Split changeset_ty using iterators instead of loops.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171829 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/DeltaAlgorithm.cpp b/lib/Support/DeltaAlgorithm.cpp
index 9e52874de832689a8b5c71d554edb1d2f3977a3f..a1e33114976bec28e3dabb0de69c4f5c8b4df689 100644 (file)
--- a/lib/Support/DeltaAlgorithm.cpp
+++ b/lib/Support/DeltaAlgorithm.cpp
@@ -27,13 +27,15 @@ bool DeltaAlgorithm::GetTestResult(const changeset_ty &Changes) {
 
 void DeltaAlgorithm::Split(const changeset_ty &S, changesetlist_ty &Res) {
   // FIXME: Allow clients to provide heuristics for improved splitting.
+  // Get the iterator to the middle.
+  unsigned N = S.size() / 2;
+  changeset_ty::iterator middle(S.begin());
+  std::advance(middle, N);
+
+  // Create each vector using the middle as the split.
+  changeset_ty LHS(S.begin(), middle);
+  changeset_ty RHS(middle, S.end());
 
-  // FIXME: This is really slow.
-  changeset_ty LHS, RHS;
-  unsigned idx = 0, N = S.size() / 2;
-  for (changeset_ty::const_iterator it = S.begin(),
-         ie = S.end(); it != ie; ++it, ++idx)
-    ((idx < N) ? LHS : RHS).insert(*it);
   if (!LHS.empty())
     Res.push_back(LHS);
   if (!RHS.empty())