libgo: update to Go1.10beta1

    
    Update the Go library to the 1.10beta1 release.
    
    Requires a few changes to the compiler for modifications to the map
    runtime code, and to handle some nowritebarrier cases in the runtime.
    
    Reviewed-on: https://go-review.googlesource.com/86455

gotools/:
	* Makefile.am (go_cmd_vet_files): New variable.
	(go_cmd_buildid_files, go_cmd_test2json_files): New variables.
	(s-zdefaultcc): Change from constants to functions.
	(noinst_PROGRAMS): Add vet, buildid, and test2json.
	(cgo$(EXEEXT)): Link against $(LIBGOTOOL).
	(vet$(EXEEXT)): New target.
	(buildid$(EXEEXT)): New target.
	(test2json$(EXEEXT)): New target.
	(install-exec-local): Install all $(noinst_PROGRAMS).
	(uninstall-local): Uninstasll all $(noinst_PROGRAMS).
	(check-go-tool): Depend on $(noinst_PROGRAMS).  Copy down
	objabi.go.
	(check-runtime): Depend on $(noinst_PROGRAMS).
	(check-cgo-test, check-carchive-test): Likewise.
	(check-vet): New target.
	(check): Depend on check-vet.  Look at cmd_vet-testlog.
	(.PHONY): Add check-vet.
	* Makefile.in: Rebuild.

From-SVN: r256365

13 files changed, 769 insertions, 340 deletions

diff --git a/libgo/go/bytes/boundary_test.go b/libgo/go/bytes/boundary_test.go
new file mode 100644
index 0000000..ea84f1e
--- /dev/null
+++ b/libgo/go/bytes/boundary_test.go
@@ -0,0 +1,84 @@
+// 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 linux
+
+package bytes_test
+
+import (
+	. "bytes"
+	"syscall"
+	"testing"
+)
+
+// This file tests the situation where byte operations are checking
+// data very near to a page boundary. We want to make sure those
+// operations do not read across the boundary and cause a page
+// fault where they shouldn't.
+
+// These tests run only on linux. The code being tested is
+// not OS-specific, so it does not need to be tested on all
+// operating systems.
+
+// dangerousSlice returns a slice which is immediately
+// preceded and followed by a faulting page.
+func dangerousSlice(t *testing.T) []byte {
+	pagesize := syscall.Getpagesize()
+	b, err := syscall.Mmap(0, 0, 3*pagesize, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANONYMOUS|syscall.MAP_PRIVATE)
+	if err != nil {
+		t.Fatalf("mmap failed %s", err)
+	}
+	err = syscall.Mprotect(b[:pagesize], syscall.PROT_NONE)
+	if err != nil {
+		t.Fatalf("mprotect low failed %s\n", err)
+	}
+	err = syscall.Mprotect(b[2*pagesize:], syscall.PROT_NONE)
+	if err != nil {
+		t.Fatalf("mprotect high failed %s\n", err)
+	}
+	return b[pagesize : 2*pagesize]
+}
+
+func TestEqualNearPageBoundary(t *testing.T) {
+	t.Parallel()
+	b := dangerousSlice(t)
+	for i := range b {
+		b[i] = 'A'
+	}
+	for i := 0; i <= len(b); i++ {
+		Equal(b[:i], b[len(b)-i:])
+		Equal(b[len(b)-i:], b[:i])
+	}
+}
+
+func TestIndexByteNearPageBoundary(t *testing.T) {
+	t.Parallel()
+	b := dangerousSlice(t)
+	for i := range b {
+		idx := IndexByte(b[i:], 1)
+		if idx != -1 {
+			t.Fatalf("IndexByte(b[%d:])=%d, want -1\n", i, idx)
+		}
+	}
+}
+
+func TestIndexNearPageBoundary(t *testing.T) {
+	t.Parallel()
+	var q [64]byte
+	b := dangerousSlice(t)
+	if len(b) > 256 {
+		// Only worry about when we're near the end of a page.
+		b = b[len(b)-256:]
+	}
+	for j := 1; j < len(q); j++ {
+		q[j-1] = 1 // difference is only found on the last byte
+		for i := range b {
+			idx := Index(b[i:], q[:j])
+			if idx != -1 {
+				t.Fatalf("Index(b[%d:], q[:%d])=%d, want -1\n", i, j, idx)
+			}
+		}
+		q[j-1] = 0
+	}
+}
diff --git a/libgo/go/bytes/buffer.go b/libgo/go/bytes/buffer.go
index 20e42bb..dc9d5e9 100644
--- a/libgo/go/bytes/buffer.go
+++ b/libgo/go/bytes/buffer.go
@@ -15,34 +15,37 @@ import (
 // A Buffer is a variable-sized buffer of bytes with Read and Write methods.
 // The zero value for Buffer is an empty buffer ready to use.
 type Buffer struct {
-	buf      []byte // contents are the bytes buf[off : len(buf)]
-	off      int    // read at &buf[off], write at &buf[len(buf)]
-	lastRead readOp // last read operation, so that Unread* can work correctly.
-	// FIXME: lastRead can fit in a single byte
+	buf       []byte   // contents are the bytes buf[off : len(buf)]
+	off       int      // read at &buf[off], write at &buf[len(buf)]
+	bootstrap [64]byte // memory to hold first slice; helps small buffers avoid allocation.
+	lastRead  readOp   // last read operation, so that Unread* can work correctly.
 
