fix intfilter expansion logic

also makes it simpler and probably faster.
someone should contrib non-gnuc popcount if they care, i ran out of patience with this (yes i know it's simple) (it probably doesn't even need to be exactly popcount).
pull/51/head
cathugger 2 years ago
parent 68a06c4ced
commit f43c3b021e
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GPG Key ID: 9BADDA2DAF6F01A8

@ -5,6 +5,7 @@ static inline size_t S(filter_len)(size_t i)
# ifndef OMITMASK
const u8 *m = (const u8 *)&VEC_BUF(filters,i).m;
# else // OMITMASK
(void) i;
const u8 *m = (const u8 *)&ifiltermask;
# endif // OMITMASK
size_t c = 0;

@ -17,112 +17,81 @@ static inline int filter_compare(const void *p1,const void *p2)
# ifdef EXPANDMASK
/*
* for mask expansion, we need to figure out how much bits
* we need to fill in with different values.
* while in big endian machines this is quite easy,
* representation we use for little endian ones may
* leave gap of bits we don't want to touch.
*
* initial idea draft:
*
* raw representation -- FF.FF.F0.00
* big endian -- 0xFFFFF000
* little endian -- 0x00F0FFFF
* b: 0xFFffF000 ^ 0xFFff0000 -> 0x0000F000
* 0x0000F000 + 1 -> 0x0000F001
* 0x0000F000 & 0x0000F001 -> 0x0000F000 <- shifted mask
* 0x0000F000 ^ 0x0000F000 -> 0x00000000 <- direct mask
* 0x0000F000 ^ 0x00000000 -> 0x0000F000 <- shifted mask
* l: 0x00f0FFff ^ 0x0000FFff -> 0x00f00000
* 0x00f00000 + 1 -> 0x00f00001
* 0x00f00000 & 0x00f00001 -> 0x00f00000 <- shifted mask
* 0x00f00000 ^ 0x00f00000 -> 0x00000000 <- direct mask
* 0x00f00000 ^ 0x00000000 -> 0x00f00000 <- shifted mask
*
* b: 0xFFffFFff ^ 0xF0000000 -> 0x0FffFFff
* 0x0FffFFff + 1 -> 0x10000000
* 0x0FffFFff & 0x10000000 -> 0x00000000 <- shifted mask
* 0x0FffFFff ^ 0x00000000 -> 0x0FffFFff <- direct mask
* 0x0FffFFff ^ 0x0FffFFff -> 0x00000000 <- shifted mask
* l: 0xFFffFFff ^ 0x000000f0 -> 0xFFffFF0f
* 0xFFffFF0f + 1 -> 0xFFffFF10
* 0xFFffFF0f & 0xFFffFF10 -> 0xFFffFF00 <- shifted mask
* 0xFFffFF0f ^ 0xFFffFF00 -> 0x0000000f <- direct mask
* 0xFFffFF0f ^ 0x0000000f -> 0xFFffFF00 <- shifted mask
*
* essentially, we have to make direct mask + shifted mask bits worth of information
* and then split it into 2 parts
* we do not need absolute shifted mask shifting value, just relative to direct mask
* 0x0sss00dd - shifted & direct mask combo
* 0x000sssdd - combined mask
* 8 - relshiftval
* generate values from 0x00000000 to 0x000sssdd
* for each value, realmask <- (val & 0x000000dd) | ((val & 0x000sss00) << relshiftval)
* or..
* realmask <- (val & 0x000000dd) | ((val << relshiftval) & 0x0sss0000)
* ...
*
* above method doesn't work in some cases. better way:
*
* l: 0x80ffFFff ^ 0x00f0FFff -> 0x800f0000
* 0x800f0000 >> 16 -> 0x0000800f
* 0x0000800f + 1 -> 0x00008010
* 0x0000800f & 0x00008010 -> 0x00008000 <- smask
* 0x0000800f ^ 0x00008000 -> 0x0000000f <- dmask
*
* cross <- difference between mask we desire and mask we currently have
* shift cross to left variable ammount of times to eliminate zeros
* save shift ammount as ishift (initial shift)
* then, we eliminate first area of ones; if there was no gap, result is already all zeros
* save this thing as smask. it's only higher bits.
* XOR smask and cross; result is only lower bits.
* shift smask to left variable ammount of times until gap is eliminated.
* save resulting mask as cmask;
* save resulting shift value as rshift.
* so we have 2 masks with basically random bits
* we first gonna find where these masks are common
* then we gonna find where new mask has more bits than old
* common areas must be unchanged
* gaps in both must be unchanged
* but new bits must be filled
