Index: llvm/include/llvm/IR/IntrinsicsSPIRV.td
===================================================================
--- llvm/include/llvm/IR/IntrinsicsSPIRV.td
+++ llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -31,4 +31,5 @@
   def int_spv_cmpxchg : Intrinsic<[llvm_i32_ty], [llvm_any_ty, llvm_vararg_ty]>;
   def int_spv_unreachable : Intrinsic<[], []>;
   def int_spv_alloca : Intrinsic<[llvm_any_ty], []>;
+  def int_spv_undef : Intrinsic<[llvm_i32_ty], []>;
 }
Index: llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp
===================================================================
--- llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp
+++ llvm/lib/Target/SPIRV/SPIRVEmitIntrinsics.cpp
@@ -56,6 +56,7 @@
   DenseMap<Instruction *, Constant *> AggrConsts;
   DenseSet<Instruction *> AggrStores;
   void preprocessCompositeConstants();
+  void preprocessUndefs();
   CallInst *buildIntrWithMD(Intrinsic::ID IntrID, ArrayRef<Type *> Types,
                             Value *Arg, Value *Arg2) {
     ConstantAsMetadata *CM = ValueAsMetadata::getConstant(Arg);
@@ -151,6 +152,28 @@
   Old->eraseFromParent();
 }
 
+void SPIRVEmitIntrinsics::preprocessUndefs() {
+  std::queue<Instruction *> Worklist;
+  for (auto &I : instructions(F))
+    Worklist.push(&I);
+
+  while (!Worklist.empty()) {
+    Instruction *I = Worklist.front();
+    Worklist.pop();
+
+    for (auto &Op : I->operands()) {
+      if (isa<UndefValue>(Op) && Op->getType()->isAggregateType()) {
+        auto *AggrUndef = dyn_cast<UndefValue>(Op);
+        IRB->SetInsertPoint(I);
+        auto *IntrUndef = IRB->CreateIntrinsic(Intrinsic::spv_undef, {}, {});
+        Worklist.push(IntrUndef);
+        I->replaceUsesOfWith(Op, IntrUndef);
+        AggrConsts[IntrUndef] = AggrUndef;
+      }
+    }
+  }
+}
+
 void SPIRVEmitIntrinsics::preprocessCompositeConstants() {
   std::queue<Instruction *> Worklist;
   for (auto &I : instructions(F))
@@ -369,7 +392,7 @@
     setInsertPointSkippingPhis(*IRB, I->getNextNode());
     Type *TypeToAssign = Ty;
     if (auto *II = dyn_cast<IntrinsicInst>(I)) {
-      if (II->getIntrinsicID() == Intrinsic::spv_const_composite) {
+      if (II->getIntrinsicID() == Intrinsic::spv_const_composite || II->getIntrinsicID() == Intrinsic::spv_undef) {
         auto t = AggrConsts.find(II);
         assert(t != AggrConsts.end());
         TypeToAssign = t->second->getType();
@@ -453,6 +476,7 @@
   for (auto &GV : Func.getParent()->globals())
     processGlobalValue(GV);
 
+  preprocessUndefs();
   preprocessCompositeConstants();
   SmallVector<Instruction *> Worklist;
   for (auto &I : instructions(Func))
Index: llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
===================================================================
--- llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -1344,6 +1344,12 @@
     assert(MI);
     return selectGlobalValue(MI->getOperand(0).getReg(), *MI, Init);
   } break;
+  case Intrinsic::spv_undef: {
+    auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpUndef))
+                   .addDef(ResVReg)
+                   .addUse(GR.getSPIRVTypeID(ResType));
+    return MIB.constrainAllUses(TII, TRI, RBI);
+  } break;
   case Intrinsic::spv_const_composite: {
     // If no values are attached, the composite is null constant.
     bool IsNull = I.getNumExplicitDefs() + 1 == I.getNumExplicitOperands();
Index: llvm/test/CodeGen/SPIRV/instructions/undef-nested-composite-store.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/SPIRV/instructions/undef-nested-composite-store.ll
@@ -0,0 +1,29 @@
+; RUN: llc -O0 -mtriple=spirv32-unknown-unknown %s -o - | FileCheck %s
+
+; CHECK-DAG: %[[#I32:]] = OpTypeInt 32
+; CHECK-DAG: %[[#I16:]] = OpTypeInt 16
+; CHECK-DAG: %[[#STRUCT:]] = OpTypeStruct %[[#I32]] %[[#I16]]
+; CHECK-DAG: %[[#NESTED_STRUCT:]] = OpTypeStruct %[[#STRUCT]] %[[#I16]]
+; CHECK-DAG: %[[#UNDEF:]] = OpUndef %[[#NESTED_STRUCT]]
+
+; CHECK: %[[#]] = OpFunction %[[#]] None %[[#]]
+; CHECK-NEXT: %[[#PTR:]] = OpFunctionParameter %[[#]]
+; CHECK-NEXT: %[[#]] = OpLabel
+; CHECK-NEXT: OpStore %[[#PTR]] %[[#UNDEF]] Aligned 4
+; CHECK-NEXT: OpReturn
+; CHECK-NEXT: OpFunctionEnd
+
+%struct = type {
+  i32,
+  i16
+}
+
+%nested_struct = type {
+  %struct,
+  i16
+}
+
+define void @foo(ptr %ptr) {
+  store %nested_struct undef, ptr %ptr
+  ret void
+}
Index: llvm/test/CodeGen/SPIRV/instructions/undef-simple-composite-store.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/SPIRV/instructions/undef-simple-composite-store.ll
@@ -0,0 +1,18 @@
+; RUN: llc -O0 -mtriple=spirv32-unknown-unknown %s -o - | FileCheck %s
+
+; CHECK-DAG: %[[#I32:]] = OpTypeInt 32
+; CHECK-DAG: %[[#I16:]] = OpTypeInt 16
+; CHECK-DAG: %[[#STRUCT:]] = OpTypeStruct %[[#I32]] %[[#I16]]
+; CHECK-DAG: %[[#UNDEF:]] = OpUndef %[[#STRUCT]]
+
+; CHECK: %[[#]] = OpFunction %[[#]] None %[[#]]
+; CHECK-NEXT: %[[#PTR:]] = OpFunctionParameter %[[#]]
+; CHECK-NEXT: %[[#]] = OpLabel
+; CHECK-NEXT: OpStore %[[#PTR]] %[[#UNDEF]] Aligned 4
+; CHECK-NEXT: OpReturn
+; CHECK-NEXT: OpFunctionEnd
+
+define void @foo(ptr %ptr) {
+  store { i32, i16 } undef, ptr %ptr
+  ret void
+}