-	// memory to hold first slice; helps small buffers avoid allocation.
 	// FIXME: it would be advisable to align Buffer to cachelines to avoid false
 	// sharing.
-	bootstrap [64]byte
 }
 
 // The readOp constants describe the last action performed on
 // the buffer, so that UnreadRune and UnreadByte can check for
 // invalid usage. opReadRuneX constants are chosen such that
 // converted to int they correspond to the rune size that was read.
-type readOp int
+type readOp int8
 
+// Don't use iota for these, as the values need to correspond with the
+// names and comments, which is easier to see when being explicit.
 const (
 	opRead      readOp = -1 // Any other read operation.
-	opInvalid          = 0  // Non-read operation.
-	opReadRune1        = 1  // Read rune of size 1.
-	opReadRune2        = 2  // Read rune of size 2.
-	opReadRune3        = 3  // Read rune of size 3.
-	opReadRune4        = 4  // Read rune of size 4.
+	opInvalid   readOp = 0  // Non-read operation.
+	opReadRune1 readOp = 1  // Read rune of size 1.
+	opReadRune2 readOp = 2  // Read rune of size 2.
+	opReadRune3 readOp = 3  // Read rune of size 3.
+	opReadRune4 readOp = 4  // Read rune of size 4.
 )
 
 // ErrTooLarge is passed to panic if memory cannot be allocated to store data in a buffer.
 var ErrTooLarge = errors.New("bytes.Buffer: too large")
+var errNegativeRead = errors.New("bytes.Buffer: reader returned negative count from Read")
+
+const maxInt = int(^uint(0) >> 1)
 
 // Bytes returns a slice of length b.Len() holding the unread portion of the buffer.
 // The slice is valid for use only until the next buffer modification (that is,
@@ -53,6 +56,8 @@ func (b *Buffer) Bytes() []byte { return b.buf[b.off:] }
 
 // String returns the contents of the unread portion of the buffer
 // as a string. If the Buffer is a nil pointer, it returns "<nil>".
+//
+// To build strings more efficiently, see the strings.Builder type.
 func (b *Buffer) String() string {
 	if b == nil {
 		// Special case, useful in debugging.
@@ -61,6 +66,9 @@ func (b *Buffer) String() string {
 	return string(b.buf[b.off:])
 }
 
