1 //===-- llvm/Support/MathExtras.h - Useful math functions -------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file contains some functions that are useful for math stuff. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #ifndef LLVM_SUPPORT_MATHEXTRAS_H 14 #define LLVM_SUPPORT_MATHEXTRAS_H 15 16 #include "llvm/Support/Compiler.h" 17 #include "llvm/Support/SwapByteOrder.h" 18 #include <algorithm> 19 #include <cassert> 20 #include <climits> 21 #include <cstring> 22 #include <limits> 23 #include <type_traits> 24 25 #ifdef __ANDROID_NDK__ 26 #include <android/api-level.h> 27 #endif 28 29 #ifdef _MSC_VER 30 // Declare these intrinsics manually rather including intrin.h. It's very 31 // expensive, and MathExtras.h is popular. 32 // #include <intrin.h> 33 extern "C" { 34 unsigned char _BitScanForward(unsigned long *_Index, unsigned long _Mask); 35 unsigned char _BitScanForward64(unsigned long *_Index, unsigned __int64 _Mask); 36 unsigned char _BitScanReverse(unsigned long *_Index, unsigned long _Mask); 37 unsigned char _BitScanReverse64(unsigned long *_Index, unsigned __int64 _Mask); 38 } 39 #endif 40 41 namespace llvm { 42 43 /// The behavior an operation has on an input of 0. 44 enum ZeroBehavior { 45 /// The returned value is undefined. 46 ZB_Undefined, 47 /// The returned value is numeric_limits<T>::max() 48 ZB_Max, 49 /// The returned value is numeric_limits<T>::digits 50 ZB_Width 51 }; 52 53 /// Mathematical constants. 54 namespace numbers { 55 // TODO: Track C++20 std::numbers. 56 // TODO: Favor using the hexadecimal FP constants (requires C++17). 57 constexpr double e = 2.7182818284590452354, // (0x1.5bf0a8b145749P+1) https://oeis.org/A001113 58 egamma = .57721566490153286061, // (0x1.2788cfc6fb619P-1) https://oeis.org/A001620 59 ln2 = .69314718055994530942, // (0x1.62e42fefa39efP-1) https://oeis.org/A002162 60 ln10 = 2.3025850929940456840, // (0x1.24bb1bbb55516P+1) https://oeis.org/A002392 61 log2e = 1.4426950408889634074, // (0x1.71547652b82feP+0) 62 log10e = .43429448190325182765, // (0x1.bcb7b1526e50eP-2) 63 pi = 3.1415926535897932385, // (0x1.921fb54442d18P+1) https://oeis.org/A000796 64 inv_pi = .31830988618379067154, // (0x1.45f306bc9c883P-2) https://oeis.org/A049541 65 sqrtpi = 1.7724538509055160273, // (0x1.c5bf891b4ef6bP+0) https://oeis.org/A002161 66 inv_sqrtpi = .56418958354775628695, // (0x1.20dd750429b6dP-1) https://oeis.org/A087197 67 sqrt2 = 1.4142135623730950488, // (0x1.6a09e667f3bcdP+0) https://oeis.org/A00219 68 inv_sqrt2 = .70710678118654752440, // (0x1.6a09e667f3bcdP-1) 69 sqrt3 = 1.7320508075688772935, // (0x1.bb67ae8584caaP+0) https://oeis.org/A002194 70 inv_sqrt3 = .57735026918962576451, // (0x1.279a74590331cP-1) 71 phi = 1.6180339887498948482; // (0x1.9e3779b97f4a8P+0) https://oeis.org/A001622 72 constexpr float ef = 2.71828183F, // (0x1.5bf0a8P+1) https://oeis.org/A001113 73 egammaf = .577215665F, // (0x1.2788d0P-1) https://oeis.org/A001620 74 ln2f = .693147181F, // (0x1.62e430P-1) https://oeis.org/A002162 75 ln10f = 2.30258509F, // (0x1.26bb1cP+1) https://oeis.org/A002392 76 log2ef = 1.44269504F, // (0x1.715476P+0) 77 log10ef = .434294482F, // (0x1.bcb7b2P-2) 78 pif = 3.14159265F, // (0x1.921fb6P+1) https://oeis.org/A000796 79 inv_pif = .318309886F, // (0x1.45f306P-2) https://oeis.org/A049541 80 sqrtpif = 1.77245385F, // (0x1.c5bf8aP+0) https://oeis.org/A002161 81 inv_sqrtpif = .564189584F, // (0x1.20dd76P-1) https://oeis.org/A087197 82 sqrt2f = 1.41421356F, // (0x1.6a09e6P+0) https://oeis.org/A002193 83 inv_sqrt2f = .707106781F, // (0x1.6a09e6P-1) 84 sqrt3f = 1.73205081F, // (0x1.bb67aeP+0) https://oeis.org/A002194 85 inv_sqrt3f = .577350269F, // (0x1.279a74P-1) 86 phif = 1.61803399F; // (0x1.9e377aP+0) https://oeis.org/A001622 87 } // namespace numbers 88 89 namespace detail { 90 template <typename T, std::size_t SizeOfT> struct TrailingZerosCounter { 91 static unsigned count(T Val, ZeroBehavior) { 92 if (!Val) 93 return std::numeric_limits<T>::digits; 94 if (Val & 0x1) 95 return 0; 96 97 // Bisection method. 