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 enable_if<is_integral_or_enum<T>, hash_code>::type hash_value(T value);
114 /// \brief Compute a hash_code for a pointer's address.
116 /// N.B.: This hashes the *address*. Not the value and not the type.
117 template <typename T> hash_code hash_value(const T *ptr);
119 /// \brief Compute a hash_code for a pair of objects.
120 template <typename T, typename U>
121 hash_code hash_value(const std::pair<T, U> &arg);
123 /// \brief Compute a hash_code for a standard string.
124 template <typename T>
125 hash_code hash_value(const std::basic_string<T> &arg);
128 /// \brief Override the execution seed with a fixed value.
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.
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
142 void set_fixed_execution_hash_seed(size_t fixed_value);
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.
151 inline uint64_t fetch64(const char *p) {
153 memcpy(&result, p, sizeof(result));
154 if (sys::isBigEndianHost())
155 return sys::SwapByteOrder(result);
159 inline uint32_t fetch32(const char *p) {
161 memcpy(&result, p, sizeof(result));
162 if (sys::isBigEndianHost())
163 return sys::SwapByteOrder(result);
167 /// Some primes between 2^63 and 2^64 for various uses.
168 static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
169 static const uint64_t k1 = 0xb492b66fbe98f273ULL;
170 static const uint64_t k2 = 0x9ae16a3b2f90404fULL;
171 static const uint64_t k3 = 0xc949d7c7509e6557ULL;
173 /// \brief Bitwise right rotate.
174 /// Normally this will compile to a single instruction, especially if the
175 /// shift is a manifest constant.
176 inline 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)));
181 inline uint64_t shift_mix(uint64_t val) {
182 return val ^ (val >> 47);
185 inline 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;
190 uint64_t b = (high ^ a) * kMul;
196 inline uint64_t hash_1to3_bytes(const char *s, size_t len, uint64_t seed) {
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;
205 inline 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));
210 inline 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;
216 inline 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);
225 inline 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);
232 a += fetch64(s + 16);
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);
239 a += fetch64(s + len - 24);
241 a += fetch64(s + len - 16);
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;
248 inline 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);
256 return hash_33to64_bytes(s, length, seed);
258 return hash_1to3_bytes(s, length, seed);
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.
267 uint64_t h0, h1, h2, h3, h4, h5, h6;
270 /// \brief Create a new hash_state structure and initialize it based on the
271 /// seed and the first 64-byte chunk.
272 /// This effectively performs the initial mix.
273 static hash_state create(const char *s, uint64_t seed) {
275 0, seed, hash_16_bytes(seed, k1), rotate(seed ^ k1, 49),
276 seed * k1, shift_mix(seed), 0, seed };
277 state.h6 = hash_16_bytes(state.h4, state.h5);
282 /// \brief Mix 32-bytes from the input sequence into the 16-bytes of 'a'
283 /// and 'b', including whatever is already in 'a' and 'b'.
284 static void mix_32_bytes(const char *s, uint64_t &a, uint64_t &b) {
286 uint64_t c = fetch64(s + 24);
287 b = rotate(b + a + c, 21);
289 a += fetch64(s + 8) + fetch64(s + 16);
290 b += rotate(a, 44) + d;
294 /// \brief Mix in a 64-byte buffer of data.
295 /// We mix all 64 bytes even when the chunk length is smaller, but we
296 /// record the actual length.
297 void mix(const char *s) {
298 h0 = rotate(h0 + h1 + h3 + fetch64(s + 8), 37) * k1;
299 h1 = rotate(h1 + h4 + fetch64(s + 48), 42) * k1;
301 h1 += h3 + fetch64(s + 40);
302 h2 = rotate(h2 + h5, 33) * k1;
305 mix_32_bytes(s, h3, h4);
307 h6 = h1 + fetch64(s + 16);
308 mix_32_bytes(s + 32, h5, h6);
312 /// \brief Compute the final 64-bit hash code value based on the current
313 /// state and the length of bytes hashed.
