diff --git a/clang/include/clang/Basic/BuiltinsWebAssembly.def b/clang/include/clang/Basic/BuiltinsWebAssembly.def
--- a/clang/include/clang/Basic/BuiltinsWebAssembly.def
+++ b/clang/include/clang/Basic/BuiltinsWebAssembly.def
@@ -118,5 +118,19 @@
 TARGET_BUILTIN(__builtin_wasm_trunc_saturate_s_i64x2_f64x2, "V2LLiV2d", "nc", "unimplemented-simd128")
 TARGET_BUILTIN(__builtin_wasm_trunc_saturate_u_i64x2_f64x2, "V2LLiV2d", "nc", "unimplemented-simd128")
 
+TARGET_BUILTIN(__builtin_wasm_narrow_s_i8x16_i16x8, "V16cV8s", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_narrow_u_i8x16_i16x8, "V16cV8s", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_narrow_s_i16x8_i32x4, "V8sV4i", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_narrow_u_i16x8_i32x4, "V8sV4i", "nc", "simd128")
+
+TARGET_BUILTIN(__builtin_wasm_widen_low_s_i16x8_i8x16, "V8sV16c", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_high_s_i16x8_i8x16, "V8sV16c", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_low_u_i16x8_i8x16, "V8sV16c", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_high_u_i16x8_i8x16, "V8sV16c", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_low_s_i32x4_i16x8, "V4iV8s", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_high_s_i32x4_i16x8, "V4iV8s", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_low_u_i32x4_i16x8, "V4iV8s", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_widen_high_u_i32x4_i16x8, "V4iV8s", "nc", "simd128")
+
 #undef BUILTIN
 #undef TARGET_BUILTIN
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -14196,6 +14196,62 @@
     Function *Callee = CGM.getIntrinsic(IntNo, A->getType());
     return Builder.CreateCall(Callee, {A, B, C});
   }
+  case WebAssembly::BI__builtin_wasm_narrow_s_i8x16_i16x8:
+  case WebAssembly::BI__builtin_wasm_narrow_u_i8x16_i16x8:
+  case WebAssembly::BI__builtin_wasm_narrow_s_i16x8_i32x4:
+  case WebAssembly::BI__builtin_wasm_narrow_u_i16x8_i32x4: {
+    Value *Vec = EmitScalarExpr(E->getArg(0));
+    unsigned IntNo;
+    switch (BuiltinID) {
+    case WebAssembly::BI__builtin_wasm_narrow_s_i8x16_i16x8:
+    case WebAssembly::BI__builtin_wasm_narrow_s_i16x8_i32x4:
+      IntNo = Intrinsic::wasm_narrow_signed;
+      break;
+    case WebAssembly::BI__builtin_wasm_narrow_u_i8x16_i16x8:
+    case WebAssembly::BI__builtin_wasm_narrow_u_i16x8_i32x4:
+      IntNo = Intrinsic::wasm_narrow_unsigned;
+      break;
+    default:
+      llvm_unreachable("unexpected builtin ID");
+    }
+    Function *Callee =
+        CGM.getIntrinsic(IntNo, {ConvertType(E->getType()), Vec->getType()});
+    return Builder.CreateCall(Callee, Vec);
+  }
+  case WebAssembly::BI__builtin_wasm_widen_low_s_i16x8_i8x16:
+  case WebAssembly::BI__builtin_wasm_widen_high_s_i16x8_i8x16:
+  case WebAssembly::BI__builtin_wasm_widen_low_u_i16x8_i8x16:
+  case WebAssembly::BI__builtin_wasm_widen_high_u_i16x8_i8x16:
+  case WebAssembly::BI__builtin_wasm_widen_low_s_i32x4_i16x8:
