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Diffstat (limited to 'include/llvm/ADT/Hashing.h')
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1 files changed, 705 insertions, 130 deletions
diff --git a/include/llvm/ADT/Hashing.h b/include/llvm/ADT/Hashing.h index 682dc22..ccf352c 100644 --- a/include/llvm/ADT/Hashing.h +++ b/include/llvm/ADT/Hashing.h @@ -7,170 +7,745 @@ // //===----------------------------------------------------------------------===// // -// This file defines utilities for computing hash values for various data types. +// This file implements the newly proposed standard C++ interfaces for hashing +// arbitrary data and building hash functions for user-defined types. This +// interface was originally proposed in N3333[1] and is currently under review +// for inclusion in a future TR and/or standard. +// +// The primary interfaces provide are comprised of one type and three functions: +// +// -- 'hash_code' class is an opaque type representing the hash code for some +// data. It is the intended product of hashing, and can be used to implement +// hash tables, checksumming, and other common uses of hashes. It is not an +// integer type (although it can be converted to one) because it is risky +// to assume much about the internals of a hash_code. In particular, each +// execution of the program has a high probability of producing a different +// hash_code for a given input. Thus their values are not stable to save or +// persist, and should only be used during the execution for the +// construction of hashing datastructures. +// +// -- 'hash_value' is a function designed to be overloaded for each +// user-defined type which wishes to be used within a hashing context. It +// should be overloaded within the user-defined type's namespace and found +// via ADL. Overloads for primitive types are provided by this library. +// +// -- 'hash_combine' and 'hash_combine_range' are functions designed to aid +// programmers in easily and intuitively combining a set of data into +// a single hash_code for their object. They should only logically be used +// within the implementation of a 'hash_value' routine or similar context. +// +// Note that 'hash_combine_range' contains very special logic for hashing +// a contiguous array of integers or pointers. This logic is *extremely* fast, +// on a modern Intel "Gainestown" Xeon (Nehalem uarch) @2.2 GHz, these were +// benchmarked at over 6.5 GiB/s for large keys, and <20 cycles/hash for keys +// under 32-bytes. // //===----------------------------------------------------------------------===// #ifndef LLVM_ADT_HASHING_H #define LLVM_ADT_HASHING_H -#include "llvm/ADT/ArrayRef.h" -#include "llvm/ADT/StringRef.h" -#include "llvm/Support/AlignOf.h" -#include "llvm/Support/Compiler.h" +#include "llvm/ADT/STLExtras.h" #include "llvm/Support/DataTypes.h" +#include "llvm/Support/type_traits.h" +#include <algorithm> +#include <cassert> #include <cstring> +#include <iterator> +#include <utility> + +// Allow detecting C++11 feature availability when building with Clang without +// breaking other compilers. +#ifndef __has_feature +# define __has_feature(x) 0 +#endif namespace llvm { -/// Class to compute a hash value from multiple data fields of arbitrary -/// types. Note that if you are hashing a single data type, such as a -/// string, it may be cheaper to use a hash algorithm that is tailored -/// for that specific data type. -/// Typical Usage: -/// GeneralHash Hash; -/// Hash.add(someValue); -/// Hash.add(someOtherValue); -/// return Hash.finish(); -/// Adapted from MurmurHash2 by Austin Appleby -class GeneralHash { -private: - enum { - M = 0x5bd1e995 - }; - unsigned Hash; - unsigned Count; +/// \brief An opaque object representing a hash code. +/// +/// This object represents the result of hashing some entity. It is intended to +/// be used to implement hashtables or other hashing-based data structures. +/// While it wraps and exposes a numeric value, this value should