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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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15
src/lj_tab.h
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@@ -8,6 +8,21 @@
#include "lj_obj.h"
/* Hash constants. Tuned using a brute force search. */
#define HASH_BIAS (-0x04c11db7)
#define HASH_ROT1 14
#define HASH_ROT2 5
#define HASH_ROT3 13
/* Scramble the bits of numbers and pointers. */
static LJ_AINLINE uint32_t hashrot(uint32_t lo, uint32_t hi)
{
lo ^= hi; hi = lj_rol(hi, HASH_ROT1);
lo -= hi; hi = lj_rol(hi, HASH_ROT2);
hi ^= lo; hi -= lj_rol(lo, HASH_ROT3);
return hi;
}
#define hsize2hbits(s) ((s) ? ((s)==1 ? 1 : 1+lj_fls((uint32_t)((s)-1))) : 0)
LJ_FUNCA GCtab *lj_tab_new(lua_State *L, uint32_t asize, uint32_t hbits);