From: Tamar Christina <Tamar.Christina@arm.com>
To: Jeff Law <jeffreyalaw@gmail.com>,
Segher Boessenkool <segher@kernel.crashing.org>,
Roger Sayle <roger@nextmovesoftware.com>
Cc: 'GCC Patches' <gcc-patches@gcc.gnu.org>,
Richard Sandiford <Richard.Sandiford@arm.com>
Subject: RE: [PATCH] PR rtl-optimization/106594: Preserve zero_extend in combine when cheap.
Date: Sun, 5 Mar 2023 20:43:20 +0000 [thread overview]
Message-ID: <VI1PR08MB53254D80DF7498ACF3E64680FFB19@VI1PR08MB5325.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <3b1ed616-5d90-7a66-63b5-bdb5e320eebf@gmail.com>
>
> On 3/5/23 12:28, Tamar Christina via Gcc-patches wrote:
> >
> > The regression was reported during stage-1. A patch was provided during
> stage 1 and the discussions around combine stalled.
> >
> > The regression for AArch64 needs to be fixed in GCC 13. The hit is too big just
> to "take".
> >
> > So we need a way forward, even if it's stage-4.
> Then it needs to be in a way that works within the design constraints of
> combine.
>
> As Segher has indicated, using a magic constant to say "this is always cheap
> enough" isn't acceptable. Furthermore, what this patch changes is combine's
> internal canonicalization of extensions into shift pairs.
>
> So I think another path forward needs to be found. I don't see hacking up
> expand_compound_operation is viable.
I'm not arguing at all about the merits of the patch. My argument was about Segher saying he doesn't think this is a P1 regression or one that should be addressed in stage-4.
We noticed and reported the regression early on during stage-1. So I'm unsure what else we should have done and it's not right to waive off fixing it now, otherwise what's the point in us filing bug reports.
Tamar.
>
> Jeff
next prev parent reply other threads:[~2023-03-05 20:43 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-04 18:32 Roger Sayle
2023-03-04 22:17 ` Segher Boessenkool
2023-03-05 19:28 ` Tamar Christina
2023-03-05 19:56 ` Jeff Law
2023-03-05 20:43 ` Tamar Christina [this message]
2023-03-05 21:33 ` Segher Boessenkool
2023-03-06 12:08 ` Segher Boessenkool
2023-03-06 12:11 ` Tamar Christina
2023-03-06 12:47 ` [PATCH] combine: Try harder to form zero_extends [PR106594] Richard Sandiford
2023-03-06 13:58 ` Segher Boessenkool
2023-03-06 15:08 ` Richard Sandiford
2023-03-06 16:18 ` Jakub Jelinek
2023-03-06 16:34 ` Richard Sandiford
2023-03-06 18:31 ` Segher Boessenkool
2023-03-06 19:13 ` Richard Sandiford
2023-03-06 23:31 ` Segher Boessenkool
2023-03-08 11:58 ` Richard Sandiford
2023-03-08 22:50 ` Segher Boessenkool
2023-03-09 10:18 ` Richard Sandiford
2023-03-06 22:58 ` Segher Boessenkool
2023-03-06 18:13 ` Segher Boessenkool
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