Merge pull request #3389 from yuriks/cityhash

Common: Replace MurmurHash3 with CityHash64

src/common/CMakeLists.txt

@@ -32,6 +32,8 @@ add_library(common STATIC
     break_points.cpp
     break_points.h
     chunk_file.h
+    cityhash.cpp
+    cityhash.h
     code_block.h
     color.h
     common_funcs.h
@@ -39,7 +41,6 @@ add_library(common STATIC
     common_types.h
     file_util.cpp
     file_util.h
-    hash.cpp
     hash.h
     linear_disk_cache.h
     logging/backend.cpp

src/common/cityhash.cpp

@@ -0,0 +1,340 @@
+// Copyright (c) 2011 Google, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+// CityHash, by Geoff Pike and Jyrki Alakuijala
+//
+// This file provides CityHash64() and related functions.
+//
+// It's probably possible to create even faster hash functions by
+// writing a program that systematically explores some of the space of
+// possible hash functions, by using SIMD instructions, or by
+// compromising on hash quality.
+
+#include <algorithm>
+#include <string.h> // for memcpy and memset
+#include "cityhash.h"
+#include "common/swap.h"
+
+// #include "config.h"
+#ifdef __GNUC__
+#define HAVE_BUILTIN_EXPECT 1
+#endif
+#ifdef COMMON_BIG_ENDIAN
+#define WORDS_BIGENDIAN 1
+#endif
+
+using namespace std;
+
+typedef uint8_t uint8;
+typedef uint32_t uint32;
+typedef uint64_t uint64;
+
+namespace Common {
+
+static uint64 UNALIGNED_LOAD64(const char* p) {
+    uint64 result;
+    memcpy(&result, p, sizeof(result));
+    return result;
+}
+
+static uint32 UNALIGNED_LOAD32(const char* p) {
+    uint32 result;
+    memcpy(&result, p, sizeof(result));
+    return result;
+}
+
+#ifdef WORDS_BIGENDIAN
+#define uint32_in_expected_order(x) (swap32(x))
+#define uint64_in_expected_order(x) (swap64(x))
+#else
+#define uint32_in_expected_order(x) (x)
+#define uint64_in_expected_order(x) (x)
+#endif
+
+#if !defined(LIKELY)
+#if HAVE_BUILTIN_EXPECT
+#define LIKELY(x) (__builtin_expect(!!(x), 1))
+#else
+#define LIKELY(x) (x)
+#endif
+#endif
+
+static uint64 Fetch64(const char* p) {
+    return uint64_in_expected_order(UNALIGNED_LOAD64(p));
+}
+
+static uint32 Fetch32(const char* p) {
+    return uint32_in_expected_order(UNALIGNED_LOAD32(p));
+}
+
+// Some primes between 2^63 and 2^64 for various uses.
+static const uint64 k0 = 0xc3a5c85c97cb3127ULL;
+static const uint64 k1 = 0xb492b66fbe98f273ULL;
+static const uint64 k2 = 0x9ae16a3b2f90404fULL;
+
+// Bitwise right rotate.  Normally this will compile to a single
+// instruction, especially if the shift is a manifest constant.
+static uint64 Rotate(uint64 val, int shift) {
+    // Avoid shifting by 64: doing so yields an undefined result.
+    return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
+}
+
+static uint64 ShiftMix(uint64 val) {
+    return val ^ (val >> 47);
+}
+
+static uint64 HashLen16(uint64 u, uint64 v) {
+    return Hash128to64(uint128(u, v));
+}
+
+static uint64 HashLen16(uint64 u, uint64 v, uint64 mul) {
+    // Murmur-inspired hashing.
+    uint64 a = (u ^ v) * mul;
+    a ^= (a >> 47);
+    uint64 b = (v ^ a) * mul;
+    b ^= (b >> 47);
+    b *= mul;
+    return b;
+}
+
+static uint64 HashLen0to16(const char* s, size_t len) {
+    if (len >= 8) {
+        uint64 mul = k2 + len * 2;
+        uint64 a = Fetch64(s) + k2;
+        uint64 b = Fetch64(s + len - 8);
+        uint64 c = Rotate(b, 37) * mul + a;
+        uint64 d = (Rotate(a, 25) + b) * mul;
+        return HashLen16(c, d, mul);
+    }
+    if (len >= 4) {
+        uint64 mul = k2 + len * 2;
+        uint64 a = Fetch32(s);
+        return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul);
+    }
+    if (len > 0) {
+        uint8 a = s[0];
+        uint8 b = s[len >> 1];
+        uint8 c = s[len - 1];
+        uint32 y = static_cast<uint32>(a) + (static_cast<uint32>(b) << 8);
+        uint32 z = static_cast<uint32>(len) + (static_cast<uint32>(c) << 2);
+        return ShiftMix(y * k2 ^ z * k0) * k2;
+    }
+    return k2;
+}
+
+// This probably works well for 16-byte strings as well, but it may be overkill
+// in that case.
+static uint64 HashLen17to32(const char* s, size_t len) {
+    uint64 mul = k2 + len * 2;
+    uint64 a = Fetch64(s) * k1;
+    uint64 b = Fetch64(s + 8);
+    uint64 c = Fetch64(s + len - 8) * mul;
+    uint64 d = Fetch64(s + len - 16) * k2;
+    return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d, a + Rotate(b + k2, 18) + c, mul);
+}
+
+// Return a 16-byte hash for 48 bytes.  Quick and dirty.
+// Callers do best to use "random-looking" values for a and b.
+static pair<uint64, uint64> WeakHashLen32WithSeeds(uint64 w, uint64 x, uint64 y, uint64 z, uint64 a,
+                                                   uint64 b) {
+    a += w;
+    b = Rotate(b + a + z, 21);
+    uint64 c = a;
+    a += x;
+    a += y;
+    b += Rotate(a, 44);
+    return make_pair(a + z, b + c);
+}
+
+// Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
+static pair<uint64, uint64> WeakHashLen32WithSeeds(const char* s, uint64 a, uint64 b) {
+    return WeakHashLen32WithSeeds(Fetch64(s), Fetch64(s + 8), Fetch64(s + 16), Fetch64(s + 24), a,
+                                  b);
+}
+
+// Return an 8-byte hash for 33 to 64 bytes.
+static uint64 HashLen33to64(const char* s, size_t len) {
+    uint64 mul = k2 + len * 2;
+    uint64 a = Fetch64(s) * k2;
+    uint64 b = Fetch64(s + 8);
+    uint64 c = Fetch64(s + len - 24);
+    uint64 d = Fetch64(s + len - 32);
+    uint64 e = Fetch64(s + 16) * k2;
+    uint64 f = Fetch64(s + 24) * 9;
+    uint64 g = Fetch64(s + len - 8);
+    uint64 h = Fetch64(s + len - 16) * mul;
+    uint64 u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9;
+    uint64 v = ((a + g) ^ d) + f + 1;
+    uint64 w = swap64((u + v) * mul) + h;
+    uint64 x = Rotate(e + f, 42) + c;
+    uint64 y = (swap64((v + w) * mul) + g) * mul;
+    uint64 z = e + f + c;
+    a = swap64((x + z) * mul + y) + b;
+    b = ShiftMix((z + a) * mul + d + h) * mul;
+    return b + x;
+}
+
+uint64 CityHash64(const char* s, size_t len) {
+    if (len <= 32) {
+        if (len <= 16) {
+            return HashLen0to16(s, len);
+        } else {
+            return HashLen17to32(s, len);
+        }
+    } else if (len <= 64) {
+        return HashLen33to64(s, len);
+    }
+
+    // For strings over 64 bytes we hash the end first, and then as we
+    // loop we keep 56 bytes of state: v, w, x, y, and z.
+    uint64 x = Fetch64(s + len - 40);
+    uint64 y = Fetch64(s + len - 16) + Fetch64(s + len - 56);
+    uint64 z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24));
+    pair<uint64, uint64> v = WeakHashLen32WithSeeds(s + len - 64, len, z);
+    pair<uint64, uint64> w = WeakHashLen32WithSeeds(s + len - 32, y + k1, x);
+    x = x * k1 + Fetch64(s);
+
+    // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
+    len = (len - 1) & ~static_cast<size_t>(63);
+    do {
+        x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
+        y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
+        x ^= w.second;
+        y += v.first + Fetch64(s + 40);
+        z = Rotate(z + w.first, 33) * k1;
+        v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
+        w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16));
+        std::swap(z, x);
+        s += 64;
+        len -= 64;
+    } while (len != 0);
+    return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,
+                     HashLen16(v.second, w.second) + x);
+}
+
+uint64 CityHash64WithSeed(const char* s, size_t len, uint64 seed) {
+    return CityHash64WithSeeds(s, len, k2, seed);
+}
+
+uint64 CityHash64WithSeeds(const char* s, size_t len, uint64 seed0, uint64 seed1) {
+    return HashLen16(CityHash64(s, len) - seed0, seed1);
+}
+
+// A subroutine for CityHash128().  Returns a decent 128-bit hash for strings
