48 lines
1.7 KiB
Diff
48 lines
1.7 KiB
Diff
From f5b973489beb1a1239dfad53e3ad6e36ff7ee958 Mon Sep 17 00:00:00 2001
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From: Segher Boessenkool <segher@kernel.crashing.org>
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Date: Thu, 9 Oct 2008 21:18:27 +0100
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Subject: [PATCH] fix-gcc-4.3-false-modulo-optimization.patch
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I tried to compile the current stable kernel
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(a2ef813d2f439a3e9f377d33a2e5baad098afb7e)
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and get the following errors:
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kernel/built-in.o: In function `timespec_add_ns':
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/mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:174:
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undefined reference to `__aeabi_uldivmod'
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/mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:179:
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undefined reference to `__aeabi_uldivmod'
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/mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:174:
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undefined reference to `__aeabi_uldivmod'
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/mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:179:
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undefined reference to `__aeabi_uldivmod'
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applying the following patch solved the problem:
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--------
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Prevent gcc-4.3 form "optimizing" the while loop into a costly modulo operation.
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Patch found at http://lkml.org/lkml/2008/2/22/464.
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Reported-by: Sven Rebhan <odinshorse@googlemail.com>
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Signed-off-by: Segher Boessenkool <segher@kernel.crashing.org>
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---
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include/linux/time.h | 4 ++++
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1 files changed, 4 insertions(+), 0 deletions(-)
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diff --git a/include/linux/time.h b/include/linux/time.h
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index b04136d..3e8fd9e 100644
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--- a/include/linux/time.h
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+++ b/include/linux/time.h
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@@ -173,6 +173,10 @@ static inline void timespec_add_ns(struct timespec *a, u64 ns)
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{
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ns += a->tv_nsec;
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while(unlikely(ns >= NSEC_PER_SEC)) {
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+ /* The following asm() prevents the compiler from
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+ * optimising this loop into a modulo operation. */
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+ asm("" : "+r"(ns));
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+
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ns -= NSEC_PER_SEC;
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a->tv_sec++;
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}
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--
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1.5.6.5
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