From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752028Ab2HCFVS (ORCPT ); Fri, 3 Aug 2012 01:21:18 -0400 Received: from science.horizon.com ([71.41.210.146]:14844 "HELO science.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751311Ab2HCFVN (ORCPT ); Fri, 3 Aug 2012 01:21:13 -0400 From: George Spelvin To: vda.linux@googlemail.com, mina86@mina86.com Cc: hughd@google.com, linux-kernel@vger.kernel.org, linux@horizon.com Subject: [PATCH 3/4] lib: vsprintf: Optimize put_dec_trunc8 Date: Fri, 3 Aug 2012 01:21:10 -0400 Message-Id: <1343971271-13355-3-git-send-email-linux@horizon.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1343971271-13355-1-git-send-email-linux@horizon.com> References: <1343971271-13355-1-git-send-email-linux@horizon.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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