On 11/22/2021 8:15 AM, Richard Biener via Gcc-patches wrote:
On Mon, Nov 22, 2021 at 3:40 PM Maxim Blinov <maxim.bli...@embecosm.com> wrote:
Hi Richard,
The purpose of this patch is to give more of the target code access to
the cumulative_args_t structure in order to enable certain (otherwise
currently impossible) stack layout constraints, specifically for
parameters that are passed over the stack. For example, there are some
targets (not yet in GCC trunk) which explicitly require the
distinction between named and variadic parameters in order to enforce
different alignment rules (when passing over the stack.) Such a
constraint would be accommodated by this patch.
The patch itself is very straightforward and simply adds the parameter
to the two functions which we'd like to extend. The motivation of
defining new target hooks was to minimize the patch size.
I would prefer to adjust the existing hooks if there's currently no way to
implement the aarch64 darwin ABI instead of optimizing for patch size.
Agreed. Additionally I don't think we want any -f options controlling
this behavior.
I have no opinion on whether passing down cummulative args is the
proper thing to do design-wise. It might be that TARGET_FUNCTION_ARG_BOUNDARY
is only one part that cummulative args using code should look at
(given you don't show the other users of function_arg_boundary that do not
conveniently have a CA struct around).
In the past I think we passed some additional parameters indicated where
the last named parameter was so that it could be used to set up the CA
struct. But if the aarch64 darwin ABI needs that info somewhere we
didn't before, then we'd likely need to add the CA structure.
Jeff
