js/src/jsbit.h

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is Mozilla Communicator client code, released
  16  * March 31, 1998.
  17  *
  18  * The Initial Developer of the Original Code is
  19  * Netscape Communications Corporation.
  20  * Portions created by the Initial Developer are Copyright (C) 1998
  21  * the Initial Developer. All Rights Reserved.
  22  *
  23  * Contributor(s):
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either of the GNU General Public License Version 2 or later (the "GPL"),
  27  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
  29  * of those above. If you wish to allow use of your version of this file only
  30  * under the terms of either the GPL or the LGPL, and not to allow others to
  31  * use your version of this file under the terms of the MPL, indicate your
  32  * decision by deleting the provisions above and replace them with the notice
  33  * and other provisions required by the GPL or the LGPL. If you do not delete
  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #ifndef jsbit_h___
  40 #define jsbit_h___
  41
  42 #include "jstypes.h"
  43 #include "jsutil.h"
  44
  45 JS_BEGIN_EXTERN_C
  46
  47 /*
  48 ** A jsbitmap_t is a long integer that can be used for bitmaps
  49 */
  50 typedef JSUword     jsbitmap_t;     /* NSPR name, a la Unix system types */
  51 typedef jsbitmap_t  jsbitmap;       /* JS-style scalar typedef name */
  52
  53 #define JS_BITMAP_SIZE(bits)    (JS_HOWMANY(bits, JS_BITS_PER_WORD) *         \
  54                                  sizeof(jsbitmap))
  55
  56 #define JS_TEST_BIT(_map,_bit)  ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] &      \
  57                                  ((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
  58 #define JS_SET_BIT(_map,_bit)   ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] |=     \
  59                                  ((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
  60 #define JS_CLEAR_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] &=     \
  61                                  ~((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
  62
  63 /*
  64 ** Compute the log of the least power of 2 greater than or equal to n
  65 */
  66 extern JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 i);
  67
  68 /*
  69 ** Compute the log of the greatest power of 2 less than or equal to n
  70 */
  71 extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
  72
  73 /*
  74  * Replace bit-scanning code sequences with CPU-specific instructions to
  75  * speedup calculations of ceiling/floor log2.
  76  *
  77  * With GCC 3.4 or later we can use __builtin_clz for that, see bug 327129.
  78  *
  79  * SWS: Added MSVC intrinsic bitscan support.  See bugs 349364 and 356856.
  80  */
  81 #if defined(_WIN32) && (_MSC_VER >= 1300) && defined(_M_IX86)
  82
  83 unsigned char _BitScanForward(unsigned long * Index, unsigned long Mask);
  84 unsigned char _BitScanReverse(unsigned long * Index, unsigned long Mask);
  85 # pragma intrinsic(_BitScanForward,_BitScanReverse)
  86
  87 __forceinline static int
  88 __BitScanForward32(unsigned int val)
  89 {
  90     unsigned long idx;
  91
  92     _BitScanForward(&idx, (unsigned long)val);
  93     return (int)idx;
  94 }
  95 __forceinline static int
  96 __BitScanReverse32(unsigned int val)
  97 {
  98     unsigned long idx;
  99
 100     _BitScanReverse(&idx, (unsigned long)val);
 101     return (int)(31-idx);
 102 }
 103 # define js_bitscan_ctz32(val)  __BitScanForward32(val)
 104 # define js_bitscan_clz32(val)  __BitScanReverse32(val)
 105 # define JS_HAS_BUILTIN_BITSCAN32
 106
 107 #elif (__GNUC__ >= 4) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
 108
 109 # define js_bitscan_ctz32(val)  __builtin_ctz(val)
 110 # define js_bitscan_clz32(val)  __builtin_clz(val)
 111 # define JS_HAS_BUILTIN_BITSCAN32
 112 # if (JS_BYTES_PER_WORD == 8)
 113 #  define js_bitscan_ctz64(val)  __builtin_ctzll(val)
 114 #  define js_bitscan_clz64(val)  __builtin_clzll(val)
 115 #  define JS_HAS_BUILTIN_BITSCAN64
 116 # endif
 117
 118 #endif
 119
 120 /*
 121 ** Macro version of JS_CeilingLog2: Compute the log of the least power of
 122 ** 2 greater than or equal to _n. The result is returned in _log2.
 123 */
 124 #ifdef JS_HAS_BUILTIN_BITSCAN32
 125 /*
 126  * Use intrinsic function or count-leading-zeros to calculate ceil(log2(_n)).
 127  * The macro checks for "n <= 1" and not "n != 0" as js_bitscan_clz32(0) is
 128  * undefined.
 129  */
 130 # define JS_CEILING_LOG2(_log2,_n)                                            \
 131     JS_BEGIN_MACRO                                                            \
 132         JS_STATIC_ASSERT(sizeof(unsigned int) == sizeof(JSUint32));           \
 133         unsigned int j_ = (unsigned int)(_n);                                 \
 134         (_log2) = (j_ <= 1 ? 0 : 32 - js_bitscan_clz32(j_ - 1));              \
 135     JS_END_MACRO
 136 #else
 137 # define JS_CEILING_LOG2(_log2,_n)                                            \
 138     JS_BEGIN_MACRO                                                            \
 139         JSUint32 j_ = (JSUint32)(_n);                                         \
 140         (_log2) = 0;                                                          \
 141         if ((j_) & ((j_)-1))                                                  \
 142             (_log2) += 1;                                                     \
 143         if ((j_) >> 16)                                                       \
 144             (_log2) += 16, (j_) >>= 16;                                       \
 145         if ((j_) >> 8)                                                        \
 146             (_log2) += 8, (j_) >>= 8;                                         \
 147         if ((j_) >> 4)                                                        \
 148             (_log2) += 4, (j_) >>= 4;                                         \
 149         if ((j_) >> 2)                                                        \
 150             (_log2) += 2, (j_) >>= 2;                                         \
 151         if ((j_) >> 1)                                                        \
 152             (_log2) += 1;                                                     \
 153     JS_END_MACRO
 154 #endif
 155
 156 /*
 157 ** Macro version of JS_FloorLog2: Compute the log of the greatest power of
 158 ** 2 less than or equal to _n. The result is returned in _log2.
