diff --git a/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp b/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp
index af0bb71366b9..15dc33f2df64 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprCXX.cpp
@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/AST/CharUnits.h"
 #include "clang/CIR/Dialect/IR/CIRAttrs.h"
 #include "clang/CIR/MissingFeatures.h"
 #include <CIRGenCXXABI.h>
@@ -876,6 +877,7 @@ void CIRGenFunction::emitNewArrayInitializer(
   unsigned InitListElements = 0;
 
   const Expr *Init = E->getInitializer();
+  Address EndOfInit = Address::invalid();
   QualType::DestructionKind DtorKind = ElementType.isDestructedType();
   CleanupDeactivationScope deactivation(*this);
 
@@ -898,7 +900,13 @@ void CIRGenFunction::emitNewArrayInitializer(
     // Subtract out the size of any elements we've already initialized.
     auto RemainingSize = AllocSizeWithoutCookie;
     if (InitListElements) {
-      llvm_unreachable("NYI");
+      // We know this can't overflow; we check this when doing the allocation.
+      unsigned InitializedSize =
+          getContext().getTypeSizeInChars(ElementType).getQuantity() *
+          InitListElements;
+      auto InitSizeOp =
+          builder.getConstInt(Loc, RemainingSize.getType(), InitializedSize);
+      RemainingSize = builder.createSub(RemainingSize, InitSizeOp);
     }
 
     // Create the memset.
@@ -946,8 +954,24 @@ void CIRGenFunction::emitNewArrayInitializer(
     }
 
     CharUnits StartAlign = CurPtr.getAlignment();
+    unsigned i = 0;
     for (const Expr *IE : InitExprs) {
-      llvm_unreachable("NYI");
+      if (EndOfInit.isValid()) {
+        // This will involve DTor handling.
+        llvm_unreachable("NYI");
+      }
+      // FIXME: If the last initializer is an incomplete initializer list for
+      // an array, and we have an array filler, we can fold together the two
+      // initialization loops.
+      StoreAnyExprIntoOneUnit(*this, IE, IE->getType(), CurPtr,
+                              AggValueSlot::DoesNotOverlap);
+      auto Loc = getLoc(IE->getExprLoc());
+      auto CastOp = builder.createPtrBitcast(CurPtr.getPointer(),
+                                             convertTypeForMem(AllocType));
+      auto OffsetOp = builder.getSignedInt(Loc, 1, /*width=*/32);
+      auto DataPtr = builder.createPtrStride(Loc, CastOp, OffsetOp);
+      CurPtr = Address(DataPtr, CurPtr.getType(),
+                       StartAlign.alignmentAtOffset((++i) * ElementSize));
     }
 
