Reduce duplicated hash map lookups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162362 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index a953985..dd05f0c 100644
--- a/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -1388,10 +1388,9 @@
     // If the original WaterList entry was "new water" on this iteration,
     // propagate that to the new island.  This is just keeping NewWaterList
     // updated to match the WaterList, which will be updated below.
-    if (NewWaterList.count(WaterBB)) {
-      NewWaterList.erase(WaterBB);
+    if (NewWaterList.erase(WaterBB))
       NewWaterList.insert(NewIsland);
-    }
+
     // The new CPE goes before the following block (NewMBB).
     NewMBB = llvm::next(MachineFunction::iterator(WaterBB));