message: vertexcodec: Use 16-bit WASM shift instead of 8-bit
  v8 currently has inefficient lowering for constant 8-bit shifts; using a
  16-bit shift improves performance from 1.75 GB/s to 1.86 GB/s on latest
  Node.
diff: @@ -907,7 +907,8 @@ SIMD_TARGET
  static v128_t unzigzag8(v128_t v)
  {
  v128_t xl = wasm_i8x16_neg(wasm_v128_and(v, wasm_i8x16_splat(1)));
  - v128_t xr = wasm_u8x16_shr(v, 1);
  + // TODO: use wasm_u8x16_shr when v8 fixes codegen for constant shifts
  + v128_t xr = wasm_v128_and(wasm_u16x8_shr(v, 1), wasm_i8x16_splat(127));
  return wasm_v128_xor(xl, xr);
  }
  