LoongArch: Fix C23 (...) functions returning large aggregates [PR114175]

We were assuming TYPE_NO_NAMED_ARGS_STDARG_P don't have any named
arguments and there is nothing to advance, but that is not the case
for (...) functions returning by hidden reference which have one such
artificial argument.  This is causing gcc.dg/c23-stdarg-6.c and
gcc.dg/c23-stdarg-8.c to fail.

Fix the issue by checking if arg.type is NULL, as r14-9503 explains.

gcc/ChangeLog:

	PR target/114175
	* config/loongarch/loongarch.cc
	(loongarch_setup_incoming_varargs): Only skip
	loongarch_function_arg_advance for TYPE_NO_NAMED_ARGS_STDARG_P
	functions if arg.type is NULL.

diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 70e31bb831c7c0b86d13702a9854cc5f22b3c0dc..5344f2a6987e930d074aeba6f189c1dbd0b972ba 100644 (file)
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -767,7 +767,13 @@ loongarch_setup_incoming_varargs (cumulative_args_t cum,
      argument.  Advance a local copy of CUM past the last "real" named
      argument, to find out how many registers are left over.  */
   local_cum = *get_cumulative_args (cum);
-  if (!TYPE_NO_NAMED_ARGS_STDARG_P (TREE_TYPE (current_function_decl)))
+
+  /* For a C23 variadic function w/o any named argument, and w/o an
+     artifical argument for large return value, skip advancing args.
+     There is such an artifical argument iff. arg.type is non-NULL
+     (PR 114175).  */
+  if (!TYPE_NO_NAMED_ARGS_STDARG_P (TREE_TYPE (current_function_decl))
+      || arg.type != NULL_TREE)
     loongarch_function_arg_advance (pack_cumulative_args (&local_cum), arg);
 
   /* Found out how many registers we need to save.  */