diff --git a/libgo/MERGE b/libgo/MERGE
index 16f346a..a5808db 100644
--- a/libgo/MERGE
+++ b/libgo/MERGE
@@ -1,4 +1,4 @@
-cd6b6202dd1559b3ac63179b45f1833fcfbe7eca
+a4c18f063b6659079ca2848ca217a0587dabc001
 
 The first line of this file holds the git revision number of the
 last merge done from the master library sources.
diff --git a/libgo/VERSION b/libgo/VERSION
index 436edd9..dce1d46 100644
--- a/libgo/VERSION
+++ b/libgo/VERSION
@@ -1 +1 @@
-go1.8
+go1.8.1
diff --git a/libgo/go/cmd/go/go_test.go b/libgo/go/cmd/go/go_test.go
index 56de65c..fa78578 100644
--- a/libgo/go/cmd/go/go_test.go
+++ b/libgo/go/cmd/go/go_test.go
@@ -2227,6 +2227,24 @@
 	}
 }
 
+func TestTestRaceInstall(t *testing.T) {
+	if !canRace {
+		t.Skip("no race detector")
+	}
+
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
+
+	tg.tempDir("pkg")
+	pkgdir := tg.path("pkg")
+	tg.run("install", "-race", "-pkgdir="+pkgdir, "std")
+	tg.run("test", "-race", "-pkgdir="+pkgdir, "-i", "-v", "empty/pkg")
+	if tg.getStderr() != "" {
+		t.Error("go test -i -race: rebuilds cached packages")
+	}
+}
+
 func TestBuildDryRunWithCgo(t *testing.T) {
 	if !canCgo {
 		t.Skip("skipping because cgo not enabled")
diff --git a/libgo/go/cmd/go/pkg.go b/libgo/go/cmd/go/pkg.go
index 61c1b99..f0dc956 100644
--- a/libgo/go/cmd/go/pkg.go
+++ b/libgo/go/cmd/go/pkg.go
@@ -970,10 +970,6 @@
 		if p.Name == "main" && goarch == "arm" {
 			importPaths = append(importPaths, "math")
 		}
-		// In coverage atomic mode everything depends on sync/atomic.
-		if testCoverMode == "atomic" && (!p.Standard || (p.ImportPath != "runtime/cgo" && p.ImportPath != "runtime/race" && p.ImportPath != "sync/atomic")) {
-			importPaths = append(importPaths, "sync/atomic")
-		}
 	}
 
 	// Runtime and its internal packages depend on runtime/internal/sys,
diff --git a/libgo/go/cmd/go/test.go b/libgo/go/cmd/go/test.go
index 5c13b65..12990fe 100644
--- a/libgo/go/cmd/go/test.go
+++ b/libgo/go/cmd/go/test.go
@@ -548,6 +548,10 @@
 
 	// Prepare build + run + print actions for all packages being tested.
 	for _, p := range pkgs {
+		// sync/atomic import is inserted by the cover tool. See #18486
+		if testCover && testCoverMode == "atomic" {
+			ensureImport(p, "sync/atomic")
+		}
 		buildTest, runTest, printTest, err := b.test(p)
 		if err != nil {
 			str := err.Error()
@@ -639,6 +643,23 @@
 	b.do(root)
 }
 
+// ensures that package p imports the named package.
+func ensureImport(p *Package, pkg string) {
+	for _, d := range p.deps {
+		if d.Name == pkg {
+			return
+		}
+	}
+
+	a := loadPackage(pkg, &importStack{})
+	if a.Error != nil {
+		fatalf("load %s: %v", pkg, a.Error)
+	}
+	computeStale(a)
+
+	p.imports = append(p.imports, a)
+}
+
 func contains(x []string, s string) bool {
 	for _, t := range x {
 		if t == s {
diff --git a/libgo/go/crypto/tls/common.go b/libgo/go/crypto/tls/common.go
index 276d176..de833a9 100644
--- a/libgo/go/crypto/tls/common.go
+++ b/libgo/go/crypto/tls/common.go
@@ -563,6 +563,7 @@
 		Certificates:                c.Certificates,
 		NameToCertificate:           c.NameToCertificate,
 		GetCertificate:              c.GetCertificate,
+		GetClientCertificate:        c.GetClientCertificate,
 		GetConfigForClient:          c.GetConfigForClient,
 		VerifyPeerCertificate:       c.VerifyPeerCertificate,
 		RootCAs:                     c.RootCAs,
diff --git a/libgo/go/crypto/tls/tls_test.go b/libgo/go/crypto/tls/tls_test.go
index 8933f4f..86812f0 100644
--- a/libgo/go/crypto/tls/tls_test.go
+++ b/libgo/go/crypto/tls/tls_test.go
@@ -13,13 +13,11 @@
 	"io"
 	"io/ioutil"
 	"math"
-	"math/rand"
 	"net"
 	"os"
 	"reflect"
 	"strings"
 	"testing"
-	"testing/quick"
 	"time"
 )
 
