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authorGeorge Spelvin <linux@horizon.com>2012-10-04 17:12:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-06 03:04:48 +0900
commite49317d415f5a44bad8377a208d61902d752303e (patch)
tree2033f7152350144068f0bbe22a4735fc12fd4f30 /lib/vsprintf.c
parent6c0c0d4d1080840eabb3d055d2fd81911111c5fd (diff)
downloadlinux-stericsson-e49317d415f5a44bad8377a208d61902d752303e.tar.gz
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@horizon.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Michal Nazarewicz <mina86@mina86.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/vsprintf.c')
-rw-r--r--lib/vsprintf.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 0e337541f005..67e74cbefa90 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -243,13 +243,14 @@ char *put_dec(char *buf, unsigned long long n)
/* 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';