PATCH to add more FALLTHRU markers

[Florian Weimer]

* Marek Polacek:

> @@ -11498,21 +11508,23 @@
>          case V64QImode:
>          case V32HImode:
>            if (TARGET_AVX512F)
> -          {
> -            tmp = "p<logic>";
> -            ssesuffix = "q";
> -            break;
> -          }
> +	    {
> +	      tmp = "p<logic>";
> +	      ssesuffix = "q";
> +	      break;
> +	    }
> +	  /* FALLTHRU */
>          case V32QImode:
>          case V16HImode:
>          case V16QImode:
>          case V8HImode:
>            if (TARGET_AVX512VL || TARGET_AVX2 || TARGET_SSE2)
> -          {
> -            tmp = "p<logic>";
> -            ssesuffix = TARGET_AVX512VL ? "q" : "";
> -            break;
> -          }
> +	    {
> +	      tmp = "p<logic>";
> +	      ssesuffix = TARGET_AVX512VL ? "q" : "";
> +	      break;
> +	    }
> +	  /* FALLTHRU */
>          default:
>            gcc_unreachable ();
>        }

Why isn't this a bug?  Wouldn't we want to reach gcc_unreachable ()
if, for example !TARGET_AVX512F and TARGET_SSE2?