+// of any length representable in signed long.  Based on City and Murmur.
+static uint128 CityMurmur(const char* s, size_t len, uint128 seed) {
+    uint64 a = Uint128Low64(seed);
+    uint64 b = Uint128High64(seed);
+    uint64 c = 0;
+    uint64 d = 0;
+    signed long l = static_cast<long>(len) - 16;
+    if (l <= 0) { // len <= 16
+        a = ShiftMix(a * k1) * k1;
+        c = b * k1 + HashLen0to16(s, len);
+        d = ShiftMix(a + (len >= 8 ? Fetch64(s) : c));
+    } else { // len > 16
+        c = HashLen16(Fetch64(s + len - 8) + k1, a);
+        d = HashLen16(b + len, c + Fetch64(s + len - 16));
+        a += d;
+        do {
+            a ^= ShiftMix(Fetch64(s) * k1) * k1;
+            a *= k1;
+            b ^= a;
+            c ^= ShiftMix(Fetch64(s + 8) * k1) * k1;
+            c *= k1;
+            d ^= c;
+            s += 16;
+            l -= 16;
+        } while (l > 0);
+    }
+    a = HashLen16(a, c);
+    b = HashLen16(d, b);
+    return uint128(a ^ b, HashLen16(b, a));
+}
+
+uint128 CityHash128WithSeed(const char* s, size_t len, uint128 seed) {
+    if (len < 128) {
+        return CityMurmur(s, len, seed);
+    }
+
+    // We expect len >= 128 to be the common case.  Keep 56 bytes of state:
+    // v, w, x, y, and z.
+    pair<uint64, uint64> v, w;
+    uint64 x = Uint128Low64(seed);
+    uint64 y = Uint128High64(seed);
+    uint64 z = len * k1;
+    v.first = Rotate(y ^ k1, 49) * k1 + Fetch64(s);
+    v.second = Rotate(v.first, 42) * k1 + Fetch64(s + 8);
+    w.first = Rotate(y + z, 35) * k1 + x;
+    w.second = Rotate(x + Fetch64(s + 88), 53) * k1;
+
+    // This is the same inner loop as CityHash64(), manually unrolled.
+    do {
+        x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
+        y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
+        x ^= w.second;
+        y += v.first + Fetch64(s + 40);
+        z = Rotate(z + w.first, 33) * k1;
+        v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
+        w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16));
+        std::swap(z, x);
+        s += 64;
+        x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1;
+        y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1;
+        x ^= w.second;
+        y += v.first + Fetch64(s + 40);
+        z = Rotate(z + w.first, 33) * k1;
+        v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);
+        w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16));
+        std::swap(z, x);
+        s += 64;
+        len -= 128;
+    } while (LIKELY(len >= 128));
+    x += Rotate(v.first + z, 49) * k0;
+    y = y * k0 + Rotate(w.second, 37);
+    z = z * k0 + Rotate(w.first, 27);
+    w.first *= 9;
+    v.first *= k0;
+    // If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end of s.
+    for (size_t tail_done = 0; tail_done < len;) {
+        tail_done += 32;
+        y = Rotate(x + y, 42) * k0 + v.second;
+        w.first += Fetch64(s + len - tail_done + 16);
+        x = x * k0 + w.first;
+        z += w.second + Fetch64(s + len - tail_done);
+        w.second += v.first;
+        v = WeakHashLen32WithSeeds(s + len - tail_done, v.first + z, v.second);
+        v.first *= k0;
+    }
+    // At this point our 56 bytes of state should contain more than
+    // enough information for a strong 128-bit hash.  We use two
+    // different 56-byte-to-8-byte hashes to get a 16-byte final result.
+    x = HashLen16(x, v.first);
+    y = HashLen16(y + z, w.first);
+    return uint128(HashLen16(x + v.second, w.second) + y, HashLen16(x + w.second, y + v.second));
+}
+
+uint128 CityHash128(const char* s, size_t len) {
+    return len >= 16
+               ? CityHash128WithSeed(s + 16, len - 16, uint128(Fetch64(s), Fetch64(s + 8) + k0))
+               : CityHash128WithSeed(s, len, uint128(k0, k1));
+}
+
+} // namespace Common