not be +/// trusted to be stable or predictable across processes or executions. +/// +/// In order to obtain the hash_code for an object 'x': +/// \code +/// using llvm::hash_value; +/// llvm::hash_code code = hash_value(x); +/// \endcode +/// +/// Also note that there are two numerical values which are reserved, and the +/// implementation ensures will never be produced for real hash_codes. These +/// can be used as sentinels within hashing data structures. +class hash_code { + size_t value; + public: - GeneralHash(unsigned Seed = 0) : Hash(Seed), Count(0) {} + /// \brief Default construct a hash_code. Constructs a null code. + hash_code() : value() {} - /// Add a pointer value. - /// Note: this adds pointers to the hash using sizes and endianness that - /// depend on the host. It doesn't matter however, because hashing on - /// pointer values is inherently unstable. - template<typename T> - GeneralHash& add(const T *PtrVal) { - addBits(&PtrVal, &PtrVal + 1); - return *this; + /// \brief Form a hash code directly from a numerical value. + hash_code(size_t value) : value(value) { + // Ensure we don't form a hash_code with one of the prohibited values. + assert(value != get_null_code().value); + assert(value != get_invalid_code().value); } - /// Add an ArrayRef of arbitrary data. - template<typename T> - GeneralHash& add(ArrayRef<T> ArrayVal) { - addBits(ArrayVal.begin(), ArrayVal.end()); - return *this; + /// \brief Convert the hash code to its numerical value for use. + /*explicit*/ operator size_t() const { return value; } + + /// \brief Get a hash_code object which corresponds to a null code. + /// + /// The null code must never be the result of any 'hash_value' calls and can + /// be used to detect an unset hash_code. + static hash_code get_null_code() { return hash_code(); } + + /// \brief Get a hash_code object which corresponds to an invalid code. + /// + /// The invalid code must never be the result of any 'hash_value' calls. This + /// can be used to flag invalid hash_codes or mark entries in a hash table. + static hash_code get_invalid_code() { + hash_code invalid_code; + invalid_code.value = static_cast<size_t>(-1); + return invalid_code; } - /// Add a string - GeneralHash& add(StringRef StrVal) { - addBits(StrVal.begin(), StrVal.end()); - return *this; + friend bool operator==(const hash_code &lhs, const hash_code &rhs) { + return lhs.value == rhs.value; + } + friend bool operator!=(const hash_code &lhs, const hash_code &rhs) { + return lhs.value != rhs.value; } - /// Add an signed 32-bit integer. - GeneralHash& add(int32_t Data) { - addInt(uint32_t(Data)); - return *this; + /// \brief Allow a hash_code to be directly run through hash_value. + friend size_t hash_value(const hash_code &code) { return code.value; } +}; + + +// All of the implementation details of actually computing the various hash +// code values are held within this namespace. These routines are included in +// the header file mainly to allow inlining and constant propagation. +namespace hashing { +namespace detail { + +inline uint64_t fetch64(const char *p) { + uint64_t result; + memcpy(&result, p, sizeof(result)); + return result; +} + +inline uint32_t fetch32(const char *p) { + uint32_t result; + memcpy(&result, p, sizeof(result)); + return result; +} + +/// Some primes between 2^63 and 2^64 for various uses. +static const uint64_t k0 = 0xc3a5c85c97cb3127ULL; +static const uint64_t k1 = 0xb492b66fbe98f273ULL; +static const uint64_t k2 = 0x9ae16a3b2f90404fULL; +static const uint64_t k3 = 0xc949d7c7509e6557ULL; + +/// \brief Bitwise right rotate. +/// Normally this will compile to a single instruction, especially if the +/// shift is a manifest constant. +inline uint64_t rotate(uint64_t val, unsigned shift) { + // Avoid shifting by 64: doing so yields an undefined result. + return shift == 0 ? val : ((val >> shift) | (val << (64 - shift))); +} + +inline uint64_t shift_mix(uint64_t val) { + return val ^ (val >> 47); +} + +inline uint64_t