fbeadf50f2
We had two copies of a ffs function for longs with subtly different semantics and, for the one in bitops.h, a confusing name: the result was off-by-one compared to the library function ffsl. Unify the functions into one, and solve the name problem by calling the 0-based functions "bitops_ctzl" and "bitops_ctol" respectively. This also fixes the build on platforms with ffsl, including Mac OS X and Windows. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Tested-by: Andreas Färber <afaerber@suse.de> Tested-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
143 lines
3.5 KiB
C
143 lines
3.5 KiB
C
/*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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* Copyright (C) 2008 IBM Corporation
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* Written by Rusty Russell <rusty@rustcorp.com.au>
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* (Inspired by David Howell's find_next_bit implementation)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include "qemu/bitops.h"
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#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
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/*
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* Find the next set bit in a memory region.
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*/
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unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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const unsigned long *p = addr + BITOP_WORD(offset);
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unsigned long result = offset & ~(BITS_PER_LONG-1);
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unsigned long tmp;
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if (offset >= size) {
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return size;
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}
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size -= result;
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offset %= BITS_PER_LONG;
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if (offset) {
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tmp = *(p++);
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tmp &= (~0UL << offset);
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if (size < BITS_PER_LONG) {
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goto found_first;
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}
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if (tmp) {
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goto found_middle;
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}
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size -= BITS_PER_LONG;
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result += BITS_PER_LONG;
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}
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while (size & ~(BITS_PER_LONG-1)) {
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if ((tmp = *(p++))) {
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goto found_middle;
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}
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result += BITS_PER_LONG;
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size -= BITS_PER_LONG;
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}
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if (!size) {
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return result;
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}
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tmp = *p;
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found_first:
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tmp &= (~0UL >> (BITS_PER_LONG - size));
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if (tmp == 0UL) { /* Are any bits set? */
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return result + size; /* Nope. */
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}
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found_middle:
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return result + bitops_ctzl(tmp);
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}
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/*
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* This implementation of find_{first,next}_zero_bit was stolen from
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* Linus' asm-alpha/bitops.h.
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*/
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unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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const unsigned long *p = addr + BITOP_WORD(offset);
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unsigned long result = offset & ~(BITS_PER_LONG-1);
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unsigned long tmp;
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if (offset >= size) {
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return size;
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}
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size -= result;
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offset %= BITS_PER_LONG;
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if (offset) {
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tmp = *(p++);
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tmp |= ~0UL >> (BITS_PER_LONG - offset);
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if (size < BITS_PER_LONG) {
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goto found_first;
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}
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if (~tmp) {
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goto found_middle;
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}
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size -= BITS_PER_LONG;
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result += BITS_PER_LONG;
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}
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while (size & ~(BITS_PER_LONG-1)) {
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if (~(tmp = *(p++))) {
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goto found_middle;
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}
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result += BITS_PER_LONG;
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size -= BITS_PER_LONG;
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}
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if (!size) {
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return result;
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}
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tmp = *p;
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found_first:
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tmp |= ~0UL << size;
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if (tmp == ~0UL) { /* Are any bits zero? */
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return result + size; /* Nope. */
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}
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found_middle:
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return result + bitops_ctol(tmp);
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}
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unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
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{
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unsigned long words;
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unsigned long tmp;
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/* Start at final word. */
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words = size / BITS_PER_LONG;
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/* Partial final word? */
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if (size & (BITS_PER_LONG-1)) {
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tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
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- (size & (BITS_PER_LONG-1)))));
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if (tmp) {
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goto found;
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}
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}
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while (words) {
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tmp = addr[--words];
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if (tmp) {
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found:
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return words * BITS_PER_LONG + bitops_flsl(tmp);
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}
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}
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/* Not found */
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return size;
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}
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