From cb239d0a97d573150d6106a92c0641da0d03f6a1 Mon Sep 17 00:00:00 2001 From: George Spelvin Date: Thu, 4 Oct 2012 17:12:30 -0700 Subject: [PATCH] lib: vsprintf: optimize put_dec_trunc8() 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 Cc: Denys Vlasenko Cc: Michal Nazarewicz Cc: Rabin Vincent Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/vsprintf.c | 22 ++++++---------------- 1 file changed, 6 insertions(+), 16 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 8cb7635b2ce..c2236f14640 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -174,22 +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 */ - if (r == 0) - return buf; + while (r >= 10000) { + q = r + '0'; + r = (r * (uint64_t)0x1999999a) >> 32; + *buf++ = q - 10*r; + } + q = (r * 0x199a) >> 16; *buf++ = (r - 10 * q) + '0'; /* 6 */ if (q == 0) -- 2.20.1