1 //===-- llvm/ADT/Hashing.h - Utilities for hashing --------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
15 // The primary interfaces provide are comprised of one type and three functions:
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.
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.
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.
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
43 //===----------------------------------------------------------------------===//
45 #ifndef LLVM_ADT_HASHING_H
46 #define LLVM_ADT_HASHING_H
48 #include "llvm/ADT/STLExtras.h"
49 #include "llvm/Support/DataTypes.h"
50 #include "llvm/Support/Host.h"
51 #include "llvm/Support/SwapByteOrder.h"
52 #include "llvm/Support/type_traits.h"
59 // Allow detecting C++11 feature availability when building with Clang without
60 // breaking other compilers.
62 # define __has_feature(x) 0
67 /// \brief An opaque object representing a hash code.
69 /// This object represents the result of hashing some entity. It is intended to
70 /// be used to implement hashtables or other hashing-based data structures.
71 /// While it wraps and exposes a numeric value, this value should not be
72 /// trusted to be stable or predictable across processes or executions.
74 /// In order to obtain the hash_code for an object 'x':
76 /// using llvm::hash_value;
77 /// llvm::hash_code code = hash_value(x);
83 /// \brief Default construct a hash_code.
84 /// Note that this leaves the value uninitialized.
87 /// \brief Form a hash code directly from a numerical value.
88 hash_code(size_t value) : value(value) {}
90 /// \brief Convert the hash code to its numerical value for use.
91 /*explicit*/ operator size_t() const { return value; }
93 friend bool operator==(const hash_code &lhs, const hash_code &rhs) {
94 return lhs.value == rhs.value;
96 friend bool operator!=(const hash_code &lhs, const hash_code &rhs) {
97 return lhs.value != rhs.value;
100 /// \brief Allow a hash_code to be directly run through hash_value.
101 friend size_t hash_value(const hash_code &code) { return code.value; }
104 /// \brief Compute a hash_code for any integer value.
106 /// Note that this function is intended to compute the same hash_code for
107 /// a particular value without regard to the pre-promotion type. This is in
108 /// contrast to hash_combine which may produce different hash_codes for
109 /// differing argument types even if they would implicit promote to a common
110 /// type without changing the value.
111 template <typename T>
112 typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
115 /// \brief Compute a hash_code for a pointer's address.
117 /// N.B.: This hashes the *address*. Not the value and not the type.
118 template <typename T> hash_code hash_value(const T *ptr);
120 /// \brief Compute a hash_code for a pair of objects.
121 template <typename T, typename U>
122 hash_code hash_value(const std::pair<T, U> &arg);
124 /// \brief Compute a hash_code for a standard string.
125 template <typename T>
126 hash_code hash_value(const std::basic_string<T> &arg);
129 /// \brief Override the execution seed with a fixed value.
131 /// This hashing library uses a per-execution seed designed to change on each
132 /// run with high probability in order to ensure that the hash codes are not
133 /// attackable and to ensure that output which is intended to be stable does
134 /// not rely on the particulars of the hash codes produced.
136 /// That said, there are use cases where it is important to be able to
137 /// reproduce *exactly* a specific behavior. To that end, we provide a function
138 /// which will forcibly set the seed to a fixed value. This must be done at the
139 /// start of the program, before any hashes are computed. Also, it cannot be
140 /// undone. This makes it thread-hostile and very hard to use outside of
141 /// immediately on start of a simple program designed for reproducible
143 void set_fixed_execution_hash_seed(size_t fixed_value);
146 // All of the implementation details of actually computing the various hash
147 // code values are held within this namespace. These routines are included in
148 // the header file mainly to allow inlining and constant propagation.
152 inline uint64_t fetch64(const char *p) {
154 memcpy(&result, p, sizeof(result));
155 if (sys::IsBigEndianHost)
156 return sys::SwapByteOrder(result);
160 inline uint32_t fetch32(const char *p) {
162 memcpy(&result, p, sizeof(result));
163 if (sys::IsBigEndianHost)
164 return sys::SwapByteOrder(result);
168 /// Some primes between 2^63 and 2^64 for various uses.