@@ -568,11 +566,50 @@
 	}
 }
 
-func TestClone(t *testing.T) {
+func TestCloneFuncFields(t *testing.T) {
+	const expectedCount = 5
+	called := 0
+
+	c1 := Config{
+		Time: func() time.Time {
+			called |= 1 << 0
+			return time.Time{}
+		},
+		GetCertificate: func(*ClientHelloInfo) (*Certificate, error) {
+			called |= 1 << 1
+			return nil, nil
+		},
+		GetClientCertificate: func(*CertificateRequestInfo) (*Certificate, error) {
+			called |= 1 << 2
+			return nil, nil
+		},
+		GetConfigForClient: func(*ClientHelloInfo) (*Config, error) {
+			called |= 1 << 3
+			return nil, nil
+		},
+		VerifyPeerCertificate: func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
+			called |= 1 << 4
+			return nil
+		},
+	}
+
+	c2 := c1.Clone()
+
+	c2.Time()
+	c2.GetCertificate(nil)
+	c2.GetClientCertificate(nil)
+	c2.GetConfigForClient(nil)
+	c2.VerifyPeerCertificate(nil, nil)
+
+	if called != (1<<expectedCount)-1 {
+		t.Fatalf("expected %d calls but saw calls %b", expectedCount, called)
+	}
+}
+
+func TestCloneNonFuncFields(t *testing.T) {
 	var c1 Config
 	v := reflect.ValueOf(&c1).Elem()
 
-	rnd := rand.New(rand.NewSource(time.Now().Unix()))
 	typ := v.Type()
 	for i := 0; i < typ.NumField(); i++ {
 		f := v.Field(i)
@@ -581,40 +618,49 @@
 			continue
 		}
 
-		// testing/quick can't handle functions or interfaces.
-		fn := typ.Field(i).Name
-		switch fn {
+		// testing/quick can't handle functions or interfaces and so
+		// isn't used here.
+		switch fn := typ.Field(i).Name; fn {
 		case "Rand":
 			f.Set(reflect.ValueOf(io.Reader(os.Stdin)))
-			continue
 		case "Time", "GetCertificate", "GetConfigForClient", "VerifyPeerCertificate", "GetClientCertificate":
-			// DeepEqual can't compare functions.
-			continue
+			// DeepEqual can't compare functions. If you add a
+			// function field to this list, you must also change
+			// TestCloneFuncFields to ensure that the func field is
+			// cloned.
 		case "Certificates":
 			f.Set(reflect.ValueOf([]Certificate{
 				{Certificate: [][]byte{{'b'}}},
 			}))
-			continue
 		case "NameToCertificate":
 			f.Set(reflect.ValueOf(map[string]*Certificate{"a": nil}))
-			continue
 		case "RootCAs", "ClientCAs":
 			f.Set(reflect.ValueOf(x509.NewCertPool()))
-			continue
 		case "ClientSessionCache":
 			f.Set(reflect.ValueOf(NewLRUClientSessionCache(10)))
-			continue
 		case "KeyLogWriter":
 			f.Set(reflect.ValueOf(io.Writer(os.Stdout)))
-			continue
-
+		case "NextProtos":
+			f.Set(reflect.ValueOf([]string{"a", "b"}))
+		case "ServerName":
+			f.Set(reflect.ValueOf("b"))
+		case "ClientAuth":
+			f.Set(reflect.ValueOf(VerifyClientCertIfGiven))
+		case "InsecureSkipVerify", "SessionTicketsDisabled", "DynamicRecordSizingDisabled", "PreferServerCipherSuites":
+			f.Set(reflect.ValueOf(true))
+		case "MinVersion", "MaxVersion":
+			f.Set(reflect.ValueOf(uint16(VersionTLS12)))
+		case "SessionTicketKey":
+			f.Set(reflect.ValueOf([32]byte{}))
+		case "CipherSuites":
+			f.Set(reflect.ValueOf([]uint16{1, 2}))
+		case "CurvePreferences":
+			f.Set(reflect.ValueOf([]CurveID{CurveP256}))
+		case "Renegotiation":
+			f.Set(reflect.ValueOf(RenegotiateOnceAsClient))
+		default:
+			t.Errorf("all fields must be accounted for, but saw unknown field %q", fn)
 		}
-
-		q, ok := quick.Value(f.Type(), rnd)
-		if !ok {
-			t.Fatalf("quick.Value failed on field %s", fn)
-		}
-		f.Set(q)
 	}
 
