From: Jeff Law <jeffreyalaw@gmail.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Always enable LRA
Date: Fri, 14 Oct 2022 12:03:46 -0600 [thread overview]
Message-ID: <7b04be7e-d27d-0099-6631-6a764aed2cd7@gmail.com> (raw)
In-Reply-To: <20221014173516.GF25951@gate.crashing.org>
On 10/14/22 11:35, Segher Boessenkool wrote:
> On Fri, Oct 14, 2022 at 11:07:43AM -0600, Jeff Law wrote:
>>> LRA only ever generates insns that pass recog. The backend allows this
>>> define_insn, requiring it to be split (it returns template "#"), but
>>> then somehow it doesn't match in any split pass?
>> Nope. The elimination code will just change one register without
>> re-recognizing. That's precisely what happens here.
> That is a big oversight then. Please file a PR?
Sure. But just recognizing (for this particular case) will just move
the fault from a failure to split to a failure to recognize. From my
wanderings in the elimination code, I don't see that it has a path that
would allow it to reasonably handle this case -- ie, if the insn does
not recognize, what then? Conceptually we need to generate an
input-reload but I don't see a way to do that in the elimination code.
Maybe Vlad knows how it ought to be handled.
> It is the only way it can know if it needs to reload more. Even if it
> somehow can assume it doesn't have to check this in some cases, an
> assert (inside a CHECKING_P) would be nice?
Agreed.
jeff
next prev parent reply other threads:[~2022-10-14 18:03 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-13 23:56 Segher Boessenkool
2022-10-14 0:36 ` Koning, Paul
2022-10-14 16:18 ` Segher Boessenkool
2022-10-14 16:48 ` Koning, Paul
2022-10-14 1:07 ` Jeff Law
2022-10-14 12:37 ` Koning, Paul
2022-10-14 14:38 ` Jeff Law
2022-10-14 16:37 ` Koning, Paul
2022-10-14 17:10 ` Jeff Law
2022-10-14 17:36 ` Koning, Paul
2022-10-14 21:15 ` Jeff Law
2022-10-14 21:21 ` Koning, Paul
2022-10-14 21:30 ` Jeff Law
2022-10-15 0:19 ` Jeff Law
2022-10-14 16:39 ` Richard Biener
2022-10-14 17:11 ` Jeff Law
2022-10-14 4:47 ` Jeff Law
2022-10-14 16:37 ` Segher Boessenkool
2022-10-14 17:07 ` Jeff Law
2022-10-14 17:35 ` Segher Boessenkool
2022-10-14 18:03 ` Jeff Law [this message]
2022-10-14 19:58 ` Koning, Paul
2022-10-14 20:12 ` Segher Boessenkool
2022-10-14 20:40 ` Koning, Paul
2022-10-14 6:20 ` Takayuki 'January June' Suwa
2022-10-14 16:25 ` Segher Boessenkool
2022-10-15 3:18 ` Takayuki 'January June' Suwa
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