1//===-- llvm/ADT/Hashing.h - Utilities for hashing --------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the newly proposed standard C++ interfaces for hashing
10// arbitrary data and building hash functions for user-defined types. This
11// interface was originally proposed in N3333[1] and is currently under review
12// for inclusion in a future TR and/or standard.
13//
14// The primary interfaces provide are comprised of one type and three functions:
15//
16// -- 'hash_code' class is an opaque type representing the hash code for some
17// data. It is the intended product of hashing, and can be used to implement
18// hash tables, checksumming, and other common uses of hashes. It is not an
19// integer type (although it can be converted to one) because it is risky
20// to assume much about the internals of a hash_code. In particular, each
21// execution of the program has a high probability of producing a different
22// hash_code for a given input. Thus their values are not stable to save or
23// persist, and should only be used during the execution for the
24// construction of hashing datastructures.
25//
26// -- 'hash_value' is a function designed to be overloaded for each
27// user-defined type which wishes to be used within a hashing context. It
28// should be overloaded within the user-defined type's namespace and found
29// via ADL. Overloads for primitive types are provided by this library.
30//
31// -- 'hash_combine' and 'hash_combine_range' are functions designed to aid
32// programmers in easily and intuitively combining a set of data into
33// a single hash_code for their object. They should only logically be used
34// within the implementation of a 'hash_value' routine or similar context.
35//
36// Note that 'hash_combine_range' contains very special logic for hashing
37// a contiguous array of integers or pointers. This logic is *extremely* fast,
38// on a modern Intel "Gainestown" Xeon (Nehalem uarch) @2.2 GHz, these were
39// benchmarked at over 6.5 GiB/s for large keys, and <20 cycles/hash for keys
40// under 32-bytes.
41//
42//===----------------------------------------------------------------------===//
43
44#ifndef LLVM_ADT_HASHING_H
45#define LLVM_ADT_HASHING_H
46
47#include "llvm/Support/DataTypes.h"
48#include "llvm/Support/Host.h"
49#include "llvm/Support/SwapByteOrder.h"
50#include "llvm/Support/type_traits.h"
51#include <algorithm>
52#include <cassert>
53#include <cstring>
54#include <string>
55#include <utility>
56
57namespace llvm {
58
59/// An opaque object representing a hash code.
60///
61/// This object represents the result of hashing some entity. It is intended to
62/// be used to implement hashtables or other hashing-based data structures.
63/// While it wraps and exposes a numeric value, this value should not be
64/// trusted to be stable or predictable across processes or executions.
65///
66/// In order to obtain the hash_code for an object 'x':
67/// \code
68/// using llvm::hash_value;
69/// llvm::hash_code code = hash_value(x);
70/// \endcode
71class hash_code {
72 size_t value;
73
74public:
75 /// Default construct a hash_code.
76 /// Note that this leaves the value uninitialized.
77 hash_code() = default;
78
79 /// Form a hash code directly from a numerical value.
80 hash_code(size_t value) : value(value) {}
81
82 /// Convert the hash code to its numerical value for use.
83 /*explicit*/ operator size_t() const { return value; }
84
85 friend bool operator==(const hash_code &lhs, const hash_code &rhs) {
86 return lhs.value == rhs.value;
87 }
88 friend bool operator!=(const hash_code &lhs, const hash_code &rhs) {
89 return lhs.value != rhs.value;
90 }
91
92 /// Allow a hash_code to be directly run through hash_value.
93 friend size_t hash_value(const hash_code &code) { return code.value; }
94};
95
96/// Compute a hash_code for any integer value.
97///
98/// Note that this function is intended to compute the same hash_code for
99/// a particular value without regard to the pre-promotion type. This is in
100/// contrast to hash_combine which may produce different hash_codes for
101/// differing argument types even if they would implicit promote to a common
102/// type without changing the value.
103template <typename T>
104typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
105hash_value(T value);
106
107/// Compute a hash_code for a pointer's address.
108///
109/// N.B.: This hashes the *address*. Not the value and not the type.
110template <typename T> hash_code hash_value(const T *ptr);
111
112/// Compute a hash_code for a pair of objects.
113template <typename T, typename U>
114hash_code hash_value(const std::pair<T, U> &arg);
115
116/// Compute a hash_code for a standard string.
117template <typename T>
118hash_code hash_value(const std::basic_string<T> &arg);
119
120
121/// Override the execution seed with a fixed value.