98 unsigned ZeroBits = 0; 99 T Shift = std::numeric_limits<T>::digits >> 1; 100 T Mask = std::numeric_limits<T>::max() >> Shift; 101 while (Shift) { 102 if ((Val & Mask) == 0) { 103 Val >>= Shift; 104 ZeroBits |= Shift; 105 } 106 Shift >>= 1; 107 Mask >>= Shift; 108 } 109 return ZeroBits; 110 } 111 }; 112 113 #if defined(__GNUC__) || defined(_MSC_VER) 114 template <typename T> struct TrailingZerosCounter<T, 4> { 115 static unsigned count(T Val, ZeroBehavior ZB) { 116 if (ZB != ZB_Undefined && Val == 0) 117 return 32; 118 119 #if __has_builtin(__builtin_ctz) || defined(__GNUC__) 120 return __builtin_ctz(Val); 121 #elif defined(_MSC_VER) 122 unsigned long Index; 123 _BitScanForward(&Index, Val); 124 return Index; 125 #endif 126 } 127 }; 128 129 #if !defined(_MSC_VER) || defined(_M_X64) 130 template <typename T> struct TrailingZerosCounter<T, 8> { 131 static unsigned count(T Val, ZeroBehavior ZB) { 132 if (ZB != ZB_Undefined && Val == 0) 133 return 64; 134 135 #if __has_builtin(__builtin_ctzll) || defined(__GNUC__) 136 return __builtin_ctzll(Val); 137 #elif defined(_MSC_VER) 138 unsigned long Index; 139 _BitScanForward64(&Index, Val); 140 return Index; 141 #endif 142 } 143 }; 144 #endif 145 #endif 146 } // namespace detail 147 148 /// Count number of 0's from the least significant bit to the most 149 /// stopping at the first 1. 150 /// 151 /// Only unsigned integral types are allowed. 152 /// 153 /// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are 154 /// valid arguments. 155 template <typename T> 156 unsigned countTrailingZeros(T Val, ZeroBehavior ZB = ZB_Width) { 157 static_assert(std::numeric_limits<T>::is_integer && 158 !std::numeric_limits<T>::is_signed, 159 "Only unsigned integral types are allowed."); 160 return llvm::detail::TrailingZerosCounter<T, sizeof(T)>::count(Val, ZB); 161 } 162 163 namespace detail { 164 template <typename T, std::size_t SizeOfT> struct LeadingZerosCounter { 165 static unsigned count(T Val, ZeroBehavior) { 166 if (!Val) 167 return std::numeric_limits<T>::digits; 168 169 // Bisection method. 170 unsigned ZeroBits = 0; 171 for (T Shift = std::numeric_limits<T>::digits >> 1; Shift; Shift >>= 1) { 172 T Tmp = Val >> Shift; 173 if (Tmp) 174 Val = Tmp; 175 else 176 ZeroBits |= Shift; 177 } 178 return ZeroBits; 179 } 180 }; 181 182 #if defined(__GNUC__) || defined(_MSC_VER) 183 template <typename T> struct LeadingZerosCounter<T, 4> { 184 static unsigned count(T Val, ZeroBehavior ZB) { 185 if (ZB != ZB_Undefined && Val == 0) 186 return 32; 187 188 #if __has_builtin(__builtin_clz) || defined(__GNUC__) 189 return __builtin_clz(Val); 190 #elif defined(_MSC_VER) 191 unsigned long Index; 192 _BitScanReverse(&Index, Val); 193 return Index ^ 31; 194 #endif 195 } 196 }; 197 198 #if !defined(_MSC_VER) || defined(_M_X64) 199 template <typename T> struct LeadingZerosCounter<T, 8> { 200 static unsigned count(T Val, ZeroBehavior ZB) { 201 if (ZB != ZB_Undefined && Val == 0) 202 return 64; 203 204 #if __has_builtin(__builtin_clzll) || defined(__GNUC__) 205 return __builtin_clzll(Val); 206 #elif defined(_MSC_VER) 207 unsigned long Index; 208 _BitScanReverse64(&Index, Val); 209 return Index ^ 63; 210 #endif 211 } 212 }; 213 #endif 214 #endif 215 } // namespace detail 216 217 /// Count number of 0's from the most significant bit to the least 218 /// stopping at the first 1. 219 /// 220 /// Only unsigned integral types are allowed. 221 /// 222 /// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are 223 /// valid arguments. 224 template <typename T> 225 unsigned countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) { 226 static_assert(std::numeric_limits<T>::is_integer && 227 !std::numeric_limits<T>::is_signed, 228 "Only unsigned integral types are allowed."); 229 return llvm::detail::LeadingZerosCounter<T, sizeof(T)>::count(Val, ZB); 230 } 231 232 /// Get the index of the first set bit starting from the least 233 /// significant bit. 234 /// 235 /// Only unsigned integral types are allowed. 236 /// 237 /// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are 238 /// valid arguments. 239 template <typename T> T findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) { 240 if (ZB == ZB_Max && Val == 0) 241 return std::numeric_limits<T>::max(); 242 243 return countTrailingZeros(Val, ZB_Undefined); 244 } 245 246 /// Create a bitmask with the N right-most bits set to 1, and all other 247 /// bits set to 0. Only unsigned types are allowed. 248 template <typename T> T maskTrailingOnes(unsigned N) { 249 static_assert(std::is_unsigned<T>::value, "Invalid type!"); 250 const unsigned Bits = CHAR_BIT * sizeof(T); 251 assert(N <= Bits && "Invalid bit index"); 252 return N == 0 ? 