[Bug middle-end/114136] wrong code for c23 fully anonymous arg lists on arm

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114136

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:b5377928a2a5cd2a79eda59e2eba7d0511bf7566

commit r14-9255-gb5377928a2a5cd2a79eda59e2eba7d0511bf7566
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Mar 1 15:42:52 2024 +0100

    calls: Further fixes for TYPE_NO_NAMED_ARGS_STDARG_P handling [PR114136]

    On Tue, Feb 27, 2024 at 04:41:32PM +0000, Richard Earnshaw wrote:
    > On Arm the PR107453 change is causing all anonymous arguments to be
passed on the
    > stack, which is incorrect per the ABI.  On a target that uses
    > 'pretend_outgoing_vararg_named', why is it correct to set n_named_args to
    > zero?  Is it enough to guard both the statements you've added with
    > !targetm.calls.pretend_outgoing_args_named?

    The TYPE_NO_NAMED_ARGS_STDARG_P functions (C23 fns like void foo (...) {})
    have NULL type_arg_types, so the list_length (type_arg_types) isn't done
for
    it, but it should be handled as if it was non-NULL but list length was 0.

    So, for the
      if (type_arg_types != 0)
        n_named_args
          = (list_length (type_arg_types)
             /* Count the struct value address, if it is passed as a parm.  */
             + structure_value_addr_parm);
      else if (TYPE_NO_NAMED_ARGS_STDARG_P (funtype))
        n_named_args = 0;
      else
        /* If we know nothing, treat all args as named.  */
        n_named_args = num_actuals;
    case, I think guarding it by any target hooks is wrong, although
    I guess it should have been
        n_named_args = structure_value_addr_parm;
    instead of
        n_named_args = 0;

    For the second
      if (type_arg_types != 0
          && targetm.calls.strict_argument_naming (args_so_far))
        ;
      else if (type_arg_types != 0
               && ! targetm.calls.pretend_outgoing_varargs_named (args_so_far))
        /* Don't include the last named arg.  */
        --n_named_args;
      else if (TYPE_NO_NAMED_ARGS_STDARG_P (funtype))
        n_named_args = 0;
      else
        /* Treat all args as named.  */
        n_named_args = num_actuals;
    I think we should treat those as if type_arg_types was non-NULL
    with 0 elements in the list, except the --n_named_args would for
    !structure_value_addr_parm lead to n_named_args = -1, I think we want
    0 for that case.

    2024-03-01  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/114136
            * calls.cc (expand_call): For TYPE_NO_NAMED_ARGS_STDARG_P set
            n_named_args initially before INIT_CUMULATIVE_ARGS to
            structure_value_addr_parm rather than 0, after it don't modify
            it if strict_argument_naming and clear only if
            !pretend_outgoing_varargs_named.