122///
123/// This hashing library uses a per-execution seed designed to change on each
124/// run with high probability in order to ensure that the hash codes are not
125/// attackable and to ensure that output which is intended to be stable does
126/// not rely on the particulars of the hash codes produced.
127///
128/// That said, there are use cases where it is important to be able to
129/// reproduce *exactly* a specific behavior. To that end, we provide a function
130/// which will forcibly set the seed to a fixed value. This must be done at the
131/// start of the program, before any hashes are computed. Also, it cannot be
132/// undone. This makes it thread-hostile and very hard to use outside of
133/// immediately on start of a simple program designed for reproducible
134/// behavior.
135void set_fixed_execution_hash_seed(uint64_t fixed_value);
136
137
138// All of the implementation details of actually computing the various hash
139// code values are held within this namespace. These routines are included in
140// the header file mainly to allow inlining and constant propagation.
141namespace hashing {
142namespace detail {
143
144inline uint64_t fetch64(const char *p) {
145 uint64_t result;
146 memcpy(&result, p, sizeof(result));
147 if (sys::IsBigEndianHost)
148 sys::swapByteOrder(result);
149 return result;
150}
151
152inline uint32_t fetch32(const char *p) {
153 uint32_t result;
154 memcpy(&result, p, sizeof(result));
155 if (sys::IsBigEndianHost)
156 sys::swapByteOrder(result);
157 return result;
158}
159
160/// Some primes between 2^63 and 2^64 for various uses.
161static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
162static const uint64_t k1 = 0xb492b66fbe98f273ULL;
163static const uint64_t k2 = 0x9ae16a3b2f90404fULL;
164static const uint64_t k3 = 0xc949d7c7509e6557ULL;
165
166/// Bitwise right rotate.
167/// Normally this will compile to a single instruction, especially if the
168/// shift is a manifest constant.
169inline uint64_t rotate(uint64_t val, size_t shift) {
170 // Avoid shifting by 64: doing so yields an undefined result.
171 return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
172}
173
174inline uint64_t shift_mix(uint64_t val) {
175 return val ^ (val >> 47);
176}
177
178inline uint64_t hash_16_bytes(uint64_t low, uint64_t high) {
179 // Murmur-inspired hashing.
180 const uint64_t kMul = 0x9ddfea08eb382d69ULL;
181 uint64_t a = (low ^ high) * kMul;
182 a ^= (a >> 47);
183 uint64_t b = (high ^ a) * kMul;
184 b ^= (b >> 47);
185 b *= kMul;
186 return b;
187}
188
189inline uint64_t hash_1to3_bytes(const char *s, size_t len, uint64_t seed) {
190 uint8_t a = s[0];
191 uint8_t b = s[len >> 1];
192 uint8_t c = s[len - 1];
193 uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
194 uint32_t z = len + (static_cast<uint32_t>(c) << 2);
195 return shift_mix(y * k2 ^ z * k3 ^ seed) * k2;
196}
197
198inline uint64_t hash_4to8_bytes(const char *s, size_t len, uint64_t seed) {
199 uint64_t a = fetch32(s);
200 return hash_16_bytes(len + (a << 3), seed ^ fetch32(s + len - 4));
201}
202
203inline uint64_t hash_9to16_bytes(const char *s, size_t len, uint64_t seed) {
204 uint64_t a = fetch64(s);
205 uint64_t b = fetch64(s + len - 8);
206 return hash_16_bytes(seed ^ a, rotate(b + len, len)) ^ b;
207}
208
209inline uint64_t hash_17to32_bytes(const char *s, size_t len, uint64_t seed) {
210 uint64_t a = fetch64(s) * k1;
211 uint64_t b = fetch64(s + 8);
212 uint64_t c = fetch64(s + len - 8) * k2;
213 uint64_t d = fetch64(s + len - 16) * k0;
214 return hash_16_bytes(rotate(a - b, 43) + rotate(c ^ seed, 30) + d,
215 a + rotate(b ^ k3, 20) - c + len + seed);
216}
217
218inline uint64_t hash_33to64_bytes(const char *s, size_t len, uint64_t seed) {
