diff --git a/src/librustc_mir/pretty.rs b/src/librustc_mir/pretty.rs
index fb29cbd5fa8a..f11d0c84ec29 100644
--- a/src/librustc_mir/pretty.rs
+++ b/src/librustc_mir/pretty.rs
@@ -106,12 +106,9 @@ enum Annotation {
     ExitScope(ScopeId),
 }
 
-pub fn write_mir_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                              src: MirSource,
-                              mir: &Mir<'tcx>,
-                              w: &mut Write,
-                              auxiliary: Option<&ScopeAuxiliaryVec>)
-                              -> io::Result<()> {
+fn scope_entry_exit_annotations(auxiliary: Option<&ScopeAuxiliaryVec>)
+                                -> FnvHashMap<Location, Vec<Annotation>>
+{
     // compute scope/entry exit annotations
     let mut annotations = FnvHashMap();
     if let Some(auxiliary) = auxiliary {
@@ -129,7 +126,16 @@ pub fn write_mir_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             }
         }
     }
+    return annotations;
+}
 
+pub fn write_mir_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                              src: MirSource,
+                              mir: &Mir<'tcx>,
+                              w: &mut Write,
+                              auxiliary: Option<&ScopeAuxiliaryVec>)
+                              -> io::Result<()> {
+    let annotations = scope_entry_exit_annotations(auxiliary);
     write_mir_intro(tcx, src, mir, w)?;
     for block in mir.all_basic_blocks() {
         write_basic_block(tcx, block, mir, w, &annotations)?;