+  case WebAssembly::BI__builtin_wasm_widen_high_s_i32x4_i16x8:
+  case WebAssembly::BI__builtin_wasm_widen_low_u_i32x4_i16x8:
+  case WebAssembly::BI__builtin_wasm_widen_high_u_i32x4_i16x8: {
+    Value *Vec = EmitScalarExpr(E->getArg(0));
+    unsigned IntNo;
+    switch (BuiltinID) {
+    case WebAssembly::BI__builtin_wasm_widen_low_s_i16x8_i8x16:
+    case WebAssembly::BI__builtin_wasm_widen_low_s_i32x4_i16x8:
+      IntNo = Intrinsic::wasm_widen_low_signed;
+      break;
+    case WebAssembly::BI__builtin_wasm_widen_high_s_i16x8_i8x16:
+    case WebAssembly::BI__builtin_wasm_widen_high_s_i32x4_i16x8:
+      IntNo = Intrinsic::wasm_widen_high_signed;
+      break;
+    case WebAssembly::BI__builtin_wasm_widen_low_u_i16x8_i8x16:
+    case WebAssembly::BI__builtin_wasm_widen_low_u_i32x4_i16x8:
+      IntNo = Intrinsic::wasm_widen_low_unsigned;
+      break;
+    case WebAssembly::BI__builtin_wasm_widen_high_u_i16x8_i8x16:
+    case WebAssembly::BI__builtin_wasm_widen_high_u_i32x4_i16x8:
+      IntNo = Intrinsic::wasm_widen_high_unsigned;
+      break;
+    default:
+      llvm_unreachable("unexpected builtin ID");
+    }
+    Function *Callee =
+        CGM.getIntrinsic(IntNo, {ConvertType(E->getType()), Vec->getType()});
+    return Builder.CreateCall(Callee, Vec);
+  }
   default:
     return nullptr;
   }
diff --git a/clang/test/CodeGen/builtins-wasm.c b/clang/test/CodeGen/builtins-wasm.c
--- a/clang/test/CodeGen/builtins-wasm.c
+++ b/clang/test/CodeGen/builtins-wasm.c
@@ -463,3 +463,75 @@
   // WEBASSEMBLY: call <2 x i64> @llvm.wasm.trunc.saturate.unsigned.v2i64.v2f64(<2 x double> %f)
   // WEBASSEMBLY-NEXT: ret
 }
+
+i8x16 narrow_s_i8x16_i16x8(i16x8 v) {
+  return __builtin_wasm_narrow_s_i8x16_i16x8(v);
+  // WEBASSEMBLY: call <16 x i8> @llvm.wasm.narrow.signed.v16i8.v8i16(<8 x i16> %v)
+  // WEBASSEMBLY: ret
+}
+
+i8x16 narrow_u_i8x16_i16x8(i16x8 v) {
+  return __builtin_wasm_narrow_u_i8x16_i16x8(v);
+  // WEBASSEMBLY: call <16 x i8> @llvm.wasm.narrow.unsigned.v16i8.v8i16(<8 x i16> %v)
+  // WEBASSEMBLY: ret
+}
+
+i16x8 narrow_s_i16x8_i32x4(i32x4 v) {
+  return __builtin_wasm_narrow_s_i16x8_i32x4(v);
+  // WEBASSEMBLY: call <8 x i16> @llvm.wasm.narrow.signed.v8i16.v4i32(<4 x i32> %v)
+  // WEBASSEMBLY: ret
+}
+
+i16x8 narrow_u_i16x8_i32x4(i32x4 v) {
+  return __builtin_wasm_narrow_u_i16x8_i32x4(v);
+  // WEBASSEMBLY: call <8 x i16> @llvm.wasm.narrow.unsigned.v8i16.v4i32(<4 x i32> %v)
+  // WEBASSEMBLY: ret
+}
+
+i16x8 widen_low_s_i16x8_i8x16(i8x16 v) {
+  return __builtin_wasm_widen_low_s_i16x8_i8x16(v);
+  // WEBASSEMBLY: call <8 x i16> @llvm.wasm.widen.low.signed.v8i16.v16i8(<16 x i8> %v)
+  // WEBASSEMBLY: ret
+}
+
+i16x8 widen_high_s_i16x8_i8x16(i8x16 v) {
+  return __builtin_wasm_widen_high_s_i16x8_i8x16(v);
+  // WEBASSEMBLY: call <8 x i16> @llvm.wasm.widen.high.signed.v8i16.v16i8(<16 x i8> %v)
+  // WEBASSEMBLY: ret
+}
+
+i16x8 widen_low_u_i16x8_i8x16(i8x16 v) {
