LCOV - code coverage report
Current view: top level - include/llvm/ADT - Hashing.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 783 1108 70.7 %
Date: 2018-10-20 13:21:21 Functions: 212 511 41.5 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===-- llvm/ADT/Hashing.h - Utilities for hashing --------------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file implements the newly proposed standard C++ interfaces for hashing
      11             : // arbitrary data and building hash functions for user-defined types. This
      12             : // interface was originally proposed in N3333[1] and is currently under review
      13             : // for inclusion in a future TR and/or standard.
      14             : //
      15             : // The primary interfaces provide are comprised of one type and three functions:
      16             : //
      17             : //  -- 'hash_code' class is an opaque type representing the hash code for some
      18             : //     data. It is the intended product of hashing, and can be used to implement
      19             : //     hash tables, checksumming, and other common uses of hashes. It is not an
      20             : //     integer type (although it can be converted to one) because it is risky
      21             : //     to assume much about the internals of a hash_code. In particular, each
      22             : //     execution of the program has a high probability of producing a different
      23             : //     hash_code for a given input. Thus their values are not stable to save or
      24             : //     persist, and should only be used during the execution for the
      25             : //     construction of hashing datastructures.
      26             : //
      27             : //  -- 'hash_value' is a function designed to be overloaded for each
      28             : //     user-defined type which wishes to be used within a hashing context. It
      29             : //     should be overloaded within the user-defined type's namespace and found
      30             : //     via ADL. Overloads for primitive types are provided by this library.
      31             : //
      32             : //  -- 'hash_combine' and 'hash_combine_range' are functions designed to aid
      33             : //      programmers in easily and intuitively combining a set of data into
      34             : //      a single hash_code for their object. They should only logically be used
      35             : //      within the implementation of a 'hash_value' routine or similar context.
      36             : //
      37             : // Note that 'hash_combine_range' contains very special logic for hashing
      38             : // a contiguous array of integers or pointers. This logic is *extremely* fast,
      39             : // on a modern Intel "Gainestown" Xeon (Nehalem uarch) @2.2 GHz, these were
      40             : // benchmarked at over 6.5 GiB/s for large keys, and <20 cycles/hash for keys
      41             : // under 32-bytes.
      42             : //
      43             : //===----------------------------------------------------------------------===//
      44             : 
      45             : #ifndef LLVM_ADT_HASHING_H
      46             : #define LLVM_ADT_HASHING_H
      47             : 
      48             : #include "llvm/Support/DataTypes.h"
      49             : #include "llvm/Support/Host.h"
      50             : #include "llvm/Support/SwapByteOrder.h"
      51             : #include "llvm/Support/type_traits.h"
      52             : #include <algorithm>
      53             : #include <cassert>
      54             : #include <cstring>
      55             : #include <string>
      56             : #include <utility>
      57             : 
      58             : namespace llvm {
      59             : 
      60             : /// An opaque object representing a hash code.
      61             : ///
      62             : /// This object represents the result of hashing some entity. It is intended to
      63             : /// be used to implement hashtables or other hashing-based data structures.
      64             : /// While it wraps and exposes a numeric value, this value should not be
      65             : /// trusted to be stable or predictable across processes or executions.
      66             : ///
      67             : /// In order to obtain the hash_code for an object 'x':
      68             : /// \code
      69             : ///   using llvm::hash_value;
      70             : ///   llvm::hash_code code = hash_value(x);
      71             : /// \endcode
      72             : class hash_code {
      73             :   size_t value;
      74             : 
      75             : public:
      76             :   /// Default construct a hash_code.
      77             :   /// Note that this leaves the value uninitialized.
      78             :   hash_code() = default;
      79             : 
      80             :   /// Form a hash code directly from a numerical value.
      81        4546 :   hash_code(size_t value) : value(value) {}
      82             : 
      83             :   /// Convert the hash code to its numerical value for use.
      84           0 :   /*explicit*/ operator size_t() const { return value; }
      85             : 
      86           0 :   friend bool operator==(const hash_code &lhs, const hash_code &rhs) {
      87          70 :     return lhs.value == rhs.value;
      88             :   }
      89           0 :   friend bool operator!=(const hash_code &lhs, const hash_code &rhs) {
      90           0 :     return lhs.value != rhs.value;
      91             :   }
      92             : 
      93             :   /// Allow a hash_code to be directly run through hash_value.