 	c2 := c1.Clone()
diff --git a/libgo/go/encoding/xml/marshal_test.go b/libgo/go/encoding/xml/marshal_test.go
index 5ec7ece..0126146 100644
--- a/libgo/go/encoding/xml/marshal_test.go
+++ b/libgo/go/encoding/xml/marshal_test.go
@@ -2428,7 +2428,10 @@
 	err := Unmarshal([]byte(data), &struct {
 		B byte `xml:"b,attr,omitempty"`
 	}{})
-	if err == nil {
-		t.Errorf("Unmarshal: expected error, got nil")
+
+	// For Go 1.8.1 we've restored the old "no errors reported" behavior.
+	// We'll try again in Go 1.9 to report errors.
+	if err != nil {
+		t.Errorf("Unmarshal: expected nil, got error")
 	}
 }
diff --git a/libgo/go/encoding/xml/read.go b/libgo/go/encoding/xml/read.go
index 5a89d5f..799b57e 100644
--- a/libgo/go/encoding/xml/read.go
+++ b/libgo/go/encoding/xml/read.go
@@ -285,7 +285,8 @@
 		return nil
 	}
 
-	return copyValue(val, []byte(attr.Value))
+	copyValue(val, []byte(attr.Value))
+	return nil
 }
 
 var (
diff --git a/libgo/go/encoding/xml/xml_test.go b/libgo/go/encoding/xml/xml_test.go
index dad6ed9..f43a5e7 100644
--- a/libgo/go/encoding/xml/xml_test.go
+++ b/libgo/go/encoding/xml/xml_test.go
@@ -797,3 +797,37 @@
 		}
 	}
 }
+
+func TestIssue19333(t *testing.T) {
+	type X struct {
+		XMLName Name `xml:"X"`
+		A       int  `xml:",attr"`
+		C       int
+	}
+
+	var tests = []struct {
+		input string
+		ok    bool
+	}{
+		{`<X></X>`, true},
+		{`<X A=""></X>`, true},
+		{`<X A="bad"></X>`, true},
+		{`<X></X>`, true},
+		{`<X><C></C></X>`, false},
+		{`<X><C/></X>`, false},
+		{`<X><C>bad</C></X>`, false},
+	}
+
+	for _, tt := range tests {
+		err := Unmarshal([]byte(tt.input), new(X))
+		if tt.ok {
+			if err != nil {
+				t.Errorf("%s: unexpected error: %v", tt.input, err)
+			}
+		} else {
+			if err == nil {
+				t.Errorf("%s: unexpected success", tt.input)
+			}
+		}
+	}
+}
diff --git a/libgo/go/image/png/reader.go b/libgo/go/image/png/reader.go
index 32f78f0..8299df5 100644
--- a/libgo/go/image/png/reader.go
+++ b/libgo/go/image/png/reader.go
@@ -612,6 +612,11 @@
 				}
 			}
 		case cbG8:
+			if d.useTransparent {
+				// Match error from Go 1.7 and earlier.
+				// Go 1.9 will decode this properly.
+				return nil, chunkOrderError
+			}
 			copy(gray.Pix[pixOffset:], cdat)
 			pixOffset += gray.Stride
 		case cbGA8:
diff --git a/libgo/go/image/png/reader_test.go b/libgo/go/image/png/reader_test.go
index b9e9f4d..503b5dc 100644
--- a/libgo/go/image/png/reader_test.go
+++ b/libgo/go/image/png/reader_test.go
@@ -629,3 +629,13 @@
 func BenchmarkDecodeInterlacing(b *testing.B) {
 	benchmarkDecode(b, "testdata/benchRGB-interlace.png", 4)
 }
+
+func TestIssue19553(t *testing.T) {
+	var buf = []byte{
