c++: local function versioning [PR104669]

There were two problems with this testcase: we weren't copying the target
attribute from the second declaration to the global alias for the first
one (duplicate_decls hunk), and then we were treating the third one as
matching the earlier one even though both are versioned (decls_match hunk).
The latter change required a fix to find_last_decl (used for attribute
mismatch warnings) to give up if we see a versioned function, as in that
case we can't determine whether the decls match, because we are still in the
process of setting the attributes on the new decl.

	PR c++/104669

gcc/cp/ChangeLog:

	* decl.cc (decls_match): Compare versions even if not recording.
	(duplicate_decls): Propagate attributes to alias.
	* decl2.cc (find_last_decl): Give up if versioned.

gcc/testsuite/ChangeLog:

	* g++.target/i386/mv31.C: New test.

1 files changed, 14 insertions, 6 deletions

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 31cae4d..5f59612 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -1069,11 +1069,14 @@ decls_match (tree newdecl, tree olddecl, bool record_versions /* = true */)
       if (types_match
 	  && !DECL_EXTERN_C_P (newdecl)
 	  && !DECL_EXTERN_C_P (olddecl)
-	  && record_versions
-	  && maybe_version_functions (newdecl, olddecl,
-				      (!DECL_FUNCTION_VERSIONED (newdecl)
-				       || !DECL_FUNCTION_VERSIONED (olddecl))))
-	return 0;
+	  && targetm.target_option.function_versions (newdecl, olddecl))
+	{
+	  if (record_versions)
+	    maybe_version_functions (newdecl, olddecl,
+				     (!DECL_FUNCTION_VERSIONED (newdecl)
+				      || !DECL_FUNCTION_VERSIONED (olddecl)));
+	  return 0;
+	}
     }
   else if (TREE_CODE (newdecl) == TEMPLATE_DECL)
     {
@@ -2598,7 +2601,12 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
       else
 	{
 	  retrofit_lang_decl (newdecl);
-	  DECL_LOCAL_DECL_ALIAS (newdecl) = DECL_LOCAL_DECL_ALIAS (olddecl);
+	  tree alias = DECL_LOCAL_DECL_ALIAS (newdecl)
+	    = DECL_LOCAL_DECL_ALIAS (olddecl);
+	  DECL_ATTRIBUTES (alias)
+	    = (*targetm.merge_decl_attributes) (alias, newdecl);
+	  if (TREE_CODE (newdecl) == FUNCTION_DECL)
+	    merge_attribute_bits (newdecl, alias);
 	}
     }