      94           0 :   friend size_t hash_value(const hash_code &code) { return code.value; }
      95             : };
      96             : 
      97             : /// Compute a hash_code for any integer value.
      98             : ///
      99             : /// Note that this function is intended to compute the same hash_code for
     100             : /// a particular value without regard to the pre-promotion type. This is in
     101             : /// contrast to hash_combine which may produce different hash_codes for
     102             : /// differing argument types even if they would implicit promote to a common
     103             : /// type without changing the value.
     104             : template <typename T>
     105             : typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
     106             : hash_value(T value);
     107             : 
     108             : /// Compute a hash_code for a pointer's address.
     109             : ///
     110             : /// N.B.: This hashes the *address*. Not the value and not the type.
     111             : template <typename T> hash_code hash_value(const T *ptr);
     112             : 
     113             : /// Compute a hash_code for a pair of objects.
     114             : template <typename T, typename U>
     115             : hash_code hash_value(const std::pair<T, U> &arg);
     116             : 
     117             : /// Compute a hash_code for a standard string.
     118             : template <typename T>
     119             : hash_code hash_value(const std::basic_string<T> &arg);
     120             : 
     121             : 
     122             : /// Override the execution seed with a fixed value.
     123             : ///
     124             : /// This hashing library uses a per-execution seed designed to change on each
     125             : /// run with high probability in order to ensure that the hash codes are not
     126             : /// attackable and to ensure that output which is intended to be stable does
     127             : /// not rely on the particulars of the hash codes produced.
     128             : ///
     129             : /// That said, there are use cases where it is important to be able to
     130             : /// reproduce *exactly* a specific behavior. To that end, we provide a function
     131             : /// which will forcibly set the seed to a fixed value. This must be done at the
     132             : /// start of the program, before any hashes are computed. Also, it cannot be
     133             : /// undone. This makes it thread-hostile and very hard to use outside of
     134             : /// immediately on start of a simple program designed for reproducible
     135             : /// behavior.
     136             : void set_fixed_execution_hash_seed(uint64_t fixed_value);
     137             : 
     138             : 
     139             : // All of the implementation details of actually computing the various hash
     140             : // code values are held within this namespace. These routines are included in
     141             : // the header file mainly to allow inlining and constant propagation.
     142             : namespace hashing {
     143             : namespace detail {
     144             : 
     145             : inline uint64_t fetch64(const char *p) {
     146             :   uint64_t result;
     147  5675950800 :   memcpy(&result, p, sizeof(result));
     148             :   if (sys::IsBigEndianHost)
     149             :     sys::swapByteOrder(result);
     150             :   return result;
     151             : }
     152             : 
     153             : inline uint32_t fetch32(const char *p) {
     154             :   uint32_t result;
     155   626313028 :   memcpy(&result, p, sizeof(result));
     156             :   if (sys::IsBigEndianHost)
     157             :     sys::swapByteOrder(result);
     158             :   return result;
     159             : }
     160             : 
     161             : /// Some primes between 2^63 and 2^64 for various uses.
     162             : static const uint64_t k0 = 0xc3a5c85c97cb3127ULL;
     163             : static const uint64_t k1 = 0xb492b66fbe98f273ULL;
     164             : static const uint64_t k2 = 0x9ae16a3b2f90404fULL;
     165             : static const uint64_t k3 = 0xc949d7c7509e6557ULL;
     166             : 
     167             : /// Bitwise right rotate.
     168             : /// Normally this will compile to a single instruction, especially if the
     169             : /// shift is a manifest constant.
     170             : inline uint64_t rotate(uint64_t val, size_t shift) {
     171             :   // Avoid shifting by 64: doing so yields an undefined result.
     172  4144992665 :   return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
     173             : }
     174             : 
     175             : inline uint64_t shift_mix(uint64_t val) {
     176   511026774 :   return val ^ (val >> 47);
     177             : }
     178             : 
     179             : inline uint64_t hash_16_bytes(uint64_t low, uint64_t high) {
     180             :   // Murmur-inspired hashing.
