Re: [patch] Fix dangling references in thunks at -O0

[Eric Botcazou]

> This introduces an ICE building the glibc testsuite for alpha (bisected),
> s390 and sparc (symptoms appear the same, not bisected to confirm the
> exact revision).  See bug 97078.

Fixed thus, tested on x86_64-suse-linux, applied on mainline as obvious.


        PR middle-end/97078
        * function.c (use_register_for_decl): Test cfun->tail_call_marked
        for a parameter here instead of...
        (assign_parm_setup_reg): ...here.

        * gcc.dg/pr97078.c: New test.
        
-- 
Eric Botcazou
diff --git a/gcc/function.c b/gcc/function.c
index c4c9930d725..c6129593b9b 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -2237,6 +2237,11 @@ use_register_for_decl (const_tree decl)
   if (optimize)
     return true;
 
+  /* Thunks force a tail call even at -O0 so we need to avoid creating a
+     dangling reference in case the parameter is passed by reference.  */
+  if (TREE_CODE (decl) == PARM_DECL && cfun->tail_call_marked)
+    return true;
+
   if (!DECL_REGISTER (decl))
     return false;
 
@@ -3328,9 +3333,8 @@ assign_parm_setup_reg (struct assign_parm_data_all *all, tree parm,
      of the parameter instead.  */
   if (data->arg.pass_by_reference && TYPE_MODE (TREE_TYPE (parm)) != BLKmode)
     {
-      /* Use a stack slot for debugging purposes, except if a tail call is
-	 involved because this would create a dangling reference.  */
-      if (use_register_for_decl (parm) || cfun->tail_call_marked)
+      /* Use a stack slot for debugging purposes if possible.  */
+      if (use_register_for_decl (parm))
 	{
 	  parmreg = gen_reg_rtx (TYPE_MODE (TREE_TYPE (parm)));
 	  mark_user_reg (parmreg);

/* { dg-do compile } */
/* { dg-options "-O2 -ffloat-store" } */

extern void foo (long double);

void bar (long double d)
{
  foo (d);
}