Re: [PATCH V16] VECT: Add decrement IV iteration loop control by variable amount support

[Richard Sandiford <richard.sandiford@arm.com>]

This looks good to me.  Just a couple of very minor cosmetic things:

juzhe.zhong@rivai.ai writes:
> @@ -753,17 +846,35 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
>  	      continue;
>  	  }
>  
> -	/* See whether zero-based IV would ever generate all-false masks
> -	   or zero length before wrapping around.  */
> -	bool might_wrap_p = vect_rgroup_iv_might_wrap_p (loop_vinfo, rgc);
> -
> -	/* Set up all controls for this group.  */
> -	test_ctrl = vect_set_loop_controls_directly (loop, loop_vinfo,
> -						     &preheader_seq,
> -						     &header_seq,
> -						     loop_cond_gsi, rgc,
> -						     niters, niters_skip,
> -						     might_wrap_p);
> +	if (!LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo) || !iv_rgc
> +	    || (iv_rgc->max_nscalars_per_iter * iv_rgc->factor
> +		!= rgc->max_nscalars_per_iter * rgc->factor))

Coding style is to put each subcondition on a separate line when the
whole condition doesn't fit on a single line.  So:

	if (!LOOP_VINFO_USING_DECREMENTING_IV_P (loop_vinfo)
	    || !iv_rgc
	    || (iv_rgc->max_nscalars_per_iter * iv_rgc->factor
		!= rgc->max_nscalars_per_iter * rgc->factor))

> @@ -2725,6 +2726,17 @@ start_over:
>        && !vect_verify_loop_lens (loop_vinfo))
>      LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
>  
> +  /* If we're vectorizing an loop that uses length "controls" and

s/an loop/a loop/    (Sorry for not noticing earlier.)

OK for trunk from my POV with those changes; no need to repost unless
your policies require it.  Please give Richi a chance to comment too
though.

Thanks for your patience with the review process.  The final result
seems pretty clean to me.

Richard