From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Eric Dumazet <edumazet@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
alexanderduyck@fb.com, kbuild-all@lists.01.org,
open list <linux-kernel@vger.kernel.org>,
linux-um@lists.infradead.org, lkp@intel.com,
peterz@infradead.org, X86 ML <x86@kernel.org>
Subject: Re: [tip:x86/core 1/1] arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad'
Date: Thu, 25 Nov 2021 00:49:34 -0600 [thread overview]
Message-ID: <CAFUsyfLACUMcOZmNF3S_xAaTXTPXAMg+kJ8tV6tKk+xw0XLOtg@mail.gmail.com> (raw)
In-Reply-To: <CANn89iJsFZrm5qzAUJDgYczQiBFa6pmvPDrA_yqkGFhfm-6AnQ@mail.gmail.com>
On Thu, Nov 25, 2021 at 12:46 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Wed, Nov 24, 2021 at 10:32 PM Eric Dumazet <edumazet@google.com> wrote:
>
> > - }
> > + if (unlikely(odd))
> > + result = ror32(result, 8);
> > return (__force __wsum)result;
>
> Oh well, gcc at least removes the conditional and generates a ror and a cmov
Seems like a missed optimization for `unlikely` where dependency breaking
is pretty common.
Although still saves a uop because of `imm8` operand.
>
> mov %edx,%eax
> ror $0x8,%eax
> test %r8,%r8
> cmove %edx,%eax
> ret
>
> clang keeps the cond jmp
> test $0x1,%dil
> je 93
> rol $0x18,%eax
> 93: ret
WARNING: multiple messages have this Message-ID (diff)
From: Noah Goldstein <goldstein.w.n@gmail.com>
To: kbuild-all@lists.01.org
Subject: Re: [tip:x86/core 1/1] arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad'
Date: Thu, 25 Nov 2021 00:49:34 -0600 [thread overview]
Message-ID: <CAFUsyfLACUMcOZmNF3S_xAaTXTPXAMg+kJ8tV6tKk+xw0XLOtg@mail.gmail.com> (raw)
In-Reply-To: <CANn89iJsFZrm5qzAUJDgYczQiBFa6pmvPDrA_yqkGFhfm-6AnQ@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 789 bytes --]
On Thu, Nov 25, 2021 at 12:46 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Wed, Nov 24, 2021 at 10:32 PM Eric Dumazet <edumazet@google.com> wrote:
>
> > - }
> > + if (unlikely(odd))
> > + result = ror32(result, 8);
> > return (__force __wsum)result;
>
> Oh well, gcc at least removes the conditional and generates a ror and a cmov
Seems like a missed optimization for `unlikely` where dependency breaking
is pretty common.
Although still saves a uop because of `imm8` operand.
>
> mov %edx,%eax
> ror $0x8,%eax
> test %r8,%r8
> cmove %edx,%eax
> ret
>
> clang keeps the cond jmp
> test $0x1,%dil
> je 93
> rol $0x18,%eax
> 93: ret
WARNING: multiple messages have this Message-ID (diff)
From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Eric Dumazet <edumazet@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
alexanderduyck@fb.com, kbuild-all@lists.01.org,
open list <linux-kernel@vger.kernel.org>,
linux-um@lists.infradead.org, lkp@intel.com,
peterz@infradead.org, X86 ML <x86@kernel.org>
Subject: Re: [tip:x86/core 1/1] arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad'
Date: Thu, 25 Nov 2021 00:49:34 -0600 [thread overview]
Message-ID: <CAFUsyfLACUMcOZmNF3S_xAaTXTPXAMg+kJ8tV6tKk+xw0XLOtg@mail.gmail.com> (raw)
In-Reply-To: <CANn89iJsFZrm5qzAUJDgYczQiBFa6pmvPDrA_yqkGFhfm-6AnQ@mail.gmail.com>
On Thu, Nov 25, 2021 at 12:46 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Wed, Nov 24, 2021 at 10:32 PM Eric Dumazet <edumazet@google.com> wrote:
>
> > - }
> > + if (unlikely(odd))
> > + result = ror32(result, 8);
> > return (__force __wsum)result;
>
> Oh well, gcc at least removes the conditional and generates a ror and a cmov
Seems like a missed optimization for `unlikely` where dependency breaking
is pretty common.
Although still saves a uop because of `imm8` operand.
