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/Support/DataTypes.h"
49 #include "llvm/Support/Host.h"
50 #include "llvm/Support/SwapByteOrder.h"
51 #include "llvm/Support/type_traits.h"
58 // Allow detecting C++11 feature availability when building with Clang without
59 // breaking other compilers.
61 # define __has_feature(x) 0
66 /// \brief An opaque object representing a hash code.
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.
73 /// In order to obtain the hash_code for an object 'x':
75 /// using llvm::hash_value;
76 /// llvm::hash_code code = hash_value(x);
82 /// \brief Default construct a hash_code.
83 /// Note that this leaves the value uninitialized.
86 /// \brief Form a hash code directly from a numerical value.
87 hash_code(size_t value) : value(value) {}
89 /// \brief Convert the hash code to its numerical value for use.
90 /*explicit*/ operator size_t() const { return value; }
92 friend bool operator==(const hash_code &lhs, const hash_code &rhs) {
93 return lhs.value == rhs.value;
95 friend bool operator!=(const hash_code &lhs, const hash_code &rhs) {
96 return lhs.value != rhs.value;
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; }
103 /// \brief Compute a hash_code for any integer value.
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.
110 template <typename T>
111 typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
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 sys::swapByteOrder(result);
159 inline uint32_t fetch32(const char *p) {
161 memcpy(&result, p, sizeof(result));
162 if (sys::IsBigEndianHost)
163 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;
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) {
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);
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) {
285 uint64_t c = fetch64(s + 24);
286 b = rotate(b + a + c, 21);
288 a += fetch64(s + 8) + fetch64(s + 16);
289 b += rotate(a, 44) + d;
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;
300 h1 += h3 + fetch64(s + 40);
301 h2 = rotate(h2 + h5, 33) * k1;
304 mix_32_bytes(s, h3, h4);
306 h6 = h1 + fetch64(s + 16);
307 mix_32_bytes(s + 32, h5, h6);
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);
320 /// \brief A global, fixed seed-override variable.
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.
325 extern size_t fixed_seed_override;
327 inline 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.
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;
341 /// \brief Trait to indicate whether a type's bits can be hashed directly.
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.
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.
353 template <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)> {};
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.
362 template <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>))> {};
368 /// \brief Helper to get the hashable data representation for a type.
369 /// This variant is enabled when the type itself can be used.
370 template <typename T>
371 typename std::enable_if<is_hashable_data<T>::value, T>::type
372 get_hashable_data(const T &value) {
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.
378 template <typename T>
379 typename std::enable_if<!is_hashable_data<T>::value, size_t>::type
380 get_hashable_data(const T &value) {
381 using ::llvm::hash_value;
382 return hash_value(value);
385 /// \brief Helper to store data from a value into a buffer and advance the
386 /// pointer into that buffer.
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.
392 template <typename T>
393 bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value,
395 size_t store_size = sizeof(value) - offset;
396 if (buffer_ptr + store_size > buffer_end)
398 const char *value_data = reinterpret_cast<const char *>(&value);
399 memcpy(buffer_ptr, value_data + offset, store_size);
400 buffer_ptr += store_size;
404 /// \brief Implement the combining of integral values into a hash_code.
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.
409 template <typename InputIteratorT>
410 hash_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)))
418 return hash_short(buffer, buffer_ptr - buffer, seed);
419 assert(buffer_ptr == buffer_end);
421 hash_state state = state.create(buffer, seed);
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.
427 while (first != last && store_and_advance(buffer_ptr, buffer_end,
428 get_hashable_data(*first)))
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);
436 // Mix this chunk into the current state.
438 length += buffer_ptr - buffer;
441 return state.finalize(length);
444 /// \brief Implement the combining of integral values into a hash_code.
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.
