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+/**************************************************************************
+ *
+ * Copyright 2008 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+
+#ifndef BITSCAN_H
+#define BITSCAN_H
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#endif
+
+#if defined(__POPCNT__)
+#include <popcntintrin.h>
+#endif
+
+#include "c99_compat.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/**
+ * Find first bit set in word. Least significant bit is 1.
+ * Return 0 if no bits set.
+ */
+#ifdef HAVE___BUILTIN_FFS
+#define ffs __builtin_ffs
+#elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
+static inline
+int ffs(int i)
+{
+ unsigned long index;
+ if (_BitScanForward(&index, i))
+ return index + 1;
+ else
+ return 0;
+}
+#else
+extern
+int ffs(int i);
+#endif
+
+#ifdef HAVE___BUILTIN_FFSLL
+#define ffsll __builtin_ffsll
+#elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM64 || _M_IA64)
+static inline int
+ffsll(long long int i)
+{
+ unsigned long index;
+ if (_BitScanForward64(&index, i))
+ return index + 1;
+ else
+ return 0;
+}
+#else
+extern int
+ffsll(long long int val);
+#endif
+
+
+/* Destructively loop over all of the bits in a mask as in:
+ *
+ * while (mymask) {
+ * int i = u_bit_scan(&mymask);
+ * ... process element i
+ * }
+ *
+ */
+static inline int
+u_bit_scan(unsigned *mask)
+{
+ const int i = ffs(*mask) - 1;
+ *mask ^= (1u << i);
+ return i;
+}
+
+#define u_foreach_bit(b, dword) \
+ for (uint32_t __dword = (dword), b; \
+ ((b) = ffs(__dword) - 1, __dword); \
+ __dword &= ~(1 << (b)))
+
+static inline int
+u_bit_scan64(uint64_t *mask)
+{
+ const int i = ffsll(*mask) - 1;
+ *mask ^= (((uint64_t)1) << i);
+ return i;
+}
+
+#define u_foreach_bit64(b, dword) \
+ for (uint64_t __dword = (dword), b; \
+ ((b) = ffsll(__dword) - 1, __dword); \
+ __dword &= ~(1ull << (b)))
+
+/* Determine if an unsigned value is a power of two.
+ *
+ * \note
+ * Zero is treated as a power of two.
+ */
+static inline bool
+util_is_power_of_two_or_zero(unsigned v)
+{
+ return (v & (v - 1)) == 0;
+}
+
+/* Determine if an uint64_t value is a power of two.
+ *
+ * \note
+ * Zero is treated as a power of two.
+ */
+static inline bool
+util_is_power_of_two_or_zero64(uint64_t v)
+{
+ return (v & (v - 1)) == 0;
+}
+
+/* Determine if an unsigned value is a power of two.
+ *
+ * \note
+ * Zero is \b not treated as a power of two.
+ */
+static inline bool
+util_is_power_of_two_nonzero(unsigned v)
+{
+ /* __POPCNT__ is different from HAVE___BUILTIN_POPCOUNT. The latter
+ * indicates the existence of the __builtin_popcount function. The former
+ * indicates that _mm_popcnt_u32 exists and is a native instruction.
+ *
+ * The other alternative is to use SSE 4.2 compile-time flags. This has
+ * two drawbacks. First, there is currently no build infrastructure for
+ * SSE 4.2 (only 4.1), so that would have to be added. Second, some AMD
+ * CPUs support POPCNT but not SSE 4.2 (e.g., Barcelona).
+ */
+#ifdef __POPCNT__
+ return _mm_popcnt_u32(v) == 1;
+#else
+ return v != 0 && (v & (v - 1)) == 0;
+#endif
+}
+
+/* For looping over a bitmask when you want to loop over consecutive bits
+ * manually, for example:
+ *
+ * while (mask) {
+ * int start, count, i;
+ *
+ * u_bit_scan_consecutive_range(&mask, &start, &count);
+ *
+ * for (i = 0; i < count; i++)
+ * ... process element (start+i)
+ * }
+ */
+static inline void
+u_bit_scan_consecutive_range(unsigned *mask, int *start, int *count)
+{
+ if (*mask == 0xffffffff) {
+ *start = 0;
+ *count = 32;
+ *mask = 0;
+ return;
+ }
+ *start = ffs(*mask) - 1;
+ *count = ffs(~(*mask >> *start)) - 1;
+ *mask &= ~(((1u << *count) - 1) << *start);
+}
+
+static inline void
+u_bit_scan_consecutive_range64(uint64_t *mask, int *start, int *count)
+{
+ if (*mask == ~0ull) {
+ *start = 0;
+ *count = 64;
+ *mask = 0;
+ return;
+ }
+ *start = ffsll(*mask) - 1;
+ *count = ffsll(~(*mask >> *start)) - 1;
+ *mask &= ~(((((uint64_t)1) << *count) - 1) << *start);
+}
+
+
+/**
+ * Find last bit set in a word. The least significant bit is 1.