>
> mov %edx,%eax
> ror $0x8,%eax
> test %r8,%r8
> cmove %edx,%eax
> ret
>
> clang keeps the cond jmp
> test $0x1,%dil
> je 93
> rol $0x18,%eax
> 93: ret
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next prev parent reply other threads:[~2021-11-25 6:51 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 18:45 [tip:x86/core 1/1] arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad' kernel test robot
2021-11-17 18:45 ` kernel test robot
2021-11-17 18:55 ` Eric Dumazet
2021-11-17 18:55 ` Eric Dumazet
2021-11-17 19:40 ` Eric Dumazet
2021-11-17 19:40 ` Eric Dumazet
2021-11-18 16:00 ` Peter Zijlstra
2021-11-18 16:00 ` Peter Zijlstra
2021-11-18 16:00 ` Peter Zijlstra
2021-11-18 16:26 ` Johannes Berg
2021-11-18 16:26 ` Johannes Berg
2021-11-18 16:26 ` Johannes Berg
2021-11-18 16:57 ` Eric Dumazet
2021-11-18 16:57 ` Eric Dumazet
2021-11-18 16:57 ` Eric Dumazet
2021-11-18 17:02 ` Eric Dumazet
2021-11-18 17:02 ` Eric Dumazet
2021-11-18 17:02 ` Eric Dumazet
2021-11-25 1:58 ` Noah Goldstein
2021-11-25 1:58 ` Noah Goldstein
2021-11-25 1:58 ` Noah Goldstein
2021-11-25 2:56 ` Eric Dumazet
2021-11-25 2:56 ` Eric Dumazet
2021-11-25 2:56 ` Eric Dumazet
2021-11-25 3:41 ` Noah Goldstein
2021-11-25 3:41 ` Noah Goldstein
2021-11-25 3:41 ` Noah Goldstein
2021-11-25 4:00 ` Eric Dumazet
2021-11-25 4:00 ` Eric Dumazet
2021-11-25 4:00 ` Eric Dumazet
2021-11-25 4:08 ` Eric Dumazet
2021-11-25 4:08 ` Eric Dumazet
2021-11-25 4:08 ` Eric Dumazet
2021-11-25 4:20 ` Eric Dumazet
2021-11-25 4:20 ` Eric Dumazet
2021-11-25 4:20 ` Eric Dumazet
2021-11-25 4:56 ` Noah Goldstein
2021-11-25 4:56 ` Noah Goldstein
2021-11-25 4:56 ` Noah Goldstein
2021-11-25 5:09 ` Noah Goldstein
2021-11-25 5:09 ` Noah Goldstein
2021-11-25 5:09 ` Noah Goldstein
2021-11-25 6:32 ` Eric Dumazet
2021-11-25 6:32 ` Eric Dumazet
2021-11-25 6:32 ` Eric Dumazet
2021-11-25 6:45 ` Eric Dumazet
2021-11-25 6:45 ` Eric Dumazet
2021-11-25 6:45 ` Eric Dumazet
2021-11-25 6:49 ` Noah Goldstein [this message]
2021-11-25 6:49 ` Noah Goldstein
2021-11-25 6:49 ` Noah Goldstein
2021-11-25 6:47 ` Noah Goldstein
2021-11-25 6:47 ` Noah Goldstein
2021-11-25 6:47 ` Noah Goldstein
2021-11-26 17:18 ` David Laight
2021-11-26 17:18 ` David Laight
2021-11-26 17:18 ` David Laight
2021-11-26 18:09 ` Eric Dumazet
2021-11-26 18:09 ` Eric Dumazet
2021-11-26 18:09 ` Eric Dumazet
2021-11-26 22:41 ` David Laight
2021-11-26 22:41 ` David Laight
2021-11-26 22:41 ` David Laight
2021-11-26 23:04 ` Noah Goldstein
2021-11-26 23:04 ` Noah Goldstein
2021-11-26 23:04 ` Noah Goldstein
2021-11-28 18:30 ` David Laight
2021-11-28 18:30 ` David Laight
2021-11-28 18:30 ` David Laight
2021-12-29 6:00 ` Al Viro
2021-12-29 6:00 ` Al Viro
2021-12-29 6:00 ` Al Viro
2022-01-31 2:29 ` Al Viro
2022-01-31 2:29 ` Al Viro
2022-01-31 2:29 ` Al Viro
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