hash_16_bytes(uint64_t low, uint64_t high) { + // Murmur-inspired hashing. + const uint64_t kMul = 0x9ddfea08eb382d69ULL; + uint64_t a = (low ^ high) * kMul; + a ^= (a >> 47); + uint64_t b = (high ^ a) * kMul; + b ^= (b >> 47); + b *= kMul; + return b; +} + +inline uint64_t hash_1to3_bytes(const char *s, size_t len, uint64_t seed) { + uint8_t a = s[0]; + uint8_t b = s[len >> 1]; + uint8_t c = s[len - 1]; + uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8); + uint32_t z = len + (static_cast<uint32_t>(c) << 2); + return shift_mix(y * k2 ^ z * k3 ^ seed) * k2; +} + +inline uint64_t hash_4to8_bytes(const char *s, size_t len, uint64_t seed) { + uint64_t a = fetch32(s); + return hash_16_bytes(len + (a << 3), seed ^ fetch32(s + len - 4)); +} + +inline uint64_t hash_9to16_bytes(const char *s, size_t len, uint64_t seed) { + uint64_t a = fetch64(s); + uint64_t b = fetch64(s + len - 8); + return hash_16_bytes(seed ^ a, rotate(b + len, len)) ^ b; +} + +inline uint64_t hash_17to32_bytes(const char *s, size_t len, uint64_t seed) { + uint64_t a = fetch64(s) * k1; + uint64_t b = fetch64(s + 8); + uint64_t c = fetch64(s + len - 8) * k2; + uint64_t d = fetch64(s + len - 16) * k0; + return hash_16_bytes(rotate(a - b, 43) + rotate(c ^ seed, 30) + d, + a + rotate(b ^ k3, 20) - c + len + seed); +} + +inline uint64_t hash_33to64_bytes(const char *s, size_t len, uint64_t seed) { + uint64_t z = fetch64(s + 24); + uint64_t a = fetch64(s) + (len + fetch64(s + len - 16)) * k0; + uint64_t b = rotate(a + z, 52); + uint64_t c = rotate(a, 37); + a += fetch64(s + 8); + c += rotate(a, 7); + a += fetch64(s + 16); + uint64_t vf = a + z; + uint64_t vs = b + rotate(a, 31) + c; + a = fetch64(s + 16) + fetch64(s + len - 32); + z = fetch64(s + len - 8); + b = rotate(a + z, 52); + c = rotate(a, 37); + a += fetch64(s + len - 24); + c += rotate(a, 7); + a += fetch64(s + len - 16); + uint64_t wf = a + z; + uint64_t ws = b + rotate(a, 31) + c; + uint64_t r = shift_mix((vf + ws) * k2 + (wf + vs) * k0); + return shift_mix(seed ^ (r * k0) + vs) * k2; +} + +inline uint64_t hash_short(const char *s, size_t length, uint64_t seed) { + uint64_t hash; + if (length >= 4 && length <= 8) + hash = hash_4to8_bytes(s, length, seed); + else if (length > 8 && length <= 16) + hash = hash_9to16_bytes(s, length, seed); + else if (length > 16 && length <= 32) + hash = hash_17to32_bytes(s, length, seed); + else if (length > 32) + hash = hash_33to64_bytes(s, length, seed); + else if (length != 0) + hash = hash_1to3_bytes(s, length, seed); + else + return k2 ^ seed; + + // FIXME: The invalid hash_code check is really expensive; there should be + // a better way of ensuring these invariants hold. + if (hash == static_cast<uint64_t>(hash_code::get_null_code())) + hash = k1 ^ seed; + else if (hash == static_cast<uint64_t>(hash_code::get_invalid_code())) + hash = k3 ^ seed; + return hash; +} + +/// \brief The intermediate state used during hashing. +/// Currently, the algorithm for computing hash codes is based on CityHash and +/// keeps 56 bytes of arbitrary state. +struct hash_state { + uint64_t h0, h1, h2, h3, h4, h5, h6; + uint64_t seed; + + /// \brief Create a new hash_state structure and initialize it based on the + /// seed and the first 64-byte chunk. + /// This effectively performs the initial mix. + static hash_state create(const char *s, uint64_t seed) { + hash_state state = { + 0, seed, hash_16_bytes(seed, k1), rotate(seed ^ k1, 49), + seed * k1, shift_mix(seed), hash_16_bytes(state.h4, state.h5), + seed + }; + state.mix(s); + return state; } - /// Add an unsigned 32-bit integer. - GeneralHash& add(uint32_t Data) { - addInt(Data); - return *this; + /// \brief Mix 32-bytes from the input sequence into the 16-bytes of 'a' + /// and 'b', including whatever is already in 'a' and 'b'. + static void mix_32_bytes(const char *s, uint64_t &a, uint64_t &b) { + a += fetch64(s); + uint64_t c = fetch64(s + 24); + b = rotate(b + a + c, 21); + uint64_t d = a; + a += fetch64(s + 8) + fetch64(s + 16); + b += rotate(a, 44) + d; + a += c; } - /// Add an signed 64-bit integer. - GeneralHash& add(int64_t Data) { - addInt(uint64_t(Data)); - return *this; + /// \brief Mix in a 64-byte buffer of data. + /// We mix all 64 bytes even when the chunk length is smaller, but we + /// record the actual length. + void mix(const char *s) { + h0 = rotate(h0 + h1 + h3 + fetch64(s + 8), 37) * k1; + h1 = rotate(h1 + h4 + fetch64(s + 48), 42) * k1; + h0 ^= h6; + h1 += h3 + fetch64(s + 40); + h2 = rotate(h2 + h5, 33) * k1; + h3 = h4 * k1; + h4 = h0 + h5; + mix_32_bytes(s, h3, h4); + h5 = h2 + h6; + h6 = h1 + fetch64(s + 16); + mix_32_bytes(s + 32, h5, h6); + std::swap(h2, h0); } - /// Add an unsigned 64-bit integer. - GeneralHash& add(uint64_t Data) { - addInt(Data); - return *this; + /// \brief Compute the final 64-bit hash code value based on the current + /// state and the length of bytes hashed. + uint64_t finalize(size_t length) { + uint64_t final_value + = hash_16_bytes(hash_16_bytes(h3, h5) + shift_mix(h1) * k1 + h2, + hash_16_bytes(h4, h6) + shift_mix(length) * k1 + h0); + if (final_value == static_cast<uint64_t>(hash_code::get_null_code())) + final_value = k1 ^ seed; + if (final_value == static_cast<uint64_t>(hash_code::get_invalid_code())) + final_value = k3 ^ seed; + return final_value; } +}; - /// Add a float - GeneralHash& add(float Data) { - union { - float D; uint32_t I; - }; - D = Data; - addInt(I); - return *this; + +/// \brief A global, fixed seed-override variable. +/// +/// This variable can be set using the \see llvm::set_fixed_execution_seed +/// function. See that function for details. Do not, under any circumstances, +/// set or read this variable. +extern size_t fixed_seed_override; + +inline size_t get_execution_seed() { + // FIXME: This needs to be a per-execution seed. This is just a placeholder + // implementation. Switching to a per-execution seed is likely to flush out + // instability bugs and so will happen as its own commit. + // + // However, if there is a fixed seed override set the first time this is + // called, return that instead of the per-execution seed. + static size_t seed = fixed_seed_override ? fixed_seed_override + : 0xff51afd7ed558ccdULL; + return seed; +} + + +/// \brief Helper to hash the value of a single integer. +/// +/// Overloads for smaller integer types are not provided to ensure consistent +/// behavior in the presence of integral promotions. Essentially, +/// "hash_value('4')" and "hash_value('0' + 4)" should be the same. +inline hash_code hash_integer_value(uint64_t value) { + // Similar to hash_4to8_bytes but using a seed instead of length. + const uint64_t seed = get_execution_seed(); + const char *s = reinterpret_cast<const char *>(&value); + const uint64_t a = fetch32(s); + return hash_16_bytes(seed + (a << 3), fetch32(s + 4)); +} + +} // namespace detail +} // namespace hashing + + +/// \brief Override the execution seed with a fixed value. +/// +/// This hashing library uses a per-execution seed designed to change on each +/// run with high probability in order to ensure that the hash codes are not +/// attackable and to ensure that output which is intended to be stable does +/// not rely on the particulars of the hash codes produced. +/// +/// That said, there are use cases where it is important to be able to +/// reproduce *exactly* a specific behavior. To that end, we provide a function +/// which will forcibly set the seed to a fixed value. This must be done at the +/// start of the program, before any hashes are computed. Also, it cannot be +/// undone. This makes it thread-hostile and very hard to use outside of +/// immediately on start of a simple program designed for reproducible +/// behavior. +void set_fixed_execution_hash_seed(size_t fixed_value); + + +/// \brief Compute a hash_code for any integer value. +/// +/// Note that this function is intended to compute the same hash_code for +/// a particular value without regard to the pre-promotion type. This is