+// empty returns whether the unread portion of the buffer is empty.
+func (b *Buffer) empty() bool { return len(b.buf) <= b.off }
+
 // Len returns the number of bytes of the unread portion of the buffer;
 // b.Len() == len(b.Bytes()).
 func (b *Buffer) Len() int { return len(b.buf) - b.off }
@@ -81,7 +89,7 @@ func (b *Buffer) Truncate(n int) {
 	if n < 0 || n > b.Len() {
 		panic("bytes.Buffer: truncation out of range")
 	}
-	b.buf = b.buf[0 : b.off+n]
+	b.buf = b.buf[:b.off+n]
 }
 
 // Reset resets the buffer to be empty,
@@ -97,7 +105,7 @@ func (b *Buffer) Reset() {
 // internal buffer only needs to be resliced.
 // It returns the index where bytes should be written and whether it succeeded.
 func (b *Buffer) tryGrowByReslice(n int) (int, bool) {
-	if l := len(b.buf); l+n <= cap(b.buf) {
+	if l := len(b.buf); n <= cap(b.buf)-l {
 		b.buf = b.buf[:l+n]
 		return l, true
 	}
@@ -122,15 +130,18 @@ func (b *Buffer) grow(n int) int {
 		b.buf = b.bootstrap[:n]
 		return 0
 	}
-	if m+n <= cap(b.buf)/2 {
+	c := cap(b.buf)
+	if n <= c/2-m {
 		// We can slide things down instead of allocating a new
-		// slice. We only need m+n <= cap(b.buf) to slide, but
+		// slice. We only need m+n <= c to slide, but
 		// we instead let capacity get twice as large so we
 		// don't spend all our time copying.
-		copy(b.buf[:], b.buf[b.off:])
+		copy(b.buf, b.buf[b.off:])
+	} else if c > maxInt-c-n {
+		panic(ErrTooLarge)
 	} else {
 		// Not enough space anywhere, we need to allocate.
-		buf := makeSlice(2*cap(b.buf) + n)
+		buf := makeSlice(2*c + n)
 		copy(buf, b.buf[b.off:])
 		b.buf = buf
 	}
@@ -150,7 +161,7 @@ func (b *Buffer) Grow(n int) {
 		panic("bytes.Buffer.Grow: negative count")
 	}
 	m := b.grow(n)
-	b.buf = b.buf[0:m]
+	b.buf = b.buf[:m]
 }
 
 // Write appends the contents of p to the buffer, growing the buffer as
@@ -189,34 +200,22 @@ const MinRead = 512
 // buffer becomes too large, ReadFrom will panic with ErrTooLarge.
 func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
 	b.lastRead = opInvalid
-	// If buffer is empty, reset to recover space.
-	if b.off >= len(b.buf) {
-		b.Reset()
-	}
 	for {
-		if free := cap(b.buf) - len(b.buf); free < MinRead {
-			// not enough space at end
-			newBuf := b.buf
-			if b.off+free < MinRead {
-				// not enough space using beginning of buffer;
-				// double buffer capacity
-				newBuf = makeSlice(2*cap(b.buf) + MinRead)
-			}
-			copy(newBuf, b.buf[b.off:])
-			b.buf = newBuf[:len(b.buf)-b.off]
-			b.off = 0
+		i := b.grow(MinRead)
+		m, e := r.Read(b.buf[i:cap(b.buf)])
+		if m < 0 {
+			panic(errNegativeRead)
 		}
-		m, e := r.Read(b.buf[len(b.buf):cap(b.buf)])
-		b.buf = b.buf[0 : len(b.buf)+m]
+
+		b.buf = b.buf[:i+m]
 		n += int64(m)
 		if e == io.EOF {
-			break
+			return n, nil // e is EOF, so return nil explicitly
 		}
 		if e != nil {
 			return n, e
 		}
 	}
-	return n, nil // err is EOF, so return nil explicitly
 }
 