314 uint64_t finalize(size_t length) {
315 return hash_16_bytes(hash_16_bytes(h3, h5) + shift_mix(h1) * k1 + h2,
316 hash_16_bytes(h4, h6) + shift_mix(length) * k1 + h0);
321 /// \brief A global, fixed seed-override variable.
323 /// This variable can be set using the \see llvm::set_fixed_execution_seed
324 /// function. See that function for details. Do not, under any circumstances,
325 /// set or read this variable.
326 extern size_t fixed_seed_override;
328 inline size_t get_execution_seed() {
329 // FIXME: This needs to be a per-execution seed. This is just a placeholder
330 // implementation. Switching to a per-execution seed is likely to flush out
331 // instability bugs and so will happen as its own commit.
333 // However, if there is a fixed seed override set the first time this is
334 // called, return that instead of the per-execution seed.
335 const uint64_t seed_prime = 0xff51afd7ed558ccdULL;
336 static size_t seed = fixed_seed_override ? fixed_seed_override
337 : (size_t)seed_prime;
342 /// \brief Trait to indicate whether a type's bits can be hashed directly.
344 /// A type trait which is true if we want to combine values for hashing by
345 /// reading the underlying data. It is false if values of this type must
346 /// first be passed to hash_value, and the resulting hash_codes combined.
348 // FIXME: We want to replace is_integral_or_enum and is_pointer here with
349 // a predicate which asserts that comparing the underlying storage of two
350 // values of the type for equality is equivalent to comparing the two values
351 // for equality. For all the platforms we care about, this holds for integers
352 // and pointers, but there are platforms where it doesn't and we would like to
353 // support user-defined types which happen to satisfy this property.
354 template <typename T> struct is_hashable_data
355 : integral_constant<bool, ((is_integral_or_enum<T>::value ||
356 is_pointer<T>::value) &&
357 64 % sizeof(T) == 0)> {};
359 // Special case std::pair to detect when both types are viable and when there
360 // is no alignment-derived padding in the pair. This is a bit of a lie because
361 // std::pair isn't truly POD, but it's close enough in all reasonable
362 // implementations for our use case of hashing the underlying data.
363 template <typename T, typename U> struct is_hashable_data<std::pair<T, U> >
364 : integral_constant<bool, (is_hashable_data<T>::value &&
365 is_hashable_data<U>::value &&
366 (sizeof(T) + sizeof(U)) ==
367 sizeof(std::pair<T, U>))> {};
369 /// \brief Helper to get the hashable data representation for a type.
370 /// This variant is enabled when the type itself can be used.
371 template <typename T>
372 typename enable_if<is_hashable_data<T>, T>::type
373 get_hashable_data(const T &value) {
376 /// \brief Helper to get the hashable data representation for a type.
377 /// This variant is enabled when we must first call hash_value and use the
378 /// result as our data.
379 template <typename T>
380 typename enable_if_c<!is_hashable_data<T>::value, size_t>::type
381 get_hashable_data(const T &value) {
382 using ::llvm::hash_value;
383 return hash_value(value);
386 /// \brief Helper to store data from a value into a buffer and advance the
387 /// pointer into that buffer.
389 /// This routine first checks whether there is enough space in the provided
390 /// buffer, and if not immediately returns false. If there is space, it
391 /// copies the underlying bytes of value into the buffer, advances the
392 /// buffer_ptr past the copied bytes, and returns true.
393 template <typename T>
394 bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value,
396 size_t store_size = sizeof(value) - offset;
397 if (buffer_ptr + store_size > buffer_end)
399 const char *value_data = reinterpret_cast<const char *>(&value);
400 memcpy(buffer_ptr, value_data + offset, store_size);
401 buffer_ptr += store_size;
405 /// \brief Implement the combining of integral values into a hash_code.