src/common/cityhash.h

@@ -0,0 +1,110 @@
+// Copyright (c) 2011 Google, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+// CityHash, by Geoff Pike and Jyrki Alakuijala
+//
+// http://code.google.com/p/cityhash/
+//
+// This file provides a few functions for hashing strings.  All of them are
+// high-quality functions in the sense that they pass standard tests such
+// as Austin Appleby's SMHasher.  They are also fast.
+//
+// For 64-bit x86 code, on short strings, we don't know of anything faster than
+// CityHash64 that is of comparable quality.  We believe our nearest competitor
+// is Murmur3.  For 64-bit x86 code, CityHash64 is an excellent choice for hash
+// tables and most other hashing (excluding cryptography).
+//
+// For 64-bit x86 code, on long strings, the picture is more complicated.
+// On many recent Intel CPUs, such as Nehalem, Westmere, Sandy Bridge, etc.,
+// CityHashCrc128 appears to be faster than all competitors of comparable
+// quality.  CityHash128 is also good but not quite as fast.  We believe our
+// nearest competitor is Bob Jenkins' Spooky.  We don't have great data for
+// other 64-bit CPUs, but for long strings we know that Spooky is slightly
+// faster than CityHash on some relatively recent AMD x86-64 CPUs, for example.
+// Note that CityHashCrc128 is declared in citycrc.h.
+//
+// For 32-bit x86 code, we don't know of anything faster than CityHash32 that
+// is of comparable quality.  We believe our nearest competitor is Murmur3A.
+// (On 64-bit CPUs, it is typically faster to use the other CityHash variants.)
+//
+// Functions in the CityHash family are not suitable for cryptography.
+//
+// Please see CityHash's README file for more details on our performance
+// measurements and so on.
+//
+// WARNING: This code has been only lightly tested on big-endian platforms!
+// It is known to work well on little-endian platforms that have a small penalty
+// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs.
+// It should work on all 32-bit and 64-bit platforms that allow unaligned reads;
+// bug reports are welcome.
+//
+// By the way, for some hash functions, given strings a and b, the hash
+// of a+b is easily derived from the hashes of a and b.  This property
+// doesn't hold for any hash functions in this file.
+
+#pragma once
+
+#include <utility>
+#include <stdint.h>
+#include <stdlib.h> // for size_t.
+
+namespace Common {
+
+typedef std::pair<uint64_t, uint64_t> uint128;
+
+inline uint64_t Uint128Low64(const uint128& x) {
+    return x.first;
+}
+inline uint64_t Uint128High64(const uint128& x) {
+    return x.second;
+}
+
+// Hash function for a byte array.
+uint64_t CityHash64(const char* buf, size_t len);
+
+// Hash function for a byte array.  For convenience, a 64-bit seed is also
+// hashed into the result.
+uint64_t CityHash64WithSeed(const char* buf, size_t len, uint64_t seed);
+
+// Hash function for a byte array.  For convenience, two seeds are also
+// hashed into the result.
+uint64_t CityHash64WithSeeds(const char* buf, size_t len, uint64_t seed0, uint64_t seed1);
+
+// Hash function for a byte array.
+uint128 CityHash128(const char* s, size_t len);
+
+// Hash function for a byte array.  For convenience, a 128-bit seed is also
+// hashed into the result.
+uint128 CityHash128WithSeed(const char* s, size_t len, uint128 seed);
+
+// Hash 128 input bits down to 64 bits of output.
+// This is intended to be a reasonably good hash function.
+inline uint64_t Hash128to64(const uint128& x) {
+    // Murmur-inspired hashing.
+    const uint64_t kMul = 0x9ddfea08eb382d69ULL;
+    uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul;
+    a ^= (a >> 47);
+    uint64_t b = (Uint128High64(x) ^ a) * kMul;
+    b ^= (b >> 47);
+    b *= kMul;
+    return b;
+}
+
+} // namespace Common

