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ip2net: improve performance on big endian systems

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bol-van 2022-06-16 15:43:20 +03:00
parent 3842cbbca5
commit 9529953594
4 changed files with 35 additions and 0 deletions
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35
ip2net/ip2net.c
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@ -57,8 +57,41 @@ static uint32_t unique(uint32_t *pu, uint32_t ct)
#if defined(__GNUC__) && !defined(__llvm__)
__attribute__((optimize ("no-strict-aliasing")))
#endif
static int cmp6(const void * a, const void * b, void *arg) static int cmp6(const void * a, const void * b, void *arg)
{ {
// this function is critical to sort performance
// on big endian systems cpu byte order is equal to network byte order
// no conversion required. it's possible to improve speed by using big size compares
// assume that a and b are properly aligned
#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__==__ORDER_BIG_ENDIAN__)
#ifdef __SIZEOF_INT128__
// the fastest possible way (MIPS64/PPC64 only ?)
const unsigned __int128 *pa = (unsigned __int128*)((struct in6_addr *)a)->s6_addr;
const unsigned __int128 *pb = (unsigned __int128*)((struct in6_addr *)b)->s6_addr;
return *pa < *pb ? -1 : *pa == *pb ? 0 : 1;
#else
const uint64_t *pa = (uint64_t*)((struct in6_addr *)a)->s6_addr;
const uint64_t *pb = (uint64_t*)((struct in6_addr *)b)->s6_addr;
if (pa[0] < pb[0])
return -1;
else if (pa[0] == pb[0])
{
if (pa[1] < pb[1])
return -1;
else if (pa[1] > pb[1])
return 1;
else
return 0;
}
else
return 1; // pa[0] > pb[0]
#endif
#else
// little endian or unknown. reversing byte order voids performance improvement. so do byte comparision
for (uint8_t i = 0; i < sizeof(((struct in6_addr *)0)->s6_addr); i++) for (uint8_t i = 0; i < sizeof(((struct in6_addr *)0)->s6_addr); i++)
{ {
if (((struct in6_addr *)a)->s6_addr[i] < ((struct in6_addr *)b)->s6_addr[i]) if (((struct in6_addr *)a)->s6_addr[i] < ((struct in6_addr *)b)->s6_addr[i])
@ -67,6 +100,7 @@ static int cmp6(const void * a, const void * b, void *arg)
return 1; return 1;
} }
return 0; return 0;
#endif
} }
// make presorted array unique. return number of unique items. // make presorted array unique. return number of unique items.
static uint32_t unique6(struct in6_addr *pu, uint32_t ct) static uint32_t unique6(struct in6_addr *pu, uint32_t ct)
@ -124,6 +158,7 @@ static void ip6_and(const struct in6_addr *a, const struct in6_addr *b, struct i
// YES, from my point of view C should work as a portable assembler. It must do what I instruct it to do. // YES, from my point of view C should work as a portable assembler. It must do what I instruct it to do.
// that's why I disable strict aliasing for this function. I observed gcc can miscompile with O2/O3 setting if inlined and not coded "correct" // that's why I disable strict aliasing for this function. I observed gcc can miscompile with O2/O3 setting if inlined and not coded "correct"
// result = a & b // result = a & b
// assume that a and b are properly aligned
#if defined(__GNUC__) && !defined(__llvm__) #if defined(__GNUC__) && !defined(__llvm__)
__attribute__((optimize ("no-strict-aliasing"))) __attribute__((optimize ("no-strict-aliasing")))
#endif #endif