3 files changed, 63 insertions, 20 deletions

diff --git a/gcc/rust/ast/rust-ast-full-test.cc b/gcc/rust/ast/rust-ast-full-test.cc
index 0cdac5f..44a38ac 100644
--- a/gcc/rust/ast/rust-ast-full-test.cc
+++ b/gcc/rust/ast/rust-ast-full-test.cc
@@ -5048,18 +5048,19 @@ MacroParser::parse_meta_item_lit ()
 bool
 AttrInputMetaItemContainer::check_cfg_predicate (const Session &session) const
 {
-  /* cfg value of container is purely based on cfg of each inner item - all
-   * must be true */
-  for (const auto &inner_item : items)
+  /* NOTE: assuming that only first item must be true - cfg should only have one item, and cfg_attr only has first item as predicate. TODO ensure that this is correct. */
+  if (items.empty ())
+    return false;
+
+  return items[0]->check_cfg_predicate (session);
+
+  /*for (const auto &inner_item : items)
     {
       if (!inner_item->check_cfg_predicate (session))
 	return false;
     }
 
-  /* TODO: as far as I can tell, there should only be a single element to
-   * check here, so ensure there is only a single element in items too? */
-
-  return true;
+  return true;*/
 }
 
 bool
@@ -5346,6 +5347,53 @@ MetaItemPathLit::to_attribute () const
 			    new AttrInputLiteral (lit)));
 }
 
+std::vector<Attribute> AttrInputMetaItemContainer::separate_cfg_attrs () const {
+    rust_assert (!items.empty ());
+
+    if (items.size () == 1)
+      return {};
+
+    std::vector<Attribute> attrs;
+    attrs.reserve (items.size () - 1);
+
+    for (auto it = items.begin () + 1; it != items.end (); ++it) {
+      Attribute attr = (*it)->to_attribute ();
+      if (attr.is_empty ()) {
+        // TODO should this be an error that causes us to chuck out everything?
+        continue;
+      }
+      attrs.push_back (std::move (attr));
+    }
+
+    attrs.shrink_to_fit ();
+    return attrs;
+  }
+
+bool Attribute::check_cfg_predicate (const Session &session)
+  {
+    /* assume that cfg predicate actually can exist, i.e. attribute has cfg or
+     * cfg_attr path */
+    if (!has_attr_input () || (path.as_string () != "cfg" && path.as_string () != "cfg_attr"))
+      return false;
+
+    // TODO: maybe replace with storing a "has been parsed" variable?
+    parse_attr_to_meta_item ();
+    // can't be const because of this anyway
+
+    return attr_input->check_cfg_predicate (session);
+  }
+
+std::vector<Attribute> Attribute::separate_cfg_attrs () {
+    if (!has_attr_input () || path.as_string () != "cfg_attr")
+      return {};
+
+      // TODO: maybe replace with storing a "has been parsed" variable?
+      parse_attr_to_meta_item ();
+      // can't be const because of this anyway
+
+    return attr_input->separate_cfg_attrs ();
+  }
+
 /* Visitor implementations - these are short but inlining can't happen anyway
  * due to virtual functions and I didn't want to make the ast header includes
  * any longer than they already are. */
diff --git a/gcc/rust/ast/rust-ast.h b/gcc/rust/ast/rust-ast.h
index ad3722f..cfb5f9b 100644
--- a/gcc/rust/ast/rust-ast.h
+++ b/gcc/rust/ast/rust-ast.h
@@ -83,6 +83,8 @@ public:
   // Parse attribute input to meta item, if possible
   virtual AttrInput *parse_to_meta_item () const { return nullptr; }
 
+  virtual std::vector<Attribute> separate_cfg_attrs () const { return {}; }
+
 protected:
   // pure virtual clone implementation
   virtual AttrInput *clone_attr_input_impl () const = 0;
@@ -590,20 +592,9 @@ public:
 
   /* Determines whether cfg predicate is true and item with attribute should not
    * be stripped. */
-  bool check_cfg_predicate (const Session &session)
-  {
-    /* assume that cfg predicate actually can exist, i.e. attribute has cfg or
-     * cfg_attr path */
-
-    if (!has_attr_input ())
-      return false;
+  bool check_cfg_predicate (const Session &session);
 
-    // TODO: maybe replace with storing a "has been parsed" variable?
-    parse_attr_to_meta_item ();
-    // can't be const because of this anyway
-
-    return attr_input->check_cfg_predicate (session);
-  }
+  std::vector<Attribute> separate_cfg_attrs ();
 
 protected:
   // not virtual as currently no subclasses of Attribute, but could be in future
@@ -683,6 +674,8 @@ public:
       clone_attr_input_meta_item_container_impl ());
   }
 
+  std::vector<Attribute> separate_cfg_attrs () const override;
+
 protected:
   // Use covariance to implement clone function as returning this type
   AttrInputMetaItemContainer *clone_attr_input_impl () const override
diff --git a/gcc/rust/ast/rust-macro.h b/gcc/rust/ast/rust-macro.h
index b51b149..9ecbb51 100644
--- a/gcc/rust/ast/rust-macro.h
+++ b/gcc/rust/ast/rust-macro.h
@@ -572,6 +572,8 @@ protected:
 };
 
 // Object that parses macros from a token stream.
+/* TODO: would "AttributeParser" be a better name? MetaItems are only for
+ * attributes, I believe */
 struct MacroParser
 {
 private: