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Code Issues Releases Wiki Activity

Use GCC builtin for clz in RPZ lookup code (#42818)

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This commit is contained in:
Mukund Sivaraman
2016-07-10 19:46:17 +05:30
parent df52e5c7d5
commit 27038b159b
5 changed files with 83 additions and 10 deletions
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31
lib/dns/rpz.c
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@@ -970,34 +970,43 @@ name2data(dns_rpz_zones_t *rpzs, dns_rpz_num_t rpz_num,
(void)dns_name_concatenate(&tmp_name, dns_rootname, trig_name, NULL);
}
/*
* Find the first differing bit in a key (IP address) word.
#ifndef HAVE_BUILTIN_CLZ
/**
* \brief Count Leading Zeros: Find the location of the left-most set
* bit.
*/
static inline int
ffs_keybit(dns_rpz_cidr_word_t w) {
int bit;
static inline unsigned int
clz(dns_rpz_cidr_word_t w) {
unsigned int bit;
bit = DNS_RPZ_CIDR_WORD_BITS-1;
if ((w & 0xffff0000) != 0) {
w >>= 16;
bit -= 16;
}
if ((w & 0xff00) != 0) {
w >>= 8;
bit -= 8;
}
if ((w & 0xf0) != 0) {
w >>= 4;
bit -= 4;
}
if ((w & 0xc) != 0) {
w >>= 2;
bit -= 2;
}
if ((w & 2) != 0)
--bit;
return (bit);
}
#endif
/*
* Find the first differing bit in two keys (IP addresses).
@@ -1016,12 +1025,14 @@ diff_keys(const dns_rpz_cidr_key_t *key1, dns_rpz_prefix_t prefix1,
/*
* find the first differing words
*/
for (i = 0;
bit < maxbit;
i++, bit += DNS_RPZ_CIDR_WORD_BITS) {
for (i = 0; bit < maxbit; i++, bit += DNS_RPZ_CIDR_WORD_BITS) {
delta = key1->w[i] ^ key2->w[i];
if (delta != 0) {
bit += ffs_keybit(delta);
if (ISC_UNLIKELY(delta != 0)) {
#ifdef HAVE_BUILTIN_CLZ
bit += __builtin_clz(delta);
#else
bit += clz(delta);
#endif
break;
}
}