407 /// This overload is selected when the value type of the iterator is
408 /// integral. Rather than computing a hash_code for each object and then
409 /// combining them, this (as an optimization) directly combines the integers.
410 template <typename InputIteratorT>
411 hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) {
412 const size_t seed = get_execution_seed();
413 char buffer[64], *buffer_ptr = buffer;
414 char *const buffer_end = buffer_ptr + array_lengthof(buffer);
415 while (first != last && store_and_advance(buffer_ptr, buffer_end,
416 get_hashable_data(*first)))
419 return hash_short(buffer, buffer_ptr - buffer, seed);
420 assert(buffer_ptr == buffer_end);
422 hash_state state = state.create(buffer, seed);
424 while (first != last) {
425 // Fill up the buffer. We don't clear it, which re-mixes the last round
426 // when only a partial 64-byte chunk is left.
428 while (first != last && store_and_advance(buffer_ptr, buffer_end,
429 get_hashable_data(*first)))
432 // Rotate the buffer if we did a partial fill in order to simulate doing
433 // a mix of the last 64-bytes. That is how the algorithm works when we
434 // have a contiguous byte sequence, and we want to emulate that here.
435 std::rotate(buffer, buffer_ptr, buffer_end);
437 // Mix this chunk into the current state.
439 length += buffer_ptr - buffer;
442 return state.finalize(length);
445 /// \brief Implement the combining of integral values into a hash_code.
447 /// This overload is selected when the value type of the iterator is integral
448 /// and when the input iterator is actually a pointer. Rather than computing
449 /// a hash_code for each object and then combining them, this (as an
450 /// optimization) directly combines the integers. Also, because the integers
451 /// are stored in contiguous memory, this routine avoids copying each value
452 /// and directly reads from the underlying memory.
453 template <typename ValueT>
454 typename enable_if<is_hashable_data<ValueT>, hash_code>::type
455 hash_combine_range_impl(ValueT *first, ValueT *last) {
456 const size_t seed = get_execution_seed();
457 const char *s_begin = reinterpret_cast<const char *>(first);
458 const char *s_end = reinterpret_cast<const char *>(last);
459 const size_t length = std::distance(s_begin, s_end);
461 return hash_short(s_begin, length, seed);
463 const char *s_aligned_end = s_begin + (length & ~63);
464 hash_state state = state.create(s_begin, seed);
466 while (s_begin != s_aligned_end) {
471 state.mix(s_end - 64);
473 return state.finalize(length);
476 } // namespace detail
477 } // namespace hashing
480 /// \brief Compute a hash_code for a sequence of values.
482 /// This hashes a sequence of values. It produces the same hash_code as
483 /// 'hash_combine(a, b, c, ...)', but can run over arbitrary sized sequences
484 /// and is significantly faster given pointers and types which can be hashed as
485 /// a sequence of bytes.
486 template <typename InputIteratorT>
487 hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) {
488 return ::llvm::hashing::detail::hash_combine_range_impl(first, last);
492 // Implementation details for hash_combine.
496 /// \brief Helper class to manage the recursive combining of hash_combine
499 /// This class exists to manage the state and various calls involved in the
500 /// recursive combining of arguments used in hash_combine. It is particularly
501 /// useful at minimizing the code in the recursive calls to ease the pain
502 /// caused by a lack of variadic functions.
503 struct hash_combine_recursive_helper {
509 /// \brief Construct a recursive hash combining helper.
511 /// This sets up the state for a recursive hash combine, including getting
512 /// the seed and buffer setup.
513 hash_combine_recursive_helper()
514 : seed(get_execution_seed()) {}
516 /// \brief Combine one chunk of data into the current in-flight hash.
518 /// This merges one chunk of data into the hash. First it tries to buffer
519 /// the data. If the buffer is full, it hashes the buffer into its
520 /// hash_state, empties it, and then merges the new chunk in. This also
521 /// handles cases where the data straddles the end of the buffer.