0 : (T(-1) >> (Bits - N)); 253 } 254 255 /// Create a bitmask with the N left-most bits set to 1, and all other 256 /// bits set to 0. Only unsigned types are allowed. 257 template <typename T> T maskLeadingOnes(unsigned N) { 258 return ~maskTrailingOnes<T>(CHAR_BIT * sizeof(T) - N); 259 } 260 261 /// Create a bitmask with the N right-most bits set to 0, and all other 262 /// bits set to 1. Only unsigned types are allowed. 263 template <typename T> T maskTrailingZeros(unsigned N) { 264 return maskLeadingOnes<T>(CHAR_BIT * sizeof(T) - N); 265 } 266 267 /// Create a bitmask with the N left-most bits set to 0, and all other 268 /// bits set to 1. Only unsigned types are allowed. 269 template <typename T> T maskLeadingZeros(unsigned N) { 270 return maskTrailingOnes<T>(CHAR_BIT * sizeof(T) - N); 271 } 272 273 /// Get the index of the last set bit starting from the least 274 /// significant bit. 275 /// 276 /// Only unsigned integral types are allowed. 277 /// 278 /// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are 279 /// valid arguments. 280 template <typename T> T findLastSet(T Val, ZeroBehavior ZB = ZB_Max) { 281 if (ZB == ZB_Max && Val == 0) 282 return std::numeric_limits<T>::max(); 283 284 // Use ^ instead of - because both gcc and llvm can remove the associated ^ 285 // in the __builtin_clz intrinsic on x86. 286 return countLeadingZeros(Val, ZB_Undefined) ^ 287 (std::numeric_limits<T>::digits - 1); 288 } 289 290 /// Macro compressed bit reversal table for 256 bits. 291 /// 292 /// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable 293 static const unsigned char BitReverseTable256[256] = { 294 #define R2(n) n, n + 2 * 64, n + 1 * 64, n + 3 * 64 295 #define R4(n) R2(n), R2(n + 2 * 16), R2(n + 1 * 16), R2(n + 3 * 16) 296 #define R6(n) R4(n), R4(n + 2 * 4), R4(n + 1 * 4), R4(n + 3 * 4) 297 R6(0), R6(2), R6(1), R6(3) 298 #undef R2 299 #undef R4 300 #undef R6 301 }; 302 303 /// Reverse the bits in \p Val. 304 template <typename T> 305 T reverseBits(T Val) { 306 unsigned char in[sizeof(Val)]; 307 unsigned char out[sizeof(Val)]; 308 std::memcpy(in, &Val, sizeof(Val)); 309 for (unsigned i = 0; i < sizeof(Val); ++i) 310 out[(sizeof(Val) - i) - 1] = BitReverseTable256[in[i]]; 311 std::memcpy(&Val, out, sizeof(Val)); 312 return Val; 313 } 314 315 // NOTE: The following support functions use the _32/_64 extensions instead of 316 // type overloading so that signed and unsigned integers can be used without 317 // ambiguity. 318 319 /// Return the high 32 bits of a 64 bit value. 320 constexpr inline uint32_t Hi_32(uint64_t Value) { 321 return static_cast<uint32_t>(Value >> 32); 322 } 323 324 /// Return the low 32 bits of a 64 bit value. 325 constexpr inline uint32_t Lo_32(uint64_t Value) { 326 return static_cast<uint32_t>(Value); 327 } 328 329 /// Make a 64-bit integer from a high / low pair of 32-bit integers. 330 constexpr inline uint64_t Make_64(uint32_t High, uint32_t Low) { 331 return ((uint64_t)High << 32) | (uint64_t)Low; 332 } 333 334 /// Checks if an integer fits into the given bit width. 335 template <unsigned N> constexpr inline bool isInt(int64_t x) { 336 return N >= 64 || (-(INT64_C(1)<<(N-1)) <= x && x < (INT64_C(1)<<(N-1))); 337 } 338 // Template specializations to get better code for common cases. 339 template <> constexpr inline bool isInt<8>(int64_t x) { 340 return static_cast<int8_t>(x) == x; 341 } 342 template <> constexpr inline bool isInt<16>(int64_t x) { 343 return static_cast<int16_t>(x) == x; 344 } 345 template <> constexpr inline bool isInt<32>(int64_t x) { 346 return static_cast<int32_t>(x) == x; 347 } 348 349 /// Checks if a signed integer is an N bit number shifted left by S. 350 template <unsigned N, unsigned S> 351 constexpr inline bool isShiftedInt(int64_t x) { 352 static_assert( 353 N > 0, "isShiftedInt<0> doesn't make sense (refers to a 0-bit number."); 354 static_assert(N + S <= 64, "isShiftedInt<N, S> with N + S > 64 is too wide."); 355 return isInt<N + S>(x) && (x % (UINT64_C(1) << S) == 0); 356 } 357 358 /// Checks if an unsigned integer fits into the given bit width. 359 /// 360 /// This is written as two functions rather than as simply 361 /// 362 /// return N >= 64 || X < (UINT64_C(1) << N); 363 /// 364 /// to keep MSVC from (incorrectly) warning on isUInt<64> that we're shifting 365 /// left too many places. 