169 static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
170 static const uint64_t k1 = 0xb492b66fbe98f273ULL;
171 static const uint64_t k2 = 0x9ae16a3b2f90404fULL;
172 static const uint64_t k3 = 0xc949d7c7509e6557ULL;
174 /// \brief Bitwise right rotate.
175 /// Normally this will compile to a single instruction, especially if the
176 /// shift is a manifest constant.
177 inline uint64_t rotate(uint64_t val, size_t shift) {
178 // Avoid shifting by 64: doing so yields an undefined result.
179 return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
182 inline uint64_t shift_mix(uint64_t val) {
183 return val ^ (val >> 47);
186 inline uint64_t hash_16_bytes(uint64_t low, uint64_t high) {
187 // Murmur-inspired hashing.
188 const uint64_t kMul = 0x9ddfea08eb382d69ULL;
189 uint64_t a = (low ^ high) * kMul;
191 uint64_t b = (high ^ a) * kMul;
197 inline uint64_t hash_1to3_bytes(const char *s, size_t len, uint64_t seed) {
199 uint8_t b = s[len >> 1];
200 uint8_t c = s[len - 1];
201 uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
202 uint32_t z = len + (static_cast<uint32_t>(c) << 2);
203 return shift_mix(y * k2 ^ z * k3 ^ seed) * k2;
206 inline uint64_t hash_4to8_bytes(const char *s, size_t len, uint64_t seed) {
207 uint64_t a = fetch32(s);
208 return hash_16_bytes(len + (a << 3), seed ^ fetch32(s + len - 4));
211 inline uint64_t hash_9to16_bytes(const char *s, size_t len, uint64_t seed) {
212 uint64_t a = fetch64(s);
213 uint64_t b = fetch64(s + len - 8);
214 return hash_16_bytes(seed ^ a, rotate(b + len, len)) ^ b;
217 inline uint64_t hash_17to32_bytes(const char *s, size_t len, uint64_t seed) {
218 uint64_t a = fetch64(s) * k1;
219 uint64_t b = fetch64(s + 8);
220 uint64_t c = fetch64(s + len - 8) * k2;
221 uint64_t d = fetch64(s + len - 16) * k0;
222 return hash_16_bytes(rotate(a - b, 43) + rotate(c ^ seed, 30) + d,
223 a + rotate(b ^ k3, 20) - c + len + seed);
226 inline uint64_t hash_33to64_bytes(const char *s, size_t len, uint64_t seed) {
227 uint64_t z = fetch64(s + 24);
228 uint64_t a = fetch64(s) + (len + fetch64(s + len - 16)) * k0;
229 uint64_t b = rotate(a + z, 52);
230 uint64_t c = rotate(a, 37);
233 a += fetch64(s + 16);
235 uint64_t vs = b + rotate(a, 31) + c;
236 a = fetch64(s + 16) + fetch64(s + len - 32);
237 z = fetch64(s + len - 8);
238 b = rotate(a + z, 52);
240 a += fetch64(s + len - 24);
242 a += fetch64(s + len - 16);
244 uint64_t ws = b + rotate(a, 31) + c;
245 uint64_t r = shift_mix((vf + ws) * k2 + (wf + vs) * k0);
246 return shift_mix((seed ^ (r * k0)) + vs) * k2;
249 inline uint64_t hash_short(const char *s, size_t length, uint64_t seed) {
250 if (length >= 4 && length <= 8)
251 return hash_4to8_bytes(s, length, seed);
252 if (length > 8 && length <= 16)
253 return hash_9to16_bytes(s, length, seed);
254 if (length > 16 && length <= 32)
255 return hash_17to32_bytes(s, length, seed);
257 return hash_33to64_bytes(s, length, seed);
259 return hash_1to3_bytes(s, length, seed);
264 /// \brief The intermediate state used during hashing.
265 /// Currently, the algorithm for computing hash codes is based on CityHash and
266 /// keeps 56 bytes of arbitrary state.
268 uint64_t h0, h1, h2, h3, h4, h5, h6;
271 /// \brief Create a new hash_state structure and initialize it based on the
272 /// seed and the first 64-byte chunk.
273 /// This effectively performs the initial mix.
