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gmqcc/hash.c
Dale Weiler 103bca7284 Partially fix that.
2013-12-14 14:57:10 -05:00

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/*
* Copyright (C) 2012, 2013
* Dale Weiler
*
* 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.
*/
#include "gmqcc.h"
#include <limits.h>
/*
* This is a version of the Murmur3 hashing function optimized for various
* compilers/architectures. It uses the traditional Murmur2 mix stagin
* but fixes the mix staging inner loops.
*
* Murmur 2 contains an inner loop such as:
* while (l >= 4) {
* u32 k = *(u32*)d;
* k *= m;
* k ^= k >> r;
* k *= m;
*
* h *= m;
* h ^= k;
* d += 4;
* l -= 4;
* }
*
* The two u32s that form the key are the same value for x
* this premix stage will perform the same results for both values. Unrolled
* this produces just:
* x *= m;
* x ^= x >> r;
* x *= m;
*
* h *= m;
* h ^= x;
* h *= m;
* h ^= x;
*
* This appears to be fine, except what happens when m == 1? well x
* cancels out entierly, leaving just:
* x ^= x >> r;
* h ^= x;
* h ^= x;
*
* So all keys hash to the same value, but how often does m == 1?
* well, it turns out testing x for all possible values yeilds only
* 172,013,942 unique results instead of 2^32. So nearly ~4.6 bits
* are cancelled out on average!
*
* This means we have a 14.5% higher chance of collision. This is where
* Murmur3 comes in to save the day.
*/
/*
* Some rotation tricks:
* MSVC one shaves off six instructions, where GCC optimized one for
* x86 and amd64 shaves off four instructions. Native methods are often
* optimized rather well at -O3, but not at -O2.
*/
#if defined(_MSC_VER)
# define HASH_ROTL32(X, Y) _rotl((X), (Y))
#else
static GMQCC_FORCEINLINE uint32_t hash_rotl32(volatile uint32_t x, int8_t r) {
#if defined (__GNUC__) && (defined(__i386__) || defined(__amd64__))
__asm__ __volatile__ ("roll %1,%0" : "+r"(x) : "c"(r));
return x;
#else /* ! (defined(__GNUC__) && (defined(__i386__) || defined(__amd64__))) */
return (x << r) | (x >> (32 - r));
#endif
}
# define HASH_ROTL32(X, Y) hash_rotl32((volatile uint32_t)(X), (Y))
#endif /* !(_MSC_VER) */
static GMQCC_FORCEINLINE uint32_t hash_mix32(uint32_t hash) {
hash ^= hash >> 16;
hash *= 0x85EBCA6B;
hash ^= hash >> 13;
hash *= 0xC2B2AE35;
hash ^= hash >> 16;
return hash;
}
/*
* These constants were calculated with SMHasher to determine the best
* case senario for Murmur3:
* http://code.google.com/p/smhasher/
*/
#define HASH_MASK1 0xCC9E2D51
#define HASH_MASK2 0x1B873593
#define HASH_SEED 0x9747B28C
#if PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_LITTLE
# define HASH_NATIVE_SAFEREAD(PTR) (*((uint32_t*)(PTR)))
#elif PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_BIG
# if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR >= 3))
# define HASH_NATIVE_SAFEREAD(PTR) (__builtin_bswap32(*((uint32_t*)(PTR))))
# endif
#endif
/* Process individual bytes at this point since the endianess isn't known. */
#ifndef HASH_NATIVE_SAFEREAD
# define HASH_NATIVE_SAFEREAD(PTR) ((PTR)[0] | (PTR)[1] << 8 | (PTR)[2] << 16 | (PTR)[3] << 24)
#endif
#define HASH_NATIVE_BLOCK(H, K) \
do { \
K *= HASH_MASK1; \
K = HASH_ROTL32(K, 15); \
K *= HASH_MASK2; \
H ^= K; \
H = HASH_ROTL32(H, 13); \
H = H * 5 + 0xE6546B64; \
} while (0)
#define HASH_NATIVE_BYTES(COUNT, H, C, N, PTR, LENGTH) \
do { \
int i = COUNT; \
while (i--) { \
C = C >> 8 | *PTR++ << 24; \
N++; \
LENGTH--; \
if (N == 4) { \
HASH_NATIVE_BLOCK(H, C); \
N = 0; \
} \
} \
} while (0)
/*
* Highly unrolled at per-carry bit granularity instead of per-block granularity. This will achieve the
* highest possible instruction level parallelism.
*/
static GMQCC_FORCEINLINE void hash_native_process(uint32_t *ph1, uint32_t *carry, const void *key, int length) {
uint32_t h1 = *ph1;
uint32_t c = *carry;
const uint8_t *ptr = (uint8_t*)key;
const uint8_t *end;
/* carry count from low 2 bits of carry value */
int n = c & 3;
/*
* Unaligned word accesses are safe in LE. Thus we can obtain a little
* more speed.
