Thanks. I have read rgroup descriptions again.
Still I am not fully understand it clearly, bear with me :)

I don't known how to differentiate Case 2 and Case 3.

Case 2 is multiple rgroup for SLP.
Case 3 is multiple rgroup for non-SLP (VEC_PACK_TRUNC)

Is it correct:
case 2: rgc->max_nscalarper_iter != 1
Case 3 : rgc->max_nscalarper_iter == 1 but rgc->factor != 1?

Thanks.


juzhe.zhong@rivai.ai
 
From: Richard Sandiford
Date: 2023-05-11 19:29
To: juzhe.zhong\@rivai.ai
CC: gcc-patches; rguenther
Subject: Re: [PATCH V4] VECT: Add decrement IV iteration loop control by variable amount support
"juzhe.zhong@rivai.ai" <juzhe.zhong@rivai.ai> writes:
> Oh, I see. But I saw there is a variable using_partial_vectors_p
> in the loop data structure.
>
> Can I add a variable call using_select_vl_p ?
 
Yeah.  Please also add a wrapper macro like
LOOP_VINFO_USING_PARTIAL_VECTORS_P.  (I'm not really a fan of the
wrappers, but it's better to be consistent.)
 
> Since it may increase the size of data structure, I am not sure whether it is appropriate.
 
The structure is only temporary, and very few of them exist at
a given time.  Besides, there's already a layout hole on LP64 hosts
around those booleans (between slp_unrolling_factor and scalar_loop).
So the new boolean shouldn't grow the size of the structure.
 
We can convert the booleans to bitfields if size ever becomes a problem.
 
Thanks,
Richard