lkml.org 
[lkml]   [2009]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] x86: make use of inc/dec conditional
From
Date
On Wed, 2009-08-19 at 08:48 +0100, Jan Beulich wrote:
> According to gcc's instruction selection, inc/dec can be used without
> penalty on most CPU models, but should be avoided on others. Hence we
> should have a config option controlling the use of inc/dec, and
> respective abstraction macros to avoid making the resulting code too
> ugly. There are a few instances of inc/dec that must be retained in
> assembly code, due to that code's dependency on the instruction not
> changing the carry flag.
>
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
>
> ---
> arch/x86/Kconfig.cpu | 4 ++++
> arch/x86/include/asm/asm.h | 27 +++++++++++++++++++++++++++
> arch/x86/include/asm/atomic_32.h | 8 ++++----
> arch/x86/include/asm/atomic_64.h | 16 ++++++++--------
> arch/x86/include/asm/checksum_32.h | 2 +-
> arch/x86/include/asm/spinlock.h | 6 +++---
> arch/x86/lib/checksum_32.S | 11 ++++++-----
> arch/x86/lib/clear_page_64.S | 3 ++-
> arch/x86/lib/copy_page_64.S | 5 +++--
> arch/x86/lib/copy_user_64.S | 17 +++++++++--------
> arch/x86/lib/copy_user_nocache_64.S | 17 +++++++++--------
> arch/x86/lib/memcpy_64.S | 11 ++++++-----
> arch/x86/lib/memset_64.S | 7 ++++---
> arch/x86/lib/rwlock_64.S | 5 +++--
> arch/x86/lib/semaphore_32.S | 7 ++++---
> arch/x86/lib/string_32.c | 23 ++++++++++++-----------
> arch/x86/lib/strstr_32.c | 5 +++--
> 17 files changed, 108 insertions(+), 66 deletions(-)

What's the performance gain? This seems like a rather large and ugly
patch if the result is borderline.


\
 
 \ /
  Last update: 2009-08-19 10:03    [W:1.562 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site