* therefore, lets just fill old gaps and common areas with 1s
* before add, OR with these 1s
* then perform add. these 1s have property to push positive bits to 0s
* we already know how much new gaps we need to fill, so this wont overflow
* after this addition, AND result with NEG of combined mask, and OR with old value
* this will produce new proper value
* we need to re-fill 1s before every add to keep structure working
*/
int flattened = 0;
#define EXPVAL(init,j,dmask,smask,ishift,rshift) \
((init) | ((((j) & (dmask)) | (((j) << (rshift)) & (smask))) << (ishift)))
// add expanded set of values
// allocates space on its own
static void ifilter_addexpanded(
struct intfilter *ifltr,
IFT dmask,IFT smask,IFT cmask,
int ishift,int rshift)
register IFT newbits,
register IFT notnewbits,
register IFT newbitsum)
{
flattened = 1;
size_t i = VEC_LENGTH(filters);
VEC_ADDN(filters,cmask + 1);
VEC_ADDN(filters,newbitsum + 1);
register IFT x = ifltr->f;
register IFT y = 0;
for (size_t j = 0;;++j) {
VEC_BUF(filters,i + j).f =
EXPVAL(ifltr->f,j,dmask,smask,ishift,rshift);
if (j == cmask)
VEC_BUF(filters,i + j).f = x | y;
if (j == newbitsum)
break;
y = ((y | notnewbits) + 1) & newbits;
}
}
// expand existing stuff
// allocates needed stuff on its own
static void ifilter_expand(IFT dmask,IFT smask,IFT cmask,int ishift,int rshift)
static void ifilter_expand(
register IFT newbits,
register IFT notnewbits,
register IFT newbitsum)
{
flattened = 1;
size_t len = VEC_LENGTH(filters);
VEC_ADDN(filters,cmask * len);
size_t esz = cmask + 1; // size of expanded elements
VEC_ADDN(filters,newbitsum * len);
size_t esz = newbitsum + 1; // size of expanded elements
for (size_t i = len - 1;;--i) {
register IFT x = VEC_BUF(filters,i).f;
register IFT y = 0;
for (IFT j = 0;;++j) {
VEC_BUF(filters,i * esz + j).f =
EXPVAL(VEC_BUF(filters,i).f,j,dmask,smask,ishift,rshift);
if (j == cmask)
VEC_BUF(filters,i * esz + j).f = x | y;
if (j == newbitsum)
break;
y = ((y | notnewbits) + 1) & newbits;
}
if (i == 0)
break;
}
}
static IFT ifilter_bitsum(IFT x)
{
if (sizeof(IFT) == 16)
return (((IFT) 1) <<
(__builtin_popcountll((unsigned long long) (x >> (sizeof(IFT) * 8 / 2))) +
__builtin_popcountll((unsigned long long) x))) - 1;
if (sizeof(IFT) == 8)
return (((IFT) 1) << __builtin_popcountll((unsigned long long) x)) - 1;
return (((IFT) 1) << __builtin_popcount((unsigned int) x)) - 1;
}
static inline void ifilter_addflatten(struct intfilter *ifltr,IFT mask)
{
if (VEC_LENGTH(filters) == 0) {
@ -136,27 +105,21 @@ static inline void ifilter_addflatten(struct intfilter *ifltr,IFT mask)
VEC_ADD(filters,*ifltr);
return;
}
IFT cross = ifiltermask ^ mask;
int ishift = 0;
while ((cross & 1) == 0) {
++ishift;
cross >>= 1;
}
IFT smask = cross & (cross + 1); // shift mask
IFT dmask = cross ^ smask; // direct mask
IFT cmask; // combined mask
int rshift = 0; // relative shift
while (cmask = (smask >> rshift) | dmask,(cmask & (cmask + 1)) != 0)
++rshift;
// preparations done
IFT newbits = ifiltermask ^ mask;
IFT notnewbits = ~newbits;
IFT newbitsum = ifilter_bitsum(newbits);
if (ifiltermask > mask) {
// already existing stuff has more precise mask than we
// so we need to expand our stuff
ifilter_addexpanded(ifltr,dmask,smask,cmask,ishift,rshift);
// current mask covers more bits
// expand new filter
ifilter_addexpanded(ifltr,newbits,notnewbits,newbitsum);
}
else {
// new filter mask covers more bits
// adjust current mask and expand current filters
ifiltermask = mask;
ifilter_expand(dmask,smask,cmask,ishift,rshift);
ifilter_expand(newbits,notnewbits,newbitsum);
VEC_ADD(filters,*ifltr);
}
}

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