1//===-- llvm/ADT/Hashing.h - Utilities for hashing --------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the newly proposed standard C++ interfaces for hashing 11// arbitrary data and building hash functions for user-defined types. This 12// interface was originally proposed in N3333[1] and is currently under review 13// for inclusion in a future TR and/or standard. 14// 15// The primary interfaces provide are comprised of one type and three functions: 16// 17// -- 'hash_code' class is an opaque type representing the hash code for some 18// data. It is the intended product of hashing, and can be used to implement 19// hash tables, checksumming, and other common uses of hashes. It is not an 20// integer type (although it can be converted to one) because it is risky 21// to assume much about the internals of a hash_code. In particular, each 22// execution of the program has a high probability of producing a different 23// hash_code for a given input. Thus their values are not stable to save or 24// persist, and should only be used during the execution for the 25// construction of hashing datastructures. 26// 27// -- 'hash_value' is a function designed to be overloaded for each 28// user-defined type which wishes to be used within a hashing context. It 29// should be overloaded within the user-defined type's namespace and found 30// via ADL. Overloads for primitive types are provided by this library. 31// 32// -- 'hash_combine' and 'hash_combine_range' are functions designed to aid 33// programmers in easily and intuitively combining a set of data into 34// a single hash_code for their object. They should only logically be used 35// within the implementation of a 'hash_value' routine or similar context. 36// 37// Note that 'hash_combine_range' contains very special logic for hashing 38// a contiguous array of integers or pointers. This logic is *extremely* fast, 39// on a modern Intel "Gainestown" Xeon (Nehalem uarch) @2.2 GHz, these were 40// benchmarked at over 6.5 GiB/s for large keys, and <20 cycles/hash for keys 41// under 32-bytes. 42// 43//===----------------------------------------------------------------------===// 44 45#ifndef LLVM_ADT_HASHING_H 46#define LLVM_ADT_HASHING_H 47 48#include "llvm/Support/DataTypes.h" 49#include "llvm/Support/Host.h" 50#include "llvm/Support/SwapByteOrder.h" 51#include "llvm/Support/type_traits.h" 52#include <algorithm> 53#include <cassert> 54#include <cstring> 55#include <iterator> 56#include <utility> 57 58// Allow detecting C++11 feature availability when building with Clang without 59// breaking other compilers. 60#ifndef __has_feature 61# define __has_feature(x) 0 62#endif 63 64namespace llvm { 65 66/// \brief An opaque object representing a hash code. 67/// 68/// This object represents the result of hashing some entity. It is intended to 69/// be used to implement hashtables or other hashing-based data structures. 70/// While it wraps and exposes a numeric value, this value should not be 71/// trusted to be stable or predictable across processes or executions. 72/// 73/// In order to obtain the hash_code for an object 'x': 74/// \code 75/// using llvm::hash_value; 76/// llvm::hash_code code = hash_value(x); 77/// \endcode 78class hash_code { 79 size_t value; 80 81public: 82 /// \brief Default construct a hash_code. 83 /// Note that this leaves the value uninitialized. 84 hash_code() {} 85 86 /// \brief Form a hash code directly from a numerical value. 87 hash_code(size_t value) : value(value) {} 88 89 /// \brief Convert the hash code to its numerical value for use. 90 /*explicit*/ operator size_t() const { return value; } 91 92 friend bool operator==(const hash_code &lhs, const hash_code &rhs) { 93 return lhs.value == rhs.value; 94 } 95 friend bool operator!=(const hash_code &lhs, const hash_code &rhs) { 96 return lhs.value != rhs.value; 97 } 98 99 /// \brief Allow a hash_code to be directly run through hash_value. 100 friend size_t hash_value(const hash_code &code) { return code.value; } 101}; 102 103/// \brief Compute a hash_code for any integer value. 104/// 105/// Note that this function is intended to compute the same hash_code for 106/// a particular value without regard to the pre-promotion type. This is in 107/// contrast to hash_combine which may produce different hash_codes for 108/// differing argument types even if they would implicit promote to a common 109/// type without changing the value. 