     // The remaining elements are filled with the array filler expression.
diff --git a/clang/test/CIR/CodeGen/new.cpp b/clang/test/CIR/CodeGen/new.cpp
index 9134018d8673..2750929832e0 100644
--- a/clang/test/CIR/CodeGen/new.cpp
+++ b/clang/test/CIR/CodeGen/new.cpp
@@ -161,3 +161,31 @@ void t_constant_size_memset_init() {
 // CHECK:    %[[#ZERO:]] = cir.const #cir.int<0> : !u8i
 // CHECK:    %[[#ZERO_I32:]] = cir.cast(integral, %[[#ZERO]] : !u8i), !s32i
 // CHECK:    cir.libc.memset %[[#ALLOCATION_SIZE]] bytes from %[[#VOID_PTR]] set to %[[#ZERO_I32]] : !cir.ptr<!void>, !s32i, !u64i
+
+void t_constant_size_partial_init() {
+  auto p = new int[16] { 1, 2, 3 };
+}
+
+// CHECK:  cir.func @_Z28t_constant_size_partial_initv()
+// CHECK:    %[[#NUM_ELEMENTS:]] = cir.const #cir.int<16> : !u64i
+// CHECK:    %[[#ALLOCATION_SIZE:]] = cir.const #cir.int<64> : !u64i
+// CHECK:    %[[#ALLOC_PTR:]] = cir.call @_Znam(%[[#ALLOCATION_SIZE]]) : (!u64i) -> !cir.ptr<!void>
+// CHECK:    %[[#ELEM_0_PTR:]] = cir.cast(bitcast, %[[#ALLOC_PTR]] : !cir.ptr<!void>), !cir.ptr<!s32i>
+// CHECK:    %[[#CONST_ONE:]] = cir.const #cir.int<1> : !s32i
+// CHECK:    cir.store %[[#CONST_ONE]], %[[#ELEM_0_PTR]] : !s32i, !cir.ptr<!s32i>
+// CHECK:    %[[#OFFSET:]] = cir.const #cir.int<1> : !s32i
+// CHECK:    %[[#ELEM_1_PTR:]] = cir.ptr_stride(%[[#ELEM_0_PTR]] : !cir.ptr<!s32i>, %[[#OFFSET]] : !s32i), !cir.ptr<!s32i>
+// CHECK:    %[[#CONST_TWO:]] = cir.const #cir.int<2> : !s32i
+// CHECK:    cir.store %[[#CONST_TWO]], %[[#ELEM_1_PTR]] : !s32i, !cir.ptr<!s32i>
+// CHECK:    %[[#OFFSET1:]] = cir.const #cir.int<1> : !s32i
+// CHECK:    %[[#ELEM_2_PTR:]] = cir.ptr_stride(%[[#ELEM_1_PTR]] : !cir.ptr<!s32i>, %[[#OFFSET1]] : !s32i), !cir.ptr<!s32i>
+// CHECK:    %[[#CONST_THREE:]] = cir.const #cir.int<3> : !s32i
+// CHECK:    cir.store %[[#CONST_THREE]], %[[#ELEM_2_PTR]] : !s32i, !cir.ptr<!s32i>
+// CHECK:    %[[#OFFSET2:]] = cir.const #cir.int<1> : !s32i
+// CHECK:    %[[#ELEM_3_PTR:]] = cir.ptr_stride(%[[#ELEM_2_PTR]] : !cir.ptr<!s32i>, %[[#OFFSET2]] : !s32i), !cir.ptr<!s32i>
+// CHECK:    %[[#INIT_SIZE:]] = cir.const #cir.int<12> : !u64i
+// CHECK:    %[[#REMAINING_SIZE:]] = cir.binop(sub, %[[#ALLOCATION_SIZE]], %[[#INIT_SIZE]]) : !u64i
+// CHECK:    %[[#VOID_PTR:]] = cir.cast(bitcast, %[[#ELEM_3_PTR]] : !cir.ptr<!s32i>), !cir.ptr<!void>
+// CHECK:    %[[#ZERO:]] = cir.const #cir.int<0> : !u8i
+// CHECK:    %[[#ZERO_I32:]] = cir.cast(integral, %[[#ZERO]] : !u8i), !s32i
+// CHECK:    cir.libc.memset %[[#REMAINING_SIZE]] bytes from %[[#VOID_PTR]] set to %[[#ZERO_I32]] : !cir.ptr<!void>, !s32i, !u64i
diff --git a/clang/test/CIR/Lowering/new.cpp b/clang/test/CIR/Lowering/new.cpp
index c4c12531a6b7..bff825323e9e 100644
--- a/clang/test/CIR/Lowering/new.cpp
+++ b/clang/test/CIR/Lowering/new.cpp
@@ -67,3 +67,19 @@ void t_constant_size_memset_init() {
 // LLVM:   %[[ADDR:.*]] = call ptr @_Znam(i64 64)
 // LLVM:   call void @llvm.memset.p0.i64(ptr %[[ADDR]], i8 0, i64 64, i1 false)
 // LLVM:   store ptr %[[ADDR]], ptr %[[ALLOCA]], align 8
+
+void t_constant_size_partial_init() {
+  auto p = new int[16] { 1, 2, 3 };
+}
+
+// LLVM: @_Z28t_constant_size_partial_initv()
+// LLVM:   %[[ALLOCA:.*]] = alloca ptr, i64 1, align 8
+// LLVM:   %[[ADDR:.*]] = call ptr @_Znam(i64 64)
+// LLVM:   store i32 1, ptr %[[ADDR]], align 4
+// LLVM:   %[[ELEM_1_PTR:.*]] = getelementptr i32, ptr %[[ADDR]], i64 1
+// LLVM:   store i32 2, ptr %[[ELEM_1_PTR]], align 4
+// LLVM:   %[[ELEM_2_PTR:.*]] = getelementptr i32, ptr %[[ELEM_1_PTR]], i64 1
+// LLVM:   store i32 3, ptr %[[ELEM_2_PTR]], align 4
+// LLVM:   %[[ELEM_3_PTR:.*]] = getelementptr i32, ptr %[[ELEM_2_PTR]], i64 1
+// LLVM:   call void @llvm.memset.p0.i64(ptr %[[ELEM_3_PTR]], i8 0, i64 52, i1 false)
+// LLVM:   store ptr %[[ADDR]], ptr %[[ALLOCA]], align 8