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string.c: refactor bit operation (e.g. SWAR)

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To generate a bit mask of `0x8080...` of the word size, we prepare
`MASK01` which is `0x0101...` and multiply masking word (e.g., `0x80).
This commit is contained in:
Yukihiro "Matz" Matsumoto
2024-05-20 22:12:56 +09:00
parent bff68cbf17
commit 68e093729b
1 changed files with 17 additions and 27 deletions
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src/string.c
+17 -27
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@@ -274,10 +274,10 @@ mrb_gc_free_str(mrb_state *mrb, struct RString *str)
#ifdef MRB_64BIT
#define bitint uint64_t
#define MASK1 0x0101010101010101ull
#define MASK01 0x0101010101010101ull
#else
#define bitint uint32_t
#define MASK1 0x01010101ul
#define MASK01 0x01010101ul
#endif
#ifdef MRB_UTF8_STRING
@@ -349,7 +349,7 @@ search_nonascii(const char *p, const char *e)
bitint t0;
memcpy(&t0, p, sizeof(bitint));
const bitint t1 = t0 & (MASK1*0x80);
const bitint t1 = t0 & (MASK01*0x80);
if (t1) {
e = p + sizeof(bitint)-1;
byte_len = sizeof(bitint)-1;
@@ -408,10 +408,10 @@ mrb_utf8len(const char* p, const char* e)
#else
static inline uint32_t popcount(bitint x)
{
x = (x & (MASK1*0x55)) + ((x >> 1) & (MASK1*0x55));
x = (x & (MASK1*0x33)) + ((x >> 2) & (MASK1*0x33));
x = (x & (MASK1*0x0F)) + ((x >> 4) & (MASK1*0x0F));
return (x * MASK1) >> 56;
x = (x & (MASK01*0x55)) + ((x >> 1) & (MASK01*0x55));
x = (x & (MASK01*0x33)) + ((x >> 2) & (MASK01*0x33));
x = (x & (MASK01*0x0F)) + ((x >> 4) & (MASK01*0x0F));
return (x * MASK01) >> 56;
}
#endif
@@ -584,29 +584,20 @@ str_index_str_by_char(mrb_state *mrb, mrb_value str, mrb_value sub, mrb_int pos)
static inline mrb_int
memsearch_swar(const char *xs, mrb_int m, const char *ys, mrb_int n)
{
#ifdef MRB_64BIT
#define bitint uint64_t
#define MASK1 0x0101010101010101ull
#define MASK2 0x7f7f7f7f7f7f7f7full
#define MASK3 0x8080808080808080ull
#else
#define bitint uint32_t
#define MASK1 0x01010101ul
#define MASK2 0x7f7f7f7ful
#define MASK3 0x80808080ul
#endif
#define MASK7f (MASK01*0x7f)
#define MASK80 (MASK01*0x80)
#if defined(MRB_ENDIAN_BIG)
#ifdef MRB_64BIT
#define MASK4 0x8000000000000000ull
#define MASKtop 0x8000000000000000ull
#else
#define MASK4 0x80000000ul
#define MASKtop 0x80000000ul
#endif
#else
#define MASK4 0x80
#define MASKtop 0x80
#endif
const bitint first = MASK1 * (uint8_t)xs[0];
const bitint last = MASK1 * (uint8_t)xs[m-1];
const bitint first = MASK01 * (uint8_t)xs[0];
const bitint last = MASK01 * (uint8_t)xs[m-1];
const char *s0 = ys;
const char *s1 = ys+m-1;
@@ -621,11 +612,10 @@ memsearch_swar(const char *xs, mrb_int m, const char *ys, mrb_int n)
memcpy(&t1, s1+i, sizeof(bitint));
const bitint eq = (t0 ^ first) | (t1 ^ last);
bitint zeros = ((~eq & MASK2) + MASK1) & (~eq & MASK3);
bitint zeros = ((~eq & MASK7f) + MASK01) & (~eq & MASK80);
for (size_t j = 0; zeros; j++) {
if (zeros & MASK4) {
if (zeros & MASKtop) {
const mrb_int idx = i + j;
const char* p = s0 + idx + 1;
if (memcmp(p, xs + 1, m - 2) == 0) {
@@ -644,7 +634,7 @@ memsearch_swar(const char *xs, mrb_int m, const char *ys, mrb_int n)
if (i+m < n) {
const char *p = s0;
const char *e = ys + n;
for (;p<e;) {
while (p<e) {
p = (const char*)memchr(p, *xs, e - p);
if (p == NULL || (e - p) < m) break;
if (memcmp(p+1, xs+1, m-1) == 0) return (mrb_int)(p - ys);