274 static hash_state create(const char *s, uint64_t seed) {
276 0, seed, hash_16_bytes(seed, k1), rotate(seed ^ k1, 49),
277 seed * k1, shift_mix(seed), 0, seed };
278 state.h6 = hash_16_bytes(state.h4, state.h5);
283 /// \brief Mix 32-bytes from the input sequence into the 16-bytes of 'a'
284 /// and 'b', including whatever is already in 'a' and 'b'.
285 static void mix_32_bytes(const char *s, uint64_t &a, uint64_t &b) {
287 uint64_t c = fetch64(s + 24);
288 b = rotate(b + a + c, 21);
290 a += fetch64(s + 8) + fetch64(s + 16);
291 b += rotate(a, 44) + d;
295 /// \brief Mix in a 64-byte buffer of data.
296 /// We mix all 64 bytes even when the chunk length is smaller, but we
297 /// record the actual length.
298 void mix(const char *s) {
299 h0 = rotate(h0 + h1 + h3 + fetch64(s + 8), 37) * k1;
300 h1 = rotate(h1 + h4 + fetch64(s + 48), 42) * k1;
302 h1 += h3 + fetch64(s + 40);
303 h2 = rotate(h2 + h5, 33) * k1;
306 mix_32_bytes(s, h3, h4);
308 h6 = h1 + fetch64(s + 16);
309 mix_32_bytes(s + 32, h5, h6);
313 /// \brief Compute the final 64-bit hash code value based on the current
314 /// state and the length of bytes hashed.
315 uint64_t finalize(size_t length) {
316 return hash_16_bytes(hash_16_bytes(h3, h5) + shift_mix(h1) * k1 + h2,
317 hash_16_bytes(h4, h6) + shift_mix(length) * k1 + h0);
322 /// \brief A global, fixed seed-override variable.
324 /// This variable can be set using the \see llvm::set_fixed_execution_seed
325 /// function. See that function for details. Do not, under any circumstances,
326 /// set or read this variable.
327 extern size_t fixed_seed_override;
329 inline size_t get_execution_seed() {
330 // FIXME: This needs to be a per-execution seed. This is just a placeholder
331 // implementation. Switching to a per-execution seed is likely to flush out
332 // instability bugs and so will happen as its own commit.
334 // However, if there is a fixed seed override set the first time this is
335 // called, return that instead of the per-execution seed.
336 const uint64_t seed_prime = 0xff51afd7ed558ccdULL;
337 static size_t seed = fixed_seed_override ? fixed_seed_override
338 : (size_t)seed_prime;
343 /// \brief Trait to indicate whether a type's bits can be hashed directly.
345 /// A type trait which is true if we want to combine values for hashing by
346 /// reading the underlying data. It is false if values of this type must
347 /// first be passed to hash_value, and the resulting hash_codes combined.
349 // FIXME: We want to replace is_integral_or_enum and is_pointer here with
350 // a predicate which asserts that comparing the underlying storage of two
351 // values of the type for equality is equivalent to comparing the two values
352 // for equality. For all the platforms we care about, this holds for integers
353 // and pointers, but there are platforms where it doesn't and we would like to
354 // support user-defined types which happen to satisfy this property.
355 template <typename T> struct is_hashable_data
356 : std::integral_constant<bool, ((is_integral_or_enum<T>::value ||
357 std::is_pointer<T>::value) &&
358 64 % sizeof(T) == 0)> {};
360 // Special case std::pair to detect when both types are viable and when there
361 // is no alignment-derived padding in the pair. This is a bit of a lie because
362 // std::pair isn't truly POD, but it's close enough in all reasonable
363 // implementations for our use case of hashing the underlying data.
364 template <typename T, typename U> struct is_hashable_data<std::pair<T, U> >
365 : std::integral_constant<bool, (is_hashable_data<T>::value &&
366 is_hashable_data<U>::value &&
367 (sizeof(T) + sizeof(U)) ==
368 sizeof(std::pair<T, U>))> {};
370 /// \brief Helper to get the hashable data representation for a type.
371 /// This variant is enabled when the type itself can be used.
372 template <typename T>
373 typename std::enable_if<is_hashable_data<T>::value, T>::type
374 get_hashable_data(const T &value) {
377 /// \brief Helper to get the hashable data representation for a type.
