diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 387d144d89a3c..9bba73bcc8391 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -2637,6 +2637,9 @@ class BoUpSLP {
     }
 
     ScheduleData *getScheduleData(Instruction *I) {
+      if (BB != I->getParent())
+        // Avoid lookup if can't possibly be in map.
+        return nullptr;
       ScheduleData *SD = ScheduleDataMap[I];
       if (SD && isInSchedulingRegion(SD))
         return SD;