[RTL, i386] Use subreg instead of UNSPEC_CAST

[Richard Henderson]

On 03/19/2013 08:47 AM, Marc Glisse wrote:
>  (define_insn_and_split "avx_<castmode><avxsizesuffix>_<castmode>"
>    [(set (match_operand:AVX256MODE2P 0 "nonimmediate_operand" "=x,m")
> -	(unspec:AVX256MODE2P
> -	  [(match_operand:<ssehalfvecmode> 1 "nonimmediate_operand" "xm,x")]
> -	  UNSPEC_CAST))]
> +	(subreg:AVX256MODE2P
> +	  (match_operand:<ssehalfvecmode> 1 "nonimmediate_operand" "xm,x") 0))]
>    "TARGET_AVX"
>    "#"
>    "&& reload_completed"
>    [(const_int 0)]

I'm not fond of this, primarily because I believe the pattern should
not exist at all.

One of the following is true:

  (1) reload needs working around (thus all the reload_completed nonsense)
or
  (2) the entire pattern is useless and would be subsumed by mov<mode>
or
  (3) the entire pattern is useless and is *already* subsumed by
      mov<mode>, since mov is earlier in the md file, making this
      pattern dead code.



r~