Remove some unreachable code. Also add an assertion. NFC

Author: trentxintong

lib/SILOptimizer/ARC/ARCMatchingSet.cpp

@@ -288,19 +288,18 @@ bool ARCMatchingSetBuilder::matchUpIncDecSetsForPtr() {
   bool HaveIncInsertPts = !MatchSet.IncrementInsertPts.empty();
   bool HaveDecInsertPts = !MatchSet.DecrementInsertPts.empty();
 
+  // We should not have the case which retains have to be anchored topdown and
+  // releases do not have to be bottomup, or vice-versa.
+  assert(HaveIncInsertPts == HaveDecInsertPts &&
+         "Asymmetric insertion points for retains and releases");
+
   // If we have insertion points and partial merges, return false to avoid
   // control dependency issues.
   if ((HaveIncInsertPts || HaveDecInsertPts) && Partial) {
     DEBUG(llvm::dbgs() << "Found partial merge and insert pts. Bailing!\n");
     return false;
   }
 
-  // If we have insertion points for increments, but not for decrements (or
-  // vis-a-versa), return false. This prevents us from inserting retains and
-  // removing releases or vis-a-versa.
-  if (HaveIncInsertPts != HaveDecInsertPts)
-    return false;
-
   // If we do not have any insertion points but we do have increments, we must
   // be eliminating pairs.
   if (!HaveIncInsertPts && !MatchSet.Increments.empty())