 // makeSlice allocates a slice of size n. If the allocation fails, it panics
@@ -237,8 +236,7 @@ func makeSlice(n int) []byte {
 // encountered during the write is also returned.
 func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
 	b.lastRead = opInvalid
-	if b.off < len(b.buf) {
-		nBytes := b.Len()
+	if nBytes := b.Len(); nBytes > 0 {
 		m, e := w.Write(b.buf[b.off:])
 		if m > nBytes {
 			panic("bytes.Buffer.WriteTo: invalid Write count")
@@ -256,7 +254,7 @@ func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
 	}
 	// Buffer is now empty; reset.
 	b.Reset()
-	return
+	return n, nil
 }
 
 // WriteByte appends the byte c to the buffer, growing the buffer as needed.
@@ -298,11 +296,11 @@ func (b *Buffer) WriteRune(r rune) (n int, err error) {
 // otherwise it is nil.
 func (b *Buffer) Read(p []byte) (n int, err error) {
 	b.lastRead = opInvalid
-	if b.off >= len(b.buf) {
+	if b.empty() {
 		// Buffer is empty, reset to recover space.
 		b.Reset()
 		if len(p) == 0 {
-			return
+			return 0, nil
 		}
 		return 0, io.EOF
 	}
@@ -311,7 +309,7 @@ func (b *Buffer) Read(p []byte) (n int, err error) {
 	if n > 0 {
 		b.lastRead = opRead
 	}
-	return
+	return n, nil
 }
 
 // Next returns a slice containing the next n bytes from the buffer,
@@ -335,8 +333,7 @@ func (b *Buffer) Next(n int) []byte {
 // ReadByte reads and returns the next byte from the buffer.
 // If no byte is available, it returns error io.EOF.
 func (b *Buffer) ReadByte() (byte, error) {
-	b.lastRead = opInvalid
-	if b.off >= len(b.buf) {
+	if b.empty() {
 		// Buffer is empty, reset to recover space.
 		b.Reset()
 		return 0, io.EOF
@@ -353,8 +350,7 @@ func (b *Buffer) ReadByte() (byte, error) {
 // If the bytes are an erroneous UTF-8 encoding, it
 // consumes one byte and returns U+FFFD, 1.
 func (b *Buffer) ReadRune() (r rune, size int, err error) {
-	b.lastRead = opInvalid
-	if b.off >= len(b.buf) {
+	if b.empty() {
 		// Buffer is empty, reset to recover space.
 		b.Reset()
 		return 0, 0, io.EOF
@@ -413,7 +409,7 @@ func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
 	// return a copy of slice. The buffer's backing array may
 	// be overwritten by later calls.
 	line = append(line, slice...)
-	return
+	return line, err
 }
 
 // readSlice is like ReadBytes but returns a reference to internal buffer data.
diff --git a/libgo/go/bytes/buffer_test.go b/libgo/go/bytes/buffer_test.go
index ce2f01a..e4bbc12 100644
--- a/libgo/go/bytes/buffer_test.go
+++ b/libgo/go/bytes/buffer_test.go
@@ -6,25 +6,27 @@ package bytes_test
 
 import (
 	. "bytes"
-	"internal/testenv"
 	"io"
 	"math/rand"
-	"os/exec"
 	"runtime"
 	"testing"
 	"unicode/utf8"
 )
 
-const N = 10000      // make this bigger for a larger (and slower) test
-var data string      // test data for write tests
-var testBytes []byte // test data; same as data but as a slice.
+const N = 10000       // make this bigger for a larger (and slower) test
+var testString string // test data for write tests
+var testBytes []byte  // test data; same as testString but as a slice.
+
+type negativeReader struct{}
+
+func (r *negativeReader) Read([]byte) (int, error) { return -1, nil }
 
 func init() {
 	testBytes = make([]byte, N)
 	for i := 0; i < N; i++ {
 		testBytes[i] = 'a' + byte(i%26)
 	}
-	data = string(testBytes)
+	testString = string(testBytes)
 }
 