522 template <typename T>
523 char *combine_data(size_t &length, char *buffer_ptr, char *buffer_end, T data) {
524 if (!store_and_advance(buffer_ptr, buffer_end, data)) {
525 // Check for skew which prevents the buffer from being packed, and do
526 // a partial store into the buffer to fill it. This is only a concern
527 // with the variadic combine because that formation can have varying
529 size_t partial_store_size = buffer_end - buffer_ptr;
530 memcpy(buffer_ptr, &data, partial_store_size);
532 // If the store fails, our buffer is full and ready to hash. We have to
533 // either initialize the hash state (on the first full buffer) or mix
534 // this buffer into the existing hash state. Length tracks the *hashed*
535 // length, not the buffered length.
537 state = state.create(buffer, seed);
540 // Mix this chunk into the current state and bump length up by 64.
544 // Reset the buffer_ptr to the head of the buffer for the next chunk of
548 // Try again to store into the buffer -- this cannot fail as we only
549 // store types smaller than the buffer.
550 if (!store_and_advance(buffer_ptr, buffer_end, data,
557 #if defined(__has_feature) && __has_feature(__cxx_variadic_templates__)
559 /// \brief Recursive, variadic combining method.
561 /// This function recurses through each argument, combining that argument
562 /// into a single hash.
563 template <typename T, typename ...Ts>
564 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
565 const T &arg, const Ts &...args) {
566 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg));
568 // Recurse to the next argument.
569 return combine(length, buffer_ptr, buffer_end, args...);
573 // Manually expanded recursive combining methods. See variadic above for
576 template <typename T1, typename T2, typename T3, typename T4, typename T5,
578 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
579 const T1 &arg1, const T2 &arg2, const T3 &arg3,
580 const T4 &arg4, const T5 &arg5, const T6 &arg6) {
581 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
582 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4, arg5, arg6);
584 template <typename T1, typename T2, typename T3, typename T4, typename T5>
585 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
586 const T1 &arg1, const T2 &arg2, const T3 &arg3,
587 const T4 &arg4, const T5 &arg5) {
588 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
589 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4, arg5);
591 template <typename T1, typename T2, typename T3, typename T4>
592 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
593 const T1 &arg1, const T2 &arg2, const T3 &arg3,
595 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
596 return combine(length, buffer_ptr, buffer_end, arg2, arg3, arg4);
598 template <typename T1, typename T2, typename T3>
599 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
600 const T1 &arg1, const T2 &arg2, const T3 &arg3) {
601 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
602 return combine(length, buffer_ptr, buffer_end, arg2, arg3);
604 template <typename T1, typename T2>
605 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
606 const T1 &arg1, const T2 &arg2) {
607 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
608 return combine(length, buffer_ptr, buffer_end, arg2);
610 template <typename T1>
611 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
613 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
614 return combine(length, buffer_ptr, buffer_end);
619 /// \brief Base case for recursive, variadic combining.
621 /// The base case when combining arguments recursively is reached when all
622 /// arguments have been handled. It flushes the remaining buffer and
623 /// constructs a hash_code.
624 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end) {
625 // Check whether the entire set of values fit in the buffer. If so, we'll
626 // use the optimized short hashing routine and skip state entirely.
628 return hash_short(buffer, buffer_ptr - buffer, seed);
630 // Mix the final buffer, rotating it if we did a partial fill in order to
631 // simulate doing a mix of the last 64-bytes. That is how the algorithm
632 // works when we have a contiguous byte sequence, and we want to emulate
634 std::rotate(buffer, buffer_ptr, buffer_end);
636 // Mix this chunk into the current state.
638 length += buffer_ptr - buffer;
640 return state.finalize(length);
644 } // namespace detail
645 } // namespace hashing
648 #if __has_feature(__cxx_variadic_templates__)
650 /// \brief Combine values into a single hash_code.