+		0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x0f, 0x00, 0x00, 0x00, 0x0b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x85, 0x2c, 0x88, 0x80, 0x00, 0x00, 0x00, 0x02, 0x74, 0x52, 0x4e, 0x53, 0x00, 0xff, 0x5b, 0x91, 0x22, 0xb5, 0x00, 0x00, 0x00, 0x02, 0x62, 0x4b, 0x47, 0x44, 0x00, 0xff, 0x87, 0x8f, 0xcc, 0xbf, 0x00, 0x00, 0x00, 0x09, 0x70, 0x48, 0x59, 0x73, 0x00, 0x00, 0x0a, 0xf0, 0x00, 0x00, 0x0a, 0xf0, 0x01, 0x42, 0xac, 0x34, 0x98, 0x00, 0x00, 0x00, 0x07, 0x74, 0x49, 0x4d, 0x45, 0x07, 0xd5, 0x04, 0x02, 0x12, 0x11, 0x11, 0xf7, 0x65, 0x3d, 0x8b, 0x00, 0x00, 0x00, 0x4f, 0x49, 0x44, 0x41, 0x54, 0x08, 0xd7, 0x63, 0xf8, 0xff, 0xff, 0xff, 0xb9, 0xbd, 0x70, 0xf0, 0x8c, 0x01, 0xc8, 0xaf, 0x6e, 0x99, 0x02, 0x05, 0xd9, 0x7b, 0xc1, 0xfc, 0x6b, 0xff, 0xa1, 0xa0, 0x87, 0x30, 0xff, 0xd9, 0xde, 0xbd, 0xd5, 0x4b, 0xf7, 0xee, 0xfd, 0x0e, 0xe3, 0xef, 0xcd, 0x06, 0x19, 0x14, 0xf5, 0x1e, 0xce, 0xef, 0x01, 0x31, 0x92, 0xd7, 0x82, 0x41, 0x31, 0x9c, 0x3f, 0x07, 0x02, 0xee, 0xa1, 0xaa, 0xff, 0xff, 0x9f, 0xe1, 0xd9, 0x56, 0x30, 0xf8, 0x0e, 0xe5, 0x03, 0x00, 0xa9, 0x42, 0x84, 0x3d, 0xdf, 0x8f, 0xa6, 0x8f, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82,
+	}
+	_, err := Decode(bytes.NewReader(buf))
+	if err != chunkOrderError {
+		t.Errorf("Decode: expected chunkOrderError for transparent gray8, got %v", err)
+	}
+}
diff --git a/libgo/go/internal/testenv/testenv.go b/libgo/go/internal/testenv/testenv.go
index fdba8b2..71a692b 100644
--- a/libgo/go/internal/testenv/testenv.go
+++ b/libgo/go/internal/testenv/testenv.go
@@ -141,6 +141,15 @@
 	}
 }
 
+var haveCGO bool
+
+// MustHaveCGO calls t.Skip if cgo is not available.
+func MustHaveCGO(t *testing.T) {
+	if !haveCGO {
+		t.Skipf("skipping test: no cgo")
+	}
+}
+
 // HasSymlink reports whether the current system can use os.Symlink.
 func HasSymlink() bool {
 	ok, _ := hasSymlink()
diff --git a/libgo/go/internal/testenv/testenv_cgo.go b/libgo/go/internal/testenv/testenv_cgo.go
new file mode 100644
index 0000000..e3d4d16
--- /dev/null
+++ b/libgo/go/internal/testenv/testenv_cgo.go
@@ -0,0 +1,11 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo
+
+package testenv
+
+func init() {
+	haveCGO = true
+}
diff --git a/libgo/go/net/http/http.go b/libgo/go/net/http/http.go
index 826f7ff..b95ca89 100644
--- a/libgo/go/net/http/http.go
+++ b/libgo/go/net/http/http.go
@@ -20,7 +20,7 @@
 
 // aLongTimeAgo is a non-zero time, far in the past, used for
 // immediate cancelation of network operations.
-var aLongTimeAgo = time.Unix(233431200, 0)
+var aLongTimeAgo = time.Unix(1, 0)
 
 // TODO(bradfitz): move common stuff here. The other files have accumulated
 // generic http stuff in random places.
diff --git a/libgo/go/net/net.go b/libgo/go/net/net.go
index 81206ea..a8b5736 100644
--- a/libgo/go/net/net.go
+++ b/libgo/go/net/net.go
@@ -468,7 +468,7 @@
 var (
 	// aLongTimeAgo is a non-zero time, far in the past, used for
 	// immediate cancelation of dials.
-	aLongTimeAgo = time.Unix(233431200, 0)
+	aLongTimeAgo = time.Unix(1, 0)
 
