diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -2165,9 +2165,10 @@
     case Intrinsic::aarch64_neon_uaddlv: {
       MVT VT = Op.getOperand(1).getValueType().getSimpleVT();
       unsigned BitWidth = Known.getBitWidth();
-      if (VT == MVT::v8i8) {
-        assert(BitWidth >= 16 && "Unexpected width!");
-        APInt Mask = APInt::getHighBitsSet(BitWidth, BitWidth - 16);
+      if (VT == MVT::v8i8 || VT == MVT::v16i8) {
+        unsigned Bound = (VT == MVT::v8i8) ?  11 : 12;
+        assert(BitWidth >= Bound && "Unexpected width!");
+        APInt Mask = APInt::getHighBitsSet(BitWidth, BitWidth - Bound);
         Known.Zero |= Mask;
       }
       break;
diff --git a/llvm/test/CodeGen/AArch64/aarch64-neon-vector-insert-uaddlv.ll b/llvm/test/CodeGen/AArch64/aarch64-neon-vector-insert-uaddlv.ll
--- a/llvm/test/CodeGen/AArch64/aarch64-neon-vector-insert-uaddlv.ll
+++ b/llvm/test/CodeGen/AArch64/aarch64-neon-vector-insert-uaddlv.ll
@@ -300,7 +300,7 @@
 ; CHECK-NEXT:    stp xzr, xzr, [x0, #16]
 ; CHECK-NEXT:    uaddlv.8b h1, v0
 ; CHECK-NEXT:    mov.h v0[0], v1[0]
-; CHECK-NEXT:    bic.4h v0, #255, lsl #8
+; CHECK-NEXT:    bic.4h v0, #7, lsl #8
 ; CHECK-NEXT:    ushll.4s v0, v0, #0
 ; CHECK-NEXT:    ucvtf.4s v0, v0
 ; CHECK-NEXT:    str q0, [x0]
diff --git a/llvm/test/CodeGen/AArch64/neon-addlv.ll b/llvm/test/CodeGen/AArch64/neon-addlv.ll
--- a/llvm/test/CodeGen/AArch64/neon-addlv.ll
+++ b/llvm/test/CodeGen/AArch64/neon-addlv.ll
@@ -153,8 +153,8 @@
 
 declare i32 @llvm.aarch64.neon.uaddlv.i32.v8i8(<8 x i8>) nounwind readnone
 
-define i32 @uaddlv_known_bits(<8 x i8> %a) {
-; CHECK-LABEL: uaddlv_known_bits:
+define i32 @uaddlv_known_bits_v8i8(<8 x i8> %a) {
+; CHECK-LABEL: uaddlv_known_bits_v8i8:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    uaddlv h0, v0.8b
 ; CHECK-NEXT:    fmov w0, s0
@@ -163,3 +163,17 @@
   %tmp2 = and i32 %tmp1, 65535
   ret i32 %tmp2
 }
+
+declare i32 @llvm.aarch64.neon.uaddlv.i32.v16i8(<16 x i8>) nounwind readnone
+
+define i32 @uaddlv_known_bits_v16i8(<16 x i8> %a) {
+; CHECK-LABEL: uaddlv_known_bits_v16i8:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    uaddlv h0, v0.16b
+; CHECK-NEXT:    fmov w0, s0
+; CHECK-NEXT:    ret
+entry:
+  %vaddlv.i = tail call i32 @llvm.aarch64.neon.uaddlv.i32.v16i8(<16 x i8> %a)
+  %0 = and i32 %vaddlv.i, 65535
+  ret i32 %0
+}