+  return __builtin_wasm_widen_low_u_i16x8_i8x16(v);
+  // WEBASSEMBLY: call <8 x i16> @llvm.wasm.widen.low.unsigned.v8i16.v16i8(<16 x i8> %v)
+  // WEBASSEMBLY: ret
+}
+
+i16x8 widen_high_u_i16x8_i8x16(i8x16 v) {
+  return __builtin_wasm_widen_high_u_i16x8_i8x16(v);
+  // WEBASSEMBLY: call <8 x i16> @llvm.wasm.widen.high.unsigned.v8i16.v16i8(<16 x i8> %v)
+  // WEBASSEMBLY: ret
+}
+
+i32x4 widen_low_s_i32x4_i16x8(i16x8 v) {
+  return __builtin_wasm_widen_low_s_i32x4_i16x8(v);
+  // WEBASSEMBLY: call <4 x i32> @llvm.wasm.widen.low.signed.v4i32.v8i16(<8 x i16> %v)
+  // WEBASSEMBLY: ret
+}
+
+i32x4 widen_high_s_i32x4_i16x8(i16x8 v) {
+  return __builtin_wasm_widen_high_s_i32x4_i16x8(v);
+  // WEBASSEMBLY: call <4 x i32> @llvm.wasm.widen.high.signed.v4i32.v8i16(<8 x i16> %v)
+  // WEBASSEMBLY: ret
+}
+
+i32x4 widen_low_u_i32x4_i16x8(i16x8 v) {
+  return __builtin_wasm_widen_low_u_i32x4_i16x8(v);
+  // WEBASSEMBLY: call <4 x i32> @llvm.wasm.widen.low.unsigned.v4i32.v8i16(<8 x i16> %v)
+  // WEBASSEMBLY: ret
+}
+
+i32x4 widen_high_u_i32x4_i16x8(i16x8 v) {
+  return __builtin_wasm_widen_high_u_i32x4_i16x8(v);
+  // WEBASSEMBLY: call <4 x i32> @llvm.wasm.widen.high.unsigned.v4i32.v8i16(<8 x i16> %v)
+  // WEBASSEMBLY: ret
+}
diff --git a/llvm/include/llvm/IR/IntrinsicsWebAssembly.td b/llvm/include/llvm/IR/IntrinsicsWebAssembly.td
--- a/llvm/include/llvm/IR/IntrinsicsWebAssembly.td
+++ b/llvm/include/llvm/IR/IntrinsicsWebAssembly.td
@@ -117,6 +117,31 @@
   Intrinsic<[llvm_anyvector_ty],
             [LLVMMatchType<0>, LLVMMatchType<0>, LLVMMatchType<0>],
             [IntrNoMem, IntrSpeculatable]>;
+def int_wasm_narrow_signed :
+  Intrinsic<[llvm_anyvector_ty],
+            [llvm_anyvector_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+def int_wasm_narrow_unsigned :
+  Intrinsic<[llvm_anyvector_ty],
+            [llvm_anyvector_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+def int_wasm_widen_low_signed :
+  Intrinsic<[llvm_anyvector_ty],
+            [llvm_anyvector_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+def int_wasm_widen_high_signed :
+  Intrinsic<[llvm_anyvector_ty],
+            [llvm_anyvector_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+def int_wasm_widen_low_unsigned :
+  Intrinsic<[llvm_anyvector_ty],
+            [llvm_anyvector_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+def int_wasm_widen_high_unsigned :
+  Intrinsic<[llvm_anyvector_ty],
+            [llvm_anyvector_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+
 
 //===----------------------------------------------------------------------===//
 // Bulk memory intrinsics
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -712,6 +712,33 @@
 defm "" : SIMDConvert<v2i64, v2f64, fp_to_sint, "i64x2.trunc_sat_f64x2_s", 173>;
 defm "" : SIMDConvert<v2i64, v2f64, fp_to_uint, "i64x2.trunc_sat_f64x2_u", 174>;
 
+// Narrowing operations
+multiclass SIMDNarrow<ValueType vec_t, string vec, ValueType arg_t, string arg,