 	// nonDeadline and noCancel are just zero values for
 	// readability with functions taking too many parameters.
diff --git a/libgo/go/os/exec/exec_test.go b/libgo/go/os/exec/exec_test.go
index a9cceec..f136351 100644
--- a/libgo/go/os/exec/exec_test.go
+++ b/libgo/go/os/exec/exec_test.go
@@ -266,9 +266,13 @@
 		t.Fatalf("Start: %v", err)
 	}
 	go func() {
-		if err := cmd.Process.Kill(); err != nil {
-			t.Errorf("Kill: %v", err)
-		}
+		// We don't check the error return of Kill. It is
+		// possible that the process has already exited, in
+		// which case Kill will return an error "process
+		// already finished". The purpose of this test is to
+		// see whether the race detector reports an error; it
+		// doesn't matter whether this Kill succeeds or not.
+		cmd.Process.Kill()
 	}()
 	go func() {
 		// Send the wrong string, so that the child fails even
diff --git a/libgo/go/reflect/all_test.go b/libgo/go/reflect/all_test.go
index 859de7c..3686167 100644
--- a/libgo/go/reflect/all_test.go
+++ b/libgo/go/reflect/all_test.go
@@ -1681,6 +1681,11 @@
 }
 
 // This will be index 3.
+func (p Point) NoArgs() {
+	// Exercise no-argument/no-result paths.
+}
+
+// This will be index 4.
 func (p Point) TotalDist(points ...Point) int {
 	tot := 0
 	for _, q := range points {
@@ -1709,6 +1714,15 @@
 		t.Errorf("Type MethodByName returned %d; want 275", i)
 	}
 
+	m, ok = TypeOf(p).MethodByName("NoArgs")
+	if !ok {
+		t.Fatalf("method by name failed")
+	}
+	n := len(m.Func.Call([]Value{ValueOf(p)}))
+	if n != 0 {
+		t.Errorf("NoArgs returned %d values; want 0", n)
+	}
+
 	i = TypeOf(&p).Method(1).Func.Call([]Value{ValueOf(&p), ValueOf(12)})[0].Int()
 	if i != 300 {
 		t.Errorf("Pointer Type Method returned %d; want 300", i)
@@ -1723,6 +1737,15 @@
 		t.Errorf("Pointer Type MethodByName returned %d; want 325", i)
 	}
 
+	m, ok = TypeOf(&p).MethodByName("NoArgs")
+	if !ok {
+		t.Fatalf("method by name failed")
+	}
+	n = len(m.Func.Call([]Value{ValueOf(&p)}))
+	if n != 0 {
+		t.Errorf("NoArgs returned %d values; want 0", n)
+	}
+
 	// Curried method of value.
 	tfunc := TypeOf((func(int) int)(nil))
 	v := ValueOf(p).Method(1)
@@ -1741,6 +1764,8 @@
 	if i != 375 {
 		t.Errorf("Value MethodByName returned %d; want 375", i)
 	}
+	v = ValueOf(p).MethodByName("NoArgs")
+	v.Call(nil)
 
 	// Curried method of pointer.
 	v = ValueOf(&p).Method(1)
@@ -1759,6 +1784,8 @@
 	if i != 425 {
 		t.Errorf("Pointer Value MethodByName returned %d; want 425", i)
 	}
+	v = ValueOf(&p).MethodByName("NoArgs")
+	v.Call(nil)
 
 	// Curried method of interface value.
 	// Have to wrap interface value in a struct to get at it.
@@ -1808,6 +1835,9 @@
 	if i != 275 {
 		t.Errorf("Value MethodByName returned %d; want 275", i)
 	}
+	v = ValueOf(p).MethodByName("NoArgs")
+	ValueOf(v.Interface()).Call(nil)
+	v.Interface().(func())()
 
 	// Curried method of pointer.
 	v = ValueOf(&p).Method(1)
@@ -1826,6 +1856,9 @@
 	if i != 325 {
 		t.Errorf("Pointer Value MethodByName returned %d; want 325", i)
 	}
+	v = ValueOf(&p).MethodByName("NoArgs")
+	ValueOf(v.Interface()).Call(nil)
+	v.Interface().(func())()
 
