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
@@ -55,6 +55,11 @@
 TARGET_BUILTIN(__builtin_wasm_trunc_saturate_u_i64_f64, "LLid", "nc", "nontrapping-fptoint")
 
 // SIMD builtins
+TARGET_BUILTIN(__builtin_wasm_const_i8x16, "V16cIcIcIcIcIcIcIcIcIcIcIcIcIcIcIcIc", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_const_i16x8, "V8sIsIsIsIsIsIsIsIs", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_const_i32x4, "V4iIiIiIiIi", "nc", "simd128")
+TARGET_BUILTIN(__builtin_wasm_const_i64x2, "V2LLiILLiILLi", "nc", "unimplemented-simd128")
+
 TARGET_BUILTIN(__builtin_wasm_extract_lane_s_i8x16, "iV16cIi", "nc", "simd128")
 TARGET_BUILTIN(__builtin_wasm_extract_lane_u_i8x16, "iV16cIi", "nc", "unimplemented-simd128")
 TARGET_BUILTIN(__builtin_wasm_extract_lane_s_i16x8, "iV8sIi", "nc", "simd128")
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
@@ -13971,6 +13971,19 @@
                                      ConvertType(E->getType()));
     return Builder.CreateCall(Callee, {LHS, RHS});
   }
+  case WebAssembly::BI__builtin_wasm_const_i8x16:
+  case WebAssembly::BI__builtin_wasm_const_i16x8:
+  case WebAssembly::BI__builtin_wasm_const_i32x4:
+  case WebAssembly::BI__builtin_wasm_const_i64x2: {
+    SmallVector<llvm::Constant *, 16> Args;
+    for (size_t i = 0; i < E->getNumArgs(); ++i) {
+      llvm::APSInt Const;
+      if (!E->getArg(i)->isIntegerConstantExpr(Const, getContext()))
+        llvm_unreachable("Constant arg isn't actually constant?");
+      Args.push_back(llvm::ConstantInt::get(getLLVMContext(), Const));
+    }
+    return Builder.Insert(llvm::ConstantVector::get(Args));
+  }
   case WebAssembly::BI__builtin_wasm_extract_lane_s_i8x16:
   case WebAssembly::BI__builtin_wasm_extract_lane_u_i8x16:
   case WebAssembly::BI__builtin_wasm_extract_lane_s_i16x8:
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
@@ -140,10 +140,29 @@
   // WEBASSEMBLY-NEXT: ret
 }
 
+i8x16 const_i8x16() {
+  // MISSING-SIMD: error: '__builtin_wasm_const_i8x16' needs target feature simd128
+  // WEBASSEMBLY: ret <16 x i8> <i8 0, i8 1, i8 2, i8 3, i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15>
+  return __builtin_wasm_const_i8x16(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
+}
+
+i16x8 const_i16x8() {
+  // WEBASSEMBLY: ret <8 x i16> <i16 0, i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7>
+  return __builtin_wasm_const_i16x8(0, 1, 2, 3, 4, 5, 6, 7);
+}
+
+i32x4 const_i32x4() {
+  // WEBASSEMBLY: ret <4 x i32> <i32 0, i32 1, i32 2, i32 3>
+  return __builtin_wasm_const_i32x4(0, 1, 2, 3);
+}
+
+i64x2 const_i64x2() {
+  // WEBASSEMBLY: ret <2 x i64> <i64 0, i64 1>
+  return __builtin_wasm_const_i64x2(0, 1);
+}
 
 int extract_lane_s_i8x16(i8x16 v) {
   return __builtin_wasm_extract_lane_s_i8x16(v, 13);
-  // MISSING-SIMD: error: '__builtin_wasm_extract_lane_s_i8x16' needs target feature simd128
   // WEBASSEMBLY: extractelement <16 x i8> %v, i32 13
   // WEBASSEMBLY-NEXT: sext
   // WEBASSEMBLY-NEXT: ret