Re: [PATCH v2 1/3] RISC-V: Combine vec_duplicate + vadd.vv to vadd.vx on GR2VR cost

[Robin Dapp]

But this is not that good enough here if my understanding is correct.
As vmv.v.x is somehow equivalent to vec_dup but doesn't ref GR2VR,

But it should.  Can't we do something like:

 if (riscv_v_ext_mode_p (mode))
   {
     switch (GET_CODE (x))
        {
          case VEC_DUPLICATE:
            // will add 0, 4, 8 in case of GR2VR = 0, 1, 2
            *total += GR2VR * COST_N_INSNS (1);
            break;
          case PLUS:
            rtx op2 = XEXP (XEXP (x, 1), 0);
            if (GET_CODE (op2) == VEC_DUPLICATE)
              *total += GR2VR * COST_N_INSNS (1);
            ...
            break;


Could you give a short example where that doesn't work so I can have a quick 
look myself?

Thanks.

--
Regards
Robin