366 template <unsigned N> 367 constexpr inline typename std::enable_if<(N < 64), bool>::type 368 isUInt(uint64_t X) { 369 static_assert(N > 0, "isUInt<0> doesn't make sense"); 370 return X < (UINT64_C(1) << (N)); 371 } 372 template <unsigned N> 373 constexpr inline typename std::enable_if<N >= 64, bool>::type 374 isUInt(uint64_t X) { 375 return true; 376 } 377 378 // Template specializations to get better code for common cases. 379 template <> constexpr inline bool isUInt<8>(uint64_t x) { 380 return static_cast<uint8_t>(x) == x; 381 } 382 template <> constexpr inline bool isUInt<16>(uint64_t x) { 383 return static_cast<uint16_t>(x) == x; 384 } 385 template <> constexpr inline bool isUInt<32>(uint64_t x) { 386 return static_cast<uint32_t>(x) == x; 387 } 388 389 /// Checks if a unsigned integer is an N bit number shifted left by S. 390 template <unsigned N, unsigned S> 391 constexpr inline bool isShiftedUInt(uint64_t x) { 392 static_assert( 393 N > 0, "isShiftedUInt<0> doesn't make sense (refers to a 0-bit number)"); 394 static_assert(N + S <= 64, 395 "isShiftedUInt<N, S> with N + S > 64 is too wide."); 396 // Per the two static_asserts above, S must be strictly less than 64. So 397 // 1 << S is not undefined behavior. 398 return isUInt<N + S>(x) && (x % (UINT64_C(1) << S) == 0); 399 } 400 401 /// Gets the maximum value for a N-bit unsigned integer. 402 inline uint64_t maxUIntN(uint64_t N) { 403 assert(N > 0 && N <= 64 && "integer width out of range"); 404 405 // uint64_t(1) << 64 is undefined behavior, so we can't do 406 // (uint64_t(1) << N) - 1 407 // without checking first that N != 64. But this works and doesn't have a 408 // branch. 409 return UINT64_MAX >> (64 - N); 410 } 411 412 /// Gets the minimum value for a N-bit signed integer. 413 inline int64_t minIntN(int64_t N) { 414 assert(N > 0 && N <= 64 && "integer width out of range"); 415 416 return -(UINT64_C(1)<<(N-1)); 417 } 418 419 /// Gets the maximum value for a N-bit signed integer. 420 inline int64_t maxIntN(int64_t N) { 421 assert(N > 0 && N <= 64 && "integer width out of range"); 422 423 // This relies on two's complement wraparound when N == 64, so we convert to 424 // int64_t only at the very end to avoid UB. 425 return (UINT64_C(1) << (N - 1)) - 1; 426 } 427 428 /// Checks if an unsigned integer fits into the given (dynamic) bit width. 429 inline bool isUIntN(unsigned N, uint64_t x) { 430 return N >= 64 || x <= maxUIntN(N); 431 } 432 433 /// Checks if an signed integer fits into the given (dynamic) bit width. 434 inline bool isIntN(unsigned N, int64_t x) { 435 return N >= 64 || (minIntN(N) <= x && x <= maxIntN(N)); 436 } 437 438 /// Return true if the argument is a non-empty sequence of ones starting at the 439 /// least significant bit with the remainder zero (32 bit version). 440 /// Ex. isMask_32(0x0000FFFFU) == true. 441 constexpr inline bool isMask_32(uint32_t Value) { 442 return Value && ((Value + 1) & Value) == 0; 443 } 444 445 /// Return true if the argument is a non-empty sequence of ones starting at the 446 /// least significant bit with the remainder zero (64 bit version). 447 constexpr inline bool isMask_64(uint64_t Value) { 448 return Value && ((Value + 1) & Value) == 0; 449 } 450 451 /// Return true if the argument contains a non-empty sequence of ones with the 452 /// remainder zero (32 bit version.) Ex. isShiftedMask_32(0x0000FF00U) == true. 453 constexpr inline bool isShiftedMask_32(uint32_t Value) { 454 return Value && isMask_32((Value - 1) | Value); 455 } 456 457 /// Return true if the argument contains a non-empty sequence of ones with the 458 /// remainder zero (64 bit version.) 459 constexpr inline bool isShiftedMask_64(uint64_t Value) { 460 return Value && isMask_64((Value - 1) | Value); 461 } 462 463 /// Return true if the argument is a power of two > 0. 464 /// Ex. isPowerOf2_32(0x00100000U) == true (32 bit edition.) 465 constexpr inline bool isPowerOf2_32(uint32_t Value) { 466 return Value && !(Value & (Value - 1)); 467 } 468 469 /// Return true if the argument is a power of two > 0 (64 bit edition.) 470 constexpr inline bool isPowerOf2_64(uint64_t Value) { 471 return Value && !(Value & (Value - 1)); 472 } 473 474 /// Return a byte-swapped representation of the 16-bit argument. 475 inline uint16_t ByteSwap_16(uint16_t Value) { 476 return sys::SwapByteOrder_16(Value); 477 } 478 479 /// Return a byte-swapped representation of the 32-bit argument. 