Use __built_expect() where available (#41411)

(cherry picked from commit d1dbf6b20f)
(cherry picked from commit 6e2e0f72b1)

CHANGES

@@ -1,3 +1,6 @@
+4310.	[performance]	Use __builtin_expect() where available to annotate
+			conditions with known behavior. [RT #41411]
+
 4308.	[func]		Added operating system details to "named -V"
 			output. [RT #41452]
 

config.h.in

@@ -194,6 +194,9 @@ int sigwait(const unsigned int *set, int *sig);
    MSVC and with C++ compilers. */
 #undef FLEXIBLE_ARRAY_MEMBER
 
+/* Define to 1 if the compiler supports __builtin_expect. */
+#undef HAVE_BUILTIN_EXPECT
+
 /* Define to 1 if you have the `chroot' function. */
 #undef HAVE_CHROOT
 

configure

@@ -18752,6 +18752,45 @@ fi
 ISC_ARCH_DIR=$arch
 
 
+#
+# Check for __builtin_expect
+#
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking compiler support for __builtin_expect" >&5
+$as_echo_n "checking compiler support for __builtin_expect... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+        return (__builtin_expect(1, 1) ? 1 : 0);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+        have_builtin_expect=yes
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+else
+
+        have_builtin_expect=no
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+if test "$have_builtin_expect" = "yes"; then
+
+$as_echo "#define HAVE_BUILTIN_EXPECT 1" >>confdefs.h
+
+fi
+
 #
 # Activate "rrset-order fixed" or not?
 #

configure.in

@@ -3260,6 +3260,23 @@ AC_SUBST(ISC_PLATFORM_USEMACASM)
 ISC_ARCH_DIR=$arch
 AC_SUBST(ISC_ARCH_DIR)
 
+#
+# Check for __builtin_expect
+#
+AC_MSG_CHECKING([compiler support for __builtin_expect])
+AC_TRY_LINK(, [
+        return (__builtin_expect(1, 1) ? 1 : 0);
+], [
+        have_builtin_expect=yes
+        AC_MSG_RESULT(yes)
+], [
+        have_builtin_expect=no
+        AC_MSG_RESULT(no)
+])
+if test "$have_builtin_expect" = "yes"; then
+        AC_DEFINE(HAVE_BUILTIN_EXPECT, 1, [Define to 1 if the compiler supports __builtin_expect.])
+fi
+
 #
 # Activate "rrset-order fixed" or not?
 #

lib/dns/name.c

@@ -551,7 +551,7 @@ dns_name_fullcompare(const dns_name_t *name1, const dns_name_t *name2,
 	REQUIRE((name1->attributes & DNS_NAMEATTR_ABSOLUTE) ==
 		(name2->attributes & DNS_NAMEATTR_ABSOLUTE));
 
-	if (name1 == name2) {
+	if (ISC_UNLIKELY(name1 == name2)) {
 		*orderp = 0;
 		*nlabelsp = name1->labels;
 		return (dns_namereln_equal);
@@ -574,7 +574,7 @@ dns_name_fullcompare(const dns_name_t *name1, const dns_name_t *name2,
 	offsets1 += l1;
 	offsets2 += l2;
 
-	while (l > 0) {
+	while (ISC_LIKELY(l > 0)) {
 		l--;
 		offsets1--;
 		offsets2--;
@@ -596,7 +596,7 @@ dns_name_fullcompare(const dns_name_t *name1, const dns_name_t *name2,
 			count = count2;
 
 		/* Loop unrolled for performance */
-		while (count > 3) {
+		while (ISC_LIKELY(count > 3)) {
 			chdiff = (int)maptolower[label1[0]] -
 				 (int)maptolower[label2[0]];
 			if (chdiff != 0) {
@@ -625,7 +625,7 @@ dns_name_fullcompare(const dns_name_t *name1, const dns_name_t *name2,
 			label1 += 4;
 			label2 += 4;
 		}
-		while (count-- > 0) {
+		while (ISC_LIKELY(count-- > 0)) {
 			chdiff = (int)maptolower[*label1++] -
 				 (int)maptolower[*label2++];
 			if (chdiff != 0) {
@@ -701,7 +701,7 @@ dns_name_equal(const dns_name_t *name1, const dns_name_t *name2) {
 	REQUIRE((name1->attributes & DNS_NAMEATTR_ABSOLUTE) ==
 		(name2->attributes & DNS_NAMEATTR_ABSOLUTE));
 
