Messages in this thread Patch in this message | | | From | Daniel Wagner <> | Subject | [PATCH] lib/sort: Move the alignment check into a function | Date | Mon, 18 May 2015 11:50:09 +0200 |
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Rasmus Villemoes suggestes to move the aliment check into a separate function in order to improve the readability.
Furthermore, let's avoid the switch statement since gcc might mess it up. My gcc 4.9.2 produces the same code for the x86_64 configuration. That is
switch (size) { case 4: if (alignment_ok(base, 4)) swap_func = u32_swap; break; case 8: if (alignment_ok(base, 8)) swap_func = u64_swap; break; } if (!swap_func) swap_func = generic_swap; }
resulted into the same object code.
Link: https://lkml.org/lkml/2015/5/15/89 Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Andrew Morton <akpm@linux-foundation.org>
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Hi,
I did this patch on top of current mmotm tree [1]. Hopefully I got this right, if you want it merged into v2 of this patch or any different version just let me know. Eventually I will get this right :)
cheers, daniel
[1] http://ozlabs.org/~akpm/mmotm/ --- lib/sort.c | 30 +++++++++--------------------- 1 file changed, 9 insertions(+), 21 deletions(-)
diff --git a/lib/sort.c b/lib/sort.c index 9c6b229..fc20df4 100644 --- a/lib/sort.c +++ b/lib/sort.c @@ -8,6 +8,12 @@ #include <linux/export.h> #include <linux/sort.h> +static int alignment_ok(const void *base, int align) +{ + return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) || + ((unsigned long)base & (align - 1)) == 0; +} + static void u32_swap(void *a, void *b, int size) { u32 t = *(u32 *)a; @@ -58,29 +64,11 @@ void sort(void *base, size_t num, size_t size, int i = (num/2 - 1) * size, n = num * size, c, r; if (!swap_func) { -#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) - switch (size) { - case 4: + if (size == 4 && alignment_ok(base, 4)) swap_func = u32_swap; - break; - case 8: + else if (size == 8 && alignment_ok(base, 8)) swap_func = u64_swap; - break; - } -#else - switch (size) { - case 4: - if (((unsigned long)base & 3) == 0) - swap_func = u32_swap; - break; - case 8: - if (((unsigned long)base & 7) == 0) - swap_func = u64_swap; - break; - } -#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */ - - if (!swap_func) + else swap_func = generic_swap; } -- 2.1.0
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