diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
index 6b4d2168e7493..c2552a95ad210 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -2387,8 +2387,10 @@ SDValue NVPTXTargetLowering::LowerVECTOR_SHUFFLE(SDValue Op,
   const ShuffleVectorSDNode *SVN = cast<ShuffleVectorSDNode>(Op.getNode());
   SDValue V2 = Op.getOperand(1);
   uint32_t Selector = 0;
-  for (auto I : llvm::enumerate(SVN->getMask()))
-    Selector |= (I.value() << (I.index() * 4));
+  for (auto I : llvm::enumerate(SVN->getMask())) {
+    if (I.value() != -1) // -1 is a placeholder for undef.
+      Selector |= (I.value() << (I.index() * 4));
+  }
 
   SDLoc DL(Op);
   return DAG.getNode(NVPTXISD::PRMT, DL, MVT::v4i8, V1, V2,
diff --git a/llvm/test/CodeGen/NVPTX/shuffle-vec-undef-init.ll b/llvm/test/CodeGen/NVPTX/shuffle-vec-undef-init.ll
new file mode 100644
index 0000000000000..4f147f28e1a57
--- /dev/null
+++ b/llvm/test/CodeGen/NVPTX/shuffle-vec-undef-init.ll
@@ -0,0 +1,18 @@
+; RUN: llc < %s -march=nvptx -mcpu=sm_20 -verify-machineinstrs | FileCheck %s  
+; RUN: llc < %s -march=nvptx -mcpu=sm_20 -verify-machineinstrs | FileCheck %s   -check-prefix=CHECK-FOUND
+
+define void @kernel_func(ptr %in.vec, ptr %out.vec0) nounwind {
+  entry:
+  %wide.vec = load <32 x i8>, ptr %in.vec, align 64
+  %vec0 = shufflevector <32 x i8> %wide.vec, <32 x i8> undef, <4 x i32> <i32 0, i32 8, i32 16, i32 24>
+  store <4 x i8> %vec0, ptr %out.vec0, align 64
+  ret void
+
+; CHECK-FOUND: prmt.b32 	{{.*}} 16384;
+; CHECK-FOUND: prmt.b32 	{{.*}} 64;
+; CHECK-FOUND: prmt.b32 	{{.*}} 30224;
+
+; CHECK:  @kernel_func
+; CHECK-NOT: 	prmt.b32 	{{.*}} -1;
+; CHECK:  -- End function
+}