/*
** hash for lua_Numbers
**
** for non-complex modes, never called with 'lua_Integer' value range (s.a. 0)
*
* Note: Linux x86(_64) gcc 4.x, -O2/O3 and no '-fno-strict-aliasing' will
* optimize out essential stuff from here, unless 'union' is used.
* There is no automatic way to sniff whether compiler is having strict
* aliasing optimizations on (use '-DNO_STRICT_ALIASING' to enable the
* potentially faster code path that expects they are not on).
*/
static Node *hashnum (const Table *t, const lua_Number v) {
unsigned int i,sum;
#ifdef NO_STRICT_ALIASING
/* For compilers not using "strict aliasing" optimizations (or when compiling
* with '-fno-strict-aliasing').
*/
const unsigned int *a= cast(const unsigned int*, &v);
sum= a[0];
for (i = 1; i < NUM_INTS; i++) sum += a[i];
#else
/*
* This code is "strict aliasing" safe (to be used with gcc 4.x -O2 or above,
* if no '-fno-strict-aliasing' is specified). Otherwise you'll be screwed.
* Casting via 'char*' or 'void*' should do the same, but doesn't.
*
* Seems gcc enables strict aliasing even if '--std=c99' is not used.
* There is no predefined macro to detect, whether the compiler is doing
* strict aliasing optimizations or not. Bohoo... --AKa 7-Apr-2009
*/
union {
lua_Number v;
unsigned int a[NUM_INTS];
} u;
lua_assert( sizeof(u)==sizeof(v) );
u.v= v;
sum= u.a[0];
for (i = 1; i < NUM_INTS; i++) sum += u.a[i];
#endif
return hashmod(t, sum);
}
/*
** returns the 'main' position of an element in a table (that is,
** the index of its hash value). The key comes broken (tag in 'ktt'
** and value in 'vkl') so that we can call it on keys inserted into
** nodes.
*/
static Node *mainposition (const Table *t, int ktt, const Value *kvl) {
switch (withvariant(ktt)) {
case LUA_TNUMINT:
return hashint(t, ivalueraw(*kvl));
case LUA_TNUMFLT:
return hashmod(t, l_hashfloat(fltvalueraw(*kvl)));
case LUA_TSHRSTR:
return hashstr(t, tsvalueraw(*kvl));
case LUA_TLNGSTR:
return hashpow2(t, luaS_hashlongstr(tsvalueraw(*kvl)));
case LUA_TBOOLEAN:
return hashboolean(t, bvalueraw(*kvl));
case LUA_TLIGHTUSERDATA:
return hashpointer(t, pvalueraw(*kvl));
case LUA_TLCF:
return hashpointer(t, fvalueraw(*kvl));
default: {
GCObject *o;
lua_assert(!ttisdeadkey(kvl));
o = gcvalueraw(*kvl);
if (o->gchash == 0)
return hashpointer(t, o);
return hashint(t, withvariant(ktt) * o->gchash);
}
}
}
/*
** hash for lv_Numbers
*/
static Node *hashnum (const Table *t, lv_Number n) {
unsigned int a[numints];
int i;
if (lvi_numeq(n, 0)) /* avoid problems with -0 */
return gnode(t, 0);
memcpy(a, &n, sizeof(a));
for (i = 1; i < numints; i++) a[0] += a[i];
return hashmod(t, a[0]);
}
/*
** hash for lua_Numbers
*/
static Node *hashnum (const Table *t, lua_Number n) {
unsigned int a[numints];
int i;
n += 1; /* normalize number (avoid -0) */
lua_assert(sizeof(a) <= sizeof(n));
memcpy(a, &n, sizeof(a));
for (i = 1; i < numints; i++) a[0] += a[i];
return hashmod(t, a[0]);
}
/*
** hash for lua_Numbers
*/
static Node *hashnum (const Table *t, lua_Number n) {
int i;
luai_hashnum(i, n);
if (i < 0) {
i = -i; /* must be a positive value */
if (i < 0) i = 0; /* handle INT_MIN */
}
return hashmod(t, i);
}