 // Verify that contents of buf match the string s.
@@ -88,12 +90,12 @@ func fillBytes(t *testing.T, testname string, buf *Buffer, s string, n int, fub
 
 func TestNewBuffer(t *testing.T) {
 	buf := NewBuffer(testBytes)
-	check(t, "NewBuffer", buf, data)
+	check(t, "NewBuffer", buf, testString)
 }
 
 func TestNewBufferString(t *testing.T) {
-	buf := NewBufferString(data)
-	check(t, "NewBufferString", buf, data)
+	buf := NewBufferString(testString)
+	check(t, "NewBufferString", buf, testString)
 }
 
 // Empty buf through repeated reads into fub.
@@ -128,7 +130,7 @@ func TestBasicOperations(t *testing.T) {
 		buf.Truncate(0)
 		check(t, "TestBasicOperations (3)", &buf, "")
 
-		n, err := buf.Write([]byte(data[0:1]))
+		n, err := buf.Write(testBytes[0:1])
 		if n != 1 {
 			t.Errorf("wrote 1 byte, but n == %d", n)
 		}
@@ -137,30 +139,30 @@ func TestBasicOperations(t *testing.T) {
 		}
 		check(t, "TestBasicOperations (4)", &buf, "a")
 
-		buf.WriteByte(data[1])
+		buf.WriteByte(testString[1])
 		check(t, "TestBasicOperations (5)", &buf, "ab")
 
-		n, err = buf.Write([]byte(data[2:26]))
+		n, err = buf.Write(testBytes[2:26])
 		if n != 24 {
-			t.Errorf("wrote 25 bytes, but n == %d", n)
+			t.Errorf("wrote 24 bytes, but n == %d", n)
 		}
-		check(t, "TestBasicOperations (6)", &buf, string(data[0:26]))
+		check(t, "TestBasicOperations (6)", &buf, testString[0:26])
 
 		buf.Truncate(26)
-		check(t, "TestBasicOperations (7)", &buf, string(data[0:26]))
+		check(t, "TestBasicOperations (7)", &buf, testString[0:26])
 
 		buf.Truncate(20)
-		check(t, "TestBasicOperations (8)", &buf, string(data[0:20]))
+		check(t, "TestBasicOperations (8)", &buf, testString[0:20])
 
-		empty(t, "TestBasicOperations (9)", &buf, string(data[0:20]), make([]byte, 5))
+		empty(t, "TestBasicOperations (9)", &buf, testString[0:20], make([]byte, 5))
 		empty(t, "TestBasicOperations (10)", &buf, "", make([]byte, 100))
 