110template <typename T> 111typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type 112hash_value(T value); 113 114/// \brief Compute a hash_code for a pointer's address. 115/// 116/// N.B.: This hashes the *address*. Not the value and not the type. 117template <typename T> hash_code hash_value(const T *ptr); 118 119/// \brief Compute a hash_code for a pair of objects. 120template <typename T, typename U> 121hash_code hash_value(const std::pair<T, U> &arg); 122 123/// \brief Compute a hash_code for a standard string. 124template <typename T> 125hash_code hash_value(const std::basic_string<T> &arg); 126 127 128/// \brief Override the execution seed with a fixed value. 129/// 130/// This hashing library uses a per-execution seed designed to change on each 131/// run with high probability in order to ensure that the hash codes are not 132/// attackable and to ensure that output which is intended to be stable does 133/// not rely on the particulars of the hash codes produced. 134/// 135/// That said, there are use cases where it is important to be able to 136/// reproduce *exactly* a specific behavior. To that end, we provide a function 137/// which will forcibly set the seed to a fixed value. This must be done at the 138/// start of the program, before any hashes are computed. Also, it cannot be 139/// undone. This makes it thread-hostile and very hard to use outside of 140/// immediately on start of a simple program designed for reproducible 141/// behavior. 142void set_fixed_execution_hash_seed(size_t fixed_value); 143 144 145// All of the implementation details of actually computing the various hash 146// code values are held within this namespace. These routines are included in 147// the header file mainly to allow inlining and constant propagation. 148namespace hashing { 149namespace detail { 150 151inline uint64_t fetch64(const char *p) { 152 uint64_t result; 153 memcpy(&result, p, sizeof(result)); 154 if (sys::IsBigEndianHost) 155 sys::swapByteOrder(result); 156 return result; 157} 158 159inline uint32_t fetch32(const char *p) { 160 uint32_t result; 161 memcpy(&result, p, sizeof(result)); 162 if (sys::IsBigEndianHost) 163 sys::swapByteOrder(result); 164 return result; 165} 166 167/// Some primes between 2^63 and 2^64 for various uses. 168static const uint64_t k0 = 0xc3a5c85c97cb3127ULL; 169static const uint64_t k1 = 0xb492b66fbe98f273ULL; 170static const uint64_t k2 = 0x9ae16a3b2f90404fULL; 171static const uint64_t k3 = 0xc949d7c7509e6557ULL; 172 173/// \brief Bitwise right rotate. 174/// Normally this will compile to a single instruction, especially if the 175/// shift is a manifest constant. 176inline uint64_t rotate(uint64_t val, size_t shift) { 177 // Avoid shifting by 64: doing so yields an undefined result. 178 return shift == 0 ? val : ((val >> shift) | (val << (64 - shift))); 179} 180 181inline uint64_t shift_mix(uint64_t val) { 182 return val ^ (val >> 47); 183} 184 185inline uint64_t hash_16_bytes(uint64_t low, uint64_t high) { 186 // Murmur-inspired hashing. 187 const uint64_t kMul = 0x9ddfea08eb382d69ULL; 188 uint64_t a = (low ^ high) * kMul; 189 a ^= (a >> 47); 190 uint64_t b = (high ^ a) * kMul; 191 b ^= (b >> 47); 192 b *= kMul; 193 return b; 194} 195 196inline uint64_t hash_1to3_bytes(const char *s, size_t len, uint64_t seed) { 197 uint8_t a = s[0]; 198 uint8_t b = s[len >> 1]; 199 uint8_t c = s[len - 1]; 200 uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8); 201 uint32_t z = len + (static_cast<uint32_t>(c) << 2); 202 return shift_mix(y * k2 ^ z * k3 ^ seed) * k2; 203} 204 205inline uint64_t hash_4to8_bytes(const char *s, size_t len, uint64_t seed) { 206 uint64_t a = fetch32(s); 207 return hash_16_bytes(len + (a << 3), seed ^ fetch32(s + len - 4)); 208} 209 210inline uint64_t hash_9to16_bytes(const char *s, size_t len, uint64_t seed) { 211 uint64_t a = fetch64(s); 212 uint64_t b = fetch64(s + len - 8); 213 return hash_16_bytes(seed ^ a, rotate(b + len, len)) ^ b; 214} 215 216inline uint64_t hash_17to32_bytes(const char *s, size_t len, uint64_t seed) { 217 uint64_t a = fetch64(s) * k1; 218 uint64_t b = fetch64(s + 8); 219 uint64_t c = fetch64(s + len - 8) * k2; 220 uint64_t d = fetch64(s + len - 16) * k0; 221 return hash_16_bytes(rotate(a - b, 43) + rotate(c ^ seed, 