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Don't look at this.

This commit is contained in:
Daniel Lemire 2018-04-05 22:09:41 -04:00
parent 0e5b0f776f
commit b73cf9bcd2
6 changed files with 390 additions and 0 deletions
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scalarvssimd/avxprocessing.h Normal file
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#include <iostream>
#include <iomanip>
#include <chrono>
#include <fstream>
#include <sstream>
#include <string>
#include <cstring>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
#include <x86intrin.h>
#include <assert.h>
#include "common_defs.h"
using namespace std;
// a straightforward comparison of a mask against input. 5 uops; would be cheaper in AVX512.
really_inline u64 cmp_mask_against_input(m256 input_lo, m256 input_hi, m256 mask) {
m256 cmp_res_0 = _mm256_cmpeq_epi8(input_lo, mask);
u64 res_0 = (u32)_mm256_movemask_epi8(cmp_res_0);
m256 cmp_res_1 = _mm256_cmpeq_epi8(input_hi, mask);
u64 res_1 = _mm256_movemask_epi8(cmp_res_1);
return res_0 | (res_1 << 32);
}
never_inline bool find_structural_bits(const u8 * buf, size_t len, ParsedJson & pj) {
// Useful constant masks
const u64 even_bits = 0x5555555555555555ULL;
const u64 odd_bits = ~even_bits;
// for now, just work in 64-byte chunks
// we have padded the input out to 64 byte multiple with the remainder being zeros
// persistent state across loop
u64 prev_iter_ends_odd_backslash = 0ULL; // either 0 or 1, but a 64-bit value
u64 prev_iter_inside_quote = 0ULL; // either all zeros or all ones
u64 prev_iter_pseudo_structural_carry = 0ULL;
for (size_t idx = 0; idx < len; idx+=64) {
m256 input_lo = _mm256_load_si256((const m256 *)(buf + idx + 0));
m256 input_hi = _mm256_load_si256((const m256 *)(buf + idx + 32));
////////////////////////////////////////////////////////////////////////////////////////////
// Step 1: detect odd sequences of backslashes
////////////////////////////////////////////////////////////////////////////////////////////
u64 bs_bits = cmp_mask_against_input(input_lo, input_hi, _mm256_set1_epi8('\\'));
u64 start_edges = bs_bits & ~(bs_bits << 1);
// flip lowest if we have an odd-length run at the end of the prior iteration
u64 even_start_mask = even_bits ^ prev_iter_ends_odd_backslash;
u64 even_starts = start_edges & even_start_mask;
u64 odd_starts = start_edges & ~even_start_mask;
u64 even_carries = bs_bits + even_starts;
u64 odd_carries;
// must record the carry-out of our odd-carries out of bit 63; this indicates whether the
// sense of any edge going to the next iteration should be flipped
bool iter_ends_odd_backslash = __builtin_uaddll_overflow(bs_bits, odd_starts, &odd_carries);
odd_carries |= prev_iter_ends_odd_backslash; // push in bit zero as a potential end
// if we had an odd-numbered run at the end of
// the previous iteration
prev_iter_ends_odd_backslash = iter_ends_odd_backslash ? 0x1ULL : 0x0ULL;
u64 even_carry_ends = even_carries & ~bs_bits;
u64 odd_carry_ends = odd_carries & ~bs_bits;
u64 even_start_odd_end = even_carry_ends & odd_bits;
u64 odd_start_even_end = odd_carry_ends & even_bits;
u64 odd_ends = even_start_odd_end | odd_start_even_end;
////////////////////////////////////////////////////////////////////////////////////////////