480 inline uint32_t ByteSwap_32(uint32_t Value) { 481 return sys::SwapByteOrder_32(Value); 482 } 483 484 /// Return a byte-swapped representation of the 64-bit argument. 485 inline uint64_t ByteSwap_64(uint64_t Value) { 486 return sys::SwapByteOrder_64(Value); 487 } 488 489 /// Count the number of ones from the most significant bit to the first 490 /// zero bit. 491 /// 492 /// Ex. countLeadingOnes(0xFF0FFF00) == 8. 493 /// Only unsigned integral types are allowed. 494 /// 495 /// \param ZB the behavior on an input of all ones. Only ZB_Width and 496 /// ZB_Undefined are valid arguments. 497 template <typename T> 498 unsigned countLeadingOnes(T Value, ZeroBehavior ZB = ZB_Width) { 499 static_assert(std::numeric_limits<T>::is_integer && 500 !std::numeric_limits<T>::is_signed, 501 "Only unsigned integral types are allowed."); 502 return countLeadingZeros<T>(~Value, ZB); 503 } 504 505 /// Count the number of ones from the least significant bit to the first 506 /// zero bit. 507 /// 508 /// Ex. countTrailingOnes(0x00FF00FF) == 8. 509 /// Only unsigned integral types are allowed. 510 /// 511 /// \param ZB the behavior on an input of all ones. Only ZB_Width and 512 /// ZB_Undefined are valid arguments. 513 template <typename T> 514 unsigned countTrailingOnes(T Value, ZeroBehavior ZB = ZB_Width) { 515 static_assert(std::numeric_limits<T>::is_integer && 516 !std::numeric_limits<T>::is_signed, 517 "Only unsigned integral types are allowed."); 518 return countTrailingZeros<T>(~Value, ZB); 519 } 520 521 namespace detail { 522 template <typename T, std::size_t SizeOfT> struct PopulationCounter { 523 static unsigned count(T Value) { 524 // Generic version, forward to 32 bits. 525 static_assert(SizeOfT <= 4, "Not implemented!"); 526 #if defined(__GNUC__) 527 return __builtin_popcount(Value); 528 #else 529 uint32_t v = Value; 530 v = v - ((v >> 1) & 0x55555555); 531 v = (v & 0x33333333) + ((v >> 2) & 0x33333333); 532 return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24; 533 #endif 534 } 535 }; 536 537 template <typename T> struct PopulationCounter<T, 8> { 538 static unsigned count(T Value) { 539 #if defined(__GNUC__) 540 return __builtin_popcountll(Value); 541 #else 542 uint64_t v = Value; 543 v = v - ((v >> 1) & 0x5555555555555555ULL); 544 v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL); 545 v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL; 546 return unsigned((uint64_t)(v * 0x0101010101010101ULL) >> 56); 547 #endif 548 } 549 }; 550 } // namespace detail 551 552 /// Count the number of set bits in a value. 553 /// Ex. countPopulation(0xF000F000) = 8 554 /// Returns 0 if the word is zero. 555 template <typename T> 556 inline unsigned countPopulation(T Value) { 557 static_assert(std::numeric_limits<T>::is_integer && 558 !std::numeric_limits<T>::is_signed, 559 "Only unsigned integral types are allowed."); 560 return detail::PopulationCounter<T, sizeof(T)>::count(Value); 561 } 562 563 /// Compile time Log2. 564 /// Valid only for positive powers of two. 565 template <size_t kValue> constexpr inline size_t CTLog2() { 566 static_assert(kValue > 0 && llvm::isPowerOf2_64(kValue), 567 "Value is not a valid power of 2"); 568 return 1 + CTLog2<kValue / 2>(); 569 } 570 571 template <> constexpr inline size_t CTLog2<1>() { return 0; } 572 573 /// Return the log base 2 of the specified value. 574 inline double Log2(double Value) { 575 #if defined(__ANDROID_API__) && __ANDROID_API__ < 18 576 return __builtin_log(Value) / __builtin_log(2.0); 577 #else 578 return log2(Value); 579 #endif 580 } 581 582 /// Return the floor log base 2 of the specified value, -1 if the value is zero. 583 /// (32 bit edition.) 584 /// Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1, Log2_32(6) == 2 585 inline unsigned Log2_32(uint32_t Value) { 586 return 31 - countLeadingZeros(Value); 587 } 588 589 /// Return the floor log base 2 of the specified value, -1 if the value is zero. 590 /// (64 bit edition.) 591 inline unsigned Log2_64(uint64_t Value) { 592 return 63 - countLeadingZeros(Value); 593 } 594 595 /// Return the ceil log base 2 of the specified value, 32 if the value is zero. 596 /// (32 bit edition). 597 /// Ex. Log2_32_Ceil(32) == 5, Log2_32_Ceil(1) == 0, Log2_32_Ceil(6) == 3 598 inline unsigned Log2_32_Ceil(uint32_t Value) { 599 return 32 - countLeadingZeros(Value - 1); 600 } 601 602 /// Return the ceil log base 2 of the specified value, 64 if the value is zero. 603 /// (64 bit edition.) 