From: Jeff Law <jeffreyalaw@gmail.com>
To: Tamar Christina <Tamar.Christina@arm.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 12:56:02 -0700 [thread overview]
Message-ID: <3b1ed616-5d90-7a66-63b5-bdb5e320eebf@gmail.com> (raw)
In-Reply-To: <VI1PR08MB53251080224EFA9FF000DC33FFB19@VI1PR08MB5325.eurprd08.prod.outlook.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.
Jeff
next prev parent reply other threads:[~2023-03-05 19:56 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 [this message]
2023-03-05 20:43 ` Tamar Christina
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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