378 /// This variant is enabled when we must first call hash_value and use the
379 /// result as our data.
380 template <typename T>
381 typename std::enable_if<!is_hashable_data<T>::value, size_t>::type
382 get_hashable_data(const T &value) {
383 using ::llvm::hash_value;
384 return hash_value(value);
387 /// \brief Helper to store data from a value into a buffer and advance the
388 /// pointer into that buffer.
390 /// This routine first checks whether there is enough space in the provided
391 /// buffer, and if not immediately returns false. If there is space, it
392 /// copies the underlying bytes of value into the buffer, advances the
393 /// buffer_ptr past the copied bytes, and returns true.
394 template <typename T>
395 bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value,
397 size_t store_size = sizeof(value) - offset;
398 if (buffer_ptr + store_size > buffer_end)
400 const char *value_data = reinterpret_cast<const char *>(&value);
401 memcpy(buffer_ptr, value_data + offset, store_size);
402 buffer_ptr += store_size;
406 /// \brief Implement the combining of integral values into a hash_code.
408 /// This overload is selected when the value type of the iterator is
409 /// integral. Rather than computing a hash_code for each object and then
410 /// combining them, this (as an optimization) directly combines the integers.
411 template <typename InputIteratorT>
412 hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) {
413 const size_t seed = get_execution_seed();
414 char buffer[64], *buffer_ptr = buffer;
415 char *const buffer_end = buffer_ptr + array_lengthof(buffer);
416 while (first != last && store_and_advance(buffer_ptr, buffer_end,
417 get_hashable_data(*first)))
420 return hash_short(buffer, buffer_ptr - buffer, seed);
421 assert(buffer_ptr == buffer_end);
423 hash_state state = state.create(buffer, seed);
425 while (first != last) {
426 // Fill up the buffer. We don't clear it, which re-mixes the last round
427 // when only a partial 64-byte chunk is left.
429 while (first != last && store_and_advance(buffer_ptr, buffer_end,
430 get_hashable_data(*first)))
433 // Rotate the buffer if we did a partial fill in order to simulate doing
434 // a mix of the last 64-bytes. That is how the algorithm works when we
435 // have a contiguous byte sequence, and we want to emulate that here.
436 std::rotate(buffer, buffer_ptr, buffer_end);
438 // Mix this chunk into the current state.
440 length += buffer_ptr - buffer;
443 return state.finalize(length);
446 /// \brief Implement the combining of integral values into a hash_code.
448 /// This overload is selected when the value type of the iterator is integral
449 /// and when the input iterator is actually a pointer. Rather than computing
450 /// a hash_code for each object and then combining them, this (as an
451 /// optimization) directly combines the integers. Also, because the integers
452 /// are stored in contiguous memory, this routine avoids copying each value
453 /// and directly reads from the underlying memory.
454 template <typename ValueT>
455 typename std::enable_if<is_hashable_data<ValueT>::value, hash_code>::type
456 hash_combine_range_impl(ValueT *first, ValueT *last) {
457 const size_t seed = get_execution_seed();
458 const char *s_begin = reinterpret_cast<const char *>(first);
459 const char *s_end = reinterpret_cast<const char *>(last);
460 const size_t length = std::distance(s_begin, s_end);
462 return hash_short(s_begin, length, seed);
464 const char *s_aligned_end = s_begin + (length & ~63);
465 hash_state state = state.create(s_begin, seed);
467 while (s_begin != s_aligned_end) {
472 state.mix(s_end - 64);
474 return state.finalize(length);
477 } // namespace detail
478 } // namespace hashing
481 /// \brief Compute a hash_code for a sequence of values.
483 /// This hashes a sequence of values. It produces the same hash_code as
484 /// 'hash_combine(a, b, c, ...)', but can run over arbitrary sized sequences
485 /// and is significantly faster given pointers and types which can be hashed as
486 /// a sequence of bytes.
487 template <typename InputIteratorT>
488 hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) {
489 return ::llvm::hashing::detail::hash_combine_range_impl(first, last);
493 // Implementation details for hash_combine.