604 inline unsigned Log2_64_Ceil(uint64_t Value) { 605 return 64 - countLeadingZeros(Value - 1); 606 } 607 608 /// Return the greatest common divisor of the values using Euclid's algorithm. 609 template <typename T> 610 inline T greatestCommonDivisor(T A, T B) { 611 while (B) { 612 T Tmp = B; 613 B = A % B; 614 A = Tmp; 615 } 616 return A; 617 } 618 619 inline uint64_t GreatestCommonDivisor64(uint64_t A, uint64_t B) { 620 return greatestCommonDivisor<uint64_t>(A, B); 621 } 622 623 /// This function takes a 64-bit integer and returns the bit equivalent double. 624 inline double BitsToDouble(uint64_t Bits) { 625 double D; 626 static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes"); 627 memcpy(&D, &Bits, sizeof(Bits)); 628 return D; 629 } 630 631 /// This function takes a 32-bit integer and returns the bit equivalent float. 632 inline float BitsToFloat(uint32_t Bits) { 633 float F; 634 static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes"); 635 memcpy(&F, &Bits, sizeof(Bits)); 636 return F; 637 } 638 639 /// This function takes a double and returns the bit equivalent 64-bit integer. 640 /// Note that copying doubles around changes the bits of NaNs on some hosts, 641 /// notably x86, so this routine cannot be used if these bits are needed. 642 inline uint64_t DoubleToBits(double Double) { 643 uint64_t Bits; 644 static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes"); 645 memcpy(&Bits, &Double, sizeof(Double)); 646 return Bits; 647 } 648 649 /// This function takes a float and returns the bit equivalent 32-bit integer. 650 /// Note that copying floats around changes the bits of NaNs on some hosts, 651 /// notably x86, so this routine cannot be used if these bits are needed. 652 inline uint32_t FloatToBits(float Float) { 653 uint32_t Bits; 654 static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes"); 655 memcpy(&Bits, &Float, sizeof(Float)); 656 return Bits; 657 } 658 659 /// A and B are either alignments or offsets. Return the minimum alignment that 660 /// may be assumed after adding the two together. 661 constexpr inline uint64_t MinAlign(uint64_t A, uint64_t B) { 662 // The largest power of 2 that divides both A and B. 663 // 664 // Replace "-Value" by "1+~Value" in the following commented code to avoid 665 // MSVC warning C4146 666 // return (A | B) & -(A | B); 667 return (A | B) & (1 + ~(A | B)); 668 } 669 670 /// Returns the next power of two (in 64-bits) that is strictly greater than A. 671 /// Returns zero on overflow. 672 inline uint64_t NextPowerOf2(uint64_t A) { 673 A |= (A >> 1); 674 A |= (A >> 2); 675 A |= (A >> 4); 676 A |= (A >> 8); 677 A |= (A >> 16); 678 A |= (A >> 32); 679 return A + 1; 680 } 681 682 /// Returns the power of two which is less than or equal to the given value. 683 /// Essentially, it is a floor operation across the domain of powers of two. 684 inline uint64_t PowerOf2Floor(uint64_t A) { 685 if (!A) return 0; 686 return 1ull << (63 - countLeadingZeros(A, ZB_Undefined)); 687 } 688 689 /// Returns the power of two which is greater than or equal to the given value. 690 /// Essentially, it is a ceil operation across the domain of powers of two. 691 inline uint64_t PowerOf2Ceil(uint64_t A) { 692 if (!A) 693 return 0; 694 return NextPowerOf2(A - 1); 695 } 696 697 /// Returns the next integer (mod 2**64) that is greater than or equal to 698 /// \p Value and is a multiple of \p Align. \p Align must be non-zero. 699 /// 700 /// If non-zero \p Skew is specified, the return value will be a minimal 701 /// integer that is greater than or equal to \p Value and equal to 702 /// \p Align * N + \p Skew for some integer N. If \p Skew is larger than 703 /// \p Align, its value is adjusted to '\p Skew mod \p Align'. 704 /// 705 /// Examples: 706 /// \code 707 /// alignTo(5, 8) = 8 708 /// alignTo(17, 8) = 24 709 /// alignTo(~0LL, 8) = 0 710 /// alignTo(321, 255) = 510 711 /// 712 /// alignTo(5, 8, 7) = 7 713 /// alignTo(17, 8, 1) = 17 714 /// alignTo(~0LL, 8, 3) = 3 715 /// alignTo(321, 255, 42) = 552 716 /// \endcode 717 inline uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew = 0) { 718 assert(Align != 0u && "Align can't be 0."); 719 Skew %= Align; 720 return (Value + Align - 1 - Skew) / Align * Align + Skew; 721 } 722 723 /// Returns the next integer (mod 2**64) that is greater than or equal to 724 /// \p Value and is a multiple of \c Align. \c Align must be non-zero. 725 template <uint64_t Align> constexpr inline uint64_t alignTo(uint64_t Value) { 726 static_assert(Align != 0u, "Align must be non-zero"); 727 return (Value + Align - 1) / Align * Align; 728 } 729 730 /// Returns the integer ceil(Numerator / Denominator). 