diff --git a/llvm/lib/Target/DirectX/DXILOpLowering.cpp b/llvm/lib/Target/DirectX/DXILOpLowering.cpp
index 83cc4b18824c7..efcd9970a4652 100644
--- a/llvm/lib/Target/DirectX/DXILOpLowering.cpp
+++ b/llvm/lib/Target/DirectX/DXILOpLowering.cpp
@@ -770,8 +770,20 @@ class OpLowerer {
         continue;
       Intrinsic::ID ID = F.getIntrinsicID();
       switch (ID) {
-      default:
+      // NOTE: Skip dx_resource_casthandle here. They are
+      // resolved after this loop in cleanupHandleCasts.
+      case Intrinsic::dx_resource_casthandle:
+      // NOTE: llvm.dbg.value is supported as is in DXIL.
+      case Intrinsic::dbg_value:
+      case Intrinsic::not_intrinsic:
         continue;
+      default: {
+        DiagnosticInfoUnsupported Diag(
+            F, "Unsupported intrinsic for DXIL lowering");
+        M.getContext().diagnose(Diag);
+        HasErrors |= true;
+        break;
+      }
 #define DXIL_OP_INTRINSIC(OpCode, Intrin, ...)                                 \
   case Intrin:                                                                 \
     HasErrors |= replaceFunctionWithOp(                                        \
diff --git a/llvm/test/CodeGen/DirectX/clamp.ll b/llvm/test/CodeGen/DirectX/clamp.ll
index 6345abc1789bc..54c6aa5040c4a 100644
--- a/llvm/test/CodeGen/DirectX/clamp.ll
+++ b/llvm/test/CodeGen/DirectX/clamp.ll
@@ -286,7 +286,7 @@ declare <3 x half> @llvm.dx.nclamp.v3f16(<3 x half>, <3 x half>, <3 x half>)
 declare <4 x float> @llvm.dx.nclamp.v4f32(<4 x float>, <4 x float>, <4 x float>)
 declare <2 x double> @llvm.dx.nclamp.v2f64(<2 x double>, <2 x double>, <2 x double>)
 declare <4 x i32> @llvm.dx.sclamp.v4i32(<4 x i32>, <4 x i32>, <4 x i32>)
-declare <3 x i16> @llvm.dx.uclamp.v3i32(<3 x i16>, <3 x i32>, <3 x i16>)
+declare <3 x i16> @llvm.dx.uclamp.v3i16(<3 x i16>, <3 x i16>, <3 x i16>)
 declare <4 x i32> @llvm.dx.uclamp.v4i32(<4 x i32>, <4 x i32>, <4 x i32>)
 declare <2 x i64> @llvm.dx.uclamp.v2i64(<2 x i64>, <2 x i64>, <2 x i64>)
 
diff --git a/llvm/test/CodeGen/DirectX/discard.ll b/llvm/test/CodeGen/DirectX/discard.ll
index 2a9ec59156e7c..81a96d577ba1a 100644
--- a/llvm/test/CodeGen/DirectX/discard.ll
+++ b/llvm/test/CodeGen/DirectX/discard.ll
@@ -1,4 +1,4 @@
-; RUN: opt -passes='function(scalarizer),module(dxil-op-lower,dxil-intrinsic-expansion)' -S -mtriple=dxil-pc-shadermodel6.3-pixel %s | FileCheck %s
+; RUN: opt -passes='function(scalarizer),module(dxil-intrinsic-expansion,dxil-op-lower)' -S -mtriple=dxil-pc-shadermodel6.3-pixel %s | FileCheck %s
 
 ; CHECK-LABEL: define void @test_scalar
 ; CHECK: call void @dx.op.discard(i32 82, i1 %0)
diff --git a/llvm/test/CodeGen/DirectX/unsupported_intrinsic.ll b/llvm/test/CodeGen/DirectX/unsupported_intrinsic.ll
new file mode 100644
index 0000000000000..d703f2f04c494
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/unsupported_intrinsic.ll
@@ -0,0 +1,11 @@
+; RUN: not opt -S -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s 2>&1 | FileCheck %s
+
+; CHECK: error: <unknown>:0:0: in function llvm.vector.reduce.and.v4i32 i32 (<4 x i32>): Unsupported intrinsic for DXIL lowering
+define i32 @fn_and(<4 x i32> %0) local_unnamed_addr #0 {
+  %2 = tail call i32 @llvm.vector.reduce.and.v4i32(<4 x i32> %0)
+  ret i32 %2
+}
+
+declare i32 @llvm.vector.reduce.and.v4i32(<4 x i32>)
+
+attributes #0 = { convergent norecurse nounwind "hlsl.export"}