LLVM API Documentation
00001 //===-- llvm/Support/MathExtras.h - Useful math functions -------*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file contains some functions that are useful for math stuff. 00011 // 00012 //===----------------------------------------------------------------------===// 00013 00014 #ifndef LLVM_SUPPORT_MATHEXTRAS_H 00015 #define LLVM_SUPPORT_MATHEXTRAS_H 00016 00017 #include "llvm/Support/DataTypes.h" 00018 #include "llvm/System/IncludeFile.h" 00019 00020 namespace llvm { 00021 00022 // NOTE: The following support functions use the _32/_64 extensions instead of 00023 // type overloading so that signed and unsigned integers can be used without 00024 // ambiguity. 00025 00026 00027 // Hi_32 - This function returns the high 32 bits of a 64 bit value. 00028 inline unsigned Hi_32(uint64_t Value) { 00029 return static_cast<unsigned>(Value >> 32); 00030 } 00031 00032 // Lo_32 - This function returns the low 32 bits of a 64 bit value. 00033 inline unsigned Lo_32(uint64_t Value) { 00034 return static_cast<unsigned>(Value); 00035 } 00036 00037 // is?Type - these functions produce optimal testing for integer data types. 00038 inline bool isInt8 (int Value) { 00039 return static_cast<signed char>(Value) == Value; 00040 } 00041 inline bool isUInt8 (int Value) { 00042 return static_cast<unsigned char>(Value) == Value; 00043 } 00044 inline bool isInt16 (int Value) { 00045 return static_cast<signed short>(Value) == Value; 00046 } 00047 inline bool isUInt16(int Value) { 00048 return static_cast<unsigned short>(Value) == Value; 00049 } 00050 inline bool isInt32 (int64_t Value) { 00051 return static_cast<signed int>(Value) == Value; 00052 } 00053 inline bool isUInt32(int64_t Value) { 00054 return static_cast<unsigned int>(Value) == Value; 00055 } 00056 00057 // isMask_32 - This function returns true if the argument is a sequence of ones 00058 // starting at the least significant bit with the remainder zero (32 bit version.) 00059 // Ex. isMask_32(0x0000FFFFU) == true. 00060 inline const bool isMask_32(unsigned Value) { 00061 return Value && ((Value + 1) & Value) == 0; 00062 } 00063 00064 // isMask_64 - This function returns true if the argument is a sequence of ones 00065 // starting at the least significant bit with the remainder zero (64 bit version.) 00066 inline const bool isMask_64(uint64_t Value) { 00067 return Value && ((Value + 1) & Value) == 0; 00068 } 00069 00070 // isShiftedMask_32 - This function returns true if the argument contains a 00071 // sequence of ones with the remainder zero (32 bit version.) 00072 // Ex. isShiftedMask_32(0x0000FF00U) == true. 00073 inline const bool isShiftedMask_32(unsigned Value) { 00074 return isMask_32((Value - 1) | Value); 00075 } 00076 00077 // isShiftedMask_64 - This function returns true if the argument contains a 00078 // sequence of ones with the remainder zero (64 bit version.) 00079 inline const bool isShiftedMask_64(uint64_t Value) { 00080 return isMask_64((Value - 1) | Value); 00081 } 00082 00083 // isPowerOf2_32 - This function returns true if the argument is a power of 00084 // two > 0. Ex. isPowerOf2_32(0x00100000U) == true (32 bit edition.) 00085 inline bool isPowerOf2_32(unsigned Value) { 00086 return Value && !(Value & (Value - 1)); 00087 } 00088 00089 // isPowerOf2_64 - This function returns true if the argument is a power of two 00090 // > 0 (64 bit edition.) 00091 inline bool isPowerOf2_64(uint64_t Value) { 00092 return Value && !(Value & (Value - int64_t(1L))); 00093 } 00094 00095 // ByteSwap_16 - This function returns a byte-swapped representation of the 00096 // 16-bit argument, Value. 