731 inline uint64_t divideCeil(uint64_t Numerator, uint64_t Denominator) { 732 return alignTo(Numerator, Denominator) / Denominator; 733 } 734 735 /// Returns the integer nearest(Numerator / Denominator). 736 inline uint64_t divideNearest(uint64_t Numerator, uint64_t Denominator) { 737 return (Numerator + (Denominator / 2)) / Denominator; 738 } 739 740 /// Returns the largest uint64_t less than or equal to \p Value and is 741 /// \p Skew mod \p Align. \p Align must be non-zero 742 inline uint64_t alignDown(uint64_t Value, uint64_t Align, uint64_t Skew = 0) { 743 assert(Align != 0u && "Align can't be 0."); 744 Skew %= Align; 745 return (Value - Skew) / Align * Align + Skew; 746 } 747 748 /// Sign-extend the number in the bottom B bits of X to a 32-bit integer. 749 /// Requires 0 < B <= 32. 750 template <unsigned B> constexpr inline int32_t SignExtend32(uint32_t X) { 751 static_assert(B > 0, "Bit width can't be 0."); 752 static_assert(B <= 32, "Bit width out of range."); 753 return int32_t(X << (32 - B)) >> (32 - B); 754 } 755 756 /// Sign-extend the number in the bottom B bits of X to a 32-bit integer. 757 /// Requires 0 < B < 32. 758 inline int32_t SignExtend32(uint32_t X, unsigned B) { 759 assert(B > 0 && "Bit width can't be 0."); 760 assert(B <= 32 && "Bit width out of range."); 761 return int32_t(X << (32 - B)) >> (32 - B); 762 } 763 764 /// Sign-extend the number in the bottom B bits of X to a 64-bit integer. 765 /// Requires 0 < B < 64. 766 template <unsigned B> constexpr inline int64_t SignExtend64(uint64_t x) { 767 static_assert(B > 0, "Bit width can't be 0."); 768 static_assert(B <= 64, "Bit width out of range."); 769 return int64_t(x << (64 - B)) >> (64 - B); 770 } 771 772 /// Sign-extend the number in the bottom B bits of X to a 64-bit integer. 773 /// Requires 0 < B < 64. 774 inline int64_t SignExtend64(uint64_t X, unsigned B) { 775 assert(B > 0 && "Bit width can't be 0."); 776 assert(B <= 64 && "Bit width out of range."); 777 return int64_t(X << (64 - B)) >> (64 - B); 778 } 779 780 /// Subtract two unsigned integers, X and Y, of type T and return the absolute 781 /// value of the result. 782 template <typename T> 783 typename std::enable_if<std::is_unsigned<T>::value, T>::type 784 AbsoluteDifference(T X, T Y) { 785 return std::max(X, Y) - std::min(X, Y); 786 } 787 788 /// Add two unsigned integers, X and Y, of type T. Clamp the result to the 789 /// maximum representable value of T on overflow. ResultOverflowed indicates if 790 /// the result is larger than the maximum representable value of type T. 791 template <typename T> 792 typename std::enable_if<std::is_unsigned<T>::value, T>::type 793 SaturatingAdd(T X, T Y, bool *ResultOverflowed = nullptr) { 794 bool Dummy; 795 bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy; 796 // Hacker's Delight, p. 29 797 T Z = X + Y; 798 Overflowed = (Z < X || Z < Y); 799 if (Overflowed) 800 return std::numeric_limits<T>::max(); 801 else 802 return Z; 803 } 804 805 /// Multiply two unsigned integers, X and Y, of type T. Clamp the result to the 806 /// maximum representable value of T on overflow. ResultOverflowed indicates if 807 /// the result is larger than the maximum representable value of type T. 808 template <typename T> 809 typename std::enable_if<std::is_unsigned<T>::value, T>::type 810 SaturatingMultiply(T X, T Y, bool *ResultOverflowed = nullptr) { 811 bool Dummy; 812 bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy; 813 814 // Hacker's Delight, p. 30 has a different algorithm, but we don't use that 815 // because it fails for uint16_t (where multiplication can have undefined 816 // behavior due to promotion to int), and requires a division in addition 817 // to the multiplication. 818 819 Overflowed = false; 820 821 // Log2(Z) would be either Log2Z or Log2Z + 1. 822 // Special case: if X or Y is 0, Log2_64 gives -1, and Log2Z 823 // will necessarily be less than Log2Max as desired. 