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
@@ -172,5 +172,7 @@
 TARGET_BUILTIN(__builtin_wasm_laneselect_i32x4, "V4iV4iV4iV4i", "nc", "relaxed-simd")
 TARGET_BUILTIN(__builtin_wasm_laneselect_i64x2, "V2LLiV2LLiV2LLiV2LLi", "nc", "relaxed-simd")
 
+TARGET_BUILTIN(__builtin_wasm_relaxed_swizzle_i8x16, "V16ScV16ScV16Sc", "nc", "relaxed-simd")
+
 #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
@@ -18319,6 +18319,12 @@
         CGM.getIntrinsic(Intrinsic::wasm_laneselect, A->getType());
     return Builder.CreateCall(Callee, {A, B, C});
   }
+  case WebAssembly::BI__builtin_wasm_relaxed_swizzle_i8x16: {
+    Value *Src = EmitScalarExpr(E->getArg(0));
+    Value *Indices = EmitScalarExpr(E->getArg(1));
+    Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_relaxed_swizzle);
+    return Builder.CreateCall(Callee, {Src, Indices});
+  }
   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
@@ -732,3 +732,8 @@
   // WEBASSEMBLY-SAME: <2 x i64> %a, <2 x i64> %b, <2 x i64> %c)
   // WEBASSEMBLY-NEXT: ret
 }
+
+i8x16 relaxed_swizzle_i8x16(i8x16 x, i8x16 y) {
+  return __builtin_wasm_relaxed_swizzle_i8x16(x, y);
+  // WEBASSEMBLY: call <16 x i8> @llvm.wasm.relaxed.swizzle(<16 x i8> %x, <16 x i8> %y)
+}
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
@@ -200,6 +200,11 @@
             [LLVMMatchType<0>, LLVMMatchType<0>, LLVMMatchType<0>],
             [IntrNoMem, IntrSpeculatable]>;
 
+def int_wasm_relaxed_swizzle :
+  Intrinsic<[llvm_v16i8_ty],
+            [llvm_v16i8_ty, llvm_v16i8_ty],
+            [IntrNoMem, IntrSpeculatable]>;
+
 //===----------------------------------------------------------------------===//
 // Thread-local storage intrinsics
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISD.def b/llvm/lib/Target/WebAssembly/WebAssemblyISD.def
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISD.def
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISD.def
@@ -49,3 +49,6 @@
 HANDLE_MEM_NODETYPE(GLOBAL_GET)
 HANDLE_MEM_NODETYPE(GLOBAL_SET)
 HANDLE_MEM_NODETYPE(TABLE_SET)
+
+// Relaxed SIMD proposal.
+HANDLE_NODETYPE(RELAXED_SWIZZLE)
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
@@ -1361,3 +1361,14 @@
 defm "" : SIMDLANESELECT<I16x8, 0xb3>;
 defm "" : SIMDLANESELECT<I32x4, 0xd2>;
 defm "" : SIMDLANESELECT<I64x2, 0xd3>;
+
+def wasm_relaxed_swizzle : SDNode<"WebAssemblyISD::RELAXED_SWIZZLE", wasm_swizzle_t>;
+
+defm RELAXED_SWIZZLE :
+  RELAXED_I<(outs V128:$dst), (ins V128:$src, V128:$mask), (outs), (ins),
+         [(set (v16i8 V128:$dst),
+           (wasm_relaxed_swizzle (v16i8 V128:$src), (v16i8 V128:$mask)))],
+         "i8x16.relaxed_swizzle\t$dst, $src, $mask", "i8x16.relaxed_swizzle", 162>;
+
+def : Pat<(int_wasm_relaxed_swizzle (v16i8 V128:$src), (v16i8 V128:$mask)),
+          (RELAXED_SWIZZLE $src, $mask)>;
diff --git a/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll b/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll
--- a/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll
+++ b/llvm/test/CodeGen/WebAssembly/simd-intrinsics.ll
@@ -192,6 +192,16 @@
   ret <16 x i8> %v
 }
 
+; CHECK-LABEL: relaxed_swizzle_v16i8:
+; CHECK-NEXT: .functype relaxed_swizzle_v16i8 (v128, v128) -> (v128){{$}}
+; CHECK-NEXT: i8x16.relaxed_swizzle $push[[R:[0-9]+]]=, $0, $1{{$}}
+; CHECK-NEXT: return $pop[[R]]{{$}}
+declare <16 x i8> @llvm.wasm.relaxed.swizzle(<16 x i8>, <16 x i8>)
+define <16 x i8> @relaxed_swizzle_v16i8(<16 x i8> %x, <16 x i8> %y) {
+  %a = call <16 x i8> @llvm.wasm.relaxed.swizzle(<16 x i8> %x, <16 x i8> %y)
+  ret <16 x i8> %a
+}
+
 ; ==============================================================================
 ; 8 x i16
 ; ==============================================================================
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
@@ -803,4 +803,7 @@
     # CHECK: i64x2.laneselect # encoding: [0xfd,0xd3,0x01]
     i64x2.laneselect
 
+    # CHECK: i8x16.relaxed_swizzle # encoding: [0xfd,0xa2,0x01]
+    i8x16.relaxed_swizzle
+
     end_function