Index: lib/Transforms/Vectorize/SLPVectorizer.cpp
===================================================================
--- lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -79,7 +79,7 @@
 ScheduleRegionSizeBudget("slp-schedule-budget", cl::init(100000), cl::Hidden,
     cl::desc("Limit the size of the SLP scheduling region per block"));
 
-static cl::opt<int> MinVectorRegSizeOption(
+static cl::opt<unsigned> MinVectorRegSizeOption(
     "slp-min-reg-size", cl::init(128), cl::Hidden,
     cl::desc("Attempt to vectorize for this register size in bits"));
 
@@ -331,7 +331,7 @@
     else
       MaxVecRegSize = TTI->getRegisterBitWidth(true);
 
-    MinVecRegSize = MinVectorRegSizeOption;
+    MinVecRegSize = std::min(MinVectorRegSizeOption.getValue(), MaxVecRegSize);
   }
 
   /// \brief Vectorize the tree that starts with the elements in \p VL.