 	// Curried method of pointer to pointer.
 	pp := &p
@@ -1881,7 +1914,7 @@
 
 	// Curried method of value.
 	tfunc := TypeOf((func(...Point) int)(nil))
-	v := ValueOf(p).Method(3)
+	v := ValueOf(p).Method(4)
 	if tt := v.Type(); tt != tfunc {
 		t.Errorf("Variadic Method Type is %s; want %s", tt, tfunc)
 	}
diff --git a/libgo/go/runtime/crash_unix_test.go b/libgo/go/runtime/crash_unix_test.go
index 4aeeeb6..67ef334 100644
--- a/libgo/go/runtime/crash_unix_test.go
+++ b/libgo/go/runtime/crash_unix_test.go
@@ -9,6 +9,7 @@
 import (
 	"bytes"
 	"internal/testenv"
+	"io"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -153,6 +154,78 @@
 }
 `
 
+func TestPanicSystemstack(t *testing.T) {
+	// Test that GOTRACEBACK=crash prints both the system and user
+	// stack of other threads.
+
+	// The GOTRACEBACK=crash handler takes 0.1 seconds even if
+	// it's not writing a core file and potentially much longer if
+	// it is. Skip in short mode.
+	if testing.Short() {
+		t.Skip("Skipping in short mode (GOTRACEBACK=crash is slow)")
+	}
+
+	t.Parallel()
+	cmd := exec.Command(os.Args[0], "testPanicSystemstackInternal")
+	cmd = testEnv(cmd)
+	cmd.Env = append(cmd.Env, "GOTRACEBACK=crash")
+	pr, pw, err := os.Pipe()
+	if err != nil {
+		t.Fatal("creating pipe: ", err)
+	}
+	cmd.Stderr = pw
+	if err := cmd.Start(); err != nil {
+		t.Fatal("starting command: ", err)
+	}
+	defer cmd.Process.Wait()
+	defer cmd.Process.Kill()
+	if err := pw.Close(); err != nil {
+		t.Log("closing write pipe: ", err)
+	}
+	defer pr.Close()
+
+	// Wait for "x\nx\n" to indicate readiness.
+	buf := make([]byte, 4)
+	_, err = io.ReadFull(pr, buf)
+	if err != nil || string(buf) != "x\nx\n" {
+		t.Fatal("subprocess failed; output:\n", string(buf))
+	}
+
+	// Send SIGQUIT.
+	if err := cmd.Process.Signal(syscall.SIGQUIT); err != nil {
+		t.Fatal("signaling subprocess: ", err)
+	}
+
+	// Get traceback.
+	tb, err := ioutil.ReadAll(pr)
+	if err != nil {
+		t.Fatal("reading traceback from pipe: ", err)
+	}
+
+	// Traceback should have two testPanicSystemstackInternal's
+	// and two blockOnSystemStackInternal's.
+	if bytes.Count(tb, []byte("testPanicSystemstackInternal")) != 2 {
+		t.Fatal("traceback missing user stack:\n", string(tb))
+	} else if bytes.Count(tb, []byte("blockOnSystemStackInternal")) != 2 {
+		t.Fatal("traceback missing system stack:\n", string(tb))
+	}
+}
+
+func init() {
+	if len(os.Args) >= 2 && os.Args[1] == "testPanicSystemstackInternal" {
+		// Get two threads running on the system stack with
+		// something recognizable in the stack trace.
+		runtime.GOMAXPROCS(2)
+		go testPanicSystemstackInternal()
+		testPanicSystemstackInternal()
+	}
+}
+
+func testPanicSystemstackInternal() {
+	runtime.BlockOnSystemStack()
+	os.Exit(1) // Should be unreachable.
+}
+
 func TestSignalExitStatus(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
 	exe, err := buildTestProg(t, "testprog")
diff --git a/libgo/go/runtime/export_test.go b/libgo/go/runtime/export_test.go
index ac090a3..69a13ac 100644
--- a/libgo/go/runtime/export_test.go
+++ b/libgo/go/runtime/export_test.go
@@ -244,3 +244,16 @@
 	return
 }
 */
+
+// BlockOnSystemStack switches to the system stack, prints "x\n" to
+// stderr, and blocks in a stack containing
+// "runtime.blockOnSystemStackInternal".
+func BlockOnSystemStack() {
+	systemstack(blockOnSystemStackInternal)
+}
+
+func blockOnSystemStackInternal() {
+	print("x\n")
+	lock(&deadlock)
+	lock(&deadlock)
+}
diff --git a/libgo/go/runtime/runtime1.go b/libgo/go/runtime/runtime1.go
index a41cfc8..99c0f11 100644
--- a/libgo/go/runtime/runtime1.go
+++ b/libgo/go/runtime/runtime1.go
@@ -280,6 +280,12 @@
 		throw("atomicor8")
 	}
 
