[Bug debug/96690] [10/11 Regression] ICE in write_type since r10-6087

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96690

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Forcing the mangling via generating garbage RTL early doesn't work since
the

  /* ???  The C++ FE emits debug information for using decls, so
     putting gcc_unreachable here falls over.  See PR31899.  For now
     be conservative.  */
  else if (!symtab->global_info_ready && VAR_OR_FUNCTION_DECL_P (*tp))
    return *tp;

check in reference_to_unused triggers during the early debug pass over
template params and thus no RTL is generated from there.  But the late
pass looks phishy:

  else if (TREE_CODE (*tp) == FUNCTION_DECL
           && (!DECL_EXTERNAL (*tp) || DECL_DECLARED_INLINE_P (*tp)))
    {
      /* The call graph machinery must have finished analyzing,
         optimizing and gimplifying the CU by now.
         So if *TP has no call graph node associated
         to it, it means *TP will not be emitted.  */
      if (!cgraph_node::get (*tp))
        return *tp;

but 'foo' is DECL_EXTERNAL and TREE_PUBLIC.  The following works on this
testcase though:

diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 9deca031fc2..29e011a296d 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -19756,7 +19785,7 @@ reference_to_unused (tree * tp, int * walk_subtrees,
   /* ???  The C++ FE emits debug information for using decls, so
      putting gcc_unreachable here falls over.  See PR31899.  For now
      be conservative.  */
-  else if (!symtab->global_info_ready && VAR_OR_FUNCTION_DECL_P (*tp))
+  else if (!symtab->global_info_ready && VAR_P (*tp))
     return *tp;
   else if (VAR_P (*tp))
     {
@@ -19771,7 +19800,7 @@ reference_to_unused (tree * tp, int * walk_subtrees,
          optimizing and gimplifying the CU by now.
         So if *TP has no call graph node associated
         to it, it means *TP will not be emitted.  */
-      if (!cgraph_node::get (*tp))
+      if (!symtab->global_info_ready || !cgraph_node::get (*tp))
        return *tp;
     }
   else if (TREE_CODE (*tp) == STRING_CST && !TREE_ASM_WRITTEN (*tp))
@@ -20295,12 +20324,11 @@ tree_add_const_value_attribute (dw_die_ref die, tree
t)
          return true;
        }
     }
-  if (! early_dwarf)
-    {
-      rtl = rtl_for_decl_init (init, type);
-      if (rtl)
-       return add_const_value_attribute (die, rtl);
-    }
+  /* Generate the RTL even if early_dwarf to force mangling of all refered to
+     symbols.  */
+  rtl = rtl_for_decl_init (init, type);
+  if (rtl && !early_dwarf)
+    return add_const_value_attribute (die, rtl);
   /* If the host and target are sane, try harder.  */
   if (CHAR_BIT == 8 && BITS_PER_UNIT == 8
       && initializer_constant_valid_p (init, type))