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Diffstat (limited to 'lib/ccan/ilog')
| -rw-r--r-- | lib/ccan/ilog/LICENSE | 508 | ||||
| -rw-r--r-- | lib/ccan/ilog/_info | 47 | ||||
| -rw-r--r-- | lib/ccan/ilog/ilog.c | 139 | ||||
| -rw-r--r-- | lib/ccan/ilog/ilog.h | 150 | ||||
| -rw-r--r-- | lib/ccan/ilog/test/run-out-of-line.c | 65 | ||||
| -rw-r--r-- | lib/ccan/ilog/test/run.c | 60 |
6 files changed, 969 insertions, 0 deletions
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Here is a sample; alter the names: + + Yoyodyne, Inc., hereby disclaims all copyright interest in the + library `Frob' (a library for tweaking knobs) written by James + Random Hacker. + + <signature of Ty Coon>, 1 April 1990 + Ty Coon, President of Vice + +That's all there is to it! diff --git a/lib/ccan/ilog/_info b/lib/ccan/ilog/_info new file mode 100644 index 0000000000..56de50d610 --- /dev/null +++ b/lib/ccan/ilog/_info @@ -0,0 +1,47 @@ +/** + * ilog - Integer logarithm. + * + * ilog_32() and ilog_64() compute the minimum number of bits required to store + * an unsigned 32-bit or 64-bit value without any leading zero bits. + * This can also be thought of as the location of the highest set bit, with + * counting starting from one (so that 0 returns 0, 1 returns 1, and 2**31 + * returns 32). + * When the value is known to be non-zero ilog32_nz() and ilog64_nz() can + * compile into as few as two instructions, one of which may get optimized out + * later. + * STATIC_ILOG_32 and STATIC_ILOG_64 allow computation on compile-time + * constants, so other compile-time constants can be derived from them. + * + * Example: + * #include <stdio.h> + * #include <limits.h> + * #include <ccan/ilog/ilog.h> + * + * int main(void){ + * int i; + * printf("ilog32(0x%08X)=%i\n",0,ilog32(0)); + * for(i=1;i<=STATIC_ILOG_32(USHRT_MAX);i++){ + * uint32_t v; + * v=(uint32_t)1U<<(i-1); + * //Here we know v is non-zero, so we can use ilog32_nz(). + * printf("ilog32(0x%08X)=%i\n",v,ilog32_nz(v)); + * } + * return 0; + * } + * + * License: LGPL (v2 or later) + * Author: Timothy B. Terriberry <tterribe@xiph.org> + */ +#include <string.h> +#include <stdio.h> +#include "config.h" + +int main(int _argc,const char *_argv[]){ + /*Expect exactly one argument.*/ + if(_argc!=2)return 1; + if(strcmp(_argv[1],"depends")==0){ + printf("ccan/compiler\n"); + return 0; + } + return 1; +} diff --git a/lib/ccan/ilog/ilog.c b/lib/ccan/ilog/ilog.c new file mode 100644 index 0000000000..40c5a6fd50 --- /dev/null +++ b/lib/ccan/ilog/ilog.c @@ -0,0 +1,139 @@ +/*(C) Timothy B. Terriberry (tterribe@xiph.org) 2001-2009 LGPL (v2 or later).*/ +#include "ilog.h" +#include <limits.h> + +/*The fastest fallback strategy for platforms with fast multiplication appears + to be based on de Bruijn sequences~\cite{LP98}. + Tests confirmed this to be true even on an ARM11, where it is actually faster + than using the native clz instruction. + Define ILOG_NODEBRUIJN to use a simpler fallback on platforms where + multiplication or table lookups are too expensive. + + @UNPUBLISHED{LP98, + author="Charles E. Leiserson and Harald Prokop", + title="Using de {Bruijn} Sequences to Index a 1 in a Computer Word", + month=Jun, + year=1998, + note="\url{http://supertech.csail.mit.edu/papers/debruijn.pdf}" + }*/ +static UNNEEDED const unsigned char DEBRUIJN_IDX32[32]={ + 0, 1,28, 2,29,14,24, 3,30,22,20,15,25,17, 4, 8, + 31,27,13,23,21,19,16, 7,26,12,18, 6,11, 5,10, 9 +}; + +/* We always compile these in, in case someone takes address of function. */ +#undef ilog32_nz +#undef ilog32 +#undef ilog64_nz +#undef ilog64 + +int ilog32(uint32_t _v){ +/*On a Pentium M, this branchless version tested as the fastest version without + multiplications on 1,000,000,000 random 32-bit integers, edging out a + similar version with branches, and a 256-entry LUT version.