Fix PR middle-end/98082

this fixes an ICE introduced by the fix for PR middle-end/97078 where
use_register_for_decl was changed to return true at -O0 for a parameter
of a thunk.  It turns out that we need to do the same for a result in
this case.

gcc/ChangeLog:
	PR middle-end/98082
	* function.c (use_register_for_decl): Also return true for a result
	if cfun->tail_call_marked is true.

gcc/testsuite/ChangeLog:
	* g++.dg/cpp2a/pr98082.C: New test.

1 files changed, 4 insertions, 2 deletions

diff --git a/gcc/function.c b/gcc/function.c
index 59fd72b..af9618e 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -2206,13 +2206,15 @@ use_register_for_decl (const_tree decl)
       /* Otherwise, if RESULT_DECL is DECL_BY_REFERENCE, it will take
 	 the function_result_decl's assignment.  Since it's a pointer,
 	 we can short-circuit a number of the tests below, and we must
-	 duplicat e them because we don't have the
-	 function_result_decl to test.  */
+	 duplicate them because we don't have the function_result_decl
+	 to test.  */
       if (!targetm.calls.allocate_stack_slots_for_args ())
 	return true;
       /* We don't set DECL_IGNORED_P for the function_result_decl.  */
       if (optimize)
 	return true;
+      if (cfun->tail_call_marked)
+	return true;
       /* We don't set DECL_REGISTER for the function_result_decl.  */
       return false;
     }