497 /// \brief Helper class to manage the recursive combining of hash_combine
500 /// This class exists to manage the state and various calls involved in the
501 /// recursive combining of arguments used in hash_combine. It is particularly
502 /// useful at minimizing the code in the recursive calls to ease the pain
503 /// caused by a lack of variadic functions.
504 struct hash_combine_recursive_helper {
510 /// \brief Construct a recursive hash combining helper.
512 /// This sets up the state for a recursive hash combine, including getting
513 /// the seed and buffer setup.
514 hash_combine_recursive_helper()
515 : seed(get_execution_seed()) {}
517 /// \brief Combine one chunk of data into the current in-flight hash.
519 /// This merges one chunk of data into the hash. First it tries to buffer
520 /// the data. If the buffer is full, it hashes the buffer into its
521 /// hash_state, empties it, and then merges the new chunk in. This also
522 /// handles cases where the data straddles the end of the buffer.
523 template <typename T>
524 char *combine_data(size_t &length, char *buffer_ptr, char *buffer_end, T data) {
525 if (!store_and_advance(buffer_ptr, buffer_end, data)) {
526 // Check for skew which prevents the buffer from being packed, and do
527 // a partial store into the buffer to fill it. This is only a concern
528 // with the variadic combine because that formation can have varying
530 size_t partial_store_size = buffer_end - buffer_ptr;
531 memcpy(buffer_ptr, &data, partial_store_size);
533 // If the store fails, our buffer is full and ready to hash. We have to
534 // either initialize the hash state (on the first full buffer) or mix
535 // this buffer into the existing hash state. Length tracks the *hashed*
536 // length, not the buffered length.
538 state = state.create(buffer, seed);
541 // Mix this chunk into the current state and bump length up by 64.
545 // Reset the buffer_ptr to the head of the buffer for the next chunk of
549 // Try again to store into the buffer -- this cannot fail as we only
550 // store types smaller than the buffer.
551 if (!store_and_advance(buffer_ptr, buffer_end, data,
558 #if defined(__has_feature) && __has_feature(__cxx_variadic_templates__)
560 /// \brief Recursive, variadic combining method.
562 /// This function recurses through each argument, combining that argument
563 /// into a single hash.
564 template <typename T, typename ...Ts>
565 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
566 const T &arg, const Ts &...args) {
567 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg));
569 // Recurse to the next argument.
570 return combine(length, buffer_ptr, buffer_end, args...);
574 // Manually expanded recursive combining methods. See variadic above for
577 template <typename T1, typename T2, typename T3, typename T4, typename T5,
579 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
580 const T1 &arg1, const T2 &arg2, const T3 &arg3,
581 const T4 &arg4, const T5 &arg5, const T6 &arg6) {
582 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
583 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4, arg5, arg6);
585 template <typename T1, typename T2, typename T3, typename T4, typename T5>
586 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
587 const T1 &arg1, const T2 &arg2, const T3 &arg3,
588 const T4 &arg4, const T5 &arg5) {
589 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
590 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4, arg5);
592 template <typename T1, typename T2, typename T3, typename T4>
593 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
594 const T1 &arg1, const T2 &arg2, const T3 &arg3,
596 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
597 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4);
599 template <typename T1, typename T2, typename T3>
600 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
601 const T1 &arg1, const T2 &arg2, const T3 &arg3) {
602 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
603 return combine(length, buffer_ptr, buffer_end, arg2, arg3);
605 template <typename T1, typename T2>
606 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
607 const T1 &arg1, const T2 &arg2) {
608 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
609 return combine(length, buffer_ptr, buffer_end, arg2);
611 template <typename T1>
612 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
614 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
615 return combine(length, buffer_ptr, buffer_end);
620 /// \brief Base case for recursive, variadic combining.
622 /// The base case when combining arguments recursively is reached when all
623 /// arguments have been handled. It flushes the remaining buffer and
624 /// constructs a hash_code.
625 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end) {
626 // Check whether the entire set of values fit in the buffer. If so, we'll
627 // use the optimized short hashing routine and skip state entirely.
