Re: [PATCH V6] VECT: Support LEN_MASK_{LOAD,STORE} ifn && optabs

[Robin Dapp <rdapp.gcc@gmail.com>]

>>>If the pattern is not allowed to fail, then what code enforces the bias
>>>argument's restrictions?  I don't see it in the generic expander code.
> 
> I have no ideal since this is just copied from len_load/len_store which is 
> s390 target dependent stuff. 
> 
> I have sent V7 patch with fixing doc by following your suggestion.
> 

We have:

signed char
internal_len_load_store_bias (internal_fn ifn, machine_mode mode)
{
  optab optab = direct_internal_fn_optab (ifn);
  insn_code icode = direct_optab_handler (optab, mode);

  if (icode != CODE_FOR_nothing)
    {
      /* For now we only support biases of 0 or -1.  Try both of them.  */
      if (insn_operand_matches (icode, 3, GEN_INT (0)))
	return 0;
      if (insn_operand_matches (icode, 3, GEN_INT (-1)))
	return -1;
    }

  return VECT_PARTIAL_BIAS_UNSUPPORTED;
}

This is used here:

static bool
vect_verify_loop_lens (loop_vec_info loop_vinfo)
{
[..]
  signed char partial_load_bias = internal_len_load_store_bias
    (IFN_LEN_LOAD, len_load_mode);

  signed char partial_store_bias = internal_len_load_store_bias
    (IFN_LEN_STORE, len_store_mode);

  gcc_assert (partial_load_bias == partial_store_bias);

  if (partial_load_bias == VECT_PARTIAL_BIAS_UNSUPPORTED)
    return false;

  /* If the backend requires a bias of -1 for LEN_LOAD, we must not emit
     len_loads with a length of zero.  In order to avoid that we prohibit
     more than one loop length here.  */
  if (partial_load_bias == -1
      && LOOP_VINFO_LENS (loop_vinfo).length () > 1)
    return false;

Regards
 Robin