652 /// This routine accepts a varying number of arguments of any type. It will
653 /// attempt to combine them into a single hash_code. For user-defined types it
654 /// attempts to call a \see hash_value overload (via ADL) for the type. For
655 /// integer and pointer types it directly combines their data into the
656 /// resulting hash_code.
658 /// The result is suitable for returning from a user's hash_value
659 /// *implementation* for their user-defined type. Consumers of a type should
660 /// *not* call this routine, they should instead call 'hash_value'.
661 template <typename ...Ts> hash_code hash_combine(const Ts &...args) {
662 // Recursively hash each argument using a helper class.
663 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
664 return helper.combine(0, helper.buffer, helper.buffer + 64, args...);
669 // What follows are manually exploded overloads for each argument width. See
670 // the above variadic definition for documentation and specification.
672 template <typename T1, typename T2, typename T3, typename T4, typename T5,
674 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
675 const T4 &arg4, const T5 &arg5, const T6 &arg6) {
676 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
677 return helper.combine(0, helper.buffer, helper.buffer + 64,
678 arg1, arg2, arg3, arg4, arg5, arg6);
680 template <typename T1, typename T2, typename T3, typename T4, typename T5>
681 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
682 const T4 &arg4, const T5 &arg5) {
683 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
684 return helper.combine(0, helper.buffer, helper.buffer + 64,
685 arg1, arg2, arg3, arg4, arg5);
687 template <typename T1, typename T2, typename T3, typename T4>
688 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
690 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
691 return helper.combine(0, helper.buffer, helper.buffer + 64,
692 arg1, arg2, arg3, arg4);
694 template <typename T1, typename T2, typename T3>
695 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3) {
696 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
697 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1, arg2, arg3);
699 template <typename T1, typename T2>
700 hash_code hash_combine(const T1 &arg1, const T2 &arg2) {
701 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
702 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1, arg2);
704 template <typename T1>
705 hash_code hash_combine(const T1 &arg1) {
706 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
707 return helper.combine(0, helper.buffer, helper.buffer + 64, arg1);
713 // Implementation details for implementations of hash_value overloads provided
718 /// \brief Helper to hash the value of a single integer.
720 /// Overloads for smaller integer types are not provided to ensure consistent
721 /// behavior in the presence of integral promotions. Essentially,
722 /// "hash_value('4')" and "hash_value('0' + 4)" should be the same.
723 inline hash_code hash_integer_value(uint64_t value) {
724 // Similar to hash_4to8_bytes but using a seed instead of length.
725 const uint64_t seed = get_execution_seed();
726 const char *s = reinterpret_cast<const char *>(&value);
727 const uint64_t a = fetch32(s);
728 return hash_16_bytes(seed + (a << 3), fetch32(s + 4));
731 } // namespace detail
732 } // namespace hashing
734 // Declared and documented above, but defined here so that any of the hashing
735 // infrastructure is available.
736 template <typename T>
737 typename enable_if<is_integral_or_enum<T>, hash_code>::type
738 hash_value(T value) {
739 return ::llvm::hashing::detail::hash_integer_value(value);
742 // Declared and documented above, but defined here so that any of the hashing
743 // infrastructure is available.
744 template <typename T> hash_code hash_value(const T *ptr) {
745 return ::llvm::hashing::detail::hash_integer_value(
746 reinterpret_cast<uintptr_t>(ptr));
749 // Declared and documented above, but defined here so that any of the hashing
750 // infrastructure is available.
751 template <typename T, typename U>
752 hash_code hash_value(const std::pair<T, U> &arg) {
753 return hash_combine(arg.first, arg.second);
756 // Declared and documented above, but defined here so that any of the hashing
757 // infrastructure is available.
758 template <typename T>
759 hash_code hash_value(const std::basic_string<T> &arg) {
760 return hash_combine_range(arg.begin(), arg.end());