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