00097 inline unsigned short ByteSwap_16(unsigned short Value) { 00098 unsigned short Hi = Value << 8; 00099 unsigned short Lo = Value >> 8; 00100 return Hi | Lo; 00101 } 00102 00103 // ByteSwap_32 - This function returns a byte-swapped representation of the 00104 // 32-bit argument, Value. 00105 inline unsigned ByteSwap_32(unsigned Value) { 00106 unsigned Byte0 = Value & 0x000000FF; 00107 unsigned Byte1 = Value & 0x0000FF00; 00108 unsigned Byte2 = Value & 0x00FF0000; 00109 unsigned Byte3 = Value & 0xFF000000; 00110 return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24); 00111 } 00112 00113 // ByteSwap_64 - This function returns a byte-swapped representation of the 00114 // 64-bit argument, Value. 00115 inline uint64_t ByteSwap_64(uint64_t Value) { 00116 uint64_t Hi = ByteSwap_32(unsigned(Value)); 00117 uint64_t Lo = ByteSwap_32(unsigned(Value >> 32)); 00118 return (Hi << 32) | Lo; 00119 } 00120 00121 // CountLeadingZeros_32 - this function performs the platform optimal form of 00122 // counting the number of zeros from the most significant bit to the first one 00123 // bit. Ex. CountLeadingZeros_32(0x00F000FF) == 8. 00124 // Returns 32 if the word is zero. 00125 inline unsigned CountLeadingZeros_32(unsigned Value) { 00126 unsigned Count; // result 00127 #if __GNUC__ >= 4 00128 // PowerPC is defined for __builtin_clz(0) 00129 #if !defined(__ppc__) && !defined(__ppc64__) 00130 if (!Value) return 32; 00131 #endif 00132 Count = __builtin_clz(Value); 00133 #else 00134 if (!Value) return 32; 00135 Count = 0; 00136 // bisecton method for count leading zeros 00137 for (unsigned Shift = 32 >> 1; Shift; Shift >>= 1) { 00138 unsigned Tmp = Value >> Shift; 00139 if (Tmp) { 00140 Value = Tmp; 00141 } else { 00142 Count |= Shift; 00143 } 00144 } 00145 #endif 00146 return Count; 00147 } 00148 00149 // CountLeadingZeros_64 - This function performs the platform optimal form 00150 // of counting the number of zeros from the most significant bit to the first 00151 // one bit (64 bit edition.) 00152 // Returns 64 if the word is zero. 00153 inline unsigned CountLeadingZeros_64(uint64_t Value) { 00154 unsigned Count; // result 00155 #if __GNUC__ >= 4 00156 // PowerPC is defined for __builtin_clzll(0) 00157 #if !defined(__ppc__) && !defined(__ppc64__) 00158 if (!Value) return 64; 00159 #endif 00160 Count = __builtin_clzll(Value); 00161 #else 00162 if (sizeof(long) == sizeof(int64_t)) { 00163 if (!Value) return 64; 00164 Count = 0; 00165 // bisecton method for count leading zeros 00166 for (uint64_t Shift = 64 >> 1; Shift; Shift >>= 1) { 00167 uint64_t Tmp = Value >> Shift; 00168 if (Tmp) { 00169 Value = Tmp; 00170 } else { 00171 Count |= Shift; 00172 } 00173 } 00174 } else { 00175 // get hi portion 00176 unsigned Hi = Hi_32(Value); 00177 00178 // if some bits in hi portion 00179 if (Hi) { 00180 // leading zeros in hi portion plus all bits in lo portion 00181 Count = CountLeadingZeros_32(Hi); 00182 } else { 00183 // get lo portion 00184 unsigned Lo = Lo_32(Value); 00185 // same as 32 bit value 00186 Count = CountLeadingZeros_32(Lo)+32; 00187 } 00188 } 00189 #endif 00190 return Count; 00191 } 00192 00193 // CountTrailingZeros_32 - this function performs the platform optimal form of 00194 // counting the number of zeros from the least significant bit to the first one 00195 // bit. Ex. CountTrailingZeros_32(0xFF00FF00) == 8. 00196 // Returns 32 if the word is zero. 00197 inline unsigned CountTrailingZeros_32(unsigned Value) { 00198 return 32 - CountLeadingZeros_32(~Value & (Value - 1)); 00199 } 00200 00201 // CountTrailingZeros_64 - This function performs the platform optimal form 00202 // of counting the number of zeros from the least significant bit to the first 00203 // one bit (64 bit edition.) 