     181             :   const uint64_t kMul = 0x9ddfea08eb382d69ULL;
     182  1576398364 :   uint64_t a = (low ^ high) * kMul;
     183  1576398364 :   a ^= (a >> 47);
     184  1576398364 :   uint64_t b = (high ^ a) * kMul;
     185  1576398364 :   b ^= (b >> 47);
     186  1576398364 :   b *= kMul;
     187             :   return b;
     188             : }
     189             : 
     190             : inline uint64_t hash_1to3_bytes(const char *s, size_t len, uint64_t seed) {
     191     1533845 :   uint8_t a = s[0];
     192     1533845 :   uint8_t b = s[len >> 1];
     193     1533845 :   uint8_t c = s[len - 1];
     194     1533845 :   uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
     195     1533845 :   uint32_t z = len + (static_cast<uint32_t>(c) << 2);
     196     3067690 :   return shift_mix(y * k2 ^ z * k3 ^ seed) * k2;
     197             : }
     198             : 
     199             : inline uint64_t hash_4to8_bytes(const char *s, size_t len, uint64_t seed) {
     200   313155705 :   uint64_t a = fetch32(s);
     201   626311410 :   return hash_16_bytes(len + (a << 3), seed ^ fetch32(s + len - 4));
     202             : }
     203             : 
     204             : inline uint64_t hash_9to16_bytes(const char *s, size_t len, uint64_t seed) {
     205             :   uint64_t a = fetch64(s);
     206   474249665 :   uint64_t b = fetch64(s + len - 8);
     207  1422748995 :   return hash_16_bytes(seed ^ a, rotate(b + len, len)) ^ b;
     208             : }
     209             : 
     210   557195098 : inline uint64_t hash_17to32_bytes(const char *s, size_t len, uint64_t seed) {
     211   557195098 :   uint64_t a = fetch64(s) * k1;
     212             :   uint64_t b = fetch64(s + 8);
     213  1114390196 :   uint64_t c = fetch64(s + len - 8) * k2;
     214  1114390196 :   uint64_t d = fetch64(s + len - 16) * k0;
     215  1671585294 :   return hash_16_bytes(rotate(a - b, 43) + rotate(c ^ seed, 30) + d,
     216  1671585294 :                        a + rotate(b ^ k3, 20) - c + len + seed);
     217             : }
     218             : 
     219   185208404 : inline uint64_t hash_33to64_bytes(const char *s, size_t len, uint64_t seed) {
     220             :   uint64_t z = fetch64(s + 24);
     221   370416808 :   uint64_t a = fetch64(s) + (len + fetch64(s + len - 16)) * k0;
     222   185208404 :   uint64_t b = rotate(a + z, 52);
     223             :   uint64_t c = rotate(a, 37);
     224   185208404 :   a += fetch64(s + 8);
     225   185208404 :   c += rotate(a, 7);
     226   185208404 :   a += fetch64(s + 16);
     227   185208404 :   uint64_t vf = a + z;
     228   185208404 :   uint64_t vs = b + rotate(a, 31) + c;
     229   370416808 :   a = fetch64(s + 16) + fetch64(s + len - 32);
     230   185208404 :   z = fetch64(s + len - 8);
     231   185208404 :   b = rotate(a + z, 52);
     232             :   c = rotate(a, 37);
     233   370416808 :   a += fetch64(s + len - 24);
     234   185208404 :   c += rotate(a, 7);
     235   185208404 :   a += fetch64(s + len - 16);
     236   185208404 :   uint64_t wf = a + z;
     237   185208404 :   uint64_t ws = b + rotate(a, 31) + c;
     238   185208404 :   uint64_t r = shift_mix((vf + ws) * k2 + (wf + vs) * k0);
     239   370416808 :   return shift_mix((seed ^ (r * k0)) + vs) * k2;
     240             : }
     241             : 
     242  1553601475 : inline uint64_t hash_short(const char *s, size_t length, uint64_t seed) {
     243  1553601475 :   if (length >= 4 && length <= 8)
     244   313155705 :     return hash_4to8_bytes(s, length, seed);
     245  1240445770 :   if (length > 8 && length <= 16)
     246   474249665 :     return hash_9to16_bytes(s, length, seed);
     247   766196105 :   if (length > 16 && length <= 32)
     248   557195098 :     return hash_17to32_bytes(s, length, seed);
     249   209001007 :   if (length > 32)
     250   185208404 :     return hash_33to64_bytes(s, length, seed);
     251    23792603 :   if (length != 0)
     252     1533845 :     return hash_1to3_bytes(s, length, seed);
     253             : 
     254    22258758 :   return k2 ^ seed;
     255             : }
     256             : 
     257             : /// The intermediate state used during hashing.