in +/// contrast to hash_combine which may produce different hash_codes for +/// differing argument types even if they would implicit promote to a common +/// type without changing the value. +template <typename T> +typename enable_if<is_integral<T>, hash_code>::type hash_value(T value) { + return ::llvm::hashing::detail::hash_integer_value(value); +} + +/// \brief Compute a hash_code for a pointer's address. +/// +/// N.B.: This hashes the *address*. Not the value and not the type. +template <typename T> hash_code hash_value(const T *ptr) { + return ::llvm::hashing::detail::hash_integer_value( + reinterpret_cast<uintptr_t>(ptr)); +} + + +// Implementation details for implementing hash combining functions. +namespace hashing { +namespace detail { + +/// \brief Trait to indicate whether a type's bits can be hashed directly. +/// +/// A type trait which is true if we want to combine values for hashing by +/// reading the underlying data. It is false if values of this type must +/// first be passed to hash_value, and the resulting hash_codes combined. +// +// FIXME: We want to replace is_integral and is_pointer here with a predicate +// which asserts that comparing the underlying storage of two values of the +// type for equality is equivalent to comparing the two values for equality. +// For all the platforms we care about, this holds for integers and pointers, +// but there are platforms where it doesn't and we would like to support +// user-defined types which happen to satisfy this property. +template <typename T> struct is_hashable_data + : integral_constant<bool, ((is_integral<T>::value || is_pointer<T>::value) && + 64 % sizeof(T) == 0)> {}; + +/// \brief Helper to get the hashable data representation for a type. +/// This variant is enabled when the type itself can be used. +template <typename T> +typename enable_if<is_hashable_data<T>, T>::type +get_hashable_data(const T &value) { + return value; +} +/// \brief Helper to get the hashable data representation for a type. +/// This variant is enabled when we must first call hash_value and use the +/// result as our data. +template <typename T> +typename enable_if_c<!is_hashable_data<T>::value, size_t>::type +get_hashable_data(const T &value) { + using ::llvm::hash_value; + return hash_value(value); +} + +/// \brief Helper to store data from a value into a buffer and advance the +/// pointer into that buffer. +/// +/// This routine first checks whether there is enough space in the provided +/// buffer, and if not immediately returns false. If there is space, it +/// copies the underlying bytes of value into the buffer, advances the +/// buffer_ptr past the copied bytes, and returns true. +template <typename T> +bool store_and_advance(char *&buffer_ptr, char *buffer_end, const T& value, + size_t offset = 0) { + size_t store_size = sizeof(value) - offset; + if (buffer_ptr + store_size > buffer_end) + return false; + const char *value_data = reinterpret_cast<const char *>(&value); + memcpy(buffer_ptr, value_data + offset, store_size); + buffer_ptr += store_size; + return true; +} + +/// \brief Implement the combining of integral values into a hash_code. +/// +/// This overload is selected when the value type of the iterator is +/// integral. Rather than computing a hash_code for each object and then +/// combining them, this (as an optimization) directly combines the integers. +template <typename InputIteratorT> +hash_code hash_combine_range_impl(InputIteratorT first, InputIteratorT last) { + typedef typename std::iterator_traits<InputIteratorT>::value_type ValueT; + const size_t seed = get_execution_seed(); + char buffer[64], *buffer_ptr = buffer; + char *const buffer_end = buffer_ptr + array_lengthof(buffer); + while (first != last && store_and_advance(buffer_ptr, buffer_end, + get_hashable_data(*first))) + ++first; +/// \brief Metafunction that determines whether the given type is an integral +/// type. + if (first == last) + return hash_short(buffer, buffer_ptr - buffer, seed); + assert(buffer_ptr == buffer_end); + + hash_state state = state.create(buffer, seed); + size_t length = 64; + while (first != last) { + // Fill up the buffer. We don't clear it, which re-mixes the last round + // when only a partial 64-byte chunk is left. + buffer_ptr = buffer; + while (first != last && store_and_advance(buffer_ptr, buffer_end, + get_hashable_data(*first))) + ++first; + + // Rotate the buffer if we did a partial fill in order to simulate doing + // a mix of the last 64-bytes. That is how the algorithm works when we + // have a contiguous byte sequence, and we want to emulate that here. + std::rotate(buffer, buffer_ptr, buffer_end); + + // Mix this chunk into the current state. + state.mix(buffer); + length += buffer_ptr - buffer; + }; + + return state.finalize(length); +} + +/// \brief Implement the combining of integral values into a hash_code. +/// +/// This overload is selected when the value type of the iterator is integral +/// and when the input iterator is actually a pointer. Rather than computing +/// a hash_code for each object and then combining them, this (as an +/// optimization) directly combines the integers. Also, because the integers +/// are stored in contiguous memory, this routine avoids copying each value +/// and directly reads from the underlying memory. +template <typename ValueT> +typename enable_if<is_hashable_data<ValueT>, hash_code>::type +hash_combine_range_impl(const ValueT *first, const ValueT *last) { + const size_t seed = get_execution_seed(); + const char *s_begin = reinterpret_cast<const char *>(first); + const char *s_end = reinterpret_cast<const char *>(last); + const size_t length = std::distance(s_begin, s_end); + if (length <= 64) + return hash_short(s_begin, length, seed); + + const char *s_aligned_end = s_begin + (length & ~63); + hash_state state = state.create(s_begin, seed); + s_begin += 64; + while (s_begin != s_aligned_end) { + state.mix(s_begin); + s_begin += 64; } + if (length & 63) + state.mix(s_end - 64); - /// Add a double - GeneralHash& add(double Data) { - union { - double D; uint64_t I; - }; - D = Data; - addInt(I); - return *this; - } - - // Do a few final mixes of the hash to ensure the last few - // bytes are well-incorporated. - unsigned finish() { - mix(Count); - Hash ^= Hash >> 13; - Hash *= M; - Hash ^= Hash >> 15; - return Hash; - } - -private: - void mix(uint32_t Data) { - ++Count; - Data *= M; - Data ^= Data >> 24; - Data *= M; - Hash *= M; - Hash ^= Data; - } - - // Add a single uint32 value - void addInt(uint32_t Val) { - mix(Val); - } - - // Add a uint64 value - void addInt(uint64_t Val) { - mix(uint32_t(Val >> 32)); - mix(uint32_t(Val)); - } - - // Add a range of bytes from I to E. - template<bool ElementsHaveEvenLength> - void addBytes(const char *I, const char *E) { - uint32_t Data; - // Note that aliasing rules forbid us from dereferencing - // reinterpret_cast<uint32_t *>(I) even if I happens to be suitably - // aligned, so we use memcpy instead. - for (; E - I >= ptrdiff_t(sizeof Data); I += sizeof Data) { - // A clever compiler should be able to turn this memcpy into a single - // aligned or unaligned load (depending on the alignment of the type T - // that was used in the call to addBits). - std::memcpy(&Data, I, sizeof Data); - mix(Data); - } - if (!ElementsHaveEvenLength && I != E) { - Data = 0; - std::memcpy(&Data, I, E - I); - mix(Data); + return state.finalize(length); +} + +} // namespace detail +} // namespace hashing + + +/// \brief Compute a hash_code for a sequence of values. +/// +/// This hashes a sequence of values. It produces the same hash_code as +/// 'hash_combine(a, b, c, ...)', but can run over arbitrary sized sequences +/// and is significantly faster given pointers and types which can be hashed as +/// a sequence of bytes. +template <typename InputIteratorT> +hash_code hash_combine_range(InputIteratorT first, InputIteratorT last) { + return ::llvm::hashing::detail::hash_combine_range_impl(first, last); +} + + +// Implementation