target/linux/s3c24xx/patches-2.6.24/1300-fix-gcc-4.3-false-modulo-optimization.patch.patch

   1 From f5b973489beb1a1239dfad53e3ad6e36ff7ee958 Mon Sep 17 00:00:00 2001
   2 From: Segher Boessenkool <segher@kernel.crashing.org>
   3 Date: Thu, 9 Oct 2008 21:18:27 +0100
   4 Subject: [PATCH] fix-gcc-4.3-false-modulo-optimization.patch
   5
   6 I tried to compile the current stable kernel
   7 (a2ef813d2f439a3e9f377d33a2e5baad098afb7e)
   8 and get the following errors:
   9
  10 kernel/built-in.o: In function `timespec_add_ns':
  11 /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:174:
  12 undefined reference to `__aeabi_uldivmod'
  13 /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:179:
  14 undefined reference to `__aeabi_uldivmod'
  15 /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:174:
  16 undefined reference to `__aeabi_uldivmod'
  17 /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:179:
  18 undefined reference to `__aeabi_uldivmod'
  19
  20 applying the following patch solved the problem:
  21 --------
  22 Prevent gcc-4.3 form "optimizing" the while loop into a costly modulo operation.
  23 Patch found at http://lkml.org/lkml/2008/2/22/464.
  24
  25 Reported-by: Sven Rebhan <odinshorse@googlemail.com>
  26 Signed-off-by: Segher Boessenkool <segher@kernel.crashing.org>
  27 ---
  28  include/linux/time.h |    4 ++++
  29  1 files changed, 4 insertions(+), 0 deletions(-)
  30
  31 diff --git a/include/linux/time.h b/include/linux/time.h
  32 index b04136d..3e8fd9e 100644
  33 --- a/include/linux/time.h
  34 +++ b/include/linux/time.h
  35 @@ -173,6 +173,10 @@ static inline void timespec_add_ns(struct timespec *a, u64 ns)
  36  {
  37         ns += a->tv_nsec;
  38         while(unlikely(ns >= NSEC_PER_SEC)) {
  39 +               /* The following asm() prevents the compiler from
  40 +                * optimising this loop into a modulo operation.  */
  41 +               asm("" : "+r"(ns));
  42 +
  43                 ns -= NSEC_PER_SEC;
  44                 a->tv_sec++;
  45         }
  46 --
  47 1.5.6.5
  48