#if !defined(_ilog_H)
# define _ilog_H (1)
+# include "config.h"
# include <stdint.h>
-
-# ifdef __GNUC_PREREQ
-/*Tag our functions as idempotent to aid optimization, if possible.*/
-# if __GNUC_PREREQ(2,5)
-# define IDEMPOTENT __attribute__((const))
-# endif
-# if __GNUC_PREREQ(3,4)
-# include <limits.h>
-/*Note the casts to (int) below: this prevents CLZ{32|64}_OFFS from "upgrading"
- the type of an entire expression to an (unsigned) size_t.*/
-# if INT_MAX>=2147483647
-# define CLZ32_OFFS ((int)sizeof(unsigned)*CHAR_BIT)
-# define CLZ32(_x) (__builtin_clz(_x))
-# elif LONG_MAX>=2147483647L
-# define CLZ32_OFFS ((int)sizeof(unsigned long)*CHAR_BIT)
-# define CLZ32(_x) (__builtin_clzl(_x))
-# endif
-# if INT_MAX>=9223372036854775807LL
-# define CLZ64_OFFS ((int)sizeof(unsigned)*CHAR_BIT)
-# define CLZ64(_x) (__builtin_clz(_x))
-# elif LONG_MAX>=9223372036854775807LL
-# define CLZ64_OFFS ((int)sizeof(unsigned long)*CHAR_BIT)
-# define CLZ64(_x) (__builtin_clzl(_x))
-# elif LLONG_MAX>=9223372036854775807LL
-# define CLZ64_OFFS ((int)sizeof(unsigned long long)*CHAR_BIT)
-# define CLZ64(_x) (__builtin_clzll(_x))
-# endif
-# endif
-# endif
-
-/*If you have some other compiler which defines its own clz-style builtin,
- implement a check for it here.*/
-
-# if !defined(IDEMPOTENT)
-# define IDEMPOTENT
-# endif
-
-
+# include <limits.h>
+# include <ccan/compiler/compiler.h>
/**
* ilog32 - Integer binary logarithm of a 32-bit value.
* Returns floor(log2(_v))+1, or 0 if _v==0.
* This is the number of bits that would be required to represent _v in two's
* complement notation with all of the leading zeros stripped.
- * The ILOG_32() or ILOGNZ_32() macros may be able to use a builtin function
- * instead, which should be faster.
+ * Note that many uses will resolve to the fast macro version instead.
+ *
+ * See Also:
+ * ilog32_nz(), ilog64()
+ *
+ * Example:
+ * // Rounds up to next power of 2 (if not a power of 2).
+ * static uint32_t round_up32(uint32_t i)
+ * {
+ * assert(i != 0);
+ * return 1U << ilog32(i-1);
+ * }
*/
-int ilog32(uint32_t _v)IDEMPOTENT;
+int ilog32(uint32_t _v) IDEMPOTENT;
+
/**
- * ilog64 - Integer binary logarithm of a 64-bit value.
- * @_v: A 64-bit value.
- * Returns floor(log2(_v))+1, or 0 if _v==0.
+ * ilog32_nz - Integer binary logarithm of a non-zero 32-bit value.
+ * @_v: A 32-bit value.
+ * Returns floor(log2(_v))+1, or undefined if _v==0.
* This is the number of bits that would be required to represent _v in two's
* complement notation with all of the leading zeros stripped.
- * The ILOG_64() or ILOGNZ_64() macros may be able to use a builtin function
- * instead, which should be faster.
+ * Note that many uses will resolve to the fast macro version instead.
+ * See Also:
+ * ilog32(), ilog64_nz()
+ * Example:
+ * // Find Last Set (ie. highest bit set, 0 to 31).
+ * static uint32_t fls32(uint32_t i)
+ * {
+ * assert(i != 0);
+ * return ilog32_nz(i) - 1;
+ * }
*/
-int ilog64(uint64_t _v)IDEMPOTENT;
-
-# undef IDEMPOTENT
-
+int ilog32_nz(uint32_t _v) IDEMPOTENT;
-# if defined(CLZ32)
/**
- * ILOGNZ_32 - Integer binary logarithm of a non-zero 32-bit value.