30) + d, 222 a + rotate(b ^ k3, 20) - c + len + seed); 223} 224 225inline uint64_t hash_33to64_bytes(const char *s, size_t len, uint64_t seed) { 226 uint64_t z = fetch64(s + 24); 227 uint64_t a = fetch64(s) + (len + fetch64(s + len - 16)) * k0; 228 uint64_t b = rotate(a + z, 52); 229 uint64_t c = rotate(a, 37); 230 a += fetch64(s + 8); 231 c += rotate(a, 7); 232 a += fetch64(s + 16); 233 uint64_t vf = a + z; 234 uint64_t vs = b + rotate(a, 31) + c; 235 a = fetch64(s + 16) + fetch64(s + len - 32); 236 z = fetch64(s + len - 8); 237 b = rotate(a + z, 52); 238 c = rotate(a, 37); 239 a += fetch64(s + len - 24); 240 c += rotate(a, 7); 241 a += fetch64(s + len - 16); 242 uint64_t wf = a + z; 243 uint64_t ws = b + rotate(a, 31) + c; 244 uint64_t r = shift_mix((vf + ws) * k2 + (wf + vs) * k0); 245 return shift_mix((seed ^ (r * k0)) + vs) * k2; 246} 247 248inline uint64_t hash_short(const char *s, size_t length, uint64_t seed) { 249 if (length >= 4 && length <= 8) 250 return hash_4to8_bytes(s, length, seed); 251 if (length > 8 && length <= 16) 252 return hash_9to16_bytes(s, length, seed); 253 if (length > 16 && length <= 32) 254 return hash_17to32_bytes(s, length, seed); 255 if (length > 32) 256 return hash_33to64_bytes(s, length, seed); 257 if (length != 0) 258 return hash_1to3_bytes(s, length, seed); 259 260 return k2 ^ seed; 261} 262 263/// \brief The intermediate state used during hashing. 264/// Currently, the algorithm for computing hash codes is based on CityHash and 265/// keeps 56 bytes of arbitrary state. 266struct hash_state { 267 uint64_t h0, h1, h2, h3, h4, h5, h6; 268 269 /// \brief Create a new hash_state structure and initialize it based on the 270 /// seed and the first 64-byte chunk. 271 /// This effectively performs the initial mix. 272 static hash_state create(const char *s, uint64_t seed) { 273 hash_state state = { 274 0, seed, hash_16_bytes(seed, k1), rotate(seed ^ k1, 49), 275 seed * k1, shift_mix(seed), 0 }; 276 state.h6 = hash_16_bytes(state.h4, state.h5); 277 state.mix(s); 278 return state; 279 } 280 281 /// \brief Mix 32-bytes from the input sequence into the 16-bytes of 'a' 282 /// and 'b', including whatever is already in 'a' and 'b'. 283 static void mix_32_bytes(const char *s, uint64_t &a, uint64_t &b) { 284 a += fetch64(s); 285 uint64_t c = fetch64(s + 24); 286 b = rotate(b + a + c, 21); 287 uint64_t d = a; 288 a += fetch64(s + 8) + fetch64(s + 16); 289 b += rotate(a, 44) + d; 290 a += c; 291 } 292 293 /// \brief Mix in a 64-byte buffer of data. 294 /// We mix all 64 bytes even when the chunk length is smaller, but we 295 /// record the actual length. 296 void mix(const char *s) { 297 h0 = rotate(h0 + h1 + h3 + fetch64(s + 8), 37) * k1; 298 h1 = rotate(h1 + h4 + fetch64(s + 48), 42) * k1; 299 h0 ^= h6; 300 h1 += h3 + fetch64(s + 40); 301 h2 = rotate(h2 + h5, 33) * k1; 302 h3 = h4 * k1; 303 h4 = h0 + h5; 304 mix_32_bytes(s, h3, h4); 305 h5 = h2 + h6; 306 h6 = h1 + fetch64(s + 16); 307 mix_32_bytes(s + 32, h5, h6); 308 std::swap(h2, h0); 309 } 310 311 /// \brief Compute the final 64-bit hash code value based on the current 312 /// state and the length of bytes hashed. 313 uint64_t finalize(size_t length) { 314 return hash_16_bytes(hash_16_bytes(h3, h5) + shift_mix(h1) * k1 + h2, 315 hash_16_bytes(h4, h6) + shift_mix(length) * k1 + h0); 316 } 317}; 318 319 320/// \brief A global, fixed seed-override variable. 321/// 322/// This variable can be set using the \see llvm::set_fixed_execution_seed 323/// function. See that function for details. Do not, under any circumstances, 324/// set or read this variable. 325extern size_t fixed_seed_override; 326 327inline size_t get_execution_seed() { 328 // FIXME: This needs to be a per-execution seed. This is just a placeholder 329 // implementation. Switching to a per-execution seed is likely to flush out 330 // instability bugs and so will happen as its own commit. 331 // 332 // However, if there is a fixed seed override set the first time this is 333 // called, return that instead of the per-execution seed. 334 const uint64_t seed_prime = 0xff51afd7ed558ccdULL; 335 static size_t seed = fixed_seed_override ? fixed_seed_override 336 : (size_t)seed_prime; 337 return seed; 338} 339 340 341/// \brief Trait to indicate whether a type's bits can be hashed directly. 