+	m = [4]byte{0xff, 0xff, 0xff, 0xff}
+	atomic.And8(&m[1], 0x1)
+	if m[0] != 0xff || m[1] != 0x1 || m[2] != 0xff || m[3] != 0xff {
+		throw("atomicand8")
+	}
+
 	*(*uint64)(unsafe.Pointer(&j)) = ^uint64(0)
 	if j == j {
 		throw("float64nan")
diff --git a/libgo/go/runtime/sema.go b/libgo/go/runtime/sema.go
index 576a1fb..37318ff 100644
--- a/libgo/go/runtime/sema.go
+++ b/libgo/go/runtime/sema.go
@@ -171,6 +171,7 @@
 			for x := root.head; x != nil; x = x.next {
 				if x.elem == unsafe.Pointer(addr) {
 					x.acquiretime = t0
+					break
 				}
 			}
 			mutexevent(t0-s.acquiretime, 3)
diff --git a/libgo/go/text/template/multi_test.go b/libgo/go/text/template/multi_test.go
index 8142f00..5d8c08f 100644
--- a/libgo/go/text/template/multi_test.go
+++ b/libgo/go/text/template/multi_test.go
@@ -363,7 +363,7 @@
 		{[]string{"{{.}}", ""}, "twice", ""},
 	}
 
-	for _, c := range cases {
+	for i, c := range cases {
 		root := New("root")
 
 		var (
@@ -378,10 +378,43 @@
 		}
 		buf := &bytes.Buffer{}
 		if err := m.Execute(buf, c.in); err != nil {
-			t.Fatal(err)
+			t.Error(i, err)
+			continue
 		}
 		if buf.String() != c.want {
 			t.Errorf("expected string %q: got %q", c.want, buf.String())
 		}
 	}
 }
+
+// Issue 19249 was a regression in 1.8 caused by the handling of empty
+// templates added in that release, which got different answers depending
+// on the order templates appeared in the internal map.
+func TestIssue19294(t *testing.T) {
+	// The empty block in "xhtml" should be replaced during execution
+	// by the contents of "stylesheet", but if the internal map associating
+	// names with templates is built in the wrong order, the empty block
+	// looks non-empty and this doesn't happen.
+	var inlined = map[string]string{
+		"stylesheet": `{{define "stylesheet"}}stylesheet{{end}}`,
+		"xhtml":      `{{block "stylesheet" .}}{{end}}`,
+	}
+	all := []string{"stylesheet", "xhtml"}
+	for i := 0; i < 100; i++ {
+		res, err := New("title.xhtml").Parse(`{{template "xhtml" .}}`)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, name := range all {
+			_, err := res.New(name).Parse(inlined[name])
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		var buf bytes.Buffer
+		res.Execute(&buf, 0)
+		if buf.String() != "stylesheet" {
+			t.Fatalf("iteration %d: got %q; expected %q", i, buf.String(), "stylesheet")
+		}
+	}
+}
diff --git a/libgo/go/text/template/template.go b/libgo/go/text/template/template.go
index b6fceb1..3b4f34b 100644
--- a/libgo/go/text/template/template.go
+++ b/libgo/go/text/template/template.go
@@ -127,7 +127,7 @@
 	// Even if nt == t, we need to install it in the common.tmpl map.
 	if replace, err := t.associate(nt, tree); err != nil {
 		return nil, err
-	} else if replace {
+	} else if replace || nt.Tree == nil {
 		nt.Tree = tree
 	}
 	return nt, nil
@@ -215,7 +215,7 @@
 	if new.common != t.common {
 		panic("internal error: associate not common")
 	}
-	if t.tmpl[new.name] != nil && parse.IsEmptyTree(tree.Root) && t.Tree != nil {
+	if old := t.tmpl[new.name]; old != nil && parse.IsEmptyTree(tree.Root) && old.Tree != nil {
 		// If a template by that name exists,
 		// don't replace it with an empty template.
 		return false, nil