219 uint64_t z = fetch64(s + 24);
220 uint64_t a = fetch64(s) + (len + fetch64(s + len - 16)) * k0;
221 uint64_t b = rotate(a + z, 52);
222 uint64_t c = rotate(a, 37);
223 a += fetch64(s + 8);
224 c += rotate(a, 7);
225 a += fetch64(s + 16);
226 uint64_t vf = a + z;
227 uint64_t vs = b + rotate(a, 31) + c;
228 a = fetch64(s + 16) + fetch64(s + len - 32);
229 z = fetch64(s + len - 8);
230 b = rotate(a + z, 52);
231 c = rotate(a, 37);
232 a += fetch64(s + len - 24);
233 c += rotate(a, 7);
234 a += fetch64(s + len - 16);
235 uint64_t wf = a + z;
236 uint64_t ws = b + rotate(a, 31) + c;
237 uint64_t r = shift_mix((vf + ws) * k2 + (wf + vs) * k0);
238 return shift_mix((seed ^ (r * k0)) + vs) * k2;
239}
240
241inline uint64_t hash_short(const char *s, size_t length, uint64_t seed) {
242 if (length >= 4 && length <= 8)
243 return hash_4to8_bytes(s, length, seed);
244 if (length > 8 && length <= 16)
245 return hash_9to16_bytes(s, length, seed);
246 if (length > 16 && length <= 32)
247 return hash_17to32_bytes(s, length, seed);
248 if (length > 32)
249 return hash_33to64_bytes(s, length, seed);
250 if (length != 0)
251 return hash_1to3_bytes(s, length, seed);
252
253 return k2 ^ seed;
254}
255
256/// The intermediate state used during hashing.
257/// Currently, the algorithm for computing hash codes is based on CityHash and
258/// keeps 56 bytes of arbitrary state.
259struct hash_state {
260 uint64_t h0, h1, h2, h3, h4, h5, h6;
261
262 /// Create a new hash_state structure and initialize it based on the
263 /// seed and the first 64-byte chunk.
264 /// This effectively performs the initial mix.
265 static hash_state create(const char *s, uint64_t seed) {
266 hash_state state = {
267 0, seed, hash_16_bytes(seed, k1), rotate(seed ^ k1, 49),
268 seed * k1, shift_mix(seed), 0 };
269 state.h6 = hash_16_bytes(state.h4, state.h5);
270 state.mix(s);
271 return state;
272 }
273
274 /// Mix 32-bytes from the input sequence into the 16-bytes of 'a'
275 /// and 'b', including whatever is already in 'a' and 'b'.
276 static void mix_32_bytes(const char *s, uint64_t &a, uint64_t &b) {
277 a += fetch64(s);
278 uint64_t c = fetch64(s + 24);
279 b = rotate(b + a + c, 21);
280 uint64_t d = a;
281 a += fetch64(s + 8) + fetch64(s + 16);
282 b += rotate(a, 44) + d;
283 a += c;
284 }
285
286 /// Mix in a 64-byte buffer of data.
287 /// We mix all 64 bytes even when the chunk length is smaller, but we
288 /// record the actual length.
289 void mix(const char *s) {
290 h0 = rotate(h0 + h1 + h3 + fetch64(s + 8), 37) * k1;
291 h1 = rotate(h1 + h4 + fetch64(s + 48), 42) * k1;
292 h0 ^= h6;
293 h1 += h3 + fetch64(s + 40);
294 h2 = rotate(h2 + h5, 33) * k1;
295 h3 = h4 * k1;
296 h4 = h0 + h5;
297 mix_32_bytes(s, h3, h4);
298 h5 = h2 + h6;
299 h6 = h1 + fetch64(s + 16);
300 mix_32_bytes(s + 32, h5, h6);
301 std::swap(h2, h0);
302 }
303
304 /// Compute the final 64-bit hash code value based on the current
305 /// state and the length of bytes hashed.
306 uint64_t finalize(size_t length) {
307 return hash_16_bytes(hash_16_bytes(h3, h5) + shift_mix(h1) * k1 + h2,
308 hash_16_bytes(h4, h6) + shift_mix(length) * k1 + h0);
309 }
310};
311
312
313/// A global, fixed seed-override variable.
314///
315/// This variable can be set using the \see llvm::set_fixed_execution_seed
316/// function. See that function for details. Do not, under any circumstances,
317/// set or read this variable.
318extern uint64_t fixed_seed_override;
319
320inline uint64_t get_execution_seed() {
321 // FIXME: This needs to be a per-execution seed. This is just a placeholder
322 // implementation. Switching to a per-execution seed is likely to flush out
323 // instability bugs and so will happen as its own commit.
