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Abstract out pointer hash to hashrot(). Tune hash constants.

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This commit is contained in:
Mike Pall
2010-07-21 21:42:40 +02:00
parent 6667ab0f26
commit d05873ee0a
4 changed files with 32 additions and 32 deletions
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21
src/lj_tab.c
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@@ -17,22 +17,19 @@
/* -- Object hashing ------------------------------------------------------ */
/* Hash values are masked with the table hash mask and used as an index. */
#define hashmask(t, x) (&noderef(t->node)[(x) & t->hmask])
static LJ_AINLINE Node *hashmask(const GCtab *t, uint32_t hash)
{
Node *n = noderef(t->node);
return &n[hash & t->hmask];
}
/* String hashes are precomputed when they are interned. */
#define hashstr(t, s) hashmask(t, (s)->hash)
#define hashnum(t, o) hashrot(t, (o)->u32.lo, ((o)->u32.hi << 1))
#define hashgcref(t, r) hashrot(t, gcrefu(r), gcrefu(r)-0x04c11db7)
/* Scramble the bits of numbers and pointers. */
static LJ_AINLINE Node *hashrot(const GCtab *t, uint32_t lo, uint32_t hi)
{
lo ^= hi; hi = lj_rol(hi, 14);
lo -= hi; hi = lj_rol(hi, 5);
hi ^= lo; hi -= lj_rol(lo, 27);
return hashmask(t, hi);
}
#define hashlohi(t, lo, hi) hashmask((t), hashrot((lo), (hi)))
#define hashnum(t, o) hashlohi((t), (o)->u32.lo, ((o)->u32.hi << 1))
#define hashptr(t, p) hashlohi((t), u32ptr(p), u32ptr(p) + HASH_BIAS)
#define hashgcref(t, r) hashlohi((t), gcrefu(r), gcrefu(r) + HASH_BIAS)
/* Hash an arbitrary key and return its anchor position in the hash table. */
static Node *hashkey(const GCtab *t, cTValue *key)