-	if (name1 == name2)
+	if (ISC_UNLIKELY(name1 == name2))
 		return (ISC_TRUE);
 
 	if (name1->length != name2->length)
@@ -714,7 +714,7 @@ dns_name_equal(const dns_name_t *name1, const dns_name_t *name2) {
 
 	label1 = name1->ndata;
 	label2 = name2->ndata;
-	while (l-- > 0) {
+	while (ISC_LIKELY(l-- > 0)) {
 		count = *label1++;
 		if (count != *label2++)
 			return (ISC_FALSE);
@@ -722,7 +722,7 @@ dns_name_equal(const dns_name_t *name1, const dns_name_t *name2) {
 		INSIST(count <= 63); /* no bitstring support */
 
 		/* Loop unrolled for performance */
-		while (count > 3) {
+		while (ISC_LIKELY(count > 3)) {
 			c = maptolower[label1[0]];
 			if (c != maptolower[label2[0]])
 				return (ISC_FALSE);
@@ -739,7 +739,7 @@ dns_name_equal(const dns_name_t *name1, const dns_name_t *name2) {
 			label1 += 4;
 			label2 += 4;
 		}
-		while (count-- > 0) {
+		while (ISC_LIKELY(count-- > 0)) {
 			c = maptolower[*label1++];
 			if (c != maptolower[*label2++])
 				return (ISC_FALSE);

lib/dns/rbt.c

@@ -414,7 +414,7 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
 	add_name = dns_fixedname_name(&fixedcopy);
 	dns_name_clone(name, add_name);
 
-	if (rbt->root == NULL) {
+	if (ISC_UNLIKELY(rbt->root == NULL)) {
 		result = create_node(rbt->mctx, add_name, &new_current);
 		if (result == ISC_R_SUCCESS) {
 			rbt->nodecount++;
@@ -655,12 +655,12 @@ dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep) {
 
 		}
 
-	} while (child != NULL);
+	} while (ISC_LIKELY(child != NULL));
 
-	if (result == ISC_R_SUCCESS)
+	if (ISC_LIKELY(result == ISC_R_SUCCESS))
 		result = create_node(rbt->mctx, add_name, &new_current);
 
-	if (result == ISC_R_SUCCESS) {
+	if (ISC_LIKELY(result == ISC_R_SUCCESS)) {
 #ifdef DNS_RBT_USEHASH
 		if (*root == NULL)
 			UPPERNODE(new_current) = current;
@@ -743,7 +743,7 @@ dns_rbt_findnode(dns_rbt_t *rbt, dns_name_t *name, dns_name_t *foundname,
 	} else
 		dns_rbtnodechain_reset(chain);
 
-	if (rbt->root == NULL)
+	if (ISC_UNLIKELY(rbt->root == NULL))
 		return (ISC_R_NOTFOUND);
 	else {
 		/*
@@ -775,7 +775,7 @@ dns_rbt_findnode(dns_rbt_t *rbt, dns_name_t *name, dns_name_t *foundname,
 	current = rbt->root;
 	current_root = rbt->root;
 
-	while (current != NULL) {
+	while (ISC_LIKELY(current != NULL)) {
 		NODENAME(current, &current_name);
 		compared = dns_name_fullcompare(search_name, &current_name,
 						&order, &common_labels);
@@ -831,13 +831,20 @@ dns_rbt_findnode(dns_rbt_t *rbt, dns_name_t *name, dns_name_t *foundname,
 			{
 				dns_name_t hnode_name;
 
-				if (hash != HASHVAL(hnode))
+				if (ISC_LIKELY(hash != HASHVAL(hnode)))
 					continue;
-				if (get_upper_node(hnode) != up_current)
+				/*
+				 * This checks that the hashed label
+				 * sequence being looked up is at the
+				 * same tree level, so that we don't
+				 * match a labelsequence from some other
+				 * subdomain.
+				 */
+				if (ISC_LIKELY(get_upper_node(hnode) != up_current))
 					continue;
 				dns_name_init(&hnode_name, NULL);
 				NODENAME(hnode, &hnode_name);
-				if (dns_name_equal(&hnode_name, &hash_name))
+				if (ISC_LIKELY(dns_name_equal(&hnode_name, &hash_name)))
 					break;
 			}
 

lib/isc/hash.c

@@ -488,7 +488,7 @@ isc_hash_function_reverse(const void *data, size_t length,
 
 	RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);
 