+                      bits<32> baseInst> {
+  defm "" : SIMDConvert<vec_t, arg_t, int_wasm_narrow_signed,
+                        vec#".narrow_"#arg#"_s", baseInst>;
+  defm "" : SIMDConvert<vec_t, arg_t, int_wasm_narrow_unsigned,
+                        vec#".narrow_"#arg#"_u", !add(baseInst, 1)>;
+}
+defm "" : SIMDNarrow<v16i8, "i8x16", v8i16, "i16x8", 198>;
+defm "" : SIMDNarrow<v8i16, "i16x8", v4i32, "i32x4", 200>;
+
+// Widening operations
+multiclass SIMDWiden<ValueType vec_t, string vec, ValueType arg_t, string arg,
+                     bits<32> baseInst> {
+  defm "" : SIMDConvert<vec_t, arg_t, int_wasm_widen_low_signed,
+                        vec#".widen_low_"#arg#"_s", baseInst>;
+  defm "" : SIMDConvert<vec_t, arg_t, int_wasm_widen_high_signed,
+                        vec#".widen_high_"#arg#"_s", !add(baseInst, 1)>;
+  defm "" : SIMDConvert<vec_t, arg_t, int_wasm_widen_low_unsigned,
+                        vec#".widen_low_"#arg#"_u", !add(baseInst, 2)>;
+  defm "" : SIMDConvert<vec_t, arg_t, int_wasm_widen_high_unsigned,
+                        vec#".widen_high_"#arg#"_u", !add(baseInst, 3)>;
+}
+
+defm "" : SIMDWiden<v8i16, "i16x8", v16i8, "i8x16", 202>;
+defm "" : SIMDWiden<v4i32, "i32x4", v8i16, "i16x8", 206>;
+
 // Lower llvm.wasm.trunc.saturate.* to saturating instructions
 def : Pat<(v4i32 (int_wasm_trunc_saturate_signed (v4f32 V128:$src))),
           (fp_to_sint_v4i32_v4f32 (v4f32 V128:$src))>;
diff --git a/llvm/test/MC/WebAssembly/simd-encodings.s b/llvm/test/MC/WebAssembly/simd-encodings.s
--- a/llvm/test/MC/WebAssembly/simd-encodings.s
+++ b/llvm/test/MC/WebAssembly/simd-encodings.s
@@ -463,4 +463,40 @@
     # CHECK: f64x2.convert_i64x2_u # encoding: [0xfd,0xb2,0x01]
     f64x2.convert_i64x2_u
 
+    # CHECK: i8x16.narrow_i16x8_s # encoding: [0xfd,0xc6,0x01]
+    i8x16.narrow_i16x8_s
+
+    # CHECK: i8x16.narrow_i16x8_u # encoding: [0xfd,0xc7,0x01]
+    i8x16.narrow_i16x8_u
+
+    # CHECK: i16x8.narrow_i32x4_s # encoding: [0xfd,0xc8,0x01]
+    i16x8.narrow_i32x4_s
+
+    # CHECK: i16x8.narrow_i32x4_u # encoding: [0xfd,0xc9,0x01]
+    i16x8.narrow_i32x4_u
+
+    # CHECK: i16x8.widen_low_i8x16_s # encoding: [0xfd,0xca,0x01]
+    i16x8.widen_low_i8x16_s
+
+    # CHECK: i16x8.widen_high_i8x16_s # encoding: [0xfd,0xcb,0x01]
+    i16x8.widen_high_i8x16_s
+
+    # CHECK: i16x8.widen_low_i8x16_u # encoding: [0xfd,0xcc,0x01]
+    i16x8.widen_low_i8x16_u
+
+    # CHECK: i16x8.widen_high_i8x16_u # encoding: [0xfd,0xcd,0x01]
+    i16x8.widen_high_i8x16_u
+
+    # CHECK: i32x4.widen_low_i16x8_s # encoding: [0xfd,0xce,0x01]
+    i32x4.widen_low_i16x8_s
+
+    # CHECK: i32x4.widen_high_i16x8_s # encoding: [0xfd,0xcf,0x01]
+    i32x4.widen_high_i16x8_s
+
+    # CHECK: i32x4.widen_low_i16x8_u # encoding: [0xfd,0xd0,0x01]
+    i32x4.widen_low_i16x8_u
+
+    # CHECK: i32x4.widen_high_i16x8_u # encoding: [0xfd,0xd1,0x01]
+    i32x4.widen_high_i16x8_u
+
     end_function