diff --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -228,12 +228,39 @@
         {ISD::ZERO_EXTEND, MVT::v4i32, MVT::v4i8, 0},
         {ISD::SIGN_EXTEND, MVT::v8i16, MVT::v8i8, 0},
         {ISD::ZERO_EXTEND, MVT::v8i16, MVT::v8i8, 0},
+        // The following extend from a legal type to an illegal type, so need to
+        // split the load. This introduced an extra load operation, but the
+        // extend is still "free".
+        {ISD::SIGN_EXTEND, MVT::v8i32, MVT::v8i16, 1},
+        {ISD::ZERO_EXTEND, MVT::v8i32, MVT::v8i16, 1},
+        {ISD::SIGN_EXTEND, MVT::v16i32, MVT::v16i8, 3},
+        {ISD::ZERO_EXTEND, MVT::v16i32, MVT::v16i8, 3},
+        {ISD::SIGN_EXTEND, MVT::v16i16, MVT::v16i8, 1},
+        {ISD::ZERO_EXTEND, MVT::v16i16, MVT::v16i8, 1},
     };
     if (SrcTy.isVector() && ST->hasMVEIntegerOps()) {
       if (const auto *Entry =
               ConvertCostTableLookup(MVELoadConversionTbl, ISD,
                                      DstTy.getSimpleVT(), SrcTy.getSimpleVT()))
-        return AdjustCost(Entry->Cost);
+        return AdjustCost(Entry->Cost * ST->getMVEVectorCostFactor());
+    }
+  }
+
+  // The truncate of a store is free. This is the mirror of extends above.
+  if (I && I->hasOneUse() && isa<StoreInst>(*I->user_begin())) {
+    static const TypeConversionCostTblEntry MVELoadConversionTbl[] = {
+        {ISD::TRUNCATE, MVT::v4i32, MVT::v4i16, 0},
+        {ISD::TRUNCATE, MVT::v4i32, MVT::v4i8, 0},
+        {ISD::TRUNCATE, MVT::v8i16, MVT::v8i8, 0},
+        {ISD::TRUNCATE, MVT::v8i32, MVT::v8i16, 1},
+        {ISD::TRUNCATE, MVT::v16i32, MVT::v16i8, 3},
+        {ISD::TRUNCATE, MVT::v16i16, MVT::v16i8, 1},
+    };
+    if (SrcTy.isVector() && ST->hasMVEIntegerOps()) {
+      if (const auto *Entry =
+              ConvertCostTableLookup(MVELoadConversionTbl, ISD, SrcTy.getSimpleVT(),
+                                     DstTy.getSimpleVT()))
+        return AdjustCost(Entry->Cost * ST->getMVEVectorCostFactor());
     }
   }
 
diff --git a/llvm/test/Analysis/CostModel/ARM/cast_ldst.ll b/llvm/test/Analysis/CostModel/ARM/cast_ldst.ll
--- a/llvm/test/Analysis/CostModel/ARM/cast_ldst.ll
+++ b/llvm/test/Analysis/CostModel/ARM/cast_ldst.ll
@@ -122,8 +122,8 @@
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 74 for instruction: %v8864u = zext <8 x i8> %loadv8i8 to <8 x i64>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v16816s = sext <16 x i8> %loadv16i8 to <16 x i16>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v16816u = zext <16 x i8> %loadv16i8 to <16 x i16>
-; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %v16832s = sext <16 x i8> %loadv16i8 to <16 x i32>
-; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %v16832u = zext <16 x i8> %loadv16i8 to <16 x i32>
+; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v16832s = sext <16 x i8> %loadv16i8 to <16 x i32>
+; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v16832u = zext <16 x i8> %loadv16i8 to <16 x i32>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 1322 for instruction: %v16864s = sext <16 x i8> %loadv16i8 to <16 x i64>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 298 for instruction: %v16864u = zext <16 x i8> %loadv16i8 to <16 x i64>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %v21632s = sext <2 x i16> %loadv2i16 to <2 x i32>
@@ -758,7 +758,7 @@
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v8832 = trunc <8 x i32> undef to <8 x i8>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %v8864 = trunc <8 x i64> undef to <8 x i8>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v16816 = trunc <16 x i16> undef to <16 x i8>
-; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %v16832 = trunc <16 x i32> undef to <16 x i8>
+; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v16832 = trunc <16 x i32> undef to <16 x i8>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 42 for instruction: %v16864 = trunc <16 x i64> undef to <16 x i8>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %v21632 = trunc <2 x i32> undef to <2 x i16>
 ; CHECK-MVE-RECIP-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %v21664 = trunc <2 x i64> undef to <2 x i16>