     258             : /// Currently, the algorithm for computing hash codes is based on CityHash and
     259             : /// keeps 56 bytes of arbitrary state.
     260             : struct hash_state {
     261             :   uint64_t h0, h1, h2, h3, h4, h5, h6;
     262             : 
     263             :   /// Create a new hash_state structure and initialize it based on the
     264             :   /// seed and the first 64-byte chunk.
     265             :   /// This effectively performs the initial mix.
     266    46358707 :   static hash_state create(const char *s, uint64_t seed) {
     267    46358707 :     hash_state state = {
     268             :       0, seed, hash_16_bytes(seed, k1), rotate(seed ^ k1, 49),
     269   185434828 :       seed * k1, shift_mix(seed), 0 };
     270    46358707 :     state.h6 = hash_16_bytes(state.h4, state.h5);
     271    46358707 :     state.mix(s);
     272    46358706 :     return state;
     273             :   }
     274             : 
     275             :   /// Mix 32-bytes from the input sequence into the 16-bytes of 'a'
     276             :   /// and 'b', including whatever is already in 'a' and 'b'.
     277             :   static void mix_32_bytes(const char *s, uint64_t &a, uint64_t &b) {
     278   240442450 :     a += fetch64(s);
     279             :     uint64_t c = fetch64(s + 24);
     280   480884900 :     b = rotate(b + a + c, 21);
     281             :     uint64_t d = a;
     282   240442450 :     a += fetch64(s + 8) + fetch64(s + 16);
     283   240442450 :     b += rotate(a, 44) + d;
     284   240442450 :     a += c;
     285             :   }
     286             : 
     287             :   /// Mix in a 64-byte buffer of data.
     288             :   /// We mix all 64 bytes even when the chunk length is smaller, but we
     289             :   /// record the actual length.
     290   120221225 :   void mix(const char *s) {
     291   360663675 :     h0 = rotate(h0 + h1 + h3 + fetch64(s + 8), 37) * k1;
     292   360663675 :     h1 = rotate(h1 + h4 + fetch64(s + 48), 42) * k1;
     293   120221225 :     h0 ^= h6;
     294   120221225 :     h1 += h3 + fetch64(s + 40);
     295   240442450 :     h2 = rotate(h2 + h5, 33) * k1;
     296   120221225 :     h3 = h4 * k1;
     297   120221225 :     h4 = h0 + h5;
     298             :     mix_32_bytes(s, h3, h4);
     299   120221225 :     h5 = h2 + h6;
     300   120221225 :     h6 = h1 + fetch64(s + 16);
     301             :     mix_32_bytes(s + 32, h5, h6);
     302             :     std::swap(h2, h0);
     303   120221225 :   }
     304             : 
     305             :   /// Compute the final 64-bit hash code value based on the current
     306             :   /// state and the length of bytes hashed.
     307    46358707 :   uint64_t finalize(size_t length) {
     308   139076121 :     return hash_16_bytes(hash_16_bytes(h3, h5) + shift_mix(h1) * k1 + h2,
     309   139076121 :                          hash_16_bytes(h4, h6) + shift_mix(length) * k1 + h0);
     310             :   }
     311             : };
     312             : 
     313             : 
     314             : /// A global, fixed seed-override variable.
     315             : ///
     316             : /// This variable can be set using the \see llvm::set_fixed_execution_seed
     317             : /// function. See that function for details. Do not, under any circumstances,
     318             : /// set or read this variable.
     319             : extern uint64_t fixed_seed_override;
     320             : 
     321  1599961800 : inline uint64_t get_execution_seed() {
     322             :   // FIXME: This needs to be a per-execution seed. This is just a placeholder
     323             :   // implementation. Switching to a per-execution seed is likely to flush out
     324             :   // instability bugs and so will happen as its own commit.
     325             :   //
     326             :   // However, if there is a fixed seed override set the first time this is
     327             :   // called, return that instead of the per-execution seed.
     328             :   const uint64_t seed_prime = 0xff51afd7ed558ccdULL;
     329  1599961800 :   static uint64_t seed = fixed_seed_override ? fixed_seed_override : seed_prime;
     330  1599961800 :   return seed;
     331             : }
     332             : 
     333             : 
     334             : /// Trait to indicate whether a type's bits can be hashed directly.
     335             : ///
     336             : /// A type trait which is true if we want to combine values for hashing by
     337             : /// reading the underlying data. It is false if values of this type must
     338             : /// first be passed to hash_value, and the resulting hash_codes combined.