- * @_v: A non-zero 32-bit value.
- * Returns floor(log2(_v))+1.
+ * ilog64 - Integer binary logarithm of a 64-bit value.
+ * @_v: A 64-bit value.
+ * Returns floor(log2(_v))+1, or 0 if _v==0.
* This is the number of bits that would be required to represent _v in two's
* complement notation with all of the leading zeros stripped.
- * If _v is zero, the return value is undefined; use ILOG_32() instead.
+ * Note that many uses will resolve to the fast macro version instead.
+ * See Also:
+ * ilog64_nz(), ilog32()
*/
-# define ILOGNZ_32(_v) (CLZ32_OFFS-CLZ32(_v))
+int ilog64(uint64_t _v) IDEMPOTENT;
+
/**
- * ILOG_32 - Integer binary logarithm of a 32-bit value.
- * @_v: A 32-bit value.
- * Returns floor(log2(_v))+1, or 0 if _v==0.
+ * ilog64_nz - Integer binary logarithm of a non-zero 64-bit value.
+ * @_v: A 64-bit value.
+ * Returns floor(log2(_v))+1, or undefined if _v==0.
* This is the number of bits that would be required to represent _v in two's
* complement notation with all of the leading zeros stripped.
+ * Note that many uses will resolve to the fast macro version instead.
+ * See Also:
+ * ilog64(), ilog32_nz()
*/
-# define ILOG_32(_v) (ILOGNZ_32(_v)&-!!(_v))
-# else
-# define ILOGNZ_32(_v) (ilog32(_v))
-# define ILOG_32(_v) (ilog32(_v))
-# endif
+int ilog64_nz(uint64_t _v) IDEMPOTENT;
-# if defined(CLZ64)
/**
- * ILOGNZ_64 - Integer binary logarithm of a non-zero 64-bit value.
- * @_v: A non-zero 64-bit value.
- * Returns floor(log2(_v))+1.
+ * STATIC_ILOG_32 - The integer logarithm of an (unsigned, 32-bit) constant.
+ * @_v: A non-negative 32-bit constant.
+ * Returns floor(log2(_v))+1, or 0 if _v==0.
* This is the number of bits that would be required to represent _v in two's
* complement notation with all of the leading zeros stripped.
- * If _v is zero, the return value is undefined; use ILOG_64() instead.
+ * This macro should only be used when you need a compile-time constant,
+ * otherwise ilog32 or ilog32_nz are just as fast and more flexible.
+ *
+ * Example:
+ * #define MY_PAGE_SIZE 4096
+ * #define MY_PAGE_BITS (STATIC_ILOG_32(PAGE_SIZE) - 1)
*/
-# define ILOGNZ_64(_v) (CLZ64_OFFS-CLZ64(_v))
+#define STATIC_ILOG_32(_v) (STATIC_ILOG5((uint32_t)(_v)))
+
/**
- * ILOG_64 - Integer binary logarithm of a 64-bit value.
- * @_v: A 64-bit value.
+ * STATIC_ILOG_64 - The integer logarithm of an (unsigned, 64-bit) constant.
+ * @_v: A non-negative 64-bit constant.
* Returns floor(log2(_v))+1, or 0 if _v==0.
* This is the number of bits that would be required to represent _v in two's
* complement notation with all of the leading zeros stripped.
+ * This macro should only be used when you need a compile-time constant,
+ * otherwise ilog64 or ilog64_nz are just as fast and more flexible.