+ * Return 0 if no bits are set.
+ * Essentially ffs() in the reverse direction.
+ */
+static inline unsigned
+util_last_bit(unsigned u)
+{
+#if defined(HAVE___BUILTIN_CLZ)
+ return u == 0 ? 0 : 32 - __builtin_clz(u);
+#elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
+ unsigned long index;
+ if (_BitScanReverse(&index, u))
+ return index + 1;
+ else
+ return 0;
+#else
+ unsigned r = 0;
+ while (u) {
+ r++;
+ u >>= 1;
+ }
+ return r;
+#endif
+}
+
+/**
+ * Find last bit set in a word. The least significant bit is 1.
+ * Return 0 if no bits are set.
+ * Essentially ffsll() in the reverse direction.
+ */
+static inline unsigned
+util_last_bit64(uint64_t u)
+{
+#if defined(HAVE___BUILTIN_CLZLL)
+ return u == 0 ? 0 : 64 - __builtin_clzll(u);
+#elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM64 || _M_IA64)
+ unsigned long index;
+ if (_BitScanReverse64(&index, u))
+ return index + 1;
+ else
+ return 0;
+#else
+ unsigned r = 0;
+ while (u) {
+ r++;
+ u >>= 1;
+ }
+ return r;
+#endif
+}
+
+/**
+ * Find last bit in a word that does not match the sign bit. The least
+ * significant bit is 1.
+ * Return 0 if no bits are set.
+ */
+static inline unsigned
+util_last_bit_signed(int i)
+{
+ if (i >= 0)
+ return util_last_bit(i);
+ else
+ return util_last_bit(~(unsigned)i);
+}
+
+/* Returns a bitfield in which the first count bits starting at start are
+ * set.
+ */
+static inline unsigned
+u_bit_consecutive(unsigned start, unsigned count)
+{
+ assert(start + count <= 32);
+ if (count == 32)
+ return ~0;
+ return ((1u << count) - 1) << start;
+}
+
+static inline uint64_t
+u_bit_consecutive64(unsigned start, unsigned count)
+{
+ assert(start + count <= 64);
+ if (count == 64)
+ return ~(uint64_t)0;
+ return (((uint64_t)1 << count) - 1) << start;
+}
+
+/**
+ * Return number of bits set in n.
+ */
+static inline unsigned
+util_bitcount(unsigned n)
+{
+#if defined(HAVE___BUILTIN_POPCOUNT)
+ return __builtin_popcount(n);
+#else
+ /* K&R classic bitcount.
+ *
+ * For each iteration, clear the LSB from the bitfield.
+ * Requires only one iteration per set bit, instead of
+ * one iteration per bit less than highest set bit.
+ */
+ unsigned bits;
+ for (bits = 0; n; bits++) {
+ n &= n - 1;
+ }
+ return bits;
+#endif
+}
+
+/**
+ * Return the number of bits set in n using the native popcnt instruction.
+ * The caller is responsible for ensuring that popcnt is supported by the CPU.
+ *
+ * gcc doesn't use it if -mpopcnt or -march= that has popcnt is missing.
+ *
+ */
+static inline unsigned
+util_popcnt_inline_asm(unsigned n)
+{
+#if defined(USE_X86_64_ASM) || defined(USE_X86_ASM)
+ uint32_t out;
+ __asm volatile("popcnt %1, %0" : "=r"(out) : "r"(n));
+ return out;
+#else
+ /* We should never get here by accident, but I'm sure it'll happen. */
+ return util_bitcount(n);
+#endif
+}
+
+static inline unsigned
+util_bitcount64(uint64_t n)
+{
+#ifdef HAVE___BUILTIN_POPCOUNTLL
+ return __builtin_popcountll(n);
+#else
+ return util_bitcount(n) + util_bitcount(n >> 32);
+#endif
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BITSCAN_H */
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