     339             : //
     340             : // FIXME: We want to replace is_integral_or_enum and is_pointer here with
     341             : // a predicate which asserts that comparing the underlying storage of two
     342             : // values of the type for equality is equivalent to comparing the two values
     343             : // for equality. For all the platforms we care about, this holds for integers
     344             : // and pointers, but there are platforms where it doesn't and we would like to
     345             : // support user-defined types which happen to satisfy this property.
     346             : template <typename T> struct is_hashable_data
     347             :   : std::integral_constant<bool, ((is_integral_or_enum<T>::value ||
     348             :                                    std::is_pointer<T>::value) &&
     349             :                                   64 % sizeof(T) == 0)> {};
     350             : 
     351             : // Special case std::pair to detect when both types are viable and when there
     352             : // is no alignment-derived padding in the pair. This is a bit of a lie because
     353             : // std::pair isn't truly POD, but it's close enough in all reasonable
     354             : // implementations for our use case of hashing the underlying data.
     355             : template <typename T, typename U> struct is_hashable_data<std::pair<T, U> >
     356             :   : std::integral_constant<bool, (is_hashable_data<T>::value &&
     357             :                                   is_hashable_data<U>::value &&
     358             :                                   (sizeof(T) + sizeof(U)) ==
     359             :                                    sizeof(std::pair<T, U>))> {};
     360             : 
     361             : /// Helper to get the hashable data representation for a type.
     362             : /// This variant is enabled when the type itself can be used.
     363             : template <typename T>
     364             : typename std::enable_if<is_hashable_data<T>::value, T>::type
     365           0 : get_hashable_data(const T &value) {
     366          13 :   return value;
     367             : }
     368           0 : /// Helper to get the hashable data representation for a type.
     369           0 : /// This variant is enabled when we must first call hash_value and use the
     370             : /// result as our data.
     371           0 : template <typename T>
     372           0 : typename std::enable_if<!is_hashable_data<T>::value, size_t>::type
     373           0 : get_hashable_data(const T &value) {
     374           0 :   using ::llvm::hash_value;
     375     1014057 :   return hash_value(value);
     376             : }
     377           0 : 
     378           0 : /// Helper to store data from a value into a buffer and advance the
     379             : /// pointer into that buffer.
     380           0 : ///
     381    13141822 : /// This routine first checks whether there is enough space in the provided
     382           0 : /// buffer, and if not immediately returns false. If there is space, it
     383           0 : /// copies the underlying bytes of value into the buffer, advances the
     384        5864 : /// buffer_ptr past the copied bytes, and returns true.
     385           0 : template <typename T>
     386           0 : bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value,
     387     1824421 :                        size_t offset = 0) {
     388           0 :   size_t store_size = sizeof(value) - offset;
     389   138433778 :   if (buffer_ptr + store_size > buffer_end)
     390           0 :     return false;
     391             :   const char *value_data = reinterpret_cast<const char *>(&value);
     392   134308981 :   memcpy(buffer_ptr, value_data + offset, store_size);
     393     1347540 :   buffer_ptr += store_size;
     394           0 :   return true;
     395    41062978 : }
     396    42839590 : 
     397           0 : /// Implement the combining of integral values into a hash_code.
     398    42794548 : ///
     399           0 : /// This overload is selected when the value type of the iterator is
     400           0 : /// integral. Rather than computing a hash_code for each object and then
     401     7276220 : /// combining them, this (as an optimization) directly combines the integers.
     402           0 : template <typename InputIteratorT>
     403     1882091 : hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) {
     404     7581033 :   const uint64_t seed = get_execution_seed();
     405           0 :   char buffer[64], *buffer_ptr = buffer;
     406          16 :   char *const buffer_end = std::end(buffer);
     407     7378968 :   while (first != last && store_and_advance(buffer_ptr, buffer_end,
     408         230 :                                             get_hashable_data(*first)))
     409      136246 :     ++first;
     410   151974777 :   if (first == last)
     411     1859325 :     return hash_short(buffer, buffer_ptr - buffer, seed);
     412         494 :   assert(buffer_ptr == buffer_end);
     413   200635599 : 
     414       22766 :   hash_state state = state.create(buffer, seed);
     415       44839 :   size_t length = 64;
     416    43710262 :   while (first != last) {
     417       20284 :     // Fill up the buffer. We don't clear it, which re-mixes the last round
     418         558 :     // when only a partial 64-byte chunk is left.
