Messages in this thread Patch in this message | | | From | George Spelvin <> | Subject | [PATCH 3/4] lib: vsprintf: Optimize put_dec_trunc8 | Date | Fri, 3 Aug 2012 01:21:10 -0400 |
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If you're going to have a conditional branch after each 32x32->64-bit multiply, might as well shrink the code and make it a loop.
This also avoids using the long multiply for small integers.
(This leaves the comments in a confusing state, but that's a separate patch to make review easier.)
Signed-off-by: George Spelvin <linux@horizon.com> --- lib/vsprintf.c | 20 ++++++-------------- 1 file changed, 6 insertions(+), 14 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index a8e7392..3ca77b8 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -174,20 +174,12 @@ char *put_dec_trunc8(char *buf, unsigned r) unsigned q; /* Copy of previous function's body with added early returns */ - q = (r * (uint64_t)0x1999999a) >> 32; - *buf++ = (r - 10 * q) + '0'; /* 2 */ - if (q == 0) - return buf; - r = (q * (uint64_t)0x1999999a) >> 32; - *buf++ = (q - 10 * r) + '0'; /* 3 */ - if (r == 0) - return buf; - q = (r * (uint64_t)0x1999999a) >> 32; - *buf++ = (r - 10 * q) + '0'; /* 4 */ - if (q == 0) - return buf; - r = (q * (uint64_t)0x1999999a) >> 32; - *buf++ = (q - 10 * r) + '0'; /* 5 */ + while (r >= 10000) { + q = r + '0'; + r = (r * (uint64_t)0x1999999a) >> 32; + *buf++ = q - 10*r; + } + if (r == 0) return buf; q = (r * 0x199a) >> 16; -- 1.7.10.4
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