[llvm-commits] [llvm] r103962 - /llvm/trunk/include/llvm/ADT/DenseMap.h

[Jakob Stoklund Olesen]

Author: stoklund
Date: Mon May 17 15:01:24 2010
New Revision: 103962

URL: http://llvm.org/viewvc/llvm-project?rev=103962&view=rev
Log:
Optimize empty DenseMap iteration.

Modified:
    llvm/trunk/include/llvm/ADT/DenseMap.h

Modified: llvm/trunk/include/llvm/ADT/DenseMap.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/DenseMap.h?rev=103962&r1=103961&r2=103962&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/DenseMap.h (original)
+++ llvm/trunk/include/llvm/ADT/DenseMap.h Mon May 17 15:01:24 2010
@@ -79,13 +79,14 @@
   typedef DenseMapIterator<KeyT, ValueT,
                            KeyInfoT, ValueInfoT, true> const_iterator;
   inline iterator begin() {
-     return iterator(Buckets, Buckets+NumBuckets);
+    // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets().
+    return empty() ? end() : iterator(Buckets, Buckets+NumBuckets);
   }
   inline iterator end() {
     return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
   }
   inline const_iterator begin() const {
-    return const_iterator(Buckets, Buckets+NumBuckets);
+    return empty() ? end() : const_iterator(Buckets, Buckets+NumBuckets);
   }
   inline const_iterator end() const {
     return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);