Shrink the reciprocal approximations used in put_dec_full4
based on the comments in put_dec_full9.
Signed-off-by: George Spelvin <li...@horizon.com>
Cc: Denys Vlasenko <vda.li...@googlemail.com>
Cc: Michal Nazarewicz <min...@mina86.com>
---
lib/vsprintf.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
I was looking over the code and noticed that the constants could be smaller.
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c3f36d41..2f32fe8 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';
--
1.7.10.4
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