     419     1720152 :     buffer_ptr = buffer;
     420    38729871 :     while (first != last && store_and_advance(buffer_ptr, buffer_end,
     421          16 :                                               get_hashable_data(*first)))
     422    32901510 :       ++first;
     423       27751 : 
     424           0 :     // Rotate the buffer if we did a partial fill in order to simulate doing
     425         150 :     // a mix of the last 64-bytes. That is how the algorithm works when we
     426       17220 :     // have a contiguous byte sequence, and we want to emulate that here.
     427           3 :     std::rotate(buffer, buffer_ptr, buffer_end);
     428       40082 : 
     429          15 :     // Mix this chunk into the current state.
     430     4124797 :     state.mix(buffer);
     431     4124797 :     length += buffer_ptr - buffer;
     432      764145 :   };
     433      747056 : 
     434    91155102 :   return state.finalize(length);
     435           0 : }
     436           0 : 
     437    91132334 : /// Implement the combining of integral values into a hash_code.
     438           2 : ///
     439           1 : /// This overload is selected when the value type of the iterator is integral
     440           0 : /// and when the input iterator is actually a pointer. Rather than computing
     441           0 : /// a hash_code for each object and then combining them, this (as an
     442       22978 : /// optimization) directly combines the integers. Also, because the integers
     443       22978 : /// are stored in contiguous memory, this routine avoids copying each value
     444             : /// and directly reads from the underlying memory.
     445             : template <typename ValueT>
     446       17088 : typename std::enable_if<is_hashable_data<ValueT>::value, hash_code>::type
     447  1374734963 : hash_combine_range_impl(ValueT *first, ValueT *last) {
     448  1374734964 :   const uint64_t seed = get_execution_seed();
     449           1 :   const char *s_begin = reinterpret_cast<const char *>(first);
     450             :   const char *s_end = reinterpret_cast<const char *>(last);
     451  1374734964 :   const size_t length = std::distance(s_begin, s_end);
     452  1374734965 :   if (length <= 64)
     453  1338487031 :     return hash_short(s_begin, length, seed);
     454    10026031 : 
     455    46273964 :   const char *s_aligned_end = s_begin + (length & ~63);
     456    46276586 :   hash_state state = state.create(s_begin, seed);
     457    56302612 :   s_begin += 64;
     458    81356364 :   while (s_begin != s_aligned_end) {
     459    35232693 :     state.mix(s_begin);
     460    25228009 :     s_begin += 64;
     461       21395 :   }
     462    46295353 :   if (length & 63)
     463    44738963 :     state.mix(s_end - 64);
     464      190885 : 
     465    46445946 :   return state.finalize(length);
     466        3061 : }
     467         136 : 
     468    21743888 : } // namespace detail
     469    21743358 : } // namespace hashing
     470         134 : 
     471       18769 : 
     472    21724988 : /// Compute a hash_code for a sequence of values.
     473    21730992 : ///
     474    21706530 : /// This hashes a sequence of values. It produces the same hash_code as
     475         134 : /// 'hash_combine(a, b, c, ...)', but can run over arbitrary sized sequences
     476       24596 : /// and is significantly faster given pointers and types which can be hashed as
     477       30735 : /// a sequence of bytes.
     478       30601 : template <typename InputIteratorT>
     479       93303 : hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) {
     480  1351002959 :   return ::llvm::hashing::detail::hash_combine_range_impl(first, last);
     481       62711 : }
     482           5 : 
     483       24600 : 
     484        7269 : // Implementation details for hash_combine.
     485           1 : namespace hashing {
     486    13186144 : namespace detail {
     487           9 : 
     488          13 : /// Helper class to manage the recursive combining of hash_combine
     489         711 : /// arguments.
     490             : ///
     491          88 : /// This class exists to manage the state and various calls involved in the
     492      118273 : /// recursive combining of arguments used in hash_combine. It is particularly
     493           0 : /// useful at minimizing the code in the recursive calls to ease the pain
     494           9 : /// caused by a lack of variadic functions.
     495           9 : struct hash_combine_recursive_helper {
     496           0 :   char buffer[64];
     497           0 :   hash_state state;
     498           0 :   const uint64_t seed;
     499           0 : 
     500           0 : public:
     501     1334816 :   /// Construct a recursive hash combining helper.