 159 **
 160 ** This is equivalent to finding the highest set bit in the word.
 161 */
 162 #ifdef JS_HAS_BUILTIN_BITSCAN32
 163 /*
 164  * Use js_bitscan_clz32 or count-leading-zeros to calculate floor(log2(_n)).
 165  * Since js_bitscan_clz32(0) is undefined, the macro set the loweset bit to 1
 166  * to ensure 0 result when _n == 0.
 167  */
 168 # define JS_FLOOR_LOG2(_log2,_n)                                              \
 169     JS_BEGIN_MACRO                                                            \
 170         JS_STATIC_ASSERT(sizeof(unsigned int) == sizeof(JSUint32));           \
 171         (_log2) = 31 - js_bitscan_clz32(((unsigned int)(_n)) | 1);            \
 172     JS_END_MACRO
 173 #else
 174 # define JS_FLOOR_LOG2(_log2,_n)                                              \
 175     JS_BEGIN_MACRO                                                            \
 176         JSUint32 j_ = (JSUint32)(_n);                                         \
 177         (_log2) = 0;                                                          \
 178         if ((j_) >> 16)                                                       \
 179             (_log2) += 16, (j_) >>= 16;                                       \
 180         if ((j_) >> 8)                                                        \
 181             (_log2) += 8, (j_) >>= 8;                                         \
 182         if ((j_) >> 4)                                                        \
 183             (_log2) += 4, (j_) >>= 4;                                         \
 184         if ((j_) >> 2)                                                        \
 185             (_log2) += 2, (j_) >>= 2;                                         \
 186         if ((j_) >> 1)                                                        \
 187             (_log2) += 1;                                                     \
 188     JS_END_MACRO
 189 #endif
 190
 191 /*
 192  * Internal function.
 193  * Compute the log of the least power of 2 greater than or equal to n.
 194  * This is a version of JS_CeilingLog2 that operates on jsuword with
 195  * CPU-dependant size.
 196  */
 197 #define JS_CEILING_LOG2W(n) ((n) <= 1 ? 0 : 1 + JS_FLOOR_LOG2W((n) - 1))
 198
 199 /*
 200  * Internal function.
 201  * Compute the log of the greatest power of 2 less than or equal to n.
 202  * This is a version of JS_FloorLog2 that operates on jsuword with
 203  * CPU-dependant size and requires that n != 0.
 204  */
 205 #define JS_FLOOR_LOG2W(n) (JS_ASSERT((n) != 0), js_FloorLog2wImpl(n))
 206
 207 #if JS_BYTES_PER_WORD == 4
 208
 209 # ifdef JS_HAS_BUILTIN_BITSCAN32
 210 JS_STATIC_ASSERT(sizeof(unsigned) == sizeof(JSUword));
 211 #  define js_FloorLog2wImpl(n)                                                \
 212     ((JSUword)(JS_BITS_PER_WORD - 1 - js_bitscan_clz32(n)))
 213 # else
 214 #  define js_FloorLog2wImpl(n) ((JSUword)JS_FloorLog2(n))
 215 #endif
 216
 217 #elif JS_BYTES_PER_WORD == 8
 218
 219 # ifdef JS_HAS_BUILTIN_BITSCAN64
 220 JS_STATIC_ASSERT(sizeof(unsigned long long) == sizeof(JSUword));
 221 #  define js_FloorLog2wImpl(n)                                                \
 222     ((JSUword)(JS_BITS_PER_WORD - 1 - js_bitscan_clz64(n)))
 223 # else
 224 extern JSUword js_FloorLog2wImpl(JSUword n);
 225 # endif
 226
 227 #else
 228
 229 # error "NOT SUPPORTED"
 230
 231 #endif
 232
 233 /*
 234  * Macros for rotate left. There is no rotate operation in the C Language so
 235  * the construct (a << 4) | (a >> 28) is used instead. Most compilers convert
 236  * this to a rotate instruction but some versions of MSVC don't without a
 237  * little help.  To get MSVC to generate a rotate instruction, we have to use
 238  * the _rotl intrinsic and use a pragma to make _rotl inline.
 239  *
 240  * MSVC in VS2005 will do an inline rotate instruction on the above construct.
 241  */
 242
 243 #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64) || \
 244     defined(_M_X64))
 245 #include <stdlib.h>
 246 #pragma intrinsic(_rotl)
 247 #define JS_ROTATE_LEFT32(a, bits) _rotl(a, bits)
 248 #else
 249 #define JS_ROTATE_LEFT32(a, bits) (((a) << (bits)) | ((a) >> (32 - (bits))))
 250 #endif
 251
 252 JS_END_EXTERN_C
 253 #endif /* jsbit_h___ */