342/// 343/// A type trait which is true if we want to combine values for hashing by 344/// reading the underlying data. It is false if values of this type must 345/// first be passed to hash_value, and the resulting hash_codes combined. 346// 347// FIXME: We want to replace is_integral_or_enum and is_pointer here with 348// a predicate which asserts that comparing the underlying storage of two 349// values of the type for equality is equivalent to comparing the two values 350// for equality. For all the platforms we care about, this holds for integers 351// and pointers, but there are platforms where it doesn't and we would like to 352// support user-defined types which happen to satisfy this property. 353template <typename T> struct is_hashable_data 354 : std::integral_constant<bool, ((is_integral_or_enum<T>::value || 355 std::is_pointer<T>::value) && 356 64 % sizeof(T) == 0)> {}; 357 358// Special case std::pair to detect when both types are viable and when there 359// is no alignment-derived padding in the pair. This is a bit of a lie because 360// std::pair isn't truly POD, but it's close enough in all reasonable 361// implementations for our use case of hashing the underlying data. 362template <typename T, typename U> struct is_hashable_data<std::pair<T, U> > 363 : std::integral_constant<bool, (is_hashable_data<T>::value && 364 is_hashable_data<U>::value && 365 (sizeof(T) + sizeof(U)) == 366 sizeof(std::pair<T, U>))> {}; 367 368/// \brief Helper to get the hashable data representation for a type. 369/// This variant is enabled when the type itself can be used. 370template <typename T> 371typename std::enable_if<is_hashable_data<T>::value, T>::type 372get_hashable_data(const T &value) { 373 return value; 374} 375/// \brief Helper to get the hashable data representation for a type. 376/// This variant is enabled when we must first call hash_value and use the 377/// result as our data. 378template <typename T> 379typename std::enable_if<!is_hashable_data<T>::value, size_t>::type 380get_hashable_data(const T &value) { 381 using ::llvm::hash_value; 382 return hash_value(value); 383} 384 385/// \brief Helper to store data from a value into a buffer and advance the 386/// pointer into that buffer. 387/// 388/// This routine first checks whether there is enough space in the provided 389/// buffer, and if not immediately returns false. If there is space, it 390/// copies the underlying bytes of value into the buffer, advances the 391/// buffer_ptr past the copied bytes, and returns true. 392template <typename T> 393bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value, 394 size_t offset = 0) { 395 size_t store_size = sizeof(value) - offset; 396 if (buffer_ptr + store_size > buffer_end) 397 return false; 398 const char *value_data = reinterpret_cast<const char *>(&value); 399 memcpy(buffer_ptr, value_data + offset, store_size); 400 buffer_ptr += store_size; 401 return true; 402} 403 404/// \brief Implement the combining of integral values into a hash_code. 405/// 406/// This overload is selected when the value type of the iterator is 407/// integral. Rather than computing a hash_code for each object and then 408/// combining them, this (as an optimization) directly combines the integers. 409template <typename InputIteratorT> 410hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) { 411 const size_t seed = get_execution_seed(); 412 char buffer[64], *buffer_ptr = buffer; 413 char *const buffer_end = std::end(buffer); 414 while (first != last && store_and_advance(buffer_ptr, buffer_end, 415 get_hashable_data(*first))) 416 ++first; 417 if (first == last) 418 return hash_short(buffer, buffer_ptr - buffer, seed); 419 assert(buffer_ptr == buffer_end); 420 421 hash_state state = state.create(buffer, seed); 422 size_t length = 64; 423 while (first != last) { 424 // Fill up the buffer. We don't clear it, which re-mixes the last round 425 // when only a partial 64-byte chunk is left. 426 buffer_ptr = buffer; 427 while (first != last && store_and_advance(buffer_ptr, buffer_end, 428 get_hashable_data(*first))) 429 ++first; 430 431 // Rotate the buffer if we did a partial fill in order to simulate doing 432 // a mix of the last 64-bytes. That is how the algorithm works when we 433 // have a contiguous byte sequence, and we want to emulate that here. 434 std::rotate(buffer, buffer_ptr, buffer_end); 435 436 // Mix this chunk into the current state. 