libgo: update to Go1.16beta1 release

This does not yet include support for the //go:embed directive added
in this release.

	* Makefile.am (check-runtime): Don't create check-runtime-dir.
	(mostlyclean-local): Don't remove check-runtime-dir.
	(check-go-tool, check-vet): Copy in go.mod and modules.txt.
	(check-cgo-test, check-carchive-test): Add go.mod file.
	* Makefile.in: Regenerate.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/280172

1 files changed, 16 insertions, 3 deletions

diff --git a/libgo/go/net/dnsclient.go b/libgo/go/net/dnsclient.go
index b5bb3a4..e9c7384 100644
--- a/libgo/go/net/dnsclient.go
+++ b/libgo/go/net/dnsclient.go
@@ -5,12 +5,25 @@
 package net
 
 import (
-	"math/rand"
 	"sort"
 
 	"golang.org/x/net/dns/dnsmessage"
 )
 
+// provided by runtime
+func fastrand() uint32
+
+func randInt() int {
+	x, y := fastrand(), fastrand()    // 32-bit halves
+	u := uint(x)<<31 ^ uint(int32(y)) // full uint, even on 64-bit systems; avoid 32-bit shift on 32-bit systems
+	i := int(u >> 1)                  // clear sign bit, even on 32-bit systems
+	return i
+}
+
+func randIntn(n int) int {
+	return randInt() % n
+}
+
 // reverseaddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
 // address addr suitable for rDNS (PTR) record lookup or an error if it fails
 // to parse the IP address.
@@ -162,7 +175,7 @@ func (addrs byPriorityWeight) shuffleByWeight() {
 	}
 	for sum > 0 && len(addrs) > 1 {
 		s := 0
-		n := rand.Intn(sum)
+		n := randIntn(sum)
 		for i := range addrs {
 			s += int(addrs[i].Weight)
 			if s > n {
@@ -206,7 +219,7 @@ func (s byPref) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 // sort reorders MX records as specified in RFC 5321.
 func (s byPref) sort() {
 	for i := range s {
-		j := rand.Intn(i + 1)
+		j := randIntn(i + 1)
 		s[i], s[j] = s[j], s[i]
 	}
 	sort.Sort(s)