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| author | George Spelvin <linux@horizon.com> | 2012-10-04 17:12:27 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-06 03:04:48 +0900 |
| commit | e49317d415f5a44bad8377a208d61902d752303e (patch) | |
| tree | 2033f7152350144068f0bbe22a4735fc12fd4f30 | |
| parent | 6c0c0d4d1080840eabb3d055d2fd81911111c5fd (diff) | |
| download | linux-e49317d415f5a44bad8377a208d61902d752303e.tar.gz linux-e49317d415f5a44bad8377a208d61902d752303e.tar.bz2 linux-e49317d415f5a44bad8377a208d61902d752303e.zip | |
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>
| -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) /* 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'; |