1 | #ifndef INCLUDED_tlsfbits
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2 | #define INCLUDED_tlsfbits
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3 |
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4 | #if defined(__cplusplus)
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5 | #define tlsf_decl inline
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6 | #else
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7 | #define tlsf_decl static
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8 | #endif
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9 |
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10 | /*
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11 | ** Architecture-specific bit manipulation routines.
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12 | **
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13 | ** TLSF achieves O(1) cost for malloc and free operations by limiting
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14 | ** the search for a free block to a free list of guaranteed size
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15 | ** adequate to fulfill the request, combined with efficient free list
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16 | ** queries using bitmasks and architecture-specific bit-manipulation
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17 | ** routines.
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18 | **
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19 | ** Most modern processors provide instructions to count leading zeroes
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20 | ** in a word, find the lowest and highest set bit, etc. These
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21 | ** specific implementations will be used when available, falling back
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22 | ** to a reasonably efficient generic implementation.
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23 | **
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24 | ** NOTE: TLSF spec relies on ffs/fls returning value 0..31.
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25 | ** ffs/fls return 1-32 by default, returning 0 for error.
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26 | */
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27 |
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28 | /*
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29 | ** Detect whether or not we are building for a 32- or 64-bit (LP/LLP)
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30 | ** architecture. There is no reliable portable method at compile-time.
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31 | */
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32 | #if defined (__alpha__) || defined (__ia64__) || defined (__x86_64__) \
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33 | || defined (_WIN64) || defined (__LP64__) || defined (__LLP64__)
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34 | #define TLSF_64BIT
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35 | #endif
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36 |
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37 | /*
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38 | ** gcc 3.4 and above have builtin support, specialized for architecture.
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39 | ** Some compilers masquerade as gcc; patchlevel test filters them out.
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40 | */
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41 | #if defined (__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) \
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42 | && defined (__GNUC_PATCHLEVEL__)
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43 |
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44 | tlsf_decl int tlsf_ffs(unsigned int word)
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45 | {
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46 | return __builtin_ffs(word) - 1;
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47 | }
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48 |
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49 | tlsf_decl int tlsf_fls(unsigned int word)
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50 | {
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51 | const int bit = word ? 32 - __builtin_clz(word) : 0;
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52 | return bit - 1;
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53 | }
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54 |
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55 | #elif defined (_MSC_VER) && (_MSC_VER >= 1400) && (defined (_M_IX86) || defined (_M_X64))
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56 | /* Microsoft Visual C++ support on x86/X64 architectures. */
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57 |
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58 | #include <intrin.h>
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59 |
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60 | #pragma intrinsic(_BitScanReverse)
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61 | #pragma intrinsic(_BitScanForward)
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62 |
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63 | tlsf_decl int tlsf_fls(unsigned int word)
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64 | {
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65 | unsigned long index;
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66 | return _BitScanReverse(&index, word) ? index : -1;
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67 | }
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68 |
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69 | tlsf_decl int tlsf_ffs(unsigned int word)
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70 | {
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71 | unsigned long index;
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72 | return _BitScanForward(&index, word) ? index : -1;
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73 | }
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74 |
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75 | #elif defined (_MSC_VER) && defined (_M_PPC)
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76 | /* Microsoft Visual C++ support on PowerPC architectures. */
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77 |
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78 | #include <ppcintrinsics.h>
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79 |
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80 | tlsf_decl int tlsf_fls(unsigned int word)
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81 | {
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82 | const int bit = 32 - _CountLeadingZeros(word);
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83 | return bit - 1;
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84 | }
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85 |
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86 | tlsf_decl int tlsf_ffs(unsigned int word)
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87 | {
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88 | const unsigned int reverse = word & (~word + 1);
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89 | const int bit = 32 - _CountLeadingZeros(reverse);
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90 | return bit - 1;
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91 | }
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92 |
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93 | #elif defined (__ARMCC_VERSION)
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94 | /* RealView Compilation Tools for ARM */
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95 |
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96 | tlsf_decl int tlsf_ffs(unsigned int word)
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97 | {
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98 | const unsigned int reverse = word & (~word + 1);
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99 | const int bit = 32 - __clz(reverse);
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100 | return bit - 1;
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101 | }
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102 |
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103 | tlsf_decl int tlsf_fls(unsigned int word)
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104 | {
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105 | const int bit = word ? 32 - __clz(word) : 0;
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106 | return bit - 1;
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107 | }
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108 |
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109 | #elif defined (__ghs__)
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110 | /* Green Hills support for PowerPC */
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111 |
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112 | #include <ppc_ghs.h>
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113 |
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114 | tlsf_decl int tlsf_ffs(unsigned int word)
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115 | {
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116 | const unsigned int reverse = word & (~word + 1);
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117 | const int bit = 32 - __CLZ32(reverse);
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118 | return bit - 1;
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119 | }
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120 |
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121 | tlsf_decl int tlsf_fls(unsigned int word)
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122 | {
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123 | const int bit = word ? 32 - __CLZ32(word) : 0;
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124 | return bit - 1;
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125 | }
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126 |
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127 | #else
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128 | /* Fall back to generic implementation. */
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129 |
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130 | tlsf_decl int tlsf_fls_generic(unsigned int word)
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131 | {
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132 | int bit = 32;
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133 |
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134 | if (!word) bit -= 1;
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135 | if (!(word & 0xffff0000)) { word <<= 16; bit -= 16; }
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136 | if (!(word & 0xff000000)) { word <<= 8; bit -= 8; }
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137 | if (!(word & 0xf0000000)) { word <<= 4; bit -= 4; }
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138 | if (!(word & 0xc0000000)) { word <<= 2; bit -= 2; }
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139 | if (!(word & 0x80000000)) { word <<= 1; bit -= 1; }
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140 |
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141 | return bit;
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142 | }
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143 |
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144 | /* Implement ffs in terms of fls. */
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145 | tlsf_decl int tlsf_ffs(unsigned int word)
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146 | {
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147 | return tlsf_fls_generic(word & (~word + 1)) - 1;
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148 | }
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149 |
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150 | tlsf_decl int tlsf_fls(unsigned int word)
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151 | {
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152 | return tlsf_fls_generic(word) - 1;
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153 | }
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154 |
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155 | #endif
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156 |
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157 | /* Possibly 64-bit version of tlsf_fls. */
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158 | #if defined (TLSF_64BIT)
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159 | tlsf_decl int tlsf_fls_sizet(size_t size)
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160 | {
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161 | int high = (int)(size >> 32);
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162 | int bits = 0;
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163 | if (high)
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164 | {
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165 | bits = 32 + tlsf_fls(high);
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166 | }
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167 | else
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168 | {
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169 | bits = tlsf_fls((int)size & 0xffffffff);
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170 |
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171 | }
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172 | return bits;
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173 | }
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174 | #else
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175 | #define tlsf_fls_sizet tlsf_fls
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176 | #endif
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177 |
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178 | #undef tlsf_decl
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179 |
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180 | #endif
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