// Step 2: detect insides of quote pairs
////////////////////////////////////////////////////////////////////////////////////////////
u64 quote_bits = cmp_mask_against_input(input_lo, input_hi, _mm256_set1_epi8('"'));
quote_bits = quote_bits & ~odd_ends;
dumpbits(quote_bits, "quote_bits");
u64 quote_mask = _mm_cvtsi128_si64(_mm_clmulepi64_si128(_mm_set_epi64x(0ULL, quote_bits),
_mm_set1_epi8(0xFF), 0));
quote_mask ^= prev_iter_inside_quote;
prev_iter_inside_quote = (u64)((s64)quote_mask>>63);
dumpbits(quote_mask, "quote_mask");
// How do we build up a user traversable data structure
// first, do a 'shufti' to detect structural JSON characters
// they are { 0x7b } 0x7d : 0x3a [ 0x5b ] 0x5d , 0x2c
// these go into the first 3 buckets of the comparison (1/2/4)
// we are also interested in the four whitespace characters
// space 0x20, linefeed 0x0a, horizontal tab 0x09 and carriage return 0x0d
// these go into the next 2 buckets of the comparison (8/16)
const m256 low_nibble_mask = _mm256_setr_epi8(
// 0 9 a b c d
16, 0, 0, 0, 0, 0, 0, 0, 0, 8, 12, 1, 2, 9, 0, 0,
16, 0, 0, 0, 0, 0, 0, 0, 0, 8, 12, 1, 2, 9, 0, 0
);
const m256 high_nibble_mask = _mm256_setr_epi8(
// 0 2 3 5 7
8, 0, 18, 4, 0, 1, 0, 1, 0, 0, 0, 3, 2, 1, 0, 0,
8, 0, 18, 4, 0, 1, 0, 1, 0, 0, 0, 3, 2, 1, 0, 0
);
m256 structural_shufti_mask = _mm256_set1_epi8(0x7);
m256 whitespace_shufti_mask = _mm256_set1_epi8(0x18);
m256 v_lo = _mm256_and_si256(
_mm256_shuffle_epi8(low_nibble_mask, input_lo),
_mm256_shuffle_epi8(high_nibble_mask,
_mm256_and_si256(_mm256_srli_epi32(input_lo, 4), _mm256_set1_epi8(0x7f))));
m256 v_hi = _mm256_and_si256(
_mm256_shuffle_epi8(low_nibble_mask, input_hi),
_mm256_shuffle_epi8(high_nibble_mask,
_mm256_and_si256(_mm256_srli_epi32(input_hi, 4), _mm256_set1_epi8(0x7f))));
m256 tmp_lo = _mm256_cmpeq_epi8(_mm256_and_si256(v_lo, structural_shufti_mask),
_mm256_set1_epi8(0));
m256 tmp_hi = _mm256_cmpeq_epi8(_mm256_and_si256(v_hi, structural_shufti_mask),
_mm256_set1_epi8(0));
u64 structural_res_0 = (u32)_mm256_movemask_epi8(tmp_lo);
u64 structural_res_1 = _mm256_movemask_epi8(tmp_hi);
u64 structurals = ~(structural_res_0 | (structural_res_1 << 32));
// this additional mask and transfer is non-trivially expensive, unfortunately
m256 tmp_ws_lo = _mm256_cmpeq_epi8(_mm256_and_si256(v_lo, whitespace_shufti_mask),
_mm256_set1_epi8(0));
m256 tmp_ws_hi = _mm256_cmpeq_epi8(_mm256_and_si256(v_hi, whitespace_shufti_mask),
_mm256_set1_epi8(0));
u64 ws_res_0 = (u32)_mm256_movemask_epi8(tmp_ws_lo);
u64 ws_res_1 = _mm256_movemask_epi8(tmp_ws_hi);
u64 whitespace = ~(ws_res_0 | (ws_res_1 << 32));
// mask off anything inside quotes
structurals &= ~quote_mask;
// whitespace inside our quotes also doesn't count; otherwise " foo" would generate a spurious
// pseudo-structural-character at 'foo'
whitespace &= ~quote_mask;
// add the real quote bits back into our bitmask as well, so we can
// quickly traverse the strings we've spent all this trouble gathering
structurals |= quote_bits;
// Now, establish "pseudo-structural characters". These are characters that follow a structural
// character followed by zero or more whitespace
// this allows us to discover true/false/null and numbers in any location where they might legally
