPERAND (*expr_p, 0);
if (is_gimple_reg (*expr_p))
*expr_p = get_initialized_tmp_var (*expr_p, seq_p, NULL);
}
With this fix in place, we were able pass the various checks
in tree-cfg.c, and to generate the expected code.
