From: Richard Biener <rguenther@suse.de>
To: Richard Sandiford <richard.sandiford@arm.com>
Cc: Tamar Christina via Gcc-patches <gcc-patches@gcc.gnu.org>,
Tamar Christina <Tamar.Christina@arm.com>,
Richard Biener <richard.guenther@gmail.com>, nd <nd@arm.com>
Subject: Re: [PATCH 1/8]middle-end: Recognize scalar reductions from bitfields and array_refs
Date: Tue, 22 Nov 2022 10:58:55 +0000 (UTC) [thread overview]
Message-ID: <nycvar.YFH.7.77.849.2211221057230.3995@jbgna.fhfr.qr> (raw)
In-Reply-To: <mpttu2r9sxz.fsf@arm.com>
On Tue, 22 Nov 2022, Richard Sandiford wrote:
> Tamar Christina via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> >> So it's not easily possible the within current infrastructure. But it does look
> >> like ARM might eventually benefit from something like STV on x86?
> >>
> >
> > I'm not sure. The problem with trying to do this in RTL is that you'd have to be
> > able to decide from two psuedos whether they come from extracts that are
> > sequential. When coming in from a hard register that's easy yes. When coming in
> > from a load, or any other operation that produces psuedos that becomes harder.
>
> Yeah.
>
> Just in case anyone reading the above is tempted to implement STV for
> AArch64: I think it would set a bad precedent if we had a paste-&-adjust
> version of the x86 pass. AFAIK, the target capabilities and constraints
> are mostly modelled correctly using existing mechanisms, so I don't
> think there's anything particularly target-specific about the process
> of forcing things to be on the general or SIMD/FP side.
>
> So if we did have an STV-ish thing for AArch64, I think it should be
> a target-independent pass that uses hooks and recog, even if the pass
> is initially enabled for AArch64 only.
Agreed - maybe some of the x86 code can be leveraged, but of course
the cost modeling is the most difficult to get right - IIRC the x86
backend resorts to backend specific tuning flags rather than trying
to get rtx_cost or insn_cost "correct" here.
> (FWIW, on the patch itself, I tend to agree that this is really an
> SLP optimisation. If the vectoriser fails to see the benefit, or if
> it fails to handle more complex cases, then it would be good to try
> to fix that.)
Also agreed - but costing is hard ;)
Richard.
next prev parent reply other threads:[~2022-11-22 10:58 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-31 11:56 Tamar Christina
2022-10-31 11:57 ` [PATCH 2/8]middle-end: Recognize scalar widening reductions Tamar Christina
2022-10-31 21:42 ` Jeff Law
2022-11-07 13:21 ` Richard Biener
2022-10-31 11:57 ` [PATCH 3/8]middle-end: Support extractions of subvectors from arbitrary element position inside a vector Tamar Christina
2022-10-31 21:44 ` Jeff Law
2022-11-01 14:25 ` Richard Sandiford
2022-11-11 14:33 ` Tamar Christina
2022-11-15 8:35 ` Hongtao Liu
2022-11-15 8:51 ` Tamar Christina
2022-11-15 9:37 ` Hongtao Liu
2022-11-15 10:00 ` Tamar Christina
2022-11-15 17:39 ` Richard Sandiford
2022-11-17 8:04 ` Hongtao Liu
2022-11-17 9:39 ` Richard Sandiford
2022-11-17 10:20 ` Hongtao Liu
2022-11-17 13:59 ` Richard Sandiford
2022-11-18 2:31 ` Hongtao Liu
2022-11-18 9:16 ` Richard Sandiford
2022-10-31 11:58 ` [PATCH 4/8]AArch64 aarch64: Implement widening reduction patterns Tamar Christina
2022-11-01 14:41 ` Richard Sandiford
2022-10-31 11:58 ` [PATCH 5/8]AArch64 aarch64: Make existing V2HF be usable Tamar Christina
2022-11-01 14:58 ` Richard Sandiford
2022-11-01 15:11 ` Tamar Christina
2022-11-11 14:39 ` Tamar Christina
2022-11-22 16:01 ` Tamar Christina
2022-11-30 4:26 ` Tamar Christina
2022-12-06 10:28 ` Richard Sandiford
2022-12-06 10:58 ` Tamar Christina
2022-12-06 11:05 ` Richard Sandiford
2022-10-31 11:59 ` [PATCH 6/8]AArch64: Add peephole and scheduling logic for pairwise operations that appear late in RTL Tamar Christina
2022-10-31 11:59 ` [PATCH 7/8]AArch64: Consolidate zero and sign extension patterns and add missing ones Tamar Christina
2022-11-30 4:28 ` Tamar Christina
2022-12-06 15:59 ` Richard Sandiford
2022-10-31 12:00 ` [PATCH 8/8]AArch64: Have reload not choose to do add on the scalar side if both values exist on the SIMD side Tamar Christina
2022-11-01 15:04 ` Richard Sandiford
2022-11-01 15:20 ` Tamar Christina
2022-10-31 21:41 ` [PATCH 1/8]middle-end: Recognize scalar reductions from bitfields and array_refs Jeff Law
2022-11-05 11:32 ` Richard Biener
2022-11-07 7:16 ` Tamar Christina
2022-11-07 10:17 ` Richard Biener
2022-11-07 11:00 ` Tamar Christina
2022-11-07 11:22 ` Richard Biener
2022-11-07 11:56 ` Tamar Christina
2022-11-22 10:36 ` Richard Sandiford
2022-11-22 10:58 ` Richard Biener [this message]
2022-11-22 11:02 ` Tamar Christina
2022-11-22 11:06 ` Richard Sandiford
2022-11-22 11:08 ` Richard Biener
2022-11-22 14:33 ` Jeff Law
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