324 //
325 // However, if there is a fixed seed override set the first time this is
326 // called, return that instead of the per-execution seed.
327 const uint64_t seed_prime = 0xff51afd7ed558ccdULL;
328 static uint64_t seed = fixed_seed_override ? fixed_seed_override : seed_prime;
329 return seed;
330}
331
332
333/// Trait to indicate whether a type's bits can be hashed directly.
334///
335/// A type trait which is true if we want to combine values for hashing by
336/// reading the underlying data. It is false if values of this type must
337/// first be passed to hash_value, and the resulting hash_codes combined.
338//
339// FIXME: We want to replace is_integral_or_enum and is_pointer here with
340// a predicate which asserts that comparing the underlying storage of two
341// values of the type for equality is equivalent to comparing the two values
342// for equality. For all the platforms we care about, this holds for integers
343// and pointers, but there are platforms where it doesn't and we would like to
344// support user-defined types which happen to satisfy this property.
345template <typename T> struct is_hashable_data
346 : std::integral_constant<bool, ((is_integral_or_enum<T>::value ||
347 std::is_pointer<T>::value) &&
348 64 % sizeof(T) == 0)> {};
349
350// Special case std::pair to detect when both types are viable and when there
351// is no alignment-derived padding in the pair. This is a bit of a lie because
352// std::pair isn't truly POD, but it's close enough in all reasonable
353// implementations for our use case of hashing the underlying data.
354template <typename T, typename U> struct is_hashable_data<std::pair<T, U> >
355 : std::integral_constant<bool, (is_hashable_data<T>::value &&
356 is_hashable_data<U>::value &&
357 (sizeof(T) + sizeof(U)) ==
358 sizeof(std::pair<T, U>))> {};
359
360/// Helper to get the hashable data representation for a type.
361/// This variant is enabled when the type itself can be used.
362template <typename T>
363typename std::enable_if<is_hashable_data<T>::value, T>::type
364get_hashable_data(const T &value) {
365 return value;
366}
367/// Helper to get the hashable data representation for a type.
368/// This variant is enabled when we must first call hash_value and use the
369/// result as our data.
370template <typename T>
371typename std::enable_if<!is_hashable_data<T>::value, size_t>::type
372get_hashable_data(const T &value) {
373 using ::llvm::hash_value;
374 return hash_value(value);
375}
376
377/// Helper to store data from a value into a buffer and advance the
378/// pointer into that buffer.
379///
380/// This routine first checks whether there is enough space in the provided
381/// buffer, and if not immediately returns false. If there is space, it
382/// copies the underlying bytes of value into the buffer, advances the
383/// buffer_ptr past the copied bytes, and returns true.
384template <typename T>
385bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value,
386 size_t offset = 0) {
387 size_t store_size = sizeof(value) - offset;
388 if (buffer_ptr + store_size > buffer_end)
389 return false;
390 const char *value_data = reinterpret_cast<const char *>(&value);
391 memcpy(buffer_ptr, value_data + offset, store_size);
392 buffer_ptr += store_size;
393 return true;
394}
395
396/// Implement the combining of integral values into a hash_code.
397///
398/// This overload is selected when the value type of the iterator is
399/// integral. Rather than computing a hash_code for each object and then
400/// combining them, this (as an optimization) directly combines the integers.
401template <typename InputIteratorT>
402hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) {
403 const uint64_t seed = get_execution_seed();
404 char buffer[64], *buffer_ptr = buffer;
405 char *const buffer_end = std::end(buffer);
406 while (first != last && store_and_advance(buffer_ptr, buffer_end,
407 get_hashable_data(*first)))
408 ++first;
409 if (first == last)
410 return hash_short(buffer, buffer_ptr - buffer, seed);
411 assert(buffer_ptr == buffer_end);
412
413 hash_state state = state.create(buffer, seed);
414 size_t length = 64;
415 while (first != last) {
416 // Fill up the buffer. We don't clear it, which re-mixes the last round
417 // when only a partial 64-byte chunk is left.
418 buffer_ptr = buffer;
419 while (first != last && store_and_advance(buffer_ptr, buffer_end,
420 get_hashable_data(*first)))
421 ++first;
422
423 // Rotate the buffer if we did a partial fill in order to simulate doing
424 // a mix of the last 64-bytes. That is how the algorithm works when we
425 // have a contiguous byte sequence, and we want to emulate that here.