details for hash_combine. +namespace hashing { +namespace detail { + +/// \brief Helper class to manage the recursive combining of hash_combine +/// arguments. +/// +/// This class exists to manage the state and various calls involved in the +/// recursive combining of arguments used in hash_combine. It is particularly +/// useful at minimizing the code in the recursive calls to ease the pain +/// caused by a lack of variadic functions. +class hash_combine_recursive_helper { + const size_t seed; + char buffer[64]; + char *const buffer_end; + char *buffer_ptr; + size_t length; + hash_state state; + +public: + /// \brief Construct a recursive hash combining helper. + /// + /// This sets up the state for a recursive hash combine, including getting + /// the seed and buffer setup. + hash_combine_recursive_helper() + : seed(get_execution_seed()), + buffer_end(buffer + array_lengthof(buffer)), + buffer_ptr(buffer), + length(0) {} + + /// \brief Combine one chunk of data into the current in-flight hash. + /// + /// This merges one chunk of data into the hash. First it tries to buffer + /// the data. If the buffer is full, it hashes the buffer into its + /// hash_state, empties it, and then merges the new chunk in. This also + /// handles cases where the data straddles the end of the buffer. + template <typename T> void combine_data(T data) { + if (!store_and_advance(buffer_ptr, buffer_end, data)) { + // Check for skew which prevents the buffer from being packed, and do + // a partial store into the buffer to fill it. This is only a concern + // with the variadic combine because that formation can have varying + // argument types. + size_t partial_store_size = buffer_end - buffer_ptr; + memcpy(buffer_ptr, &data, partial_store_size); + + // If the store fails, our buffer is full and ready to hash. We have to + // either initialize the hash state (on the first full buffer) or mix + // this buffer into the existing hash state. Length tracks the *hashed* + // length, not the buffered length. + if (length == 0) { + state = state.create(buffer, seed); + length = 64; + } else { + // Mix this chunk into the current state and bump length up by 64. + state.mix(buffer); + length += 64; + } + // Reset the buffer_ptr to the head of the buffer for the next chunk of + // data. + buffer_ptr = buffer; + + // Try again to store into the buffer -- this cannot fail as we only + // store types smaller than the buffer. + if (!store_and_advance(buffer_ptr, buffer_end, data, + partial_store_size)) + abort(); } } - // Add a range of bits from I to E. - template<typename T> - void addBits(const T *I, const T *E) { - addBytes<sizeof (T) % sizeof (uint32_t) == 0>( - reinterpret_cast<const char *>(I), - reinterpret_cast<const char *>(E)); +#if defined(__has_feature) && __has_feature(__cxx_variadic_templates__) + + /// \brief Recursive, variadic combining method. + /// + /// This function recurses through each argument, combining that argument + /// into a single hash. + template <typename T, typename ...Ts> + hash_code combine(const T &arg, const Ts &...args) { + combine_data( get_hashable_data(arg)); + + // Recurse to the next argument. + return combine(args...); + } + +#else + // Manually expanded recursive combining methods. See variadic above for + // documentation. + + template <typename T1, typename T2, typename T3, typename T4, typename T5, + typename T6> + hash_code combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, + const T4 &arg4, const T5 &arg5, const T6 &arg6) { + combine_data(get_hashable_data(arg1)); + return combine(arg2, arg3, arg4, arg5, arg6); + } + template <typename T1, typename T2, typename T3, typename T4, typename T5> + hash_code combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, + const T4 &arg4, const T5 &arg5) { + combine_data(get_hashable_data(arg1)); + return combine(arg2, arg3, arg4, arg5); + } + template <typename T1, typename T2, typename T3, typename T4> + hash_code combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, + const T4 &arg4) { + combine_data(get_hashable_data(arg1)); + return combine(arg2, arg3, arg4); + } + template <typename T1, typename T2, typename T3> + hash_code combine(const T1 &arg1, const T2 &arg2, const T3 &arg3) { + combine_data(get_hashable_data(arg1)); + return combine(arg2, arg3); + } + template <typename T1, typename T2> + hash_code combine(const T1 &arg1, const T2 &arg2) { + combine_data(get_hashable_data(arg1)); + return combine(arg2); + } + template <typename T1> + hash_code combine(const T1 &arg1) { + combine_data(get_hashable_data(arg1)); + return combine(); + } + +#endif + + /// \brief Base case for recursive, variadic combining. + /// + /// The base case when combining arguments recursively is reached when all + /// arguments have been handled. It flushes the remaining buffer and + /// constructs a hash_code. + hash_code combine() { + // Check whether the entire set of values fit in the buffer. If so, we'll + // use the optimized short hashing routine and skip state entirely. + if (length == 0) + return hash_short(buffer, buffer_ptr - buffer, seed); + + // Mix the final buffer, rotating it if we did a partial fill in order to + // simulate doing a mix of the last 64-bytes. That is how the algorithm + // works when we have a contiguous byte sequence, and we want to emulate + // that here. + std::rotate(buffer, buffer_ptr, buffer_end); + + // Mix this chunk into the current state. + state.mix(buffer); + length += buffer_ptr - buffer; + + return state.finalize(length); } }; -} // end namespace llvm +} // namespace detail +} // namespace hashing + + +#if __has_feature(__cxx_variadic_templates__) + +/// \brief Combine values into a single hash_code. +/// +/// This routine accepts a varying number of arguments of any type. It will +/// attempt to combine them into a single hash_code. For user-defined types it +/// attempts to call a \see hash_value overload (via ADL) for the type. For +/// integer and pointer types it directly combines their data into the +/// resulting hash_code. +/// +/// The result is suitable for returning from a user's hash_value +/// *implementation* for their user-defined type. Consumers of a type should +/// *not* call this routine, they should instead call 'hash_value'. +template <typename ...Ts> hash_code hash_combine(const Ts &...args) { + // Recursively hash each argument using a helper class. + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(args...); +} + +#else + +// What follows are manually exploded overloads for each argument width. See +// the above variadic definition for documentation and specification. + +template <typename T1, typename T2, typename T3, typename T4, typename T5, + typename T6> +hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, + const T4 &arg4, const T5 &arg5, const T6 &arg6) { + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(arg1, arg2, arg3, arg4, arg5, arg6); +} +template <typename T1, typename T2, typename T3, typename T4, typename T5> +hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, + const T4 &arg4, const T5 &arg5) { + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(arg1, arg2, arg3, arg4, arg5); +} +template <typename T1, typename T2, typename T3, typename T4> +hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3, + const T4 &arg4) { + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(arg1, arg2, arg3, arg4); +} +template <typename T1, typename T2, typename T3> +hash_code hash_combine(const T1 &arg1, const T2 &arg2, const T3 &arg3) { + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(arg1, arg2, arg3); +} +template <typename T1, typename T2> +hash_code hash_combine(const T1 &arg1, const T2 &arg2) { + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(arg1, arg2); +} +template <typename T1> +hash_code hash_combine(const T1 &arg1) { + ::llvm::hashing::detail::hash_combine_recursive_helper helper; + return helper.combine(arg1); +} + +#endif + +} // namespace llvm #endif |