*/
# if PLATFORM_BYTE_ORDER == GMQCC_BYTE_ORDER_LITTLE
/* Consume carry bits */
int it = (4 - n) & 3;
if (it && it <= length)
HASH_NATIVE_BYTES(it, h1, c, n, ptr, length);
/* word size chunk consumption */
end = ptr + length/4*4;
for (; ptr < end; ptr += 4) {
uint32_t k1 = HASH_NATIVE_SAFEREAD(ptr);
HASH_NATIVE_BLOCK(h1, k1);
}
# else
/*
* Unsafe to assume unaligned word accesses. Thus we'll need to consume
* to alignment then process in aligned block chunks.
*/
uint32_t k1;
int it = -(long)ptr & 3;
if (it && it <= length)
HASH_NATIVE_BYTES(it, h1, c, n, ptr, length);
/*
* Alignment has been reached, deal with aligned blocks, specializing for
* all possible carry counts.
*/
end = ptr + length / 4 * 4;
switch (n) {
case 0:
for (; ptr < end; ptr += 4) {
k1 = HASH_NATIVE_SAFEREAD(ptr);
HASH_NATIVE_BLOCK(h1, k1);
}
break;
case 1:
for (; ptr < end; ptr += 4) {
k1 = c >> 24;
c = HASH_NATIVE_SAFEREAD(ptr);
k1 |= c << 8;
HASH_NATIVE_BLOCK(h1, k1);
}
break;
case 2:
for (; ptr < end; ptr += 4) {
k1 = c >> 16;
c = HASH_NATIVE_SAFEREAD(ptr);
k1 |= c << 16;
HASH_NATIVE_BLOCK(h1, k1);
}
break;
case 3:
for (; ptr < end; ptr += 4) {
k1 = c >> 8;
c = HASH_NATIVE_SAFEREAD(ptr);
k1 |= c << 24;
HASH_NATIVE_BLOCK(h1, k1);
}
break;
}
#endif /* misaligned reads */
/*
* Advanced over 32-bit chunks, this can possibly leave 1..3 bytes of
* additional trailing content to process.
*/
length -= length/4*4;
HASH_NATIVE_BYTES(length, h1, c, n, ptr, length);
*ph1 = h1;
*carry = (c & ~0xFF) | n;
}
static GMQCC_FORCEINLINE uint32_t hash_native_result(uint32_t hash, uint32_t carry, size_t length) {
uint32_t k1;
int n = carry & 3;
if (GMQCC_LIKELY(n)) {
k1 = carry >> (4 - n) * 8;
k1 *= HASH_MASK1;
k1 = HASH_ROTL32(k1, 15);
k1 *= HASH_MASK2;
hash ^= k1;
}
hash ^= length;
hash = hash_mix32(hash);
return hash;
}
static GMQCC_FORCEINLINE uint32_t hash_native(const void *GMQCC_RESTRICT key, size_t length) {
uint32_t hash = HASH_SEED;
uint32_t carry = 0;
/* Seperate calls for inliner to deal with */
hash_native_process(&hash, &carry, key, length);
return hash_native_result(hash, carry, length);
}
/*
* Inline assembly optimized SSE version for when SSE is present via CPUID
* or the host compiler has __SSE__. This is about 16 cycles faster than
* native at -O2 for GCC and 11 cycles for -O3.
*
* Tested with -m32 on a Phenom II X4 with:
* gcc version 4.8.1 20130725 (prerelease) (GCC)
*/
#if defined(__GNUC__) && defined(__i386__)
static GMQCC_FORCEINLINE uint32_t hash_sse(const void *GMQCC_RESTRICT key, size_t length) {
uint32_t ret;
__asm__ __volatile__ (
" mov %%eax, %%ebx\n"
" mov %2, %%eax\n"
" movd %%eax, %%xmm7\n"
" shufps $0, %%xmm7, %%xmm7\n"
" mov %3, %%eax\n"
" movd %%eax, %%xmm6\n"
" shufps $0, %%xmm6, %%xmm6\n"
" lea (%%esi, %%ecx, 1), %%edi\n"
" jmp 2f\n"
"1:\n"
" movaps (%%esi), %%xmm0\n"
" pmulld %%xmm7, %%xmm0\n"
" movaps %%xmm0, %%xmm2\n"
" pslld $15, %%xmm0\n"
" psrld $17, %%xmm2\n"
" orps %%xmm2, %%xmm0\n"
" pmulld %%xmm6, %%xmm0\n"
" movd %%xmm0, %%eax\n"
" xor %%eax, %%ebx\n"
" rol $13, %%ebx\n"
" imul $5, %%ebx\n"
" add $0xE6546B64, %%ebx\n"
" shufps $0x39, %%xmm0, %%xmm0\n"
" movd %%xmm0, %%eax\n"
" xor %%eax, %%ebx\n"
" rol $13, %%ebx\n"
" imul $5, %%ebx\n"
" add $0xE6546B64, %%ebx\n"
" shufps $0x39, %%xmm0, %%xmm0\n"
" movd %%xmm0, %%eax\n"
" xor %%eax, %%ebx\n"
" rol $13, %%ebx\n"
" imul $5, %%ebx\n"
" add $0xE6546B64, %%ebx\n"