-	hval = previous_hashp != NULL ? *previous_hashp : fnv_offset_basis;
+	hval = ISC_UNLIKELY(previous_hashp != NULL) ? *previous_hashp : fnv_offset_basis;
 
 	bp = (const unsigned char *) data;
 	be = bp + length;

lib/isc/include/isc/assertions.h

@@ -83,7 +83,7 @@ isc_assertion_typetotext(isc_assertiontype_t type);
 
 #if ISC_CHECK_REQUIRE != 0
 #define ISC_REQUIRE(cond) \
-	((void) ((cond) || \
+	((void) (ISC_LIKELY(cond) || \
 		 ((isc_assertion_failed)(__FILE__, __LINE__, \
 					 isc_assertiontype_require, \
 					 #cond), 0)))
@@ -93,7 +93,7 @@ isc_assertion_typetotext(isc_assertiontype_t type);
 
 #if ISC_CHECK_ENSURE != 0
 #define ISC_ENSURE(cond) \
-	((void) ((cond) || \
+	((void) (ISC_LIKELY(cond) || \
 		 ((isc_assertion_failed)(__FILE__, __LINE__, \
 					 isc_assertiontype_ensure, \
 					 #cond), 0)))
@@ -103,7 +103,7 @@ isc_assertion_typetotext(isc_assertiontype_t type);
 
 #if ISC_CHECK_INSIST != 0
 #define ISC_INSIST(cond) \
-	((void) ((cond) || \
+	((void) (ISC_LIKELY(cond) || \
 		 ((isc_assertion_failed)(__FILE__, __LINE__, \
 					 isc_assertiontype_insist, \
 					 #cond), 0)))
@@ -113,7 +113,7 @@ isc_assertion_typetotext(isc_assertiontype_t type);
 
 #if ISC_CHECK_INVARIANT != 0
 #define ISC_INVARIANT(cond) \
-	((void) ((cond) || \
+	((void) (ISC_LIKELY(cond) || \
 		 ((isc_assertion_failed)(__FILE__, __LINE__, \
 					 isc_assertiontype_invariant, \
 					 #cond), 0)))

lib/isc/include/isc/error.h

@@ -55,7 +55,7 @@ void
 isc_error_runtimecheck(const char *, int, const char *);
 
 #define ISC_ERROR_RUNTIMECHECK(cond) \
-	((void) ((cond) || \
+	((void) (ISC_LIKELY(cond) || \
 		 ((isc_error_runtimecheck)(__FILE__, __LINE__, #cond), 0)))
 
 ISC_LANG_ENDDECLS

lib/isc/include/isc/magic.h

@@ -20,6 +20,8 @@
 #ifndef ISC_MAGIC_H
 #define ISC_MAGIC_H 1
 
+#include <isc/util.h>
+
 /*! \file isc/magic.h */
 
 typedef struct {
@@ -33,8 +35,8 @@ typedef struct {
  * The intent of this is to allow magic numbers to be checked even though
  * the object is otherwise opaque.
  */
-#define ISC_MAGIC_VALID(a,b)	(((a) != NULL) && \
-				 (((const isc__magic_t *)(a))->magic == (b)))
+#define ISC_MAGIC_VALID(a,b)	(ISC_LIKELY((a) != NULL) && \
+				 ISC_LIKELY(((const isc__magic_t *)(a))->magic == (b)))
 
 #define ISC_MAGIC(a, b, c, d)	((a) << 24 | (b) << 16 | (c) << 8 | (d))
 

lib/isc/include/isc/util.h

@@ -206,6 +206,17 @@
 #define INSERTAFTER(li, a, e, ln)	ISC_LIST_INSERTAFTER(li, a, e, ln)
 #define APPENDLIST(list1, list2, link)	ISC_LIST_APPENDLIST(list1, list2, link)
 
+/*%
+ * Performance
+ */
+#ifdef HAVE_BUILTIN_EXPECT
+#define ISC_LIKELY(x)            __builtin_expect(!!(x), 1)
+#define ISC_UNLIKELY(x)          __builtin_expect(!!(x), 0)
+#else
+#define ISC_LIKELY(x)            (x)
+#define ISC_UNLIKELY(x)          (x)
+#endif
+
 /*
  * Assertions
  */