-		buf.WriteByte(data[1])
+		buf.WriteByte(testString[1])
 		c, err := buf.ReadByte()
 		if err != nil {
 			t.Error("ReadByte unexpected eof")
 		}
-		if c != data[1] {
+		if c != testString[1] {
 			t.Errorf("ReadByte wrong value c=%v", c)
 		}
 		c, err = buf.ReadByte()
@@ -177,8 +179,8 @@ func TestLargeStringWrites(t *testing.T) {
 		limit = 9
 	}
 	for i := 3; i < limit; i += 3 {
-		s := fillString(t, "TestLargeWrites (1)", &buf, "", 5, data)
-		empty(t, "TestLargeStringWrites (2)", &buf, s, make([]byte, len(data)/i))
+		s := fillString(t, "TestLargeWrites (1)", &buf, "", 5, testString)
+		empty(t, "TestLargeStringWrites (2)", &buf, s, make([]byte, len(testString)/i))
 	}
 	check(t, "TestLargeStringWrites (3)", &buf, "")
 }
@@ -191,7 +193,7 @@ func TestLargeByteWrites(t *testing.T) {
 	}
 	for i := 3; i < limit; i += 3 {
 		s := fillBytes(t, "TestLargeWrites (1)", &buf, "", 5, testBytes)
-		empty(t, "TestLargeByteWrites (2)", &buf, s, make([]byte, len(data)/i))
+		empty(t, "TestLargeByteWrites (2)", &buf, s, make([]byte, len(testString)/i))
 	}
 	check(t, "TestLargeByteWrites (3)", &buf, "")
 }
@@ -199,8 +201,8 @@ func TestLargeByteWrites(t *testing.T) {
 func TestLargeStringReads(t *testing.T) {
 	var buf Buffer
 	for i := 3; i < 30; i += 3 {
-		s := fillString(t, "TestLargeReads (1)", &buf, "", 5, data[0:len(data)/i])
-		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
+		s := fillString(t, "TestLargeReads (1)", &buf, "", 5, testString[0:len(testString)/i])
+		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(testString)))
 	}
 	check(t, "TestLargeStringReads (3)", &buf, "")
 }
@@ -209,7 +211,7 @@ func TestLargeByteReads(t *testing.T) {
 	var buf Buffer
 	for i := 3; i < 30; i += 3 {
 		s := fillBytes(t, "TestLargeReads (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
-		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
+		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(testString)))
 	}
 	check(t, "TestLargeByteReads (3)", &buf, "")
 }
@@ -218,14 +220,14 @@ func TestMixedReadsAndWrites(t *testing.T) {
 	var buf Buffer
 	s := ""
 	for i := 0; i < 50; i++ {
-		wlen := rand.Intn(len(data))
+		wlen := rand.Intn(len(testString))
 		if i%2 == 0 {
-			s = fillString(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, data[0:wlen])
+			s = fillString(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testString[0:wlen])
 		} else {
 			s = fillBytes(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testBytes[0:wlen])
 		}
 
-		rlen := rand.Intn(len(data))
+		rlen := rand.Intn(len(testString))
 		fub := make([]byte, rlen)
 		n, _ := buf.Read(fub)
 		s = s[n:]
@@ -263,17 +265,37 @@ func TestReadFrom(t *testing.T) {
 		s := fillBytes(t, "TestReadFrom (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
 		var b Buffer
 		b.ReadFrom(&buf)
-		empty(t, "TestReadFrom (2)", &b, s, make([]byte, len(data)))
+		empty(t, "TestReadFrom (2)", &b, s, make([]byte, len(testString)))
 	}
 }
 
+func TestReadFromNegativeReader(t *testing.T) {
+	var b Buffer
+	defer func() {
+		switch err := recover().(type) {
+		case nil:
+			t.Fatal("bytes.Buffer.ReadFrom didn't panic")
+		case error:
+			// this is the error string of errNegativeRead
+			wantError := "bytes.Buffer: reader returned negative count from Read"
+			if err.Error() != wantError {
+				t.Fatalf("recovered panic: got %v, want %v", err.Error(), wantError)
+			}
+		default:
+			t.Fatalf("unexpected panic value: %#v", err)
+		}
+	}()
+
+	b.ReadFrom(new(negativeReader))
+}
+
 func TestWriteTo(t *testing.T) {
 	var buf Buffer
 	for i := 3; i < 30; i += 3 {
 		s := fillBytes(t, "TestWriteTo (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
 		var b Buffer
 		buf.WriteTo(&b)
-		empty(t, "TestWriteTo (2)", &b, s, make([]byte, len(data)))
+		empty(t, "TestWriteTo (2)", &b, s, make([]byte, len(testString)))
 	}
 }
 
@@ -473,6 +495,18 @@ func TestGrow(t *testing.T) {
 	}
 }
 
+func TestGrowOverflow(t *testing.T) {
+	defer func() {
+		if err := recover(); err != ErrTooLarge {
+			t.Errorf("after too-large Grow, recover() = %v; want %v", err, ErrTooLarge)
+		}
+	}()
+
+	buf := NewBuffer(make([]byte, 1))
+	const maxInt = int(^uint(0) >> 1)
+	buf.Grow(maxInt)
+}
+
 // Was a bug: used to give EOF reading empty slice at EOF.
 func TestReadEmptyAtEOF(t *testing.T) {
 	b := new(Buffer)
@@ -548,26 +582,6 @@ func TestBufferGrowth(t *testing.T) {
 	}
 }
 