" shufps $0x39, %%xmm0, %%xmm0\n"
" movd %%xmm0, %%eax\n"
" xor %%eax, %%ebx\n"
" rol $13, %%ebx\n"
" imul $5, %%ebx\n"
" add $0xE6546B64, %%ebx\n"
" add $16, %%esi\n"
"2:\n"
" cmp %%esi, %%edi\n"
" jne 1b\n"
" xor %%ecx, %%ebx\n"
" mov %%ebx, %%eax\n"
" shr $16, %%ebx\n"
" xor %%ebx, %%eax\n"
" imul $0x85EBCA6b, %%eax\n"
" mov %%eax, %%ebx\n"
" shr $13, %%ebx\n"
" xor %%ebx, %%eax\n"
" imul $0xC2B2AE35, %%eax\n"
" mov %%eax, %%ebx\n"
" shr $16, %%ebx\n"
" xor %%ebx, %%eax\n"
: "=a" (ret)
: "a" (HASH_SEED),
"i" (HASH_MASK1),
"i" (HASH_MASK2),
"S" (key),
"c" (length)
: "%ebx",
"%edi"
);
return ret;
}
#endif
#if defined (__GNUC__) && defined(__i386__) && !defined(__SSE__)
/*
* Emulate MSVC _cpuid intrinsic for GCC/MinGW/Clang, this will be used
* to determine if we should use the SSE route.
*/
static GMQCC_FORCEINLINE void hash_cpuid(int *lanes, int entry) {
__asm__ __volatile__ (
"cpuid"
: "=a"(lanes[0]),
"=b"(lanes[1]),
"=c"(lanes[2]),
"=d"(lanes[3])
: "a" (entry)
);
}
#endif /* !(defined(__GNUC__) && defined(__i386__) */
static uint32_t hash_entry(const void *GMQCC_RESTRICT key, size_t length) {
/*
* No host SSE instruction set assumed do runtime test instead. This
* is for MinGW32 mostly which doesn't define SSE.
*/
#if defined (__GNUC__) && defined(__i386__) && !defined(__SSE__)
static bool memoize = false;
static bool sse = false;
if (GMQCC_UNLIKELY(!memoize)) {
/*
* Only calculate SSE one time, thus it's unlikely that this branch
* is taken more than once.
*/
static int lanes[4];
hash_cpuid(lanes, 0);
/*
* It's very likely that lanes[0] will contain a value unless it
* isn't a modern x86.
*/
if (GMQCC_LIKELY(*lanes >= 1))
sse = (lanes[3] & ((int)1 << 25)) != 0;
memoize = true;
}
return (GMQCC_LIKELY(sse))
? hash_sse(key, length);
: hash_native(key, length);
/*
* Same as above but this time host compiler was defined with SSE support.
* This handles MinGW32 builds for i686+
*/
#elif defined (__GNUC__) && defined(__i386__) && defined(__SSE__)
return hash_sse(key, length);
#else
/*
* Go the native route which itself is highly optimized as well for
* unaligned load/store when dealing with LE.
*/
return hash_native(key, length);
#endif
}
#define HASH_LEN_ALIGN (sizeof(size_t))
#define HASH_LEN_ONES ((size_t)-1/UCHAR_MAX)
#define HASH_LEN_HIGHS (HASH_LEN_ONES * (UCHAR_MAX / 2 + 1))
#define HASH_LEN_HASZERO(X) (((X)-HASH_LEN_ONES) & ~(X) & HASH_LEN_HIGHS)
size_t hash(const char *key) {
const char *s = key;
const char *a = s;
const size_t *w;
/* Align for fast staging */
for (; (uintptr_t)s % HASH_LEN_ALIGN; s++) {
/* Quick stage if terminated before alignment */
if (!*s)
return hash_entry(key, s-a);
}
/*
* Efficent staging of words for string length calculation, this is
* faster than ifunc resolver of strlen call.
*
* On a x64 this becomes literally two masks, and a quick skip through
* bytes along the string with the following masks:
* movabs $0xFEFEFEFEFEFEFEFE,%r8
* movabs $0x8080808080808080,%rsi
*/
for (w = (const void *)s; !HASH_LEN_HASZERO(*w); w++);
for (s = (const void *)w; *s; s++);
return hash_entry(key, s-a);
}
#undef HASH_LEN_HASZERO
#undef HASH_LEN_HIGHS
#undef HASH_LEN_ONES
#undef HASH_LEN_ALIGN
#undef HASH_SEED
#undef HASH_MASK2
#undef HASH_MASK1
#undef HASH_ROTL32
#undef HASH_NATIVE_BLOCK
#undef HASH_NATIVE_BYTES
#undef HASH_NATIVE_SAFEREAD
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