Re: 回复:[RISC-V] [tech-vector-ext] RISC-V Vector Spec version 1.0-rc1-20210608

Roger Ferrer Ibanez

Hi Linjie,

I'm not sure I understood your question. I think a vid.v (with a vl of your choice) that then you (logical) shift right 1 bit ( would generate an index like the one you have now the "index[]" array.

This looks like it does not require to hardcode any size and you don't have to load a materialised value from memory (you compute it instead).

Hope this helps.

Kind regards,

On 11/6/21 9:22, Linjie Yu via wrote:
Hi, all

    I encountered a difficulty of applying  "vrgather" instruction recently.  The details are shown blow:
    The date from source should be duplicated as pair in a upsample application. 
     Eg:  src = [0, 1, 2, 3, 4, 5, 6, 7, 8]
           dst =  [0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8]
     So, my relazation is:
  int inex[64] = {0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5 ........,31,31};// to be compatibled of all the VLEN(128 ~ 1024)

   vfloat32m2_t data = vundefined_f32m2();
    vfloat32m1_t  zero = ( vfloat32m1_t )vmv_v_i_i32m1(0);
   while(length >0)
         int gvl = vsetvl_e32m1(length);
        vuint32m2_t v_index = vle32_v_u32m2(index, gvl);
         vfloat32m1_t src_data = vle32_v_f32m1(src, gvl);
         data = vset_f32m2(data, src_data, 0);
         data  = vset_f32m2(data, zero, 1);
         vfloat32m2_t res = vrrgather_vv_f32m2(data, v_index, gvl);  
         length -=gvl;
         src += gvl;
        vse32_v_f32m2(out, res, gvl);
        dst +=gvl;
    As shown before, the index data should be  initialized as the max VLEN to make the code  compatibled.
So do all the applications, that need a constant.
    I think it is contrary to the idea of RISC-V, that one code can run on all the RISC-V hardware.  Does anyone have a better method ? 

Best Regards
Damon Yu

------------------原始邮件 ------------------
发送时间:06/09/21 14:46:30
主题:[RISC-V] [tech-vector-ext] RISC-V Vector Spec version 1.0-rc1-20210608

I've just tagged the first release candidate for v1.0 of the vector
spec in github.  PDF attached below.

I've included the TG agreed updates and handled almost all of the
outstanding issues for v1.0.  Thanks for all the feedback.

I would appreciate if folks could read through the whole thing and
give comments over email and through Github issues.  Please also
submit PRs for typos and other wording improvements.

I'd like to try and settle most concerns over email if possible, and
assume it'll take a little while for everyone to go through the doc.

I'll tentatively schedule a vector TG meeting on Friday June 25 to go
over issues best dealt with on a call.  I'm hoping we can enter public
review at the same point in time.  Remember, we don't have to reach
agreement on all the issues before starting public review, just be OK
as a group with putting this out for public review.


Roger Ferrer Ibáñez - roger.ferrer@...
Barcelona Supercomputing Center - Centro Nacional de Supercomputación

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