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.

diff --git a/gcc/calls.cc b/gcc/calls.cc
index 01f44734743711510240f9393b69670822589dda..21d78f9779fedaad7443d28d7c1d466530ea9881 100644 (file)
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -2938,7 +2938,7 @@ expand_call (tree exp, rtx target, int ignore)
         /* 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;
+    n_named_args = structure_value_addr_parm;
   else
     /* If we know nothing, treat all args as named.  */
     n_named_args = num_actuals;
@@ -2970,14 +2970,15 @@ expand_call (tree exp, rtx target, int ignore)
      we do not have any reliable way to pass unnamed args in
      registers, so we must force them into memory.  */
 
-  if (type_arg_types != 0
+  if ((type_arg_types != 0 || TYPE_NO_NAMED_ARGS_STDARG_P (funtype))
       && 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))
+  else if (TYPE_NO_NAMED_ARGS_STDARG_P (funtype)
+          && ! targetm.calls.pretend_outgoing_varargs_named (args_so_far))
     n_named_args = 0;
   else
     /* Treat all args as named.  */