Re: Re: [PATCH] RISC-V: Fix vmerge optimization bug in vec_perm vectorization

["juzhe.zhong@rivai.ai" <juzhe.zhong@rivai.ai>]

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Do you mean like this ?

  /* We need to use precomputed mask for such situation and such mask
     can only be computed in compile-time known size modes.  */
  bool indices_fit_selector_p
    = maybe_ge (vec_len, 2 << GET_MODE_BITSIZE (GET_MODE_INNER (vmode)));
  if (GET_MODE_BITSIZE (GET_MODE_INNER (vmode)) == 8、
      && indices_fit_selector_p
      && !vec_len.is_constant ())
    return false;



juzhe.zhong@rivai.ai
 
From: Robin Dapp
Date: 2023-12-15 20:25
To: juzhe.zhong@rivai.ai; gcc-patches
CC: rdapp.gcc; kito.cheng; Kito.cheng; jeffreyalaw
Subject: Re: [PATCH] RISC-V: Fix vmerge optimization bug in vec_perm vectorization
On 12/15/23 13:16, juzhe.zhong@rivai.ai wrote:
> 
>>> bool indices_fit_selector = maybe_ge (vec_len, 2 << GET_MODE_BITSIZE (GET_MODE_INNER (vmode)));
> No, I think it will make us miss some optimization.
> 
> For example, for poly value [16,16]  maybe_ge ([16,16], 65536) which makes us missed merge optimization but
> we definitely can do merge optimization.
 
I didn't mean to skip the && !vec_len.is_constant (), that should
stay.  Just the first part of condition that can be re-used in the
if as well (inverted).
 
Regards
Robin