The patch titled
Subject: lib: vsprintf: optimize division by 10 for small integers
has been added to the -mm tree. Its filename is
lib-vsprintf-optimize-division-by-10-for-small-integers.patch
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------------------------------------------------------
From: George Spelvin <linux@xxxxxxxxxxx>
Subject: lib: vsprintf: optimize division by 10 for small integers
Shrink the reciprocal approximations used in put_dec_full4() based on the
comments in put_dec_full9().
Signed-off-by: George Spelvin <linux@xxxxxxxxxxx>
Cc: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>
Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/vsprintf.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN lib/vsprintf.c~lib-vsprintf-optimize-division-by-10-for-small-integers lib/vsprintf.c
--- a/lib/vsprintf.c~lib-vsprintf-optimize-division-by-10-for-small-integers
+++ a/lib/vsprintf.c
@@ -243,13 +243,14 @@ char *put_dec(char *buf, unsigned long l
/* Second algorithm: valid only for 64-bit long longs */
+/* See comment in put_dec_full9 for choice of constants */
static noinline_for_stack
char *put_dec_full4(char *buf, unsigned q)
{
unsigned r;
- r = (q * 0xcccd) >> 19;
+ r = (q * 0xccd) >> 15;
*buf++ = (q - 10 * r) + '0';
- q = (r * 0x199a) >> 16;
+ q = (r * 0xcd) >> 11;
*buf++ = (r - 10 * q) + '0';
r = (q * 0xcd) >> 11;
*buf++ = (q - 10 * r) + '0';
_
Patches currently in -mm which might be from linux@xxxxxxxxxxx are
lib-vsprintf-optimize-division-by-10-for-small-integers.patch
lib-vsprintf-optimize-division-by-10000.patch
lib-vsprintf-optimize-put_dec_trunc8.patch
lib-vsprintf-fix-broken-comments.patch
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