-// Test that tryGrowByReslice is inlined.
-// Only execute on "linux-amd64" builder in order to avoid breakage.
-func TestTryGrowByResliceInlined(t *testing.T) {
-	targetBuilder := "linux-amd64"
-	if testenv.Builder() != targetBuilder {
-		t.Skipf("%q gets executed on %q builder only", t.Name(), targetBuilder)
-	}
-	t.Parallel()
-	goBin := testenv.GoToolPath(t)
-	out, err := exec.Command(goBin, "tool", "nm", goBin).CombinedOutput()
-	if err != nil {
-		t.Fatalf("go tool nm: %v: %s", err, out)
-	}
-	// Verify this doesn't exist:
-	sym := "bytes.(*Buffer).tryGrowByReslice"
-	if Contains(out, []byte(sym)) {
-		t.Errorf("found symbol %q in cmd/go, but should be inlined", sym)
-	}
-}
-
 func BenchmarkWriteByte(b *testing.B) {
 	const n = 4 << 10
 	b.SetBytes(n)
diff --git a/libgo/go/bytes/bytes.go b/libgo/go/bytes/bytes.go
index 7c878af..9af177f 100644
--- a/libgo/go/bytes/bytes.go
+++ b/libgo/go/bytes/bytes.go
@@ -39,7 +39,7 @@ func explode(s []byte, n int) [][]byte {
 			break
 		}
 		_, size = utf8.DecodeRune(s)
-		a[na] = s[0:size]
+		a[na] = s[0:size:size]
 		s = s[size:]
 		na++
 	}
@@ -68,12 +68,12 @@ func Contains(b, subslice []byte) bool {
 	return Index(b, subslice) != -1
 }
 
-// ContainsAny reports whether any of the UTF-8-encoded Unicode code points in chars are within b.
+// ContainsAny reports whether any of the UTF-8-encoded code points in chars are within b.
 func ContainsAny(b []byte, chars string) bool {
 	return IndexAny(b, chars) >= 0
 }
 
-// ContainsRune reports whether the Unicode code point r is within b.
+// ContainsRune reports whether the rune is contained in the UTF-8-encoded byte slice b.
 func ContainsRune(b []byte, r rune) bool {
 	return IndexRune(b, r) >= 0
 }
@@ -112,7 +112,7 @@ func LastIndexByte(s []byte, c byte) int {
 	return -1
 }
 
