diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index ec25d7c5ecce..44e92b4ec08d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2393,8 +2393,9 @@ static bool isVectorReductionOp(const User *I) {
         // ElemNumToReduce / 2 elements in another vector.
 
         unsigned ResultElements = ShufInst->getType()->getVectorNumElements();
-        ElemNumToReduce = ResultElements <= ElemNumToReduce ? ResultElements
-                                                            : ElemNumToReduce;
+        if (ResultElements < ElemNum)
+          return false;
+
         if (ElemNumToReduce == 1)
           return false;
         if (!isa<UndefValue>(U->getOperand(1)))
@@ -2407,8 +2408,7 @@ static bool isVectorReductionOp(const User *I) {
             return false;
 
         // There is only one user of this ShuffleVector instruction, which
-        // must
-        // be a reduction operation.
+        // must be a reduction operation.
         if (!U->hasOneUse())
           return false;
 
diff --git a/llvm/test/CodeGen/AArch64/arm64-detect-vec-redux.ll b/llvm/test/CodeGen/AArch64/arm64-detect-vec-redux.ll
new file mode 100644
index 000000000000..68130f1c9f88
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/arm64-detect-vec-redux.ll
@@ -0,0 +1,52 @@
+; RUN: llc -mtriple=arm64-darwin-unknown < %s
+
+target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64"
+
+; Function Attrs: nounwind readnone
+define i32 @dotests_56() #0 {
+entry:
+  %vqshrn_n4 = tail call <2 x i32> @llvm.aarch64.neon.uqshrn.v2i32(<2 x i64> zeroinitializer, i32 19)
+  %shuffle.i109 = shufflevector <2 x i32> %vqshrn_n4, <2 x i32> undef, <4 x i32> <i32 undef, i32 1, i32 undef, i32 undef>
+  %neg = xor <4 x i32> %shuffle.i109, <i32 undef, i32 -1, i32 undef, i32 undef>
+  %shuffle = shufflevector <4 x i32> %neg, <4 x i32> undef, <2 x i32> <i32 1, i32 undef>
+  %mul = mul <2 x i32> %shuffle, <i32 add (i32 extractelement (<2 x i32> bitcast (<1 x i64> <i64 -4264345899313889281> to <2 x i32>), i32 0), i32 sub (i32 0, i32 extractelement (<2 x i32> bitcast (<1 x i64> <i64 -9223231295071453185> to <2 x i32>), i32 0))), i32 undef>
+  %shuffle27 = shufflevector <2 x i32> %mul, <2 x i32> undef, <4 x i32> zeroinitializer
+  %0 = bitcast <4 x i32> %shuffle27 to <8 x i16>
+  %shuffle.i108 = shufflevector <8 x i16> %0, <8 x i16> undef, <8 x i32> <i32 3, i32 2, i32 1, i32 0, i32 7, i32 6, i32 5, i32 4>
+  %vqshrn_n38 = tail call <8 x i8> @llvm.aarch64.neon.uqshrn.v8i8(<8 x i16> %shuffle.i108, i32 1)
+  %shuffle.i = shufflevector <8 x i8> %vqshrn_n38, <8 x i8> undef, <16 x i32> <i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %1 = bitcast <16 x i8> %shuffle.i to <2 x i64>
+  %vpaddq_v2.i = tail call <2 x i64> @llvm.aarch64.neon.addp.v2i64(<2 x i64> undef, <2 x i64> %1) #2
+  %vqdmlal2.i = tail call <2 x i64> @llvm.aarch64.neon.sqdmull.v2i64(<2 x i32> undef, <2 x i32> undef) #2
+  %vqdmlal_v3.i = tail call <2 x i64> @llvm.aarch64.neon.sqadd.v2i64(<2 x i64> %vpaddq_v2.i, <2 x i64> %vqdmlal2.i) #2
+  %vmovn.i = trunc <2 x i64> %vqdmlal_v3.i to <2 x i32>
+  %vqdmulh_v2.i = tail call <2 x i32> @llvm.aarch64.neon.sqdmulh.v2i32(<2 x i32> %vmovn.i, <2 x i32> zeroinitializer) #2
+  %2 = bitcast <2 x i32> %vqdmulh_v2.i to <1 x i64>
+  %vget_lane = extractelement <1 x i64> %2, i32 0
+  %cmp = icmp ne i64 %vget_lane, -7395147708962464393
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}
+
+; Function Attrs: nounwind readnone
+declare <2 x i32> @llvm.aarch64.neon.uqshrn.v2i32(<2 x i64>, i32) #1
+
+; Function Attrs: nounwind readnone
+declare <8 x i8> @llvm.aarch64.neon.uqshrn.v8i8(<8 x i16>, i32) #1
+
+; Function Attrs: nounwind readnone
+declare <2 x i64> @llvm.aarch64.neon.sqdmull.v2i64(<2 x i32>, <2 x i32>) #1
+
+; Function Attrs: nounwind readnone
+declare <2 x i64> @llvm.aarch64.neon.sqadd.v2i64(<2 x i64>, <2 x i64>) #1
+
+; Function Attrs: nounwind readnone
+declare <2 x i64> @llvm.aarch64.neon.addp.v2i64(<2 x i64>, <2 x i64>) #1
+
+; Function Attrs: nounwind readnone
+declare <2 x i32> @llvm.aarch64.neon.sqdmulh.v2i32(<2 x i32>, <2 x i32>) #1
+
+attributes #0 = { nounwind readnone "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+neon" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }