1 files changed, 131 insertions, 0 deletions
diff --git a/include/linux/log2.h b/include/linux/log2.h
new file mode 100644
index 000000000000..3979c60325ff
--- /dev/null
+++ b/include/linux/log2.h
@@ -0,0 +1,131 @@
+/* Integer base 2 logarithm calculation
+ *
+ * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#ifndef _LINUX_LOG2_H
+#define _LINUX_LOG2_H
+#include <linux/types.h>
+#include <linux/bitops.h>
+/*
+ * deal with unrepresentable constant logarithms
+ */
+extern __attribute__((const, noreturn))
+int ____ilog2_NaN(void);
+/*
+ * non-constant log of base 2 calculators
+ * - the arch may override these in asm/bitops.h if they can be implemented
+ *   more efficiently than using fls() and fls64()
+ * - the arch is not required to handle n==0 if implementing the fallback
+ */
+#ifndef CONFIG_ARCH_HAS_ILOG2_U32
+static inline __attribute__((const))
+int __ilog2_u32(u32 n)
+{
+        return fls(n) - 1;
+}
+#endif
+#ifndef CONFIG_ARCH_HAS_ILOG2_U64
+static inline __attribute__((const))
+int __ilog2_u64(u64 n)
+{
+        return fls64(n) - 1;
+}
+#endif
+/**
+ * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
+ * @n - parameter
+ *
+ * constant-capable log of base 2 calculation
+ * - this can be used to initialise global variables from constant data, hence
+ *   the massive ternary operator construction
+ *
+ * selects the appropriately-sized optimised version depending on sizeof(n)
+ */
+#define ilog2(n)                                \
+(                                               \
+        __builtin_constant_p(n) ? (             \
+                (n) < 1 ? ____ilog2_NaN() :     \
+                (n) & (1ULL << 63) ? 63 :       \
+                (n) & (1ULL << 62) ? 62 :       \
+                (n) & (1ULL << 61) ? 61 :       \
+                (n) & (1ULL << 60) ? 60 :       \
+                (n) & (1ULL << 59) ? 59 :       \
+                (n) & (1ULL << 58) ? 58 :       \
+                (n) & (1ULL << 57) ? 57 :       \
+                (n) & (1ULL << 56) ? 56 :       \
+                (n) & (1ULL << 55) ? 55 :       \
+                (n) & (1ULL << 54) ? 54 :       \
+                (n) & (1ULL << 53) ? 53 :       \
+                (n) & (1ULL << 52) ? 52 :       \
+                (n) & (1ULL << 51) ? 51 :       \
+                (n) & (1ULL << 50) ? 50 :       \
+                (n) & (1ULL << 49) ? 49 :       \
+                (n) & (1ULL << 48) ? 48 :       \
+                (n) & (1ULL << 47) ? 47 :       \
+                (n) & (1ULL << 46) ? 46 :       \
+                (n) & (1ULL << 45) ? 45 :       \
+                (n) & (1ULL << 44) ? 44 :       \
+                (n) & (1ULL << 43) ? 43 :       \
+                (n) & (1ULL << 42) ? 42 :       \
+                (n) & (1ULL << 41) ? 41 :       \
+                (n) & (1ULL << 40) ? 40 :       \
+                (n) & (1ULL << 39) ? 39 :       \
+                (n) & (1ULL << 38) ? 38 :       \
+                (n) & (1ULL << 37) ? 37 :       \
+                (n) & (1ULL << 36) ? 36 :       \
+                (n) & (1ULL << 35) ? 35 :       \
+                (n) & (1ULL << 34) ? 34 :       \
+                (n) & (1ULL << 33) ? 33 :       \
+                (n) & (1ULL << 32) ? 32 :       \
+                (n) & (1ULL << 31) ? 31 :       \
+                (n) & (1ULL << 30) ? 30 :       \
+                (n) & (1ULL << 29) ? 29 :       \
+                (n) & (1ULL << 28) ? 28 :       \
+                (n) & (1ULL << 27) ? 27 :       \
+                (n) & (1ULL << 26) ? 26 :       \
+                (n) & (1ULL << 25) ? 25 :       \
+                (n) & (1ULL << 24) ? 24 :       \
+                (n) & (1ULL << 23) ? 23 :       \
+                (n) & (1ULL << 22) ? 22 :       \
+                (n) & (1ULL << 21) ? 21 :       \
+                (n) & (1ULL << 20) ? 20 :       \
+                (n) & (1ULL << 19) ? 19 :       \
+                (n) & (1ULL << 18) ? 18 :       \
+                (n) & (1ULL << 17) ? 17 :       \
+                (n) & (1ULL << 16) ? 16 :       \
+                (n) & (1ULL << 15) ? 15 :       \
+                (n) & (1ULL << 14) ? 14 :       \
+                (n) & (1ULL << 13) ? 13 :       \
+                (n) & (1ULL << 12) ? 12 :       \
+                (n) & (1ULL << 11) ? 11 :       \
+                (n) & (1ULL << 10) ? 10 :       \
+                (n) & (1ULL <<  9) ?  9 :       \
+                (n) & (1ULL <<  8) ?  8 :       \
+                (n) & (1ULL <<  7) ?  7 :       \
+                (n) & (1ULL <<  6) ?  6 :       \
+                (n) & (1ULL <<  5) ?  5 :       \
+                (n) & (1ULL <<  4) ?  4 :       \
+                (n) & (1ULL <<  3) ?  3 :       \
+                (n) & (1ULL <<  2) ?  2 :       \
+                (n) & (1ULL <<  1) ?  1 :       \
+                (n) & (1ULL <<  0) ?  0 :       \
+                ____ilog2_NaN()                 \
+                                   ) :          \
+        (sizeof(n) <= 4) ?                      \
+        __ilog2_u32(n) :                        \
+        __ilog2_u64(n)                          \
+ )
+#endif /* _LINUX_LOG2_H */

diff --git a/include/linux/log2.h b/include/linux/log2.h new file mode 100644 index 000000000000..3979c60325ff --- /dev/null +++ b/include/linux/log2.h
@@ -0,0 +1,131 @@
	1	/* Integer base 2 logarithm calculation
	2	*
	3	* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11
	12	#ifndef _LINUX_LOG2_H
	13	#define _LINUX_LOG2_H
	14
	15	#include <linux/types.h>
	16	#include <linux/bitops.h>
	17
	18	/*
	19	* deal with unrepresentable constant logarithms
	20	*/
	21	extern __attribute__((const, noreturn))
	22	int ____ilog2_NaN(void);
	23
	24	/*
	25	* non-constant log of base 2 calculators
	26	* - the arch may override these in asm/bitops.h if they can be implemented
	27	* more efficiently than using fls() and fls64()
	28	* - the arch is not required to handle n==0 if implementing the fallback
