Index: lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- lib/Transforms/Vectorize/LoopVectorize.cpp
+++ lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -4673,6 +4673,11 @@
           !isAccessInterleaved(&I) && !isLegalGatherOrScatter(&I))
         continue;
 
+      // If the loaded value is truncated, consider the truncated type.
+      if (isa<LoadInst>(&I) && I.hasOneUse() &&
+         (isa<TruncInst>(*I.user_begin()) || isa<FPTruncInst>(*I.user_begin())))
+        T = (*I.user_begin())->getType();
+
       MinWidth = std::min(MinWidth,
                           (unsigned)DL.getTypeSizeInBits(T->getScalarType()));
       MaxWidth = std::max(MaxWidth,