437 state.mix(buffer); 438 length += buffer_ptr - buffer; 439 }; 440 441 return state.finalize(length); 442} 443 444/// \brief Implement the combining of integral values into a hash_code. 445/// 446/// This overload is selected when the value type of the iterator is integral 447/// and when the input iterator is actually a pointer. Rather than computing 448/// a hash_code for each object and then combining them, this (as an 449/// optimization) directly combines the integers. Also, because the integers 450/// are stored in contiguous memory, this routine avoids copying each value 451/// and directly reads from the underlying memory. 452template <typename ValueT> 453typename std::enable_if<is_hashable_data<ValueT>::value, hash_code>::type 454hash_combine_range_impl(ValueT *first, ValueT *last) { 455 const size_t seed = get_execution_seed(); 456 const char *s_begin = reinterpret_cast<const char *>(first); 457 const char *s_end = reinterpret_cast<const char *>(last); 458 const size_t length = std::distance(s_begin, s_end); 459 if (length <= 64) 460 return hash_short(s_begin, length, seed); 461 462 const char *s_aligned_end = s_begin + (length & ~63); 463 hash_state state = state.create(s_begin, seed); 464 s_begin += 64; 465 while (s_begin != s_aligned_end) { 466 state.mix(s_begin); 467 s_begin += 64; 468 } 469 if (length & 63) 470 state.mix(s_end - 64); 471 472 return state.finalize(length); 473} 474 475} // namespace detail 476} // namespace hashing 477 478 479/// \brief Compute a hash_code for a sequence of values. 480/// 481/// This hashes a sequence of values. It produces the same hash_code as 482/// 'hash_combine(a, b, c, ...)', but can run over arbitrary sized sequences 483/// and is significantly faster given pointers and types which can be hashed as 484/// a sequence of bytes. 485template <typename InputIteratorT> 486hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) { 487 return ::llvm::hashing::detail::hash_combine_range_impl(first, last); 488} 489 490 491// Implementation details for hash_combine. 492namespace hashing { 493namespace detail { 494 495/// \brief Helper class to manage the recursive combining of hash_combine 496/// arguments. 497/// 498/// This class exists to manage the state and various calls involved in the 499/// recursive combining of arguments used in hash_combine. It is particularly 500/// useful at minimizing the code in the recursive calls to ease the pain 501/// caused by a lack of variadic functions. 502struct hash_combine_recursive_helper { 503 char buffer[64]; 504 hash_state state; 505 const size_t seed; 506 507public: 508 /// \brief Construct a recursive hash combining helper. 509 /// 510 /// This sets up the state for a recursive hash combine, including getting 511 /// the seed and buffer setup. 512 hash_combine_recursive_helper() 513 : seed(get_execution_seed()) {} 514 515 /// \brief Combine one chunk of data into the current in-flight hash. 516 /// 517 /// This merges one chunk of data into the hash. First it tries to buffer 518 /// the data. If the buffer is full, it hashes the buffer into its 519 /// hash_state, empties it, and then merges the new chunk in. This also 520 /// handles cases where the data straddles the end of the buffer. 521 template <typename T> 522 char *combine_data(size_t &length, char *buffer_ptr, char *buffer_end, T data) { 523 if (!store_and_advance(buffer_ptr, buffer_end, data)) { 524 // Check for skew which prevents the buffer from being packed, and do 525 // a partial store into the buffer to fill it. This is only a concern 526 // with the variadic combine because that formation can have varying 527 // argument types. 528 size_t partial_store_size = buffer_end - buffer_ptr; 529 memcpy(buffer_ptr, &data, partial_store_size); 530 531 // If the store fails, our buffer is full and ready to hash. We have to 532 // either initialize the hash state (on the first full buffer) or mix 533 // this buffer into the existing hash state. Length tracks the *hashed* 534 // length, not the buffered length. 535 if (length == 0) { 536 state = state.create(buffer, seed); 537 length = 64; 538 } else { 539 // Mix this chunk into the current state and bump length up by 64. 540 state.mix(buffer); 541 length += 64; 542 } 543 // Reset the buffer_ptr to the head of the buffer for the next chunk of 544 // data. 545 buffer_ptr = buffer; 546 547 // Try again to store into the buffer -- this cannot fail as we only 548 // store types smaller than the buffer. 