[gcc r12-4974] Fix can_be_discarded_p wrt partitioned functions.

[Jan Hubicka <hubicka@gcc.gnu.org>]

https://gcc.gnu.org/g:6078eb7452aa89cb9aeecac30932b58967389459

commit r12-4974-g6078eb7452aa89cb9aeecac30932b58967389459
Author: Jan Hubicka <hubicka@ucw.cz>
Date:   Sat Nov 6 23:36:08 2021 +0100

    Fix can_be_discarded_p wrt partitioned functions.
    
    gcc/ChangeLog:
    
            * cgraph.h (cgraph_node::can_be_discarded_p): Do not
            return true on functions from other partition.
    
    gcc/lto/ChangeLog:
    
            PR ipa/103070
            PR ipa/103058
            * lto-partition.c (must_not_rename): Update comment.
            (promote_symbol): Set resolution to LDPR_PREVAILING_DEF_IRONLY.

Diff:
---
 gcc/cgraph.h            | 3 ++-
 gcc/lto/lto-partition.c | 8 +++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/gcc/cgraph.h b/gcc/cgraph.h
index 4cdb3738b4d..0a1f7c8960e 100644
--- a/gcc/cgraph.h
+++ b/gcc/cgraph.h
@@ -404,7 +404,8 @@ public:
   inline bool
   can_be_discarded_p (void)
   {
-    return (DECL_EXTERNAL (decl)
+    return ((DECL_EXTERNAL (decl)
+	     && !in_other_partition)
 	    || ((get_comdat_group ()
 		 || DECL_COMMON (decl)
 		 || (DECL_SECTION_NAME (decl) && DECL_WEAK (decl)))
diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c
index 15761ac9eb5..bee40218159 100644
--- a/gcc/lto/lto-partition.c
+++ b/gcc/lto/lto-partition.c
@@ -852,7 +852,9 @@ must_not_rename (symtab_node *node, const char *name)
   /* Avoid mangling of already mangled clones. 
      ???  should have a flag whether a symbol has a 'private' name already,
      since we produce some symbols like that i.e. for global constructors
-     that are not really clones.  */
+     that are not really clones.
+     ???  it is what unique_name means.  We only need to set it when doing
+     private symbols.  */
   if (node->unique_name)
     {
       if (dump_file)
@@ -995,6 +997,10 @@ promote_symbol (symtab_node *node)
      defined by the non-LTO part.  */
   privatize_symbol_name (node);
   TREE_PUBLIC (node->decl) = 1;
+  /* After privatization the node should not conflict with any other symbol,
+     so it is prevailing.  This is important to keep binds_to_current_def_p
+     to work across partitions.  */
+  node->resolution = LDPR_PREVAILING_DEF_IRONLY;
   DECL_VISIBILITY (node->decl) = VISIBILITY_HIDDEN;
   DECL_VISIBILITY_SPECIFIED (node->decl) = true;
   if (dump_file)