452 template <typename ValueT>
453 typename std::enable_if<is_hashable_data<ValueT>::value, hash_code>::type
454 hash_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);
460 return hash_short(s_begin, length, seed);
462 const char *s_aligned_end = s_begin + (length & ~63);
463 hash_state state = state.create(s_begin, seed);
465 while (s_begin != s_aligned_end) {
470 state.mix(s_end - 64);
472 return state.finalize(length);
475 } // namespace detail
476 } // namespace hashing
479 /// \brief Compute a hash_code for a sequence of values.
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.
485 template <typename InputIteratorT>
486 hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) {
487 return ::llvm::hashing::detail::hash_combine_range_impl(first, last);
491 // Implementation details for hash_combine.
495 /// \brief Helper class to manage the recursive combining of hash_combine
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.
502 struct hash_combine_recursive_helper {
508 /// \brief Construct a recursive hash combining helper.
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()) {}
515 /// \brief Combine one chunk of data into the current in-flight hash.
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
528 size_t partial_store_size = buffer_end - buffer_ptr;
529 memcpy(buffer_ptr, &data, partial_store_size);
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.
536 state = state.create(buffer, seed);
539 // Mix this chunk into the current state and bump length up by 64.
543 // Reset the buffer_ptr to the head of the buffer for the next chunk of
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,
556 #if defined(__has_feature) && __has_feature(__cxx_variadic_templates__)
558 /// \brief Recursive, variadic combining method.
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));
567 // Recurse to the next argument.
568 return combine(length, buffer_ptr, buffer_end, args...);
572 // Manually expanded recursive combining methods. See variadic above for
575 template <typename T1, typename T2, typename T3, typename T4, typename T5,
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);
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);
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,
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);
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);
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);
609 template <typename T1>
610 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
612 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg1));
613 return combine(length, buffer_ptr, buffer_end);
618 /// \brief Base case for recursive, variadic combining.
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.
627 return hash_short(buffer, buffer_ptr - buffer, seed);
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
633 std::rotate(buffer, buffer_ptr, buffer_end);
635 // Mix this chunk into the current state.
637 length += buffer_ptr - buffer;
639 return state.finalize(length);
643 } // namespace detail
644 } // namespace hashing
647 #if __has_feature(__cxx_variadic_templates__)
649 /// \brief Combine values into a single hash_code.
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.
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'.
660 template <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...);
668 // What follows are manually exploded overloads for each argument width. See
669 // the above variadic definition for documentation and specification.
671 template <typename T1, typename T2, typename T3, typename T4, typename T5,
673 hash_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);
679 template <typename T1, typename T2, typename T3, typename T4, typename T5>
680 hash_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);
686 template <typename T1, typename T2, typename T3, typename T4>
687 hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3,
689 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
690 return helper.combine(0, helper.buffer, helper.buffer + 64,
691 arg1, arg2, arg3, arg4);
693 template <typename T1, typename T2, typename T3>
694 hash_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);
698 template <typename T1, typename T2>
699 hash_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);
703 template <typename T1>
704 hash_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);
712 // Implementation details for implementations of hash_value overloads provided
717 /// \brief Helper to hash the value of a single integer.
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.
722 inline 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));
730 } // namespace detail
731 } // namespace hashing
733 // Declared and documented above, but defined here so that any of the hashing
734 // infrastructure is available.
735 template <typename T>
736 typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
737 hash_value(T value) {
738 return ::llvm::hashing::detail::hash_integer_value(value);
741 // Declared and documented above, but defined here so that any of the hashing
742 // infrastructure is available.
743 template <typename T> hash_code hash_value(const T *ptr) {
744 return ::llvm::hashing::detail::hash_integer_value(
745 reinterpret_cast<uintptr_t>(ptr));
748 // Declared and documented above, but defined here so that any of the hashing
749 // infrastructure is available.
750 template <typename T, typename U>
751 hash_code hash_value(const std::pair<T, U> &arg) {
752 return hash_combine(arg.first, arg.second);
755 // Declared and documented above, but defined here so that any of the hashing
756 // infrastructure is available.
757 template <typename T>
758 hash_code hash_value(const std::basic_string<T> &arg) {
759 return hash_combine_range(arg.begin(), arg.end());