*/ +# if defined(ILOG_NODEBRUIJN) + int ret; + int m; + ret=_v>0; + m=(_v>0xFFFFU)<<4; + _v>>=m; + ret|=m; + m=(_v>0xFFU)<<3; + _v>>=m; + ret|=m; + m=(_v>0xFU)<<2; + _v>>=m; + ret|=m; + m=(_v>3)<<1; + _v>>=m; + ret|=m; + ret+=_v>1; + return ret; +/*This de Bruijn sequence version is faster if you have a fast multiplier.*/ +# else + int ret; + ret=_v>0; + _v|=_v>>1; + _v|=_v>>2; + _v|=_v>>4; + _v|=_v>>8; + _v|=_v>>16; + _v=(_v>>1)+1; + ret+=DEBRUIJN_IDX32[_v*0x77CB531U>>27&0x1F]; + return ret; +# endif +} + +int ilog32_nz(uint32_t _v) +{ + return ilog32(_v); +} + +int ilog64(uint64_t _v){ +# if defined(ILOG_NODEBRUIJN) + uint32_t v; + int ret; + int m; + ret=_v>0; + m=(_v>0xFFFFFFFFU)<<5; + v=(uint32_t)(_v>>m); + ret|=m; + m=(v>0xFFFFU)<<4; + v>>=m; + ret|=m; + m=(v>0xFFU)<<3; + v>>=m; + ret|=m; + m=(v>0xFU)<<2; + v>>=m; + ret|=m; + m=(v>3)<<1; + v>>=m; + ret|=m; + ret+=v>1; + return ret; +# else +/*If we don't have a 64-bit word, split it into two 32-bit halves.*/ +# if LONG_MAX<9223372036854775807LL + uint32_t v; + int ret; + int m; + ret=_v>0; + m=(_v>0xFFFFFFFFU)<<5; + v=(uint32_t)(_v>>m); + ret|=m; + v|=v>>1; + v|=v>>2; + v|=v>>4; + v|=v>>8; + v|=v>>16; + v=(v>>1)+1; + ret+=DEBRUIJN_IDX32[v*0x77CB531U>>27&0x1F]; + return ret; +/*Otherwise do it in one 64-bit operation.*/ +# else + static const unsigned char DEBRUIJN_IDX64[64]={ + 0, 1, 2, 7, 3,13, 8,19, 4,25,14,28, 9,34,20,40, + 5,17,26,38,15,46,29,48,10,31,35,54,21,50,41,57, + 63, 6,12,18,24,27,33,39,16,37,45,47,30,53,49,56, + 62,11,23,32,36,44,52,55,61,22,43,51,60,42,59,58 + }; + int ret; + ret=_v>0; + _v|=_v>>1; + _v|=_v>>2; + _v|=_v>>4; + _v|=_v>>8; + _v|=_v>>16; + _v|=_v>>32; + _v=(_v>>1)+1; + ret+=DEBRUIJN_IDX64[_v*0x218A392CD3D5DBF>>58&0x3F]; + return ret; +# endif +# endif +} + +int ilog64_nz(uint64_t _v) +{ + return ilog64(_v); +} diff --git a/lib/ccan/ilog/ilog.h b/lib/ccan/ilog/ilog.h new file mode 100644 index 0000000000..55dd009885 --- /dev/null +++ b/lib/ccan/ilog/ilog.h @@ -0,0 +1,150 @@ +#if !defined(_ilog_H) +# define _ilog_H (1) +# include "config.h" +# include <stdint.h> +# include <limits.h> +# include <ccan/compiler/compiler.h> + +/** + * ilog32 - Integer binary logarithm of a 32-bit value. + * @_v: 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. + * 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; + +/** + * 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. + * 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 ilog32_nz(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. + * 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_nz(), ilog32() + */ +int ilog64(uint64_t _v) IDEMPOTENT; + +/** + * 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() + */ +int ilog64_nz(uint64_t _v) IDEMPOTENT; + +/** + * 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 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 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 should only be used when you need a compile-time constant, + * otherwise ilog64 or ilog64_nz are just as fast and more flexible. + */ +#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)) +# define STATIC_ILOG3(_v) \ + (((_v)&0xF0)?4+STATIC_ILOG2((_v)>>4):STATIC_ILOG2(_v)) +# define STATIC_ILOG4(_v) \ + (((_v)&0xFF00)?8+STATIC_ILOG3((_v)>>8):STATIC_ILOG3(_v)) +# define STATIC_ILOG5(_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)) + +#endif /* _ilog_H */ diff --git a/lib/ccan/ilog/test/run-out-of-line.c b/lib/ccan/ilog/test/run-out-of-line.c new file mode 100644 index 0000000000..48205d380e --- /dev/null +++ b/lib/ccan/ilog/test/run-out-of-line.c @@ -0,0 +1,65 @@ +#include <ccan/ilog/ilog.h> +#include <ccan/ilog/ilog.c> +#include <stdio.h> +#include <ccan/tap/tap.h> + +/*Dead simple (but slow) versions to compare against.