     502           0 :   ///
     503           0 :   /// This sets up the state for a recursive hash combine, including getting
     504       68125 :   /// the seed and buffer setup.
     505           0 :   hash_combine_recursive_helper()
     506   190741469 :     : seed(get_execution_seed()) {}
     507             : 
     508    21724987 :   /// Combine one chunk of data into the current in-flight hash.
     509    21724987 :   ///
     510             :   /// This merges one chunk of data into the hash. First it tries to buffer
     511           0 :   /// the data. If the buffer is full, it hashes the buffer into its
     512    50039799 :   /// hash_state, empties it, and then merges the new chunk in. This also
     513    21724987 :   /// handles cases where the data straddles the end of the buffer.
     514    21700391 :   template <typename T>
     515    96876461 :   char *combine_data(size_t &length, char *buffer_ptr, char *buffer_end, T data) {
     516    96475633 :     if (!store_and_advance(buffer_ptr, buffer_end, data)) {
     517       24596 :       // Check for skew which prevents the buffer from being packed, and do
     518     2717360 :       // a partial store into the buffer to fill it. This is only a concern
     519       87302 :       // with the variadic combine because that formation can have varying
     520       62707 :       // argument types.
     521    41072128 :       size_t partial_store_size = buffer_end - buffer_ptr;
     522    40965243 :       memcpy(buffer_ptr, &data, partial_store_size);
     523       24596 : 
     524     2267851 :       // If the store fails, our buffer is full and ready to hash. We have to
     525     1731012 :       // either initialize the hash state (on the first full buffer) or mix
     526       30604 :       // this buffer into the existing hash state. Length tracks the *hashed*
     527    10895886 :       // length, not the buffered length.
     528     3106246 :       if (length == 0) {
     529           0 :         state = state.create(buffer, seed);
     530    15923688 :         length = 64;
     531      176712 :       } else {
     532             :         // Mix this chunk into the current state and bump length up by 64.
     533      374891 :         state.mix(buffer);
     534      374891 :         length += 64;
     535           0 :       }
     536    11373523 :       // Reset the buffer_ptr to the head of the buffer for the next chunk of
     537    11373523 :       // data.
     538           0 :       buffer_ptr = buffer;
     539    39497082 : 
     540    39497082 :       // Try again to store into the buffer -- this cannot fail as we only
     541    21727402 :       // store types smaller than the buffer.
     542           0 :       if (!store_and_advance(buffer_ptr, buffer_end, data,
     543           0 :                              partial_store_size))
     544           0 :         abort();
     545           0 :     }
     546    96451037 :     return buffer_ptr;
     547           0 :   }
     548     1014230 : 
     549     1014230 :   /// Recursive, variadic combining method.
     550           0 :   ///
     551    50394260 :   /// This function recurses through each argument, combining that argument
     552    40993511 :   /// into a single hash.
     553           1 :   template <typename T, typename ...Ts>
     554    13150839 :   hash_code combine(size_t length, char *buffer_ptr, char *buffer_end,
     555    14878802 :                     const T &arg, const Ts &...args) {
     556        3048 :     buffer_ptr = combine_data(length, buffer_ptr, buffer_end, get_hashable_data(arg));
     557      419498 : 
     558     3525742 :     // Recurse to the next argument.
     559        3048 :     return combine(length, buffer_ptr, buffer_end, args...);
     560    91238587 :   }
     561    91467177 : 
     562       50354 :   /// Base case for recursive, variadic combining.
     563       23613 :   ///
     564      396980 :   /// The base case when combining arguments recursively is reached when all
     565           0 :   /// arguments have been handled. It flushes the remaining buffer and
     566        1532 :   /// constructs a hash_code.
     567   191620058 :   hash_code combine(size_t length, char *buffer_ptr, char *buffer_end) {
     568        1524 :     // Check whether the entire set of values fit in the buffer. If so, we'll
     569      341822 :     // use the optimized short hashing routine and skip state entirely.
     570   134131243 :     if (length == 0)
     571    94290815 :       return hash_short(buffer, buffer_ptr - buffer, seed);
     572       32706 : 
     573       34230 :     // Mix the final buffer, rotating it if we did a partial fill in order to
     574           0 :     // simulate doing a mix of the last 64-bytes. That is how the algorithm
     575           0 :     // works when we have a contiguous byte sequence, and we want to emulate
     576   149697393 :     // that here.
