From: Linus Torvalds <torvalds@linux-foundation.org>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: bit tweaks [was: Re: [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11]
Date: Tue, 14 Nov 2017 14:43:14 -0800 [thread overview]
Message-ID: <CA+55aFxrqdRwV+WOBJiXw+xgZ5nSCFM97w+a89sxHwMsEvjTmw@mail.gmail.com> (raw)
In-Reply-To: <CAKwiHFgXDxpQc279NUrO8X3E+UysBoVQ63s=y5oVu0jKysT7Rw@mail.gmail.com>
On Tue, Nov 14, 2017 at 2:24 PM, Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> Can you be more specific? That's not what I see with gcc 7.1.
I have gcc-7.2.1, and it made a horrible mess of the do_mount() code.
Look for the comment "/* Separate the per-mountpoint flags */" and do
the obvious conversion of the simple single-bit stuff.
My gcc actually turned those into jumps after _after_ I converted it
into the ternary operation, and then the ternary conversion actually
did much worse, because it actually had two sides (one with a zero
value, and one with the bit value to be set).
I didn't have time to look into _why_ that code generated
branch-overs, when the otherwise similar reverse case in fs/statfs.c
did not.
Linus
next prev parent reply other threads:[~2017-11-14 22:43 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-09 0:43 [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11 Patrick McLean
2017-11-09 2:40 ` Linus Torvalds
2017-11-09 3:45 ` Al Viro
2017-11-09 19:34 ` Patrick McLean
2017-11-09 19:38 ` Al Viro
2017-11-09 19:42 ` Patrick McLean
2017-11-09 19:37 ` Al Viro
2017-11-09 19:51 ` Patrick McLean
2017-11-09 20:04 ` Linus Torvalds
2017-11-09 21:16 ` Al Viro
2017-11-10 1:58 ` Patrick McLean
2017-11-10 13:53 ` Arnd Bergmann
2017-11-10 18:42 ` Linus Torvalds
2017-11-10 23:26 ` Patrick McLean
2017-11-11 0:27 ` Patrick McLean
2017-11-11 2:36 ` Linus Torvalds
2017-11-11 2:36 ` [kernel-hardening] " Linus Torvalds
2017-11-11 2:36 ` Linus Torvalds
2017-11-11 16:13 ` Kees Cook
2017-11-11 16:13 ` [kernel-hardening] " Kees Cook
2017-11-11 16:13 ` Kees Cook
2017-11-11 17:31 ` Linus Torvalds
2017-11-11 17:31 ` [kernel-hardening] " Linus Torvalds
2017-11-11 17:31 ` Linus Torvalds
2017-11-13 22:48 ` Patrick McLean
2017-11-13 22:48 ` [kernel-hardening] " Patrick McLean
2017-11-13 22:48 ` Patrick McLean
2017-11-17 0:54 ` Kees Cook
2017-11-17 0:54 ` [kernel-hardening] " Kees Cook
2017-11-17 0:54 ` Kees Cook
2017-11-17 19:03 ` Patrick McLean
2017-11-17 19:03 ` [kernel-hardening] " Patrick McLean
2017-11-17 19:03 ` Patrick McLean
2017-11-17 21:26 ` Kees Cook
2017-11-17 21:26 ` [kernel-hardening] " Kees Cook
2017-11-17 21:26 ` Kees Cook
2017-11-18 0:27 ` Patrick McLean
2017-11-18 0:27 ` [kernel-hardening] " Patrick McLean
2017-11-18 0:27 ` Patrick McLean
2017-11-18 0:55 ` Linus Torvalds
2017-11-18 0:55 ` [kernel-hardening] " Linus Torvalds
2017-11-18 0:55 ` Linus Torvalds
2017-11-18 1:54 ` Patrick McLean
2017-11-18 1:54 ` [kernel-hardening] " Patrick McLean
2017-11-18 1:54 ` Patrick McLean
2017-11-18 5:14 ` Kees Cook
2017-11-18 5:14 ` [kernel-hardening] " Kees Cook
2017-11-18 5:14 ` Kees Cook
2017-11-18 5:29 ` Linus Torvalds
2017-11-18 5:29 ` [kernel-hardening] " Linus Torvalds
2017-11-18 5:29 ` Linus Torvalds
2017-11-18 8:20 ` Kees Cook
2017-11-18 8:20 ` [kernel-hardening] " Kees Cook
2017-11-18 8:20 ` Kees Cook
2018-02-21 22:19 ` RANDSTRUCT structs need linux/compiler_types.h (Was: [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11) Maciej S. Szmigiero
2018-02-21 22:47 ` Linus Torvalds
2018-02-21 22:47 ` Linus Torvalds
2018-02-21 23:34 ` Kees Cook
2018-02-21 23:34 ` Kees Cook
2018-03-05 9:27 ` Masahiro Yamada
2018-03-05 9:27 ` Masahiro Yamada
2018-03-05 19:15 ` Kees Cook
2018-03-05 19:18 ` Linus Torvalds
2018-02-21 22:52 ` Kees Cook
2018-02-21 23:24 ` Linus Torvalds
2018-02-22 0:12 ` Kees Cook
2018-02-22 0:22 ` Linus Torvalds
2018-02-22 0:23 ` Kees Cook
2018-02-22 0:27 ` Kees Cook
2017-11-11 1:13 ` [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11 J. Bruce Fields
2017-11-11 2:32 ` Al Viro
2017-11-10 1:47 ` Patrick McLean
2017-11-09 20:47 ` J. Bruce Fields
2017-11-09 23:07 ` Patrick McLean
2017-11-13 22:59 ` bit tweaks [was: Re: [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11] Rasmus Villemoes
2017-11-13 23:30 ` Linus Torvalds
2017-11-13 23:54 ` Linus Torvalds
2017-11-14 22:24 ` Rasmus Villemoes
2017-11-14 22:43 ` Linus Torvalds [this message]
2017-11-14 23:53 ` Rasmus Villemoes
2017-11-15 0:02 ` Linus Torvalds
2017-11-11 2:47 ` [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11 Alan Cox
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