426 std::rotate(buffer, buffer_ptr, buffer_end);
427
428 // Mix this chunk into the current state.
429 state.mix(buffer);
430 length += buffer_ptr - buffer;
431 };
432
433 return state.finalize(length);
434}
435
436/// Implement the combining of integral values into a hash_code.
437///
438/// This overload is selected when the value type of the iterator is integral
439/// and when the input iterator is actually a pointer. Rather than computing
440/// a hash_code for each object and then combining them, this (as an
441/// optimization) directly combines the integers. Also, because the integers
442/// are stored in contiguous memory, this routine avoids copying each value
443/// and directly reads from the underlying memory.
444template <typename ValueT>
445typename std::enable_if<is_hashable_data<ValueT>::value, hash_code>::type
446hash_combine_range_impl(ValueT *first, ValueT *last) {
447 const uint64_t seed = get_execution_seed();
448 const char *s_begin = reinterpret_cast<const char *>(first);
449 const char *s_end = reinterpret_cast<const char *>(last);
450 const size_t length = std::distance(s_begin, s_end);
451 if (length <= 64)
452 return hash_short(s_begin, length, seed);
453
454 const char *s_aligned_end = s_begin + (length & ~63);
455 hash_state state = state.create(s_begin, seed);
456 s_begin += 64;
457 while (s_begin != s_aligned_end) {
458 state.mix(s_begin);
459 s_begin += 64;
460 }
461 if (length & 63)
462 state.mix(s_end - 64);
463
464 return state.finalize(length);
465}
466
467} // namespace detail
468} // namespace hashing
469
470
471/// Compute a hash_code for a sequence of values.
472///
473/// This hashes a sequence of values. It produces the same hash_code as
474/// 'hash_combine(a, b, c, ...)', but can run over arbitrary sized sequences
475/// and is significantly faster given pointers and types which can be hashed as
476/// a sequence of bytes.
477template <typename InputIteratorT>
478hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) {
479 return ::llvm::hashing::detail::hash_combine_range_impl(first, last);
480}
481
482
483// Implementation details for hash_combine.
484namespace hashing {
485namespace detail {
486
487/// Helper class to manage the recursive combining of hash_combine
488/// arguments.
489///
490/// This class exists to manage the state and various calls involved in the
491/// recursive combining of arguments used in hash_combine. It is particularly
492/// useful at minimizing the code in the recursive calls to ease the pain
493/// caused by a lack of variadic functions.
494struct hash_combine_recursive_helper {
495 char buffer[64];
496 hash_state state;
497 const uint64_t seed;
498
499public:
500 /// Construct a recursive hash combining helper.
501 ///
502 /// This sets up the state for a recursive hash combine, including getting
503 /// the seed and buffer setup.
504 hash_combine_recursive_helper()
505 : seed(get_execution_seed()) {}
506
507 /// Combine one chunk of data into the current in-flight hash.
508 ///
509 /// This merges one chunk of data into the hash. First it tries to buffer
510 /// the data. If the buffer is full, it hashes the buffer into its
511 /// hash_state, empties it, and then merges the new chunk in. This also
512 /// handles cases where the data straddles the end of the buffer.
513 template <typename T>
514 char *combine_data(size_t &length, char *buffer_ptr, char *buffer_end, T data) {
515 if (!store_and_advance(buffer_ptr, buffer_end, data)) {
516 // Check for skew which prevents the buffer from being packed, and do
517 // a partial store into the buffer to fill it. This is only a concern
518 // with the variadic combine because that formation can have varying
519 // argument types.
520 size_t partial_store_size = buffer_end - buffer_ptr;
521 memcpy(buffer_ptr, &data, partial_store_size);
522
523 // If the store fails, our buffer is full and ready to hash. We have to
524 // either initialize the hash state (on the first full buffer) or mix
525 // this buffer into the existing hash state. Length tracks the *hashed*
526 // length, not the buffered length.
527 if (length == 0) {
528 state = state.create(buffer, seed);
529 length = 64;
530 } else {
531 // Mix this chunk into the current state and bump length up by 64.
532 state.mix(buffer);
533 length += 64;
534 }
535 // Reset the buffer_ptr to the head of the buffer for the next chunk of
536 // data.