src/common/hash.cpp

@@ -1,141 +0,0 @@
-// Copyright 2015 Citra Emulator Project
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-#if defined(_MSC_VER)
-#include <stdlib.h>
-#endif
-#include "common/common_funcs.h"
-#include "common/common_types.h"
-#include "common/hash.h"
-
-namespace Common {
-
-// MurmurHash3 was written by Austin Appleby, and is placed in the public
-// domain. The author hereby disclaims copyright to this source code.
-
-// Block read - if your platform needs to do endian-swapping or can only handle aligned reads, do
-// the conversion here
-static FORCE_INLINE u64 getblock64(const u64* p, size_t i) {
-    return p[i];
-}
-
-// Finalization mix - force all bits of a hash block to avalanche
-static FORCE_INLINE u64 fmix64(u64 k) {
-    k ^= k >> 33;
-    k *= 0xff51afd7ed558ccdllu;
-    k ^= k >> 33;
-    k *= 0xc4ceb9fe1a85ec53llu;
-    k ^= k >> 33;
-
-    return k;
-}
-
-// This is the 128-bit variant of the MurmurHash3 hash function that is targeted for 64-bit
-// platforms (MurmurHash3_x64_128). It was taken from:
-// https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
-void MurmurHash3_128(const void* key, size_t len, u32 seed, void* out) {
-    const u8* data = (const u8*)key;
-    const size_t nblocks = len / 16;
-
-    u64 h1 = seed;
-    u64 h2 = seed;
-
-    const u64 c1 = 0x87c37b91114253d5llu;
-    const u64 c2 = 0x4cf5ad432745937fllu;
-
-    // Body
-
-    const u64* blocks = (const u64*)(data);
-
-    for (size_t i = 0; i < nblocks; i++) {
-        u64 k1 = getblock64(blocks, i * 2 + 0);
-        u64 k2 = getblock64(blocks, i * 2 + 1);
-
-        k1 *= c1;
-        k1 = _rotl64(k1, 31);
-        k1 *= c2;
-        h1 ^= k1;
-
-        h1 = _rotl64(h1, 27);
-        h1 += h2;
-        h1 = h1 * 5 + 0x52dce729;
-
-        k2 *= c2;
-        k2 = _rotl64(k2, 33);
-        k2 *= c1;
-        h2 ^= k2;
-
-        h2 = _rotl64(h2, 31);
-        h2 += h1;
-        h2 = h2 * 5 + 0x38495ab5;
-    }
-
-    // Tail
-
-    const u8* tail = (const u8*)(data + nblocks * 16);
-
-    u64 k1 = 0;
-    u64 k2 = 0;
-
-    switch (len & 15) {
-    case 15:
-        k2 ^= ((u64)tail[14]) << 48;
-    case 14:
-        k2 ^= ((u64)tail[13]) << 40;
-    case 13:
-        k2 ^= ((u64)tail[12]) << 32;
-    case 12:
-        k2 ^= ((u64)tail[11]) << 24;
-    case 11:
-        k2 ^= ((u64)tail[10]) << 16;
-    case 10:
-        k2 ^= ((u64)tail[9]) << 8;
-    case 9:
-        k2 ^= ((u64)tail[8]) << 0;
-        k2 *= c2;
-        k2 = _rotl64(k2, 33);
-        k2 *= c1;
-        h2 ^= k2;
-
-    case 8:
-        k1 ^= ((u64)tail[7]) << 56;
-    case 7:
-        k1 ^= ((u64)tail[6]) << 48;
-    case 6:
-        k1 ^= ((u64)tail[5]) << 40;
-    case 5:
-        k1 ^= ((u64)tail[4]) << 32;
-    case 4:
-        k1 ^= ((u64)tail[3]) << 24;
-    case 3:
-        k1 ^= ((u64)tail[2]) << 16;
-    case 2:
-        k1 ^= ((u64)tail[1]) << 8;
-    case 1:
-        k1 ^= ((u64)tail[0]) << 0;
-        k1 *= c1;
-        k1 = _rotl64(k1, 31);
-        k1 *= c2;
-        h1 ^= k1;
-    };
-
-    // Finalization
-
-    h1 ^= len;
-    h2 ^= len;
-
-    h1 += h2;
-    h2 += h1;
-
-    h1 = fmix64(h1);
-    h2 = fmix64(h2);
-
-    h1 += h2;
-    h2 += h1;
-
-    ((u64*)out)[0] = h1;
-    ((u64*)out)[1] = h2;
-}
-
-} // namespace Common

