Create a scoped arena allocator and use that for LVN.

This saves more than 0.5s of boot.oat compilation time
on Nexus 5.

TODO: Move other stuff to the scoped allocator. This CL
alone increases the peak memory allocation. By reusing
the memory for other parts of the compilation we should
reduce this overhead.

Change-Id: Ifbc00aab4f3afd0000da818dfe68b96713824a08

1 files changed, 11 insertions, 4 deletions

diff --git a/runtime/safe_map.h b/runtime/safe_map.h
index 89da927cc2..393bf92ba2 100644
--- a/runtime/safe_map.h
+++ b/runtime/safe_map.h
@@ -33,10 +33,17 @@ class SafeMap {
   typedef SafeMap<K, V, Comparator, Allocator> Self;
 
  public:
-  typedef typename ::std::map<K, V, Comparator>::iterator iterator;
-  typedef typename ::std::map<K, V, Comparator>::const_iterator const_iterator;
-  typedef typename ::std::map<K, V, Comparator>::size_type size_type;
-  typedef typename ::std::map<K, V, Comparator>::value_type value_type;
+  typedef typename ::std::map<K, V, Comparator, Allocator>::key_compare key_compare;
+  typedef typename ::std::map<K, V, Comparator, Allocator>::allocator_type allocator_type;
+  typedef typename ::std::map<K, V, Comparator, Allocator>::iterator iterator;
+  typedef typename ::std::map<K, V, Comparator, Allocator>::const_iterator const_iterator;
+  typedef typename ::std::map<K, V, Comparator, Allocator>::size_type size_type;
+  typedef typename ::std::map<K, V, Comparator, Allocator>::value_type value_type;
+
+  SafeMap() = default;
+  explicit SafeMap(const key_compare& cmp, const allocator_type& allocator = allocator_type())
+    : map_(cmp, allocator) {
+  }
 
   Self& operator=(const Self& rhs) {
     map_ = rhs.map_;