537 buffer_ptr = buffer;
538
539 // Try again to store into the buffer -- this cannot fail as we only
540 // store types smaller than the buffer.
541 if (!store_and_advance(buffer_ptr, buffer_end, data,
542 partial_store_size))
543 abort();
544 }
545 return buffer_ptr;
546 }
547
548 /// Recursive, variadic combining method.
549 ///
550 /// This function recurses through each argument, combining that argument
551 /// into a single hash.
552 template <typename T, typename ...Ts>
553 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
554 const T &arg, const Ts &...args) {
555 buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg));
556
557 // Recurse to the next argument.
558 return combine(length, buffer_ptr, buffer_end, args...);
559 }
560
561 /// Base case for recursive, variadic combining.
562 ///
563 /// The base case when combining arguments recursively is reached when all
564 /// arguments have been handled. It flushes the remaining buffer and
565 /// constructs a hash_code.
566 hash_code combine(size_t length, char *buffer_ptr, char *buffer_end) {
567 // Check whether the entire set of values fit in the buffer. If so, we'll
568 // use the optimized short hashing routine and skip state entirely.
569 if (length == 0)
570 return hash_short(buffer, buffer_ptr - buffer, seed);
571
572 // Mix the final buffer, rotating it if we did a partial fill in order to
573 // simulate doing a mix of the last 64-bytes. That is how the algorithm
574 // works when we have a contiguous byte sequence, and we want to emulate
575 // that here.
576 std::rotate(buffer, buffer_ptr, buffer_end);
577
578 // Mix this chunk into the current state.
579 state.mix(buffer);
580 length += buffer_ptr - buffer;
581
582 return state.finalize(length);
583 }
584};
585
586} // namespace detail
587} // namespace hashing
588
589/// Combine values into a single hash_code.
590///
591/// This routine accepts a varying number of arguments of any type. It will
592/// attempt to combine them into a single hash_code. For user-defined types it
593/// attempts to call a \see hash_value overload (via ADL) for the type. For
594/// integer and pointer types it directly combines their data into the
595/// resulting hash_code.
596///
597/// The result is suitable for returning from a user's hash_value
598/// *implementation* for their user-defined type. Consumers of a type should
599/// *not* call this routine, they should instead call 'hash_value'.
600template <typename ...Ts> hash_code hash_combine(const Ts &...args) {
601 // Recursively hash each argument using a helper class.
602 ::llvm::hashing::detail::hash_combine_recursive_helper helper;
603 return helper.combine(0, helper.buffer, helper.buffer + 64, args...);
604}
605
606// Implementation details for implementations of hash_value overloads provided
607// here.
608namespace hashing {
609namespace detail {
610
611/// Helper to hash the value of a single integer.
612///
613/// Overloads for smaller integer types are not provided to ensure consistent
614/// behavior in the presence of integral promotions. Essentially,
615/// "hash_value('4')" and "hash_value('0' + 4)" should be the same.
616inline hash_code hash_integer_value(uint64_t value) {
617 // Similar to hash_4to8_bytes but using a seed instead of length.
618 const uint64_t seed = get_execution_seed();
619 const char *s = reinterpret_cast<const char *>(&value);
620 const uint64_t a = fetch32(s);
621 return hash_16_bytes(seed + (a << 3), fetch32(s + 4));
622}
623
624} // namespace detail
625} // namespace hashing
626
627// Declared and documented above, but defined here so that any of the hashing
628// infrastructure is available.
629template <typename T>
630typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
631hash_value(T value) {
632 return ::llvm::hashing::detail::hash_integer_value(
633 static_cast<uint64_t>(value));
634}
635
636// Declared and documented above, but defined here so that any of the hashing
637// infrastructure is available.
638template <typename T> hash_code hash_value(const T *ptr) {
639 return ::llvm::hashing::detail::hash_integer_value(
640 reinterpret_cast<uintptr_t>(ptr));
641}
642
643// Declared and documented above, but defined here so that any of the hashing
644// infrastructure is available.
645template <typename T, typename U>
646hash_code hash_value(const std::pair<T, U> &arg) {
647 return hash_combine(arg.first, arg.second);
648}
649
650// Declared and documented above, but defined here so that any of the hashing
651// infrastructure is available.
652template <typename T>
653hash_code hash_value(const std::basic_string<T> &arg) {
654 return hash_combine_range(arg.begin(), arg.end());
655}
656
657} // namespace llvm
658
659#endif
660