// occur; it will also create another 'checkpoint' where if a non-quoted region of our input
// has whitespace after a structural character fullowed by a syntax error, we can detect this
// and get an error in a later stage (i.e. the state machine)
// Slightly more painful than it would seem. It's possible that either structurals or whitespace are
// all 1s (e.g. {{{{{{{....{{{{x64, or a really long whitespace). As such there is no safe place
// to add a '1' from the previous iteration without *that* triggering the carry we are looking
// out for, so we must check both carries for overflow
u64 tmp = structurals | whitespace;
u64 tmp2;
bool ps_carry = __builtin_uaddll_overflow(tmp, structurals, &tmp2);
u64 tmp3;
ps_carry = ps_carry | __builtin_uaddll_overflow(tmp2, prev_iter_pseudo_structural_carry, &tmp3);
prev_iter_pseudo_structural_carry = ps_carry ? 0x1ULL : 0x0ULL;
tmp3 &= ~quote_mask;
tmp3 &= ~whitespace;
structurals |= tmp3;
*(u64 *)(pj.structurals + idx/8) = structurals;
}
return true;
}
const u32 NUM_RESERVED_NODES = 2;
const u32 DUMMY_NODE = 0;
const u32 ROOT_NODE = 1;
// just transform the bitmask to a big list of 32-bit integers for now
// that's all; the type of character the offset points to will
// tell us exactly what we need to know. Naive but straightforward implementation
never_inline bool flatten_indexes(size_t len, ParsedJson & pj) {
u32 base = NUM_RESERVED_NODES;
u32 * base_ptr = pj.structural_indexes;
base_ptr[DUMMY_NODE] = base_ptr[ROOT_NODE] = 0; // really shouldn't matter
for (size_t idx = 0; idx < len; idx+=64) {
u64 s = *(u64 *)(pj.structurals + idx/8);
while (s) {
u32 si = (u32)idx + __builtin_ctzll(s);
base_ptr[base++] = si;
s &= s - 1ULL;
}
}
pj.n_structural_indexes = base;
return true;
}
// Parse our json given a big array of 32-bit integers telling us where
// the interesting stuff is
bool avx_json_parse(const u8 * buf, UNUSED size_t len, ParsedJson & pj) {
u32 last; // index of previous structure at this level or 0 if none
u32 up; // index of structure that contains this one
JsonNode * nodes = pj.nodes;
JsonNode & dummy = nodes[DUMMY_NODE];
JsonNode & root = nodes[ROOT_NODE];
dummy.prev = dummy.up = DUMMY_NODE;
root.prev = DUMMY_NODE;
root.up = ROOT_NODE;
last = up = ROOT_NODE;
for (u32 i = NUM_RESERVED_NODES; i < pj.n_structural_indexes; i++) {
u32 idx = pj.structural_indexes[i];
JsonNode & n = nodes[i];
u8 c = buf[idx];
if (unlikely((c & 0xdf) == 0x5b)) { // meaning 7b or 5b, { or [
// open a scope
n.prev = last;
n.up = up;
up = i;
last = 0;
} else if (unlikely((c & 0xdf) == 0x5d)) { // meaning 7d or 5d, } or ]
// close a scope
n.prev = up;
n.up = pj.nodes[up].up;
up = pj.nodes[up].up;
last = i;
} else {
n.prev = last;
n.up = up;
last = i;
}
n.next = 0;
nodes[n.prev].next = i;
}
dummy.next = DUMMY_NODE; // dummy.next is a sump for meaningless 'nexts', clear it
#ifdef DEBUG
for (u32 i = 0; i < pj.n_structural_indexes; i++) {
u32 idx = pj.structural_indexes[i];
JsonNode & n = nodes[i];
cout << "i: " << i;
cout << " n.up: " << n.up;
cout << " n.next: " << n.next;
cout << " n.prev: " << n.prev;
cout << " idx: " << idx << " buf[idx] " << buf[idx] << "\n";
}
#endif
return true;
}

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scalarvssimd/common_defs.h Normal file
