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Learnings from truffle.

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Nuno Cruces
2025-08-12 02:27:51 +01:00
parent d8880e4cee
commit 8f9a8e2752
1 changed files with 23 additions and 18 deletions
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41
sqlite3/libc/string.h
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@@ -242,17 +242,21 @@ char *strrchr(const char *s, int c) {
// SIMDized check which bytes are in a set (Geoff Langdale)
// http://0x80.pl/notesen/2018-10-18-simd-byte-lookup.html
// This is the same algorithm as truffle from Hyperscan:
// https://github.com/intel/hyperscan/blob/v5.4.2/src/nfa/truffle.c#L64-L81
// https://github.com/intel/hyperscan/blob/v5.4.2/src/nfa/trufflecompile.cpp
typedef struct {
__u8x16 lo;
__u8x16 hi;
} __wasm_v128_bitmap256_t;
__attribute__((always_inline))
static void __wasm_v128_setbit(__wasm_v128_bitmap256_t *bitmap, int i) {
uint8_t hi_nibble = (uint8_t)i >> 4;
uint8_t lo_nibble = (uint8_t)i & 0xf;
bitmap->lo[lo_nibble] |= (uint8_t)((uint32_t)1 << (hi_nibble - 0));
bitmap->hi[lo_nibble] |= (uint8_t)((uint32_t)1 << (hi_nibble - 8));
static void __wasm_v128_setbit(__wasm_v128_bitmap256_t *bitmap, uint8_t i) {
uint8_t hi_nibble = i >> 4;
uint8_t lo_nibble = i & 0xf;
bitmap->lo[lo_nibble] |= (uint8_t)(1u << (hi_nibble - 0));
bitmap->hi[lo_nibble] |= (uint8_t)(1u << (hi_nibble - 8));
}
#ifndef __wasm_relaxed_simd__
@@ -264,18 +268,17 @@ static void __wasm_v128_setbit(__wasm_v128_bitmap256_t *bitmap, int i) {
__attribute__((always_inline))
static v128_t __wasm_v128_chkbits(__wasm_v128_bitmap256_t bitmap, v128_t v) {
v128_t hi_nibbles = wasm_u8x16_shr(v, 4);
v128_t bitmask_lookup = wasm_u8x16_const(1, 2, 4, 8, 16, 32, 64, 128, //
1, 2, 4, 8, 16, 32, 64, 128);
v128_t bitmask_lookup = wasm_u64x2_const_splat(0x8040201008040201);
v128_t bitmask = wasm_i8x16_relaxed_swizzle(bitmask_lookup, hi_nibbles);
v128_t indices_0_7 = v & wasm_u8x16_const_splat(0x8f);
v128_t indices_8_15 = indices_0_7 ^ wasm_u8x16_const_splat(0x80);
v128_t row_0_7 = wasm_i8x16_swizzle(bitmap.lo, indices_0_7);
v128_t row_8_15 = wasm_i8x16_swizzle(bitmap.hi, indices_8_15);
v128_t row_0_7 = wasm_i8x16_swizzle((v128_t)bitmap.lo, indices_0_7);
v128_t row_8_15 = wasm_i8x16_swizzle((v128_t)bitmap.hi, indices_8_15);
v128_t bitsets = row_0_7 | row_8_15;
return wasm_i8x16_eq(bitsets & bitmask, bitmask);
return bitsets & bitmask;
}
#undef wasm_i8x16_relaxed_swizzle
@@ -317,17 +320,18 @@ size_t strspn(const char *s, const char *c) {
for (; *c; c++) {
// Terminator IS NOT on the bitmap.
__wasm_v128_setbit(&bitmap, *c);
__wasm_v128_setbit(&bitmap, (uint8_t)*c);
}
for (;;) {
v128_t v = *(v128_t *)addr;
v128_t cmp = __wasm_v128_chkbits(bitmap, v);
v128_t found = __wasm_v128_chkbits(bitmap, v);
// Bitmask is slow on AArch64, all_true is much faster.
if (!wasm_i8x16_all_true(cmp)) {
if (!wasm_i8x16_all_true(found)) {
v128_t cmp = wasm_i8x16_eq(found, (v128_t){});
// Clear the bits corresponding to align (little-endian)
// so we can count trailing zeros.
int mask = (uint16_t)~wasm_i8x16_bitmask(cmp) >> align << align;
int mask = wasm_i8x16_bitmask(cmp) >> align << align;
// At least one bit will be set, unless align cleared them.
// Knowing this helps the compiler if it unrolls the loop.
__builtin_assume(mask || align);
@@ -356,17 +360,18 @@ size_t strcspn(const char *s, const char *c) {
do {
// Terminator IS on the bitmap.
__wasm_v128_setbit(&bitmap, *c);
__wasm_v128_setbit(&bitmap, (uint8_t)*c);
} while (*c++);
for (;;) {
v128_t v = *(v128_t *)addr;
v128_t cmp = __wasm_v128_chkbits(bitmap, v);
v128_t found = __wasm_v128_chkbits(bitmap, v);
// Bitmask is slow on AArch64, any_true is much faster.
if (wasm_v128_any_true(cmp)) {
if (wasm_v128_any_true(found)) {
v128_t cmp = wasm_i8x16_eq(found, (v128_t){});
// Clear the bits corresponding to align (little-endian)
// so we can count trailing zeros.
int mask = wasm_i8x16_bitmask(cmp) >> align << align;
int mask = (uint16_t)~wasm_i8x16_bitmask(cmp) >> align << align;
// At least one bit will be set, unless align cleared them.
// Knowing this helps the compiler if it unrolls the loop.
__builtin_assume(mask || align);