Give comparator const call operator

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292043 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -3264,7 +3264,7 @@ void BoUpSLP::scheduleBlock(BlockScheduling *BS) {
   // sorted by the original instruction location. This lets the final schedule
   // be as  close as possible to the original instruction order.
   struct ScheduleDataCompare {
-    bool operator()(ScheduleData *SD1, ScheduleData *SD2) {
+    bool operator()(ScheduleData *SD1, ScheduleData *SD2) const {
       return SD2->SchedulingPriority < SD1->SchedulingPriority;
     }
   };