[gcc r12-8115] c++: local function versioning [PR104669]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:791a968630b3846b614a435b9a75a52f29147a08

commit r12-8115-g791a968630b3846b614a435b9a75a52f29147a08
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Apr 12 16:40:14 2022 -0400

    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.

Diff:
---
 gcc/cp/decl.cc                       | 20 ++++++++++++++------
 gcc/cp/decl2.cc                      | 12 ++++++++++--
 gcc/testsuite/g++.target/i386/mv31.C | 10 ++++++++++
 3 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 31cae4d1d36..5f59612fb00 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);
 	}
     }
 
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index c780702572d..e10331f8568 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -1637,8 +1637,16 @@ find_last_decl (tree decl)
 	  if (TREE_CODE (*iter) == OVERLOAD)
 	    continue;
 
-	  if (decls_match (decl, *iter, /*record_decls=*/false))
-	    return *iter;
+	  tree d = *iter;
+
+	  /* We can't compare versions in the middle of processing the
+	     attribute that has the version.  */
+	  if (TREE_CODE (d) == FUNCTION_DECL
+	      && DECL_FUNCTION_VERSIONED (d))
+	    return NULL_TREE;
+
+	  if (decls_match (decl, d, /*record_decls=*/false))
+	    return d;
 	}
       return NULL_TREE;
     }
diff --git a/gcc/testsuite/g++.target/i386/mv31.C b/gcc/testsuite/g++.target/i386/mv31.C
new file mode 100644
index 00000000000..5d8fd1ddf75
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/mv31.C
@@ -0,0 +1,10 @@
+// PR c++/104669
+
+void bar()
+{
+  int foo(void);
+  int foo(void) __attribute__((target("sse")));
+  int foo(void) __attribute__((target("default")));
+  int (*p)(void) = &foo;
+  return;
+}