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#pragma once
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;
typedef unsigned long long u64;
typedef signed char s8;
typedef signed short s16;
typedef signed int s32;
typedef signed long long s64;
#include <x86intrin.h>
#include <immintrin.h>
typedef __m128i m128;
typedef __m256i m256;
// Snippets from Hyperscan
// Align to N-byte boundary
#define ROUNDUP_N(a, n) (((a) + ((n)-1)) & ~((n)-1))
#define ROUNDDOWN_N(a, n) ((a) & ~((n)-1))
#define ISALIGNED_N(ptr, n) (((uintptr_t)(ptr) & ((n) - 1)) == 0)
#define really_inline inline __attribute__ ((always_inline, unused))
#define never_inline inline __attribute__ ((noinline, unused))
#define UNUSED __attribute__ ((unused))
#ifndef likely
#define likely(x) __builtin_expect(!!(x), 1)
#endif
#ifndef unlikely
#define unlikely(x) __builtin_expect(!!(x), 0)
#endif
static inline
u32 ctz64(u64 x) {
assert(x); // behaviour not defined for x == 0
#if defined(_WIN64)
unsigned long r;
_BitScanForward64(&r, x);
return r;
#elif defined(_WIN32)
unsigned long r;
if (_BitScanForward(&r, (u32)x)) {
return (u32)r;
}
_BitScanForward(&r, x >> 32);
return (u32)(r + 32);
#else
return (u32)__builtin_ctzll(x);
#endif
}

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scalarvssimd/demo.cpp Normal file
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scalarvssimd/jsonstruct.h Normal file
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#pragma once
struct JsonNode {
u32 up;
u32 next;
u32 prev;
};
struct ParsedJson {
u8 * structurals;
u32 n_structural_indexes;
u32 * structural_indexes;
JsonNode * nodes;
};

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scalarvssimd/scalarprocessing.h Normal file
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#include "common_defs.h"
#include "jsonstruct.h"
bool scalar_json_parse(const u8 * buf, size_t len, ParsedJson & pj) {
// this is a naive attempt at this point
// it will probably be subject to failures given adversarial inputs
size_t pos = 0;
size_t last = 0;
size_t up = 0;
for(size_t i = 0; i < len; i++) {
JsonNode & n = pj.nodes[pos];
switch buf[i] {
case '[':
case '{':
n.prev = last;
n.up = up;
up = pos;
last = 0;
pos += 1;
break;
case ']':
case '}':
n.prev = up;
n.up = pj.nodes[up].up;
up = pj.nodes[up].up;
last = pos;
pos += 1;
break;
case ':':
case ',':
n.prev = last;
n.up = up;
last = pos;
pos += 1;
break;
default:
// nothing
}
n.next = 0;
nodes[n.prev].next = pos;
}
pj.n_structural_indexes = pos;
}

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scalarvssimd/util.h Normal file
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#include "common_defs.h"
// get a corpus; pad out to cache line so we can always use SIMD
static pair<u8 *, size_t> get_corpus(string filename) {
ifstream is(filename, ios::binary);
if (is) {
stringstream buffer;
buffer << is.rdbuf();
size_t length = buffer.str().size();
char * aligned_buffer;
if (posix_memalign( (void **)&aligned_buffer, 64, ROUNDUP_N(length, 64))) {
throw "Allocation failed";
};
memset(aligned_buffer, 0x20, ROUNDUP_N(length, 64));
memcpy(aligned_buffer, buffer.str().c_str(), length);
is.close();
return make_pair((u8 *)aligned_buffer, length);
}
throw "No corpus";
return make_pair((u8 *)0, (size_t)0);
}