add krate_attrs accessor

makes better edges in dep graph

Author: nikomatsakis

src/librustc/front/map/mod.rs

@@ -19,7 +19,7 @@ use dep_graph::{DepGraph, DepNode};
 
 use middle::cstore::InlinedItem;
 use middle::cstore::InlinedItem as II;
-use middle::def_id::DefId;
+use middle::def_id::{CRATE_DEF_INDEX, DefId};
 
 use syntax::abi::Abi;
 use syntax::ast::{self, Name, NodeId, DUMMY_NODE_ID};
@@ -388,6 +388,15 @@ impl<'ast> Map<'ast> {
         self.forest.krate()
     }
 
+    /// Get the attributes on the krate. This is preferable to
+    /// invoking `krate.attrs` because it registers a tighter
+    /// dep-graph access.
+    pub fn krate_attrs(&self) -> &'ast [ast::Attribute] {
+        let crate_root_def_id = DefId::local(CRATE_DEF_INDEX);
+        self.dep_graph.read(DepNode::Hir(crate_root_def_id));
+        &self.forest.krate.attrs
+    }
+
     /// Retrieve the Node corresponding to `id`, panicking if it cannot
     /// be found.
     pub fn get(&self, id: NodeId) -> Node<'ast> {

src/librustc_trans/trans/debuginfo/gdb.rs

@@ -90,10 +90,7 @@ pub fn get_or_insert_gdb_debug_scripts_section_global(ccx: &CrateContext)
 
 pub fn needs_gdb_debug_scripts_section(ccx: &CrateContext) -> bool {
     let omit_gdb_pretty_printer_section =
-        attr::contains_name(&ccx.tcx()
-                                .map
-                                .krate()
-                                .attrs,
+        attr::contains_name(&ccx.tcx().map.krate_attrs(),
                             "omit_gdb_pretty_printer_section");
 
     !omit_gdb_pretty_printer_section &&