549 if (!store_and_advance(buffer_ptr, buffer_end, data, 550 partial_store_size)) 551 abort(); 552 } 553 return buffer_ptr; 554 } 555 556#if defined(__has_feature) && __has_feature(__cxx_variadic_templates__) 557 558 /// \brief Recursive, variadic combining method. 559 /// 560 /// This function recurses through each argument, combining that argument 561 /// into a single hash. 562 template <typename T, typename ...Ts> 563 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 564 const T &arg, const Ts &...args) { 565 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg)); 566 567 // Recurse to the next argument. 568 return combine(length, buffer_ptr, buffer_end, args...); 569 } 570 571#else 572 // Manually expanded recursive combining methods. See variadic above for 573 // documentation. 574 575 template <typename T1, typename T2, typename T3, typename T4, typename T5, 576 typename T6> 577 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 578 const T1 &arg1, const T2 &arg2, const T3 &arg3, 579 const T4 &arg4, const T5 &arg5, const T6 &arg6) { 580 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1)); 581 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4, arg5, arg6); 582 } 583 template <typename T1, typename T2, typename T3, typename T4, typename T5> 584 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 585 const T1 &arg1, const T2 &arg2, const T3 &arg3, 586 const T4 &arg4, const T5 &arg5) { 587 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1)); 588 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4, arg5); 589 } 590 template <typename T1, typename T2, typename T3, typename T4> 591 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 592 const T1 &arg1, const T2 &arg2, const T3 &arg3, 593 const T4 &arg4) { 594 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1)); 595 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4); 596 } 597 template <typename T1, typename T2, typename T3> 598 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 599 const T1 &arg1, const T2 &arg2, const T3 &arg3) { 600 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1)); 601 return combine(length, buffer_ptr, buffer_end, arg2, arg3); 602 } 603 template <typename T1, typename T2> 604 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 605 const T1 &arg1, const T2 &arg2) { 606 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1)); 607 return combine(length, buffer_ptr, buffer_end, arg2); 608 } 609 template <typename T1> 610 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end, 611 const T1 &arg1) { 612 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1)); 613 return combine(length, buffer_ptr, buffer_end); 614 } 615 616#endif 617 618 /// \brief Base case for recursive, variadic combining. 619 /// 620 /// The base case when combining arguments recursively is reached when all 621 /// arguments have been handled. It flushes the remaining buffer and 622 /// constructs a hash_code. 623 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end) { 624 // Check whether the entire set of values fit in the buffer. If so, we'll 625 // use the optimized short hashing routine and skip state entirely. 626 if (length == 0) 627 return hash_short(buffer, buffer_ptr - buffer, seed); 628 629 // Mix the final buffer, rotating it if we did a partial fill in order to 630 // simulate doing a mix of the last 64-bytes. That is how the algorithm 631 // works when we have a contiguous byte sequence, and we want to emulate 632 // that here. 633 std::rotate(buffer, buffer_ptr, buffer_end); 634 635 // Mix this chunk into the current state. 636 state.mix(buffer); 637 length += buffer_ptr - buffer; 638 639 return state.finalize(length); 640 } 641}; 642 643} // namespace detail 644} // namespace hashing 645 646 647#if __has_feature(__cxx_variadic_templates__) 648 649/// \brief Combine values into a single hash_code. 650/// 651/// This routine accepts a varying number of arguments of any type. It will 652/// attempt to combine them into a single hash_code. For user-defined types it 653/// attempts to call a \see hash_value overload (via ADL) for the type. For 654/// integer and pointer types it directly combines their data into the 655/// resulting hash_code. 656/// 657/// The result is suitable for returning from a user's hash_value 658/// *implementation* for their user-defined type. Consumers of a type should 659/// *not* call this routine, they should instead call 'hash_value'. 