*/
-# define ILOG_64(_v) (ILOGNZ_64(_v)&-!!(_v))
-# else
-# define ILOGNZ_64(_v) (ilog64(_v))
-# define ILOG_64(_v) (ilog64(_v))
-# endif
+#define STATIC_ILOG_64(_v) (STATIC_ILOG6((uint64_t)(_v)))
+/* Private implementation details */
+
+/*Note the casts to (int) below: this prevents "upgrading"
+ the type of an entire expression to an (unsigned) size_t.*/
+#if INT_MAX>=2147483647 && HAVE_BUILTIN_CLZ
+#define builtin_ilog32_nz(v) \
+ (((int)sizeof(unsigned)*CHAR_BIT) - __builtin_clz(v))
+#elif LONG_MAX>=2147483647L && HAVE_BUILTIN_CLZL
+#define builtin_ilog32_nz(v) \
+ (((int)sizeof(unsigned)*CHAR_BIT) - __builtin_clzl(v))
+#endif
+
+#if INT_MAX>=9223372036854775807LL && HAVE_BUILTIN_CLZ
+#define builtin_ilog64_nz(v) \
+ (((int)sizeof(unsigned)*CHAR_BIT) - __builtin_clz(v))
+#elif LONG_MAX>=9223372036854775807LL && HAVE_BUILTIN_CLZL
+#define builtin_ilog64_nz(v) \
+ (((int)sizeof(unsigned long)*CHAR_BIT) - __builtin_clzl(v))
+#elif HAVE_BUILTIN_CLZLL
+#define builtin_ilog64_nz(v) \
+ (((int)sizeof(unsigned long long)*CHAR_BIT) - __builtin_clzll(v))
+#endif
+
+#ifdef builtin_ilog32_nz
+#define ilog32(_v) (builtin_ilog32_nz(_v)&-!!(_v))
+#define ilog32_nz(_v) builtin_ilog32_nz(_v)
+#else
+#define ilog32_nz(_v) ilog32(_v)
+#define ilog32(_v) (IS_COMPILE_CONSTANT(_v) ? STATIC_ILOG_32(_v) : ilog32(_v))
+#endif /* builtin_ilog32_nz */
+
+#ifdef builtin_ilog64_nz
+#define ilog64(_v) (builtin_ilog64_nz(_v)&-!!(_v))
+#define ilog64_nz(_v) builtin_ilog64_nz(_v)
+#else
+#define ilog64_nz(_v) ilog64(_v)
+#define ilog64(_v) (IS_COMPILE_CONSTANT(_v) ? STATIC_ILOG_64(_v) : ilog64(_v))
+#endif /* builtin_ilog64_nz */
+
+/* Macros for evaluating compile-time constant ilog. */
# define STATIC_ILOG0(_v) (!!(_v))
# define STATIC_ILOG1(_v) (((_v)&0x2)?2:STATIC_ILOG0(_v))
# define STATIC_ILOG2(_v) (((_v)&0xC)?2+STATIC_ILOG1((_v)>>2):STATIC_ILOG1(_v))
(((_v)&0xFFFF0000)?16+STATIC_ILOG4((_v)>>16):STATIC_ILOG4(_v))
# define STATIC_ILOG6(_v) \
(((_v)&0xFFFFFFFF00000000ULL)?32+STATIC_ILOG5((_v)>>32):STATIC_ILOG5(_v))
-/**
- * STATIC_ILOG_32 - The integer logarithm of an (unsigned, 32-bit) constant.
- * @_v: A non-negative 32-bit constant.
- * Returns floor(log2(_v))+1, or 0 if _v==0.
- * This is the number of bits that would be required to represent _v in two's
- * complement notation with all of the leading zeros stripped.
- * This macro is suitable for evaluation at compile time, but it should not be
- * used on values that can change at runtime, as it operates via exhaustive
- * search.
- */
-# define STATIC_ILOG_32(_v) (STATIC_ILOG5((uint32_t)(_v)))
-/**
- * STATIC_ILOG_64 - The integer logarithm of an (unsigned, 64-bit) constant.
- * @_v: A non-negative 64-bit constant.
- * Returns floor(log2(_v))+1, or 0 if _v==0.
- * This is the number of bits that would be required to represent _v in two's
- * complement notation with all of the leading zeros stripped.
- * This macro is suitable for evaluation at compile time, but it should not be
- * used on values that can change at runtime, as it operates via exhaustive
- * search.
- */
-# define STATIC_ILOG_64(_v) (STATIC_ILOG6((uint64_t)(_v)))
-#endif
+#endif /* _ilog_H */
projects / ccan / blobdiff