Re: [PATCH] Support addsub/subadd as non-isomorphic operations for SLP vectorizer.

[Cong Hou <congh at google dot com>]

On Fri, Nov 15, 2013 at 1:20 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> Hello!
>
>> This patch adds the support to two non-isomorphic operations addsub
>> and subadd for SLP vectorizer. More non-isomorphic operations can be
>> added later, but the limitation is that operations on even/odd
>> elements should still be isomorphic. Once such an operation is
>> detected, the code of the operation used in vectorized code is stored
>> and later will be used during statement transformation. Two new GIMPLE
>> opeartions VEC_ADDSUB_EXPR and VEC_SUBADD_EXPR are defined. And also
>> new optabs for them. They are also documented.
>>
>> The target supports for SSE/SSE2/SSE3/AVX are added for those two new
>> operations on floating points. SSE3/AVX provides ADDSUBPD and ADDSUBPS
>> instructions. For SSE/SSE2, those two operations are emulated using
>> two instructions (selectively negate then add).
>
>    ;; SSE3
>    UNSPEC_LDDQU
> +  UNSPEC_SUBADD
> +  UNSPEC_ADDSUB
>
> No! Please avoid unspecs.


OK, got it.


>
> +(define_expand "vec_subadd_v4sf3"
> +  [(set (match_operand:V4SF 0 "register_operand")
> + (unspec:V4SF
> +  [(match_operand:V4SF 1 "register_operand")
> +   (match_operand:V4SF 2 "nonimmediate_operand")] UNSPEC_SUBADD))]
> +  "TARGET_SSE"
> +{
> +  if (TARGET_SSE3)
> +    emit_insn (gen_sse3_addsubv4sf3 (operands[0], operands[1], operands[2]));
> +  else
> +    ix86_sse_expand_fp_addsub_operator (true, V4SFmode, operands);
> +  DONE;
> +})
>
> Make the expander pattern look like correspondig sse3 insn and:
> ...
> {
>   if (!TARGET_SSE3)
>     {
>       ix86_sse_expand_fp_...();
>       DONE;
>     }
> }
>

You mean I should write two expanders for SSE and SSE3 respectively?

Thank you for your comment!



Cong



> Uros.