Re: [PATCH] rtlanal: Correct cost regularization in pattern_cost

[HAO CHEN GUI <guihaoc@linux.ibm.com>]

Hi Richard,
  Thanks for your comments.

在 2024/5/10 15:16, Richard Biener 写道:
> But if targets return sth < COSTS_N_INSNS (1) but > 0 this is now no
> longer meaningful.  So shouldn't it instead be
> 
>   return cost > 0 ? cost : 1;
Yes, it's better.

> 
> ?  Alternatively returning fractions of COSTS_N_INSNS (1) from set_src_cost
> is invalid and thus the target is at fault (I do think that making zero the
> unknown value is quite bad since that makes it impossible to have zero
> as cost represented).
> 
> It seems the check is to aovid pattern_cost return zero (unknown), so the
> comment holds to pattern_cost the same (it returns an 'int' so the better
> exceptional value would have been -1, avoiding the compare).
But sometime it adds an insn cost. If the unknown cost is -1, the total cost
might be distorted.

> 
> Richard.

Thanks
Gui Haochen