minix/common/lib/libc/string/popcount32.c
Lionel Sambuc 0cdf705cc6 Enable optional GCC install and GCC improvements
-By adding MKGCC=yes and MKGCCCMDS=yes on the make commandline
   it is now possible to compile and install GCC on the system.

   Before doing this, if you are not using the build.sh script,
   you will need to call the fetch scripts in order to retrieve
   the sources of GCC and its dependencies.

 -Reduce difference with NetBSD share/mk

   Move Minix-specific parameters from bsd.gcc.mk to bsd.own.mk,
   which is anyway patched, so that bsd.gcc.mk is now aligned
   on the NetBSD version.

 -Clean libraries dependencies, compiles stdc++ only if gcc is
   also compiled (it is part of the gcc sources)

 -Correct minix.h header sequence, cleanup spec headers.

 -Fix cross-compilation from a 32bit host targeting MINIX/arm

Change-Id: I1b234af18eed4ab5675188244e931b2a2b7bd943
2013-07-12 14:22:03 +02:00

83 lines
2.7 KiB
C

/* $NetBSD: popcount32.c,v 1.4 2011/08/21 21:25:04 dholland Exp $ */
/*-
* Copyright (c) 2009 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Joerg Sonnenberger.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: popcount32.c,v 1.4 2011/08/21 21:25:04 dholland Exp $");
#if !defined(_KERNEL) && !defined(_STANDALONE)
#include <limits.h>
#include <stdint.h>
#include <strings.h>
#else
#include <lib/libkern/libkern.h>
#include <machine/limits.h>
#endif
/*
* This a hybrid algorithm for bit counting between parallel counting and
* using multiplication. The idea is to sum up the bits in each Byte, so
* that the final accumulation can be done with a single multiplication.
* If the platform has a slow multiplication instruction, it can be replaced
* by the commented out version below.
*/
unsigned int
popcount32(uint32_t v)
{
unsigned int c;
v = v - ((v >> 1) & 0x55555555U);
v = (v & 0x33333333U) + ((v >> 2) & 0x33333333U);
v = (v + (v >> 4)) & 0x0f0f0f0fU;
c = (v * 0x01010101U) >> 24;
/*
* v = (v >> 16) + v;
* v = (v >> 8) + v;
* c = v & 255;
*/
return c;
}
#if UINT_MAX == 0xffffffffU
__strong_alias(popcount, popcount32)
#endif
#if ULONG_MAX == 0xffffffffU
__strong_alias(popcountl, popcount32)
#endif
#if defined(__minix)
__strong_alias(__popcountsi2, popcount32)
__strong_alias(__popcountdi2, popcount32)
#endif