     577   149697393 :     std::rotate(buffer, buffer_ptr, buffer_end);
     578           0 : 
     579     1014230 :     // Mix this chunk into the current state.
     580           0 :     state.mix(buffer);
     581     1080302 :     length += buffer_ptr - buffer;
     582     1014612 : 
     583           0 :     return state.finalize(length);
     584       65690 :   }
     585    13213480 : };
     586           1 : 
     587    13761323 : } // namespace detail
     588    14180816 : } // namespace hashing
     589           0 : 
     590      629827 : /// Combine values into a single hash_code.
     591    91868412 : ///
     592       50354 : /// This routine accepts a varying number of arguments of any type. It will
     593      499507 : /// attempt to combine them into a single hash_code. For user-defined types it
     594      529548 : /// attempts to call a \see hash_value overload (via ADL) for the type. For
     595        7952 : /// integer and pointer types it directly combines their data into the
     596       22089 : /// resulting hash_code.
     597       22097 : ///
     598           0 : /// The result is suitable for returning from a user's hash_value
     599           3 : /// *implementation* for their user-defined type. Consumers of a type should
     600      341825 : /// *not* call this routine, they should instead call 'hash_value'.
     601    94290814 : template <typename ...Ts> hash_code hash_combine(const Ts &...args) {
     602      739585 :   // Recursively hash each argument using a helper class.
     603      772291 :   ::llvm::hashing::detail::hash_combine_recursive_helper helper;
     604    94290815 :   return helper.combine(0, helper.buffer, helper.buffer + 64, args...);
     605     6745907 : }
     606     6745907 : 
     607   149697393 : // Implementation details for implementations of hash_value overloads provided
     608           0 : // here.
     609    21248247 : namespace hashing {
     610    21248247 : namespace detail {
     611           0 : 
     612     1014612 : /// Helper to hash the value of a single integer.
     613           0 : ///
     614           0 : /// Overloads for smaller integer types are not provided to ensure consistent
     615       65690 : /// behavior in the presence of integral promotions. Essentially,
     616           0 : /// "hash_value('4')" and "hash_value('0' + 4)" should be the same.
     617         586 : inline hash_code hash_integer_value(uint64_t value) {
     618    13827012 :   // Similar to hash_4to8_bytes but using a seed instead of length.
     619         587 :   const uint64_t seed = get_execution_seed();
     620    15070189 :   const char *s = reinterpret_cast<const char *>(&value);
     621    14685954 :   const uint64_t a = fetch32(s);
     622     1015229 :   return hash_16_bytes(seed + (a << 3), fetch32(s + 4));
     623      681217 : }
     624     1180722 : 
     625     1022009 : } // namespace detail
     626    15289749 : } // namespace hashing
     627    16367933 : 
     628       42456 : // Declared and documented above, but defined here so that any of the hashing
     629     1035836 : // infrastructure is available.
     630       22092 : template <typename T>
     631          54 : typename std::enable_if<is_integral_or_enum<T>::value, hash_code>::type
     632     1013754 : hash_value(T value) {
     633      739646 :   return ::llvm::hashing::detail::hash_integer_value(
     634         310 :       static_cast<uint64_t>(value));
     635       13341 : }
     636     6759504 : 
     637           0 : // Declared and documented above, but defined here so that any of the hashing
     638      755847 : // infrastructure is available.
     639      756103 : template <typename T> hash_code hash_value(const T *ptr) {
     640    21248833 :   return ::llvm::hashing::detail::hash_integer_value(
     641           0 :     reinterpret_cast<uintptr_t>(ptr));
     642      134297 : }
     643      134297 : 
     644           0 : // Declared and documented above, but defined here so that any of the hashing
     645           0 : // infrastructure is available.
     646           0 : template <typename T, typename U>
     647         310 : hash_code hash_value(const std::pair<T, U> &arg) {
     648           0 :   return hash_combine(arg.first, arg.second);
     649           0 : }
     650         310 : 
     651    14056441 : // Declared and documented above, but defined here so that any of the hashing
     652           0 : // infrastructure is available.
     653         626 : template <typename T>
     654     1695133 : hash_code hash_value(const std::basic_string<T> &arg) {
     655       24572 :   return hash_combine_range(arg.begin(), arg.end());
     656        1108 : }
     657    16304722 : 
     658     1056322 : } // namespace llvm
     659    14966189 : 
     660     1947159 : #endif

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