*/ + +static int test_ilog32(uint32_t _v){ + int ret; + for(ret=0;_v;ret++)_v>>=1; + return ret; +} + +static int test_ilog64(uint64_t _v){ + int ret; + for(ret=0;_v;ret++)_v>>=1; + return ret; +} + +#define NTRIALS (64) + +int main(int _argc,const char *_argv[]){ + int i; + int j; + int (*il32)(uint32_t) = ilog32; + int (*il64)(uint64_t) = ilog64; + int (*il32_nz)(uint32_t) = ilog32_nz; + int (*il64_nz)(uint64_t) = ilog64_nz; + + /*This is how many tests you plan to run.*/ + plan_tests(33 * NTRIALS * 3 + 65 * NTRIALS * 3); + for(i=0;i<=32;i++){ + uint32_t v; + /*Test each bit in turn (and 0).*/ + v=i?(uint32_t)1U<<(i-1):0; + for(j=0;j<NTRIALS;j++){ + int l; + l=test_ilog32(v); + ok1(STATIC_ILOG_32(v)==l); + ok1(il32(v)==l); + ok1(il32_nz(v) == l || v == 0); + /*Also try a few more pseudo-random values with at most the same number + of bits.*/ + v=(1103515245U*v+12345U)&0xFFFFFFFFU>>((33-i)>>1)>>((32-i)>>1); + } + } + + for(i=0;i<=64;i++){ + uint64_t v; + /*Test each bit in turn (and 0).*/ + v=i?(uint64_t)1U<<(i-1):0; + for(j=0;j<NTRIALS;j++){ + int l; + l=test_ilog64(v); + ok1(STATIC_ILOG_64(v)==l); + ok1(il64(v)==l); + ok1(il64_nz(v) == l || v == 0); + /*Also try a few more pseudo-random values with at most the same number + of bits.*/ + v=(uint64_t)((2862933555777941757ULL*v+3037000493ULL) + &0xFFFFFFFFFFFFFFFFULL>>((65-i)>>1)>>((64-i)>>1)); + } + } + return exit_status(); +} diff --git a/lib/ccan/ilog/test/run.c b/lib/ccan/ilog/test/run.c new file mode 100644 index 0000000000..bda59f920a --- /dev/null +++ b/lib/ccan/ilog/test/run.c @@ -0,0 +1,60 @@ +#include <ccan/ilog/ilog.h> +#include <ccan/ilog/ilog.c> +#include <stdio.h> +#include <ccan/tap/tap.h> + +/*Dead simple (but slow) versions to compare against.*/ + +static int test_ilog32(uint32_t _v){ + int ret; + for(ret=0;_v;ret++)_v>>=1; + return ret; +} + +static int test_ilog64(uint64_t _v){ + int ret; + for(ret=0;_v;ret++)_v>>=1; + return ret; +} + +#define NTRIALS (64) + +int main(int _argc,const char *_argv[]){ + int i; + int j; + /*This is how many tests you plan to run.*/ + plan_tests(33 * NTRIALS * 3 + 65 * NTRIALS * 3); + for(i=0;i<=32;i++){ + uint32_t v; + /*Test each bit in turn (and 0).*/ + v=i?(uint32_t)1U<<(i-1):0; + for(j=0;j<NTRIALS;j++){ + int l; + l=test_ilog32(v); + ok1(STATIC_ILOG_32(v)==l); + ok1(ilog32(v)==l); + ok1(ilog32_nz(v) == l || v == 0); + /*Also try a few more pseudo-random values with at most the same number + of bits.*/ + v=(1103515245U*v+12345U)&0xFFFFFFFFU>>((33-i)>>1)>>((32-i)>>1); + } + } + + for(i=0;i<=64;i++){ + uint64_t v; + /*Test each bit in turn (and 0).*/ + v=i?(uint64_t)1U<<(i-1):0; + for(j=0;j<NTRIALS;j++){ + int l; + l=test_ilog64(v); + ok1(STATIC_ILOG_64(v)==l); + ok1(ilog64(v)==l); + ok1(ilog64_nz(v) == l || v == 0); + /*Also try a few more pseudo-random values with at most the same number + of bits.*/ + v=(uint64_t)((2862933555777941757ULL*v+3037000493ULL) + &0xFFFFFFFFFFFFFFFFULL>>((65-i)>>1)>>((64-i)>>1)); + } + } + return exit_status(); +} |