From: Jeff Law <jeffreyalaw@gmail.com>
To: Paul Koning <paulkoning@comcast.net>, Hans-Peter Nilsson <hp@axis.com>
Cc: Roger Sayle <roger@nextmovesoftware.com>,
gcc-patches@gcc.gnu.org, segher@kernel.crashing.org
Subject: Re: [committed] Convert xstormy16 to LRA
Date: Thu, 11 May 2023 12:15:20 -0600 [thread overview]
Message-ID: <e01ef42e-f998-2b4b-2a6d-d0d69223b3ad@gmail.com> (raw)
In-Reply-To: <367738E7-2E0E-4406-8BBC-6DC70EA491DD@comcast.net>
On 5/11/23 10:55, Paul Koning wrote:
>
>
>> On May 11, 2023, at 11:05 AM, Hans-Peter Nilsson via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
>>
>> ...
>> Yes, very interesting. Thank you for sharing this. I've
>> seen regressions with LRA for CRIS too, for
>> "double-register-sized" types, which for CRIS, a 32-bit
>> target, translates to 64-bit types (DFmode and DImode), and
>> where LRA does a much worse job than reload; spills a lot
>> more often to stack, even after trying every
>> register-allocation-related hook I found (and also an LRA
>> patch which helped only by a fraction, but regressed results
>> on x86_64-linux, so let's quickly forget it again).
>
> That observation makes me a bit worried. While CRIS may not be a priority platform, that description makes it sound like a case that would be significant in any 32 bit platform, which would include priority ones like i386 and ARM.
If I understood things correctly, it seems to impact more when the
target exposes double-word patterns but doesn't actually have
instructions for those operations. That's an implementation pattern
we've largely been moving away from over the last decade or so.
Jeff
next prev parent reply other threads:[~2023-05-11 18:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-01 23:37 Roger Sayle
2023-05-02 12:40 ` Paul Koning
2023-05-02 13:18 ` Roger Sayle
2023-05-02 13:49 ` Segher Boessenkool
2023-05-02 16:20 ` Roger Sayle
2023-05-02 21:55 ` Segher Boessenkool
2023-05-02 14:11 ` Paul Koning
2023-05-02 15:47 ` Segher Boessenkool
2023-05-02 15:57 ` Jeff Law
2023-05-11 15:05 ` Hans-Peter Nilsson
2023-05-11 16:55 ` Paul Koning
2023-05-11 18:15 ` Jeff Law [this message]
2023-05-11 18:32 ` Hans-Peter Nilsson
2023-05-12 13:53 ` Hans-Peter Nilsson
2023-05-12 14:01 ` Hans-Peter Nilsson
2023-05-12 14:04 ` Roger Sayle
2023-05-13 0:56 ` Hans-Peter Nilsson
2023-05-13 1:11 ` Hans-Peter Nilsson
-- strict thread matches above, loose matches on Subject: below --
2023-05-01 13:42 Jeff Law
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