[Bug target/63892] [5 Regression] gcc.dg/sibcall-3.c fails on darwin with -m32

["iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63892

--- Comment #17 from Iain Sandoe <iains at gcc dot gnu.org> ---
so .. the problem on Darwin seems to be when we have an alias which is a vtable
reference to a method.

Then we have alias->callers == NULL, and it seems we don't have anything in
place to replace the reference to the alias with a reference to the original. 
I don't know how to do this - so I hacked the following in to keep such cases. 
This allows boostrap to complete (without the
sem_item::target_supports_symbol_aliases_p ()) and all the sibcall cases pass
(the ADT/SmallVectortest.cpp also builds from llvm).  

Not sure what the "proper" fix is ?



diff --git a/gcc/ipa-icf.c b/gcc/ipa-icf.c
index e1af8bf..1539877 100644
--- a/gcc/ipa-icf.c
+++ b/gcc/ipa-icf.c
@@ -662,6 +662,7 @@ sem_function::merge (sem_item *alias_item)
       redirect_callers
     = (!original_discardable
        && !DECL_COMDAT_GROUP (alias->decl)
+       //&& sem_item::target_supports_symbol_aliases_p ()
        && alias->get_availability () > AVAIL_INTERPOSABLE
        && original->get_availability () > AVAIL_INTERPOSABLE
        && !alias->instrumented_version);
@@ -703,6 +704,14 @@ sem_function::merge (sem_item *alias_item)
       /* If alias is non-overwritable then
          all direct calls are safe to be redirected to the original.  */
       bool redirected = false;
+      bool keep = false;
+      /* If we have no callers, then I guess this is addressed by the vtable
+         and we need to move the reference, but I don't know how to do that
+         yet.  */
+      if (!alias->callers
+          && alias->address_taken)
+        keep = true;
+
       while (alias->callers)
     {
       cgraph_edge *e = alias->callers;
@@ -722,9 +731,9 @@ sem_function::merge (sem_item *alias_item)
       && local_original->lto_file_data != alias->lto_file_data)
       local_original->merged = true;

-      /* The alias function is removed if symbol address
-         does not matter.  */
-      if (!alias_address_matters)
+      /* The alias function is removed if the function is neither externally
+         visible or locally addressed.  */
+      if (!alias_address_matters && !keep)
     alias->remove ();

       if (dump_file && redirected)