diff --git a/llvm/include/llvm/Support/TypeSize.h b/llvm/include/llvm/Support/TypeSize.h
--- a/llvm/include/llvm/Support/TypeSize.h
+++ b/llvm/include/llvm/Support/TypeSize.h
@@ -146,6 +146,9 @@
     return (MinSize & 7) == 0;
   }
 
+  // Returns true if the type size is non-zero.
+  bool isNonZero() const { return MinSize != 0; }
+
   // Casts to a uint64_t if this is a fixed-width size.
   //
   // This interface is deprecated and will be removed in a future version
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3497,8 +3497,8 @@
   if (isa<UndefValue>(V))
     return UndefInt8;
 
-  const uint64_t Size = DL.getTypeStoreSize(V->getType());
-  if (!Size)
+  // Return Undef for zero-sized type.
+  if (!DL.getTypeStoreSize(V->getType()).isNonZero())
     return UndefInt8;
 
   Constant *C = dyn_cast<Constant>(V);
@@ -3816,7 +3816,7 @@
       Array = nullptr;
     } else {
       const DataLayout &DL = GV->getParent()->getDataLayout();
-      uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy);
+      uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy).getFixedSize();
       uint64_t Length = SizeInBytes / (ElementSize / 8);
       if (Length <= Offset)
         return false;
diff --git a/llvm/test/Transforms/MemCpyOpt/store-to-memset-is-nonzero-type.ll b/llvm/test/Transforms/MemCpyOpt/store-to-memset-is-nonzero-type.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/MemCpyOpt/store-to-memset-is-nonzero-type.ll
@@ -0,0 +1,73 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S < %s -memcpyopt | FileCheck %s
+
+; Array
+
+define void @array_zero([0 x i8]* %p) {
+; CHECK-LABEL: @array_zero(
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast [0 x i8]* [[P:%.*]] to i8*
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP1]], i8 undef, i64 0, i1 false)
+; CHECK-NEXT:    ret void
+;
+  store [0 x i8] zeroinitializer, [0 x i8]* %p
+  ret void
+}
+
+define void @array_nonzero([1 x i8]* %p) {
+; CHECK-LABEL: @array_nonzero(
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast [1 x i8]* [[P:%.*]] to i8*
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP1]], i8 0, i64 1, i1 false)
+; CHECK-NEXT:    ret void
+;
+  store [1 x i8] zeroinitializer, [1 x i8]* %p
+  ret void
+}
+
+; Structure
+
+define void @struct_zero({ }* %p) {
+; CHECK-LABEL: @struct_zero(
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast {}* [[P:%.*]] to i8*
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP1]], i8 undef, i64 0, i1 false)
+; CHECK-NEXT:    ret void
+;
+  store { } zeroinitializer, { }* %p
+  ret void
+}
+define void @struct_nonzero({ i8 }* %p) {
+; CHECK-LABEL: @struct_nonzero(
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast { i8 }* [[P:%.*]] to i8*
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP1]], i8 0, i64 1, i1 false)
+; CHECK-NEXT:    ret void
+;
+  store { i8 } zeroinitializer, { i8 }* %p
+  ret void
+}
+
+; Vector
+
+; Test only non-zero vector. Zero element vector is illegal
+
+define void @vector_fixed_length_nonzero(<16 x i8>* %p) {
+; CHECK-LABEL: @vector_fixed_length_nonzero(
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr <16 x i8>, <16 x i8>* [[P:%.*]], i64 0
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr <16 x i8>, <16 x i8>* [[P]], i64 1
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <16 x i8>* [[TMP0]] to i8*
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 16 [[TMP1]], i8 0, i64 32, i1 false)
+; CHECK-NEXT:    ret void
+;
+  %tmp0 = getelementptr <16 x i8>, <16 x i8>* %p, i64 0
+  store <16 x i8> zeroinitializer, <16 x i8>* %tmp0
+  %tmp1 = getelementptr <16 x i8>, <16 x i8>* %p, i64 1
+  store <16 x i8> zeroinitializer, <16 x i8>* %tmp1
+  ret void
+}
+
+define void @vector_scalable_nonzero(<vscale x 4 x i32>* %p) {
+; CHECK-LABEL: @vector_scalable_nonzero(
+; CHECK-NEXT:    store <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32>* [[P:%.*]]
+; CHECK-NEXT:    ret void
+;
+  store <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32>* %p
+  ret void
+}