	29	*/
	30	#ifndef CONFIG_ARCH_HAS_ILOG2_U32
	31	static inline __attribute__((const))
	32	int __ilog2_u32(u32 n)
	33	{
	34	return fls(n) - 1;
	35	}
	36	#endif
	37
	38	#ifndef CONFIG_ARCH_HAS_ILOG2_U64
	39	static inline __attribute__((const))
	40	int __ilog2_u64(u64 n)
	41	{
	42	return fls64(n) - 1;
	43	}
	44	#endif
	45
	46	/**
	47	* ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
	48	* @n - parameter
	49	*
	50	* constant-capable log of base 2 calculation
	51	* - this can be used to initialise global variables from constant data, hence
	52	* the massive ternary operator construction
	53	*
	54	* selects the appropriately-sized optimised version depending on sizeof(n)
	55	*/
	56	#define ilog2(n) \
	57	( \
	58	__builtin_constant_p(n) ? ( \
	59	(n) < 1 ? ____ilog2_NaN() : \
	60	(n) & (1ULL << 63) ? 63 : \
	61	(n) & (1ULL << 62) ? 62 : \
	62	(n) & (1ULL << 61) ? 61 : \
	63	(n) & (1ULL << 60) ? 60 : \
	64	(n) & (1ULL << 59) ? 59 : \
	65	(n) & (1ULL << 58) ? 58 : \
	66	(n) & (1ULL << 57) ? 57 : \
	67	(n) & (1ULL << 56) ? 56 : \
	68	(n) & (1ULL << 55) ? 55 : \
	69	(n) & (1ULL << 54) ? 54 : \
	70	(n) & (1ULL << 53) ? 53 : \
	71	(n) & (1ULL << 52) ? 52 : \
	72	(n) & (1ULL << 51) ? 51 : \
	73	(n) & (1ULL << 50) ? 50 : \
	74	(n) & (1ULL << 49) ? 49 : \
	75	(n) & (1ULL << 48) ? 48 : \
	76	(n) & (1ULL << 47) ? 47 : \
	77	(n) & (1ULL << 46) ? 46 : \
	78	(n) & (1ULL << 45) ? 45 : \
	79	(n) & (1ULL << 44) ? 44 : \
	80	(n) & (1ULL << 43) ? 43 : \
	81	(n) & (1ULL << 42) ? 42 : \
	82	(n) & (1ULL << 41) ? 41 : \
	83	(n) & (1ULL << 40) ? 40 : \
	84	(n) & (1ULL << 39) ? 39 : \
	85	(n) & (1ULL << 38) ? 38 : \
	86	(n) & (1ULL << 37) ? 37 : \
	87	(n) & (1ULL << 36) ? 36 : \
	88	(n) & (1ULL << 35) ? 35 : \
	89	(n) & (1ULL << 34) ? 34 : \
	90	(n) & (1ULL << 33) ? 33 : \
	91	(n) & (1ULL << 32) ? 32 : \
	92	(n) & (1ULL << 31) ? 31 : \
	93	(n) & (1ULL << 30) ? 30 : \
	94	(n) & (1ULL << 29) ? 29 : \
	95	(n) & (1ULL << 28) ? 28 : \
	96	(n) & (1ULL << 27) ? 27 : \
	97	(n) & (1ULL << 26) ? 26 : \
	98	(n) & (1ULL << 25) ? 25 : \
	99	(n) & (1ULL << 24) ? 24 : \
	100	(n) & (1ULL << 23) ? 23 : \
	101	(n) & (1ULL << 22) ? 22 : \
	102	(n) & (1ULL << 21) ? 21 : \
	103	(n) & (1ULL << 20) ? 20 : \
	104	(n) & (1ULL << 19) ? 19 : \
	105	(n) & (1ULL << 18) ? 18 : \
	106	(n) & (1ULL << 17) ? 17 : \
	107	(n) & (1ULL << 16) ? 16 : \
	108	(n) & (1ULL << 15) ? 15 : \
	109	(n) & (1ULL << 14) ? 14 : \
	110	(n) & (1ULL << 13) ? 13 : \
	111	(n) & (1ULL << 12) ? 12 : \
	112	(n) & (1ULL << 11) ? 11 : \
	113	(n) & (1ULL << 10) ? 10 : \
	114	(n) & (1ULL << 9) ? 9 : \
	115	(n) & (1ULL << 8) ? 8 : \
	116	(n) & (1ULL << 7) ? 7 : \
	117	(n) & (1ULL << 6) ? 6 : \
	118	(n) & (1ULL << 5) ? 5 : \
	119	(n) & (1ULL << 4) ? 4 : \
	120	(n) & (1ULL << 3) ? 3 : \
	121	(n) & (1ULL << 2) ? 2 : \
	122	(n) & (1ULL << 1) ? 1 : \
	123	(n) & (1ULL << 0) ? 0 : \
	124	____ilog2_NaN() \
	125	) : \
	126	(sizeof(n) <= 4) ? \
	127	__ilog2_u32(n) : \
	128	__ilog2_u64(n) \
	129	)
	130
	131	#endif /* _LINUX_LOG2_H */