660template <typename ...Ts> hash_code hash_combine(const Ts &...args) { 661 // Recursively hash each argument using a helper class. 662 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 663 return helper.combine(0, helper.buffer, helper.buffer + 64, args...); 664} 665 666#else 667 668// What follows are manually exploded overloads for each argument width. See 669// the above variadic definition for documentation and specification. 670 671template <typename T1, typename T2, typename T3, typename T4, typename T5, 672 typename T6> 673hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, 674 const T4 &arg4, const T5 &arg5, const T6 &arg6) { 675 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 676 return helper.combine(0, helper.buffer, helper.buffer + 64, 677 arg1, arg2, arg3, arg4, arg5, arg6); 678} 679template <typename T1, typename T2, typename T3, typename T4, typename T5> 680hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, 681 const T4 &arg4, const T5 &arg5) { 682 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 683 return helper.combine(0, helper.buffer, helper.buffer + 64, 684 arg1, arg2, arg3, arg4, arg5); 685} 686template <typename T1, typename T2, typename T3, typename T4> 687hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, 688 const T4 &arg4) { 689 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 690 return helper.combine(0, helper.buffer, helper.buffer + 64, 691 arg1, arg2, arg3, arg4); 692} 693template <typename T1, typename T2, typename T3> 694hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3) { 695 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 696 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1, arg2, arg3); 697} 698template <typename T1, typename T2> 699hash_code hash_combine(const T1 &arg1, const T2 &arg2) { 700 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 701 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1, arg2); 702} 703template <typename T1> 704hash_code hash_combine(const T1 &arg1) { 705 ::llvm::hashing::detail::hash_combine_recursive_helper helper; 706 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1); 707} 708 709#endif 710 711 712// Implementation details for implementations of hash_value overloads provided 713// here. 714namespace hashing { 715namespace detail { 716 717/// \brief Helper to hash the value of a single integer. 718/// 719/// Overloads for smaller integer types are not provided to ensure consistent 720/// behavior in the presence of integral promotions. Essentially, 721/// "hash_value('4')" and "hash_value('0' + 4)" should be the same. 722inline hash_code hash_integer_value(uint64_t value) { 723 // Similar to hash_4to8_bytes but using a seed instead of length. 724 const uint64_t seed = get_execution_seed(); 725 const char *s = reinterpret_cast<const char *>(&value); 726 const uint64_t a = fetch32(s); 727 return hash_16_bytes(seed + (a << 3), fetch32(s + 4)); 728} 729 730} // namespace detail 731} // namespace hashing 732 733// Declared and documented above, but defined here so that any of the hashing 734// infrastructure is available. 735template <typename T> 736typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type 737hash_value(T value) { 738 return ::llvm::hashing::detail::hash_integer_value(value); 739} 740 741// Declared and documented above, but defined here so that any of the hashing 742// infrastructure is available. 743template <typename T> hash_code hash_value(const T *ptr) { 744 return ::llvm::hashing::detail::hash_integer_value( 745 reinterpret_cast<uintptr_t>(ptr)); 746} 747 748// Declared and documented above, but defined here so that any of the hashing 749// infrastructure is available. 750template <typename T, typename U> 751hash_code hash_value(const std::pair<T, U> &arg) { 752 return hash_combine(arg.first, arg.second); 753} 754 755// Declared and documented above, but defined here so that any of the hashing 756// infrastructure is available. 757template <typename T> 758hash_code hash_value(const std::basic_string<T> &arg) { 759 return hash_combine_range(arg.begin(), arg.end()); 760} 761 762} // namespace llvm 763 764#endif 765