src/common/hash.h

@@ -5,12 +5,11 @@
 #pragma once
 
 #include <cstddef>
+#include "common/cityhash.h"
 #include "common/common_types.h"
 
 namespace Common {
 
-void MurmurHash3_128(const void* key, size_t len, u32 seed, void* out);
-
 /**
  * Computes a 64-bit hash over the specified block of data
  * @param data Block of data to compute hash over
@@ -18,9 +17,20 @@ void MurmurHash3_128(const void* key, size_t len, u32 seed, void* out);
  * @returns 64-bit hash value that was computed over the data block
  */
 static inline u64 ComputeHash64(const void* data, size_t len) {
-    u64 res[2];
+    return CityHash64(static_cast<const char*>(data), len);
-    MurmurHash3_128(data, len, 0, res);
+}
-    return res[0];
+
+/**
+ * Computes a 64-bit hash of a struct. In addition to being POD (trivially copyable and having
+ * standard layout), it is also critical that either the struct includes no padding, or that any
+ * padding is initialized to a known value by memsetting the struct to 0 before filling it in.
+ */
+template <typename T>
+static inline u64 ComputeStructHash64(const T& data) {
+    static_assert(
+        std::is_trivially_copyable<T>::value && std::is_standard_layout<T>::value,
+        "Type passed to ComputeStructHash64 must be trivially copyable and standard layout");
+    return ComputeHash64(&data, sizeof(data));
 }
 
 } // namespace Common

src/video_core/renderer_opengl/gl_shader_gen.cpp

@@ -65,6 +65,7 @@ PicaShaderConfig PicaShaderConfig::BuildFromRegs(const Pica::Regs& regs) {
     PicaShaderConfig res;
 
     auto& state = res.state;
+    // Memset structure to zero padding bits, so that they will be deterministic when hashing
     std::memset(&state, 0, sizeof(PicaShaderConfig::State));
 
     state.scissor_test_mode = regs.rasterizer.scissor_test.mode;

src/video_core/renderer_opengl/gl_shader_gen.h

@@ -131,10 +131,6 @@ union PicaShaderConfig {
 
     } state;
 };
-#if (__GNUC__ >= 5) || defined(__clang__) || defined(_MSC_VER)
-static_assert(std::is_trivially_copyable<PicaShaderConfig::State>::value,
-              "PicaShaderConfig::State must be trivially copyable");
-#endif
 
 /**
  * Generates the GLSL vertex shader program source code for the current Pica state
@@ -156,7 +152,7 @@ namespace std {
 template <>
 struct hash<GLShader::PicaShaderConfig> {
     size_t operator()(const GLShader::PicaShaderConfig& k) const {
-        return Common::ComputeHash64(&k.state, sizeof(GLShader::PicaShaderConfig::State));
+        return Common::ComputeStructHash64(k.state);
     }
 };
 } // namespace std