824 int Log2Z = Log2_64(X) + Log2_64(Y); 825 const T Max = std::numeric_limits<T>::max(); 826 int Log2Max = Log2_64(Max); 827 if (Log2Z < Log2Max) { 828 return X * Y; 829 } 830 if (Log2Z > Log2Max) { 831 Overflowed = true; 832 return Max; 833 } 834 835 // We're going to use the top bit, and maybe overflow one 836 // bit past it. Multiply all but the bottom bit then add 837 // that on at the end. 838 T Z = (X >> 1) * Y; 839 if (Z & ~(Max >> 1)) { 840 Overflowed = true; 841 return Max; 842 } 843 Z <<= 1; 844 if (X & 1) 845 return SaturatingAdd(Z, Y, ResultOverflowed); 846 847 return Z; 848 } 849 850 /// Multiply two unsigned integers, X and Y, and add the unsigned integer, A to 851 /// the product. Clamp the result to the maximum representable value of T on 852 /// overflow. ResultOverflowed indicates if the result is larger than the 853 /// maximum representable value of type T. 854 template <typename T> 855 typename std::enable_if<std::is_unsigned<T>::value, T>::type 856 SaturatingMultiplyAdd(T X, T Y, T A, bool *ResultOverflowed = nullptr) { 857 bool Dummy; 858 bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy; 859 860 T Product = SaturatingMultiply(X, Y, &Overflowed); 861 if (Overflowed) 862 return Product; 863 864 return SaturatingAdd(A, Product, &Overflowed); 865 } 866 867 /// Use this rather than HUGE_VALF; the latter causes warnings on MSVC. 868 extern const float huge_valf; 869 870 871 /// Add two signed integers, computing the two's complement truncated result, 872 /// returning true if overflow occured. 873 template <typename T> 874 typename std::enable_if<std::is_signed<T>::value, T>::type 875 AddOverflow(T X, T Y, T &Result) { 876 #if __has_builtin(__builtin_add_overflow) 877 return __builtin_add_overflow(X, Y, &Result); 878 #else 879 // Perform the unsigned addition. 880 using U = typename std::make_unsigned<T>::type; 881 const U UX = static_cast<U>(X); 882 const U UY = static_cast<U>(Y); 883 const U UResult = UX + UY; 884 885 // Convert to signed. 886 Result = static_cast<T>(UResult); 887 888 // Adding two positive numbers should result in a positive number. 889 if (X > 0 && Y > 0) 890 return Result <= 0; 891 // Adding two negatives should result in a negative number. 892 if (X < 0 && Y < 0) 893 return Result >= 0; 894 return false; 895 #endif 896 } 897 898 /// Subtract two signed integers, computing the two's complement truncated 899 /// result, returning true if an overflow ocurred. 900 template <typename T> 901 typename std::enable_if<std::is_signed<T>::value, T>::type 902 SubOverflow(T X, T Y, T &Result) { 903 #if __has_builtin(__builtin_sub_overflow) 904 return __builtin_sub_overflow(X, Y, &Result); 905 #else 906 // Perform the unsigned addition. 907 using U = typename std::make_unsigned<T>::type; 908 const U UX = static_cast<U>(X); 909 const U UY = static_cast<U>(Y); 910 const U UResult = UX - UY; 911 912 // Convert to signed. 913 Result = static_cast<T>(UResult); 914 915 // Subtracting a positive number from a negative results in a negative number. 916 if (X <= 0 && Y > 0) 917 return Result >= 0; 918 // Subtracting a negative number from a positive results in a positive number. 919 if (X >= 0 && Y < 0) 920 return Result <= 0; 921 return false; 922 #endif 923 } 924 925 926 /// Multiply two signed integers, computing the two's complement truncated 927 /// result, returning true if an overflow ocurred. 928 template <typename T> 929 typename std::enable_if<std::is_signed<T>::value, T>::type 930 MulOverflow(T X, T Y, T &Result) { 931 // Perform the unsigned multiplication on absolute values. 932 using U = typename std::make_unsigned<T>::type; 933 const U UX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X); 934 const U UY = Y < 0 ? (0 - static_cast<U>(Y)) : static_cast<U>(Y); 935 const U UResult = UX * UY; 936 937 // Convert to signed. 938 const bool IsNegative = (X < 0) ^ (Y < 0); 939 Result = IsNegative ? (0 - UResult) : UResult; 940 941 // If any of the args was 0, result is 0 and no overflow occurs. 942 if (UX == 0 || UY == 0) 943 return false; 944 945 // UX and UY are in [1, 2^n], where n is the number of digits. 946 // Check how the max allowed absolute value (2^n for negative, 2^(n-1) for 947 // positive) divided by an argument compares to the other. 948 if (IsNegative) 949 return UX > (static_cast<U>(std::numeric_limits<T>::max()) + U(1)) / UY; 950 else 951 return UX > (static_cast<U>(std::numeric_limits<T>::max())) / UY; 952 } 953 954 } // End llvm namespace 955 956 #endif 957