629 return hash_short(buffer, buffer_ptr - buffer, seed);
631 // Mix the final buffer, rotating it if we did a partial fill in order to
632 // simulate doing a mix of the last 64-bytes. That is how the algorithm
633 // works when we have a contiguous byte sequence, and we want to emulate
635 std::rotate(buffer, buffer_ptr, buffer_end);
637 // Mix this chunk into the current state.
639 length += buffer_ptr - buffer;
641 return state.finalize(length);
645 } // namespace detail
646 } // namespace hashing
649 #if __has_feature(__cxx_variadic_templates__)
651 /// \brief Combine values into a single hash_code.
653 /// This routine accepts a varying number of arguments of any type. It will
654 /// attempt to combine them into a single hash_code. For user-defined types it
655 /// attempts to call a \see hash_value overload (via ADL) for the type. For
656 /// integer and pointer types it directly combines their data into the
657 /// resulting hash_code.
659 /// The result is suitable for returning from a user's hash_value
660 /// *implementation* for their user-defined type. Consumers of a type should
661 /// *not* call this routine, they should instead call 'hash_value'.
662 template <typename ...Ts> hash_code hash_combine(const Ts &...args) {
663 // Recursively hash each argument using a helper class.
664 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
665 return helper.combine(0, helper.buffer, helper.buffer + 64, args...);
670 // What follows are manually exploded overloads for each argument width. See
671 // the above variadic definition for documentation and specification.
673 template <typename T1, typename T2, typename T3, typename T4, typename T5,
675 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
676 const T4 &arg4, const T5 &arg5, const T6 &arg6) {
677 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
678 return helper.combine(0, helper.buffer, helper.buffer + 64,
679 arg1, arg2, arg3, arg4, arg5, arg6);
681 template <typename T1, typename T2, typename T3, typename T4, typename T5>
682 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
683 const T4 &arg4, const T5 &arg5) {
684 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
685 return helper.combine(0, helper.buffer, helper.buffer + 64,
686 arg1, arg2, arg3, arg4, arg5);
688 template <typename T1, typename T2, typename T3, typename T4>
689 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
691 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
692 return helper.combine(0, helper.buffer, helper.buffer + 64,
693 arg1, arg2, arg3, arg4);
695 template <typename T1, typename T2, typename T3>
696 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3) {
697 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
698 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1, arg2, arg3);
700 template <typename T1, typename T2>
701 hash_code hash_combine(const T1 &arg1, const T2 &arg2) {
702 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
703 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1, arg2);
705 template <typename T1>
706 hash_code hash_combine(const T1 &arg1) {
707 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
708 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1);
714 // Implementation details for implementations of hash_value overloads provided
719 /// \brief Helper to hash the value of a single integer.
721 /// Overloads for smaller integer types are not provided to ensure consistent
722 /// behavior in the presence of integral promotions. Essentially,
723 /// "hash_value('4')" and "hash_value('0' + 4)" should be the same.
724 inline hash_code hash_integer_value(uint64_t value) {
725 // Similar to hash_4to8_bytes but using a seed instead of length.
726 const uint64_t seed = get_execution_seed();
727 const char *s = reinterpret_cast<const char *>(&value);
728 const uint64_t a = fetch32(s);
729 return hash_16_bytes(seed + (a << 3), fetch32(s + 4));
732 } // namespace detail
733 } // namespace hashing
735 // Declared and documented above, but defined here so that any of the hashing
736 // infrastructure is available.
737 template <typename T>
738 typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
739 hash_value(T value) {
740 return ::llvm::hashing::detail::hash_integer_value(value);
743 // Declared and documented above, but defined here so that any of the hashing
744 // infrastructure is available.
745 template <typename T> hash_code hash_value(const T *ptr) {
746 return ::llvm::hashing::detail::hash_integer_value(
747 reinterpret_cast<uintptr_t>(ptr));
750 // Declared and documented above, but defined here so that any of the hashing
751 // infrastructure is available.
752 template <typename T, typename U>
753 hash_code hash_value(const std::pair<T, U> &arg) {
754 return hash_combine(arg.first, arg.second);
757 // Declared and documented above, but defined here so that any of the hashing
758 // infrastructure is available.
759 template <typename T>
760 hash_code hash_value(const std::basic_string<T> &arg) {
761 return hash_combine_range(arg.begin(), arg.end());