The patch titled
Subject: lib/sort: Move the alignment check into a function
has been added to the -mm tree. Its filename is
lib-sort-add-64-bit-swap-function-v2-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-sort-add-64-bit-swap-function-v2-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-sort-add-64-bit-swap-function-v2-fix.patch
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------------------------------------------------------
From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
Subject: lib/sort: Move the alignment check into a function
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@xxxxxxxxxxxx>
Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/sort.c | 30 +++++++++---------------------
1 file changed, 9 insertions(+), 21 deletions(-)
diff -puN lib/sort.c~lib-sort-add-64-bit-swap-function-v2-fix lib/sort.c
--- a/lib/sort.c~lib-sort-add-64-bit-swap-function-v2-fix
+++ a/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
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;
}
_
Patches currently in -mm which might be from daniel.wagner@xxxxxxxxxxxx are
lib-sort-add-64-bit-swap-function.patch
lib-sort-add-64-bit-swap-function-v2.patch
lib-sort-add-64-bit-swap-function-v2-fix.patch
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