[PATCH] cgraphunit: Avoid code generation differences based on -w/TREE_NO_WARNING [PR94277]

[Jakub Jelinek via Gcc-patches]

Hi!

The following testcase FAILs with -fcompare-debug, but not because -g vs.
-g0 would make a difference, but because the second compilation is done with
-w in order not to emit warnings twice and -w seems to affect the *.gkd dump
content.
This is because TREE_NO_WARNING flag, or warn_unused_function does affect
not just whether a warning/pedwarn is printed, but also whether we set
TREE_PUBLIC on such decls.
The following patch makes sure we set it regardless of anything warning
related (TREE_NO_WARNING or warn_unused_function).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2020-03-24  Jakub Jelinek  <ja...@redhat.com>

        PR debug/94277
        * cgraphunit.c (check_global_declaration): For DECL_EXTERNAL and
        non-TREE_PUBLIC non-DECL_ARTIFICIAL FUNCTION_DECLs, set TREE_PUBLIC
        regardless of whether TREE_NO_WARNING is set on it or whether
        warn_unused_function is true or not.

        * gcc.dg/pr94277.c: New test.

--- gcc/cgraphunit.c.jj 2020-03-19 18:13:21.703789041 +0100
+++ gcc/cgraphunit.c    2020-03-23 15:49:47.160449491 +0100
@@ -1068,15 +1068,15 @@ check_global_declaration (symtab_node *s
       && DECL_INITIAL (decl) == 0
       && DECL_EXTERNAL (decl)
       && ! DECL_ARTIFICIAL (decl)
-      && ! TREE_NO_WARNING (decl)
-      && ! TREE_PUBLIC (decl)
-      && (warn_unused_function
-         || snode->referred_to_p (/*include_self=*/false)))
+      && ! TREE_PUBLIC (decl))
     {
-      if (snode->referred_to_p (/*include_self=*/false))
+      if (TREE_NO_WARNING (decl))
+       ;
+      else if (snode->referred_to_p (/*include_self=*/false))
        pedwarn (input_location, 0, "%q+F used but never defined", decl);
       else
-       warning (OPT_Wunused_function, "%q+F declared %<static%> but never 
defined", decl);
+       warning (OPT_Wunused_function, "%q+F declared %<static%> but never "
+                                      "defined", decl);
       /* This symbol is effectively an "extern" declaration now.  */
       TREE_PUBLIC (decl) = 1;
     }
--- gcc/testsuite/gcc.dg/pr94277.c.jj   2020-03-23 15:51:25.739980041 +0100
+++ gcc/testsuite/gcc.dg/pr94277.c      2020-03-23 15:51:09.616220387 +0100
@@ -0,0 +1,11 @@
+/* PR debug/94277 */
+/* { dg-do compile } */
+/* { dg-options "-fcompare-debug" } */
+
+static void foo (void);        /* { dg-warning "used but never defined" } */
+
+void
+bar (void)
+{
+  foo ();
+}

        Jakub