00204 // Returns 64 if the word is zero. 00205 inline unsigned CountTrailingZeros_64(uint64_t Value) { 00206 return 64 - CountLeadingZeros_64(~Value & (Value - 1)); 00207 } 00208 00209 // CountPopulation_32 - this function counts the number of set bits in a value. 00210 // Ex. CountPopulation(0xF000F000) = 8 00211 // Returns 0 if the word is zero. 00212 inline unsigned CountPopulation_32(unsigned Value) { 00213 unsigned x, t; 00214 x = Value - ((Value >> 1) & 0x55555555); 00215 t = ((x >> 2) & 0x33333333); 00216 x = (x & 0x33333333) + t; 00217 x = (x + (x >> 4)) & 0x0F0F0F0F; 00218 x = x + (x << 8); 00219 x = x + (x << 16); 00220 return x >> 24; 00221 } 00222 00223 // CountPopulation_64 - this function counts the number of set bits in a value, 00224 // (64 bit edition.) 00225 inline unsigned CountPopulation_64(uint64_t Value) { 00226 return CountPopulation_32(unsigned(Value >> 32)) + 00227 CountPopulation_32(unsigned(Value)); 00228 } 00229 00230 // Log2_32 - This function returns the floor log base 2 of the specified value, 00231 // -1 if the value is zero. (32 bit edition.) 00232 // Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1, Log2_32(6) == 2 00233 inline unsigned Log2_32(unsigned Value) { 00234 return 31 - CountLeadingZeros_32(Value); 00235 } 00236 00237 // Log2_64 - This function returns the floor log base 2 of the specified value, 00238 // -1 if the value is zero. (64 bit edition.) 00239 inline unsigned Log2_64(uint64_t Value) { 00240 return 63 - CountLeadingZeros_64(Value); 00241 } 00242 00243 // Log2_32_Ceil - This function returns the ceil log base 2 of the specified 00244 // value, 32 if the value is zero. (32 bit edition). 00245 // Ex. Log2_32_Ceil(32) == 5, Log2_32_Ceil(1) == 0, Log2_32_Ceil(6) == 3 00246 inline unsigned Log2_32_Ceil(unsigned Value) { 00247 return 32-CountLeadingZeros_32(Value-1); 00248 } 00249 00250 // Log2_64 - This function returns the ceil log base 2 of the specified value, 00251 // 64 if the value is zero. (64 bit edition.) 00252 inline unsigned Log2_64_Ceil(uint64_t Value) { 00253 return 64-CountLeadingZeros_64(Value-1); 00254 } 00255 00256 // BitsToDouble - This function takes a 64-bit integer and returns the bit 00257 // equivalent double. 00258 inline double BitsToDouble(uint64_t Bits) { 00259 union { 00260 uint64_t L; 00261 double D; 00262 } T; 00263 T.L = Bits; 00264 return T.D; 00265 } 00266 00267 // BitsToFloat - This function takes a 32-bit integer and returns the bit 00268 // equivalent float. 00269 inline float BitsToFloat(uint32_t Bits) { 00270 union { 00271 uint32_t I; 00272 float F; 00273 } T; 00274 T.I = Bits; 00275 return T.F; 00276 } 00277 00278 // DoubleToBits - This function takes a double and returns the bit 00279 // equivalent 64-bit integer. 00280 inline uint64_t DoubleToBits(double Double) { 00281 union { 00282 uint64_t L; 00283 double D; 00284 } T; 00285 T.D = Double; 00286 return T.L; 00287 } 00288 00289 // FloatToBits - This function takes a float and returns the bit 00290 // equivalent 32-bit integer. 00291 inline uint32_t FloatToBits(float Float) { 00292 union { 00293 uint32_t I; 00294 float F; 00295 } T; 00296 T.F = Float; 00297 return T.I; 00298 } 00299 00300 // Platform-independent wrappers for the C99 isnan() function. 00301 int IsNAN (float f); 00302 int IsNAN (double d); 00303 00304 // Platform-independent wrappers for the C99 isinf() function. 00305 int IsInf (float f); 00306 int IsInf (double d); 00307 00308 } // End llvm namespace 00309 00310 FORCE_DEFINING_FILE_TO_BE_LINKED(SupportIsInf) 00311 FORCE_DEFINING_FILE_TO_BE_LINKED(SupportIsNAN) 00312 00313 #endif