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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/110751] RISC-V: Suport undefined value that allows VSETVL PASS use TA/MA
Date: Mon, 24 Jul 2023 06:20:01 +0000	[thread overview]
Message-ID: <bug-110751-4-TwLf2w7N2C@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110751-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110751

--- Comment #21 from rguenther at suse dot de <rguenther at suse dot de> ---
On Fri, 21 Jul 2023, rsandifo at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110751
> 
> --- Comment #20 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #19)
> > Sure, I can kind of see the usefulness elsewhere.  Just for this particular
> > issue it doesn't seem necessary to sit down and design this when we can
> > represent it like we do for MASK_LOAD (omit the 'else' value).
> Yeah, that's fair.
> 
> For the ifn->optab interface, I think it'd be natural to use an actual rtx
> rather than a null pointer, since e.g. predicates are not set up to handle
> nulls.  So perhaps we should start the process there.  We could add an UNDEF
> rtl code that is initially only used for the ifn->optab interface, and expand
> it as we find new use cases.  We can grow the semantics based on those use
> cases and based on LLVM's experience.
> 
> > In other context we discussed specifying zero for MASK_LOAD masked elements
> > so we can for example CSE better.  CSE with UNDEF might be possible as well,
> > but I'm not sure what LLVM's undef would allow and whether it's defined
> > rigidly enough.
> One of the main optimisations I wanted from that was:
>   a = IFN_MASK_LOAD (?, mask)
>   b = VEC_COND_EXPR <mask, a, {0,0,?}>
> ?
>   a = IFN_MASK_LOAD (?, mask)
>   b = a
> which wouldn't be valid for undef.

Right.  It would be valid to do

  b = IFN_MASK_LOAD (?, mask, {0,0,?});

if we add ELSE to IFN_MASK_LOAD.

  parent reply	other threads:[~2023-07-24  6:20 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-20  9:03 [Bug target/110751] New: " xuli1 at eswincomputing dot com
2023-07-20  9:10 ` [Bug target/110751] " juzhe.zhong at rivai dot ai
2023-07-20  9:30 ` rguenth at gcc dot gnu.org
2023-07-20  9:37 ` rguenth at gcc dot gnu.org
2023-07-20  9:58 ` kito at gcc dot gnu.org
2023-07-20 11:28 ` rguenther at suse dot de
2023-07-20 11:43 ` juzhe.zhong at rivai dot ai
2023-07-20 12:00 ` juzhe.zhong at rivai dot ai
2023-07-20 12:35 ` rguenther at suse dot de
2023-07-20 12:42 ` juzhe.zhong at rivai dot ai
2023-07-20 12:45 ` rguenther at suse dot de
2023-07-20 12:50 ` juzhe.zhong at rivai dot ai
2023-07-20 12:56 ` rguenther at suse dot de
2023-07-20 13:29 ` rsandifo at gcc dot gnu.org
2023-07-20 13:32 ` rguenther at suse dot de
2023-07-20 22:03 ` juzhe.zhong at rivai dot ai
2023-07-21  1:53 ` xuli1 at eswincomputing dot com
2023-07-21  6:17 ` rguenth at gcc dot gnu.org
2023-07-21 12:47 ` rsandifo at gcc dot gnu.org
2023-07-21 12:53 ` rguenth at gcc dot gnu.org
2023-07-21 13:23 ` rsandifo at gcc dot gnu.org
2023-07-24  6:20 ` rguenther at suse dot de [this message]
2023-07-25  7:05 ` juzhe.zhong at rivai dot ai
2023-09-12 11:44 ` juzhe.zhong at rivai dot ai
2023-09-12 14:24 ` rsandifo at gcc dot gnu.org
2023-09-12 14:53 ` juzhe.zhong at rivai dot ai
2023-09-12 15:59 ` rsandifo at gcc dot gnu.org
2023-09-12 16:21 ` juzhe.zhong at rivai dot ai
2023-09-12 16:27 ` juzhe.zhong at rivai dot ai
2023-09-12 16:31 ` juzhe.zhong at rivai dot ai
2023-09-12 22:44 ` juzhe.zhong at rivai dot ai
2023-09-13  7:56 ` rguenth at gcc dot gnu.org
2023-09-13  8:34 ` juzhe.zhong at rivai dot ai
2023-09-13  8:39 ` juzhe.zhong at rivai dot ai
2023-09-13  9:38 ` rguenth at gcc dot gnu.org
2023-09-13  9:39 ` rguenth at gcc dot gnu.org
2023-09-13  9:48 ` juzhe.zhong at rivai dot ai
2023-09-13  9:48 ` juzhe.zhong at rivai dot ai
2023-09-13 10:15 ` rguenther at suse dot de
2023-09-13 22:39 ` rsandifo at gcc dot gnu.org
2023-09-14  8:53 ` juzhe.zhong at rivai dot ai
2023-09-14  9:15 ` richard.sandiford at arm dot com
2023-09-20 16:27 ` cvs-commit at gcc dot gnu.org
2023-09-21  9:13 ` cvs-commit at gcc dot gnu.org
2023-09-21  9:28 ` juzhe.zhong at rivai dot ai
2023-09-22  7:31 ` xuli1 at eswincomputing dot com
2023-09-22  7:33 ` xuli1 at eswincomputing dot com

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