diff --git a/src/cgutils.cpp b/src/cgutils.cpp
index 4547e693755cd..a166b0a2c4800 100644
--- a/src/cgutils.cpp
+++ b/src/cgutils.cpp
@@ -4213,7 +4213,7 @@ static jl_cgval_t emit_new_struct(jl_codectx_t &ctx, jl_value_t *ty, size_t narg
                 else {
                     strct = UndefValue::get(lt);
                     if (nargs < nf)
-                        strct = ctx.builder.CreateFreeze(strct);
+                        strct = ctx.builder.CreateFreeze(strct); // Change this to zero initialize instead?
                 }
             }
             else if (tracked.second) {
@@ -4380,25 +4380,18 @@ static jl_cgval_t emit_new_struct(jl_codectx_t &ctx, jl_value_t *ty, size_t narg
                     ctx.builder.restoreIP(savedIP);
                 }
             }
-            for (size_t i = nargs; i < nf; i++) {
-                if (!jl_field_isptr(sty, i) && jl_is_uniontype(jl_field_type(sty, i))) {
-                    ssize_t offs = jl_field_offset(sty, i);
-                    ssize_t ptrsoffs = -1;
-                    if (!inline_roots.empty())
-                        std::tie(offs, ptrsoffs) = split_value_field(sty, i);
-                    assert(ptrsoffs < 0 && offs >= 0);
-                    int fsz = jl_field_size(sty, i) - 1;
-                    if (init_as_value) {
+            if (init_as_value) {
+                for (size_t i = nargs; i < nf; i++) {
+                    if (!jl_field_isptr(sty, i) && jl_is_uniontype(jl_field_type(sty, i))) {
+                        ssize_t offs = jl_field_offset(sty, i);
+                        ssize_t ptrsoffs = -1;
+                        if (!inline_roots.empty())
+                            std::tie(offs, ptrsoffs) = split_value_field(sty, i);
+                        assert(ptrsoffs < 0 && offs >= 0);
+                        int fsz = jl_field_size(sty, i) - 1;
                         unsigned llvm_idx = convert_struct_offset(ctx, cast<StructType>(lt), offs + fsz);
                         strct = ctx.builder.CreateInsertValue(strct, ConstantInt::get(getInt8Ty(ctx.builder.getContext()), 0), ArrayRef<unsigned>(llvm_idx));
                     }
-                    else {
-                        jl_aliasinfo_t ai = jl_aliasinfo_t::fromTBAA(ctx, ctx.tbaa().tbaa_unionselbyte);
-                        Instruction *dest = cast<Instruction>(emit_ptrgep(ctx, strct, offs + fsz));
-                        if (promotion_point == nullptr)
-                            promotion_point = dest;
-                        ai.decorateInst(ctx.builder.CreateAlignedStore(ctx.builder.getInt8(0), dest, Align(1)));
-                    }
                 }
             }
             if (nargs < nf) {
@@ -4407,9 +4400,9 @@ static jl_cgval_t emit_new_struct(jl_codectx_t &ctx, jl_value_t *ty, size_t narg
                 if (promotion_point)
                     ctx.builder.SetInsertPoint(promotion_point);
                 if (strct) {
-                    promotion_point = cast<FreezeInst>(ctx.builder.CreateFreeze(UndefValue::get(lt)));
                     jl_aliasinfo_t ai = jl_aliasinfo_t::fromTBAA(ctx, ctx.tbaa().tbaa_stack);
-                    ai.decorateInst(ctx.builder.CreateStore(promotion_point, strct));
+                    promotion_point = ai.decorateInst(ctx.builder.CreateMemSet(strct, ConstantInt::get(getInt8Ty(ctx.builder.getContext()), 0),
+                                                                jl_datatype_size(ty), MaybeAlign(jl_datatype_align(ty))));
                 }
                 ctx.builder.restoreIP(savedIP);
             }
diff --git a/src/llvm-alloc-opt.cpp b/src/llvm-alloc-opt.cpp
index 188955fd50972..0dc07cbd1ae4c 100644
--- a/src/llvm-alloc-opt.cpp
+++ b/src/llvm-alloc-opt.cpp
@@ -622,14 +622,9 @@ void Optimizer::initializeAlloca(IRBuilder<> &prolog_builder, AllocaInst *buff,
         return;
     assert(!buff->isArrayAllocation());
     Type *T = buff->getAllocatedType();
-    Value *Init = UndefValue::get(T);
-    if ((allockind & AllocFnKind::Zeroed) != AllocFnKind::Unknown)
-        Init = Constant::getNullValue(T); // zero, as described
-    else if (allockind == AllocFnKind::Unknown)
-        Init = Constant::getNullValue(T); // assume zeroed since we didn't find the attribute
-    else
-        Init = prolog_builder.CreateFreeze(UndefValue::get(T)); // assume freeze, since LLVM does not natively support this case
-    prolog_builder.CreateStore(Init, buff);
+    const DataLayout &DL = F.getParent()->getDataLayout();
+    prolog_builder.CreateMemSet(buff, ConstantInt::get(Type::getInt8Ty(prolog_builder.getContext()), 0), DL.getTypeAllocSize(T), buff->getAlign());
+
 }
 
 // This function should not erase any safepoint so that the lifetime marker can find and cache
diff --git a/test/llvmpasses/alloc-opt-pass.ll b/test/llvmpasses/alloc-opt-pass.ll
index b962157120456..665687e86835d 100644
--- a/test/llvmpasses/alloc-opt-pass.ll
+++ b/test/llvmpasses/alloc-opt-pass.ll
@@ -76,7 +76,7 @@ L3:                                               ; preds = %L2, %L1, %0
 ; CHECK-LABEL: @legal_int_types
 ; CHECK: alloca [12 x i8]
 ; CHECK-NOT: alloca i96
-; CHECK: store [12 x i8] zeroinitializer,
+; CHECK: call void @llvm.memset.p0.i64(ptr align 16 %var1,
 ; CHECK: ret void
 define void @legal_int_types() {
   %pgcstack = call ptr @julia.get_pgcstack()
@@ -140,7 +140,7 @@ L2:                                               ; preds = %0
 ; CHECK: alloca
 ; CHECK-NOT: call token(...) @llvm.julia.gc_preserve_begin
 ; CHECK: call void @llvm.lifetime.start
-; CHECK: store [8 x i8] zeroinitializer,
+; CHECK: call void @llvm.memset.p0.i64(ptr align 16 %v,
 ; CHECK-NOT: call void @llvm.lifetime.end
 define void @lifetime_no_preserve_end(ptr noalias nocapture noundef nonnull sret({}) %0) {
   %pgcstack = call ptr @julia.get_pgcstack()
@@ -164,11 +164,8 @@ define void @lifetime_no_preserve_end(ptr noalias nocapture noundef nonnull sret
 ; CHECK: alloca [1 x i8]
 ; CHECK-DAG: alloca [2 x i8]
 ; CHECK-DAG: alloca [3 x i8]
-; CHECK-DAG: freeze [1 x i8] undef
-; CHECK-DAG: store [1 x i8] %
-; CHECK-DAG: store [3 x i8] zeroinitializer,
-; CHECK-NOT: store
-; CHECK-NOT: zeroinitializer
+; CHECK-DAG: call void @llvm.memset.p0.i64(ptr align 1 %var1,
+; CHECK-DAG: call void @llvm.memset.p0.i64(ptr align 4 %var7,
 ; CHECK: ret void
 define void @initializers() {
   %pgcstack = call ptr @julia.get_pgcstack()