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use dump but fast function for whole string hashing

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it fits into i386 registers, and consumes more than 2 bytes per cycle
(on Haswell)

+ add check for hashsum equality in chain traversion.
This commit is contained in:
Sokolov Yura aka funny_falcon 2016-04-28 18:03:12 +03:00
parent ac42037db0
commit ba922dbe0b
1 changed files with 14 additions and 3 deletions
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17
src/lj_str.c
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@ -130,7 +130,18 @@ GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)
lj_err_msg(L, LJ_ERR_STROV);
g = G(L);
/* Compute string hash. Constants taken from lookup3 hash by Bob Jenkins. */
if (len >= 4) { /* Caveat: unaligned access! */
if (len >= 12) { /* Caveat: unaligned access! */
MSize i = (len-1)/8;
const char *ss;
a = lj_getu32(str+len-8);
b = lj_getu32(str+len-4);
ss = str;
for (; i; i--, ss += 8) {
h = lj_rol(h ^ a, 17) + (b ^ 0xdeadbeef);
a = lj_rol(a, 13); a -= lj_getu32(ss);
b = lj_rol(b, 11); b -= lj_getu32(ss+4);
}
} else if (len >= 4) { /* Caveat: unaligned access! */
a = lj_getu32(str);
h ^= lj_getu32(str+len-4);
b = lj_getu32(str+(len>>1)-2);
@ -152,7 +163,7 @@ GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)
if (LJ_LIKELY((((uintptr_t)str+len-1) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4)) {
while (o != NULL) {
GCstr *sx = gco2str(o);
if (sx->len == len && str_fastcmp(str, strdata(sx), len) == 0) {
if (sx->hash == h && sx->len == len && str_fastcmp(str, strdata(sx), len) == 0) {
/* Resurrect if dead. Can only happen with fixstring() (keywords). */
if (isdead(g, o)) flipwhite(o);
return sx; /* Return existing string. */
@ -162,7 +173,7 @@ GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)
} else { /* Slow path: end of string is too close to a page boundary. */
while (o != NULL) {
GCstr *sx = gco2str(o);
if (sx->len == len && memcmp(str, strdata(sx), len) == 0) {
if (sx->hash == h && sx->len == len && memcmp(str, strdata(sx), len) == 0) {
/* Resurrect if dead. Can only happen with fixstring() (keywords). */
if (isdead(g, o)) flipwhite(o);
return sx; /* Return existing string. */