No, I don't think we can use first case (vid + vand -npatterns) for base != 0,
since the first element value of vid is alway 0.

Thanks.


juzhe.zhong@rivai.ai
 
From: Robin Dapp
Date: 2023-06-26 15:51
To: Juzhe-Zhong; gcc-patches
CC: rdapp.gcc; kito.cheng; kito.cheng; palmer; palmer; jeffreyalaw
Subject: Re: [PATCH] RISC-V: Enhance RVV VLA SLP auto-vectorization
Hi Juzhe,
 
> Currently, we are able to generate step vector with base == 0:
>  { 0, 0, 2, 2, 4, 4, ... }
> 
> ASM:
> 
> vid
> vand
> 
> However, we do wrong for step vector with base != 0:
> { 1, 1, 3, 3, 5, 5, ... }
> 
> Before this patch, such case will run fail.
> 
> After this patch, we are able to pass the testcase and generate the step vector with asm:
> 
> vid
> vand
> vadd
 
Can't we use the first case as long as pow2_p (base) == true
and not just for base == 0?
 
Regards
Robin