diff options
author | George Spelvin <linux@horizon.com> | 2012-10-04 20:12:27 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-05 14:04:48 -0400 |
commit | e49317d415f5a44bad8377a208d61902d752303e (patch) | |
tree | 2033f7152350144068f0bbe22a4735fc12fd4f30 /lib | |
parent | 6c0c0d4d1080840eabb3d055d2fd81911111c5fd (diff) |
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')
-rw-r--r-- | lib/vsprintf.c | 5 |
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) | |||
243 | 243 | ||
244 | /* Second algorithm: valid only for 64-bit long longs */ | 244 | /* Second algorithm: valid only for 64-bit long longs */ |
245 | 245 | ||
246 | /* See comment in put_dec_full9 for choice of constants */ | ||
246 | static noinline_for_stack | 247 | static noinline_for_stack |
247 | char *put_dec_full4(char *buf, unsigned q) | 248 | char *put_dec_full4(char *buf, unsigned q) |
248 | { | 249 | { |
249 | unsigned r; | 250 | unsigned r; |
250 | r = (q * 0xcccd) >> 19; | 251 | r = (q * 0xccd) >> 15; |
251 | *buf++ = (q - 10 * r) + '0'; | 252 | *buf++ = (q - 10 * r) + '0'; |
252 | q = (r * 0x199a) >> 16; | 253 | q = (r * 0xcd) >> 11; |
253 | *buf++ = (r - 10 * q) + '0'; | 254 | *buf++ = (r - 10 * q) + '0'; |
254 | r = (q * 0xcd) >> 11; | 255 | r = (q * 0xcd) >> 11; |
255 | *buf++ = (q - 10 * r) + '0'; | 256 | *buf++ = (q - 10 * r) + '0'; |