-// IndexRune interprets s as a sequence of UTF-8-encoded Unicode code points.
+// IndexRune interprets s as a sequence of UTF-8-encoded code points.
 // It returns the byte index of the first occurrence in s of the given rune.
 // It returns -1 if rune is not present in s.
 // If r is utf8.RuneError, it returns the first instance of any
@@ -144,29 +144,31 @@ func IndexRune(s []byte, r rune) int {
 // code points in chars. It returns -1 if chars is empty or if there is no code
 // point in common.
 func IndexAny(s []byte, chars string) int {
-	if len(chars) > 0 {
-		if len(s) > 8 {
-			if as, isASCII := makeASCIISet(chars); isASCII {
-				for i, c := range s {
-					if as.contains(c) {
-						return i
-					}
+	if chars == "" {
+		// Avoid scanning all of s.
+		return -1
+	}
+	if len(s) > 8 {
+		if as, isASCII := makeASCIISet(chars); isASCII {
+			for i, c := range s {
+				if as.contains(c) {
+					return i
 				}
-				return -1
 			}
+			return -1
 		}
-		var width int
-		for i := 0; i < len(s); i += width {
-			r := rune(s[i])
-			if r < utf8.RuneSelf {
-				width = 1
-			} else {
-				r, width = utf8.DecodeRune(s[i:])
-			}
-			for _, ch := range chars {
-				if r == ch {
-					return i
-				}
+	}
+	var width int
+	for i := 0; i < len(s); i += width {
+		r := rune(s[i])
+		if r < utf8.RuneSelf {
+			width = 1
+		} else {
+			r, width = utf8.DecodeRune(s[i:])
+		}
+		for _, ch := range chars {
+			if r == ch {
+				return i
 			}
 		}
 	}
@@ -178,24 +180,26 @@ func IndexAny(s []byte, chars string) int {
 // the Unicode code points in chars. It returns -1 if chars is empty or if
 // there is no code point in common.
 func LastIndexAny(s []byte, chars string) int {
-	if len(chars) > 0 {
-		if len(s) > 8 {
-			if as, isASCII := makeASCIISet(chars); isASCII {
-				for i := len(s) - 1; i >= 0; i-- {
-					if as.contains(s[i]) {
-						return i
-					}
+	if chars == "" {
+		// Avoid scanning all of s.
+		return -1
+	}
+	if len(s) > 8 {
+		if as, isASCII := makeASCIISet(chars); isASCII {
+			for i := len(s) - 1; i >= 0; i-- {
+				if as.contains(s[i]) {
+					return i
 				}
-				return -1
 			}
+			return -1
 		}
-		for i := len(s); i > 0; {
-			r, size := utf8.DecodeLastRune(s[:i])
-			i -= size
-			for _, c := range chars {
-				if r == c {
-					return i
-				}
+	}
+	for i := len(s); i > 0; {
+		r, size := utf8.DecodeLastRune(s[:i])
+		i -= size
+		for _, c := range chars {
+			if r == c {
+				return i
 			}
 		}
 	}
@@ -223,7 +227,7 @@ func genSplit(s, sep []byte, sepSave, n int) [][]byte {
 		if m < 0 {
 			break
 		}
-		a[i] = s[:m+sepSave]
+		a[i] = s[: m+sepSave : m+sepSave]
 		s = s[m+len(sep):]
 		i++
 	}
@@ -265,52 +269,112 @@ func SplitAfter(s, sep []byte) [][]byte {
 	return genSplit(s, sep, len(sep), -1)
 }
 
-// Fields splits the slice s around each instance of one or more consecutive white space
-// characters, returning a slice of subslices of s or an empty list if s contains only white space.
+var asciiSpace = [256]uint8{'\t': 1, '\n': 1, '\v': 1, '\f': 1, '\r': 1, ' ': 1}
+
+// Fields interprets s as a sequence of UTF-8-encoded code points.
+// It splits the slice s around each instance of one or more consecutive white space
+// characters, as defined by unicode.IsSpace, returning a slice of subslices of s or an
+// empty slice if s contains only white space.
 func Fields(s []byte) [][]byte {
-	return FieldsFunc(s, unicode.IsSpace)
+	// First count the fields.
+	// This is an exact count if s is ASCII, otherwise it is an approximation.
+	n := 0
+	wasSpace := 1
+	// setBits is used to track which bits are set in the bytes of s.
+	setBits := uint8(0)
+	for i := 0; i < len(s); i++ {
+		r := s[i]
+		setBits |= r
+		isSpace := int(asciiSpace[r])
+		n += wasSpace & ^isSpace
+		wasSpace = isSpace
+	}
+
+	if setBits >= utf8.RuneSelf {
+		// Some runes in the input slice are not ASCII.
+		return FieldsFunc(s, unicode.IsSpace)
+	}
+
+	// ASCII fast path
+	a := make([][]byte, n)
+	na := 0
+	fieldStart := 0
+	i := 0
+	// Skip spaces in the front of the input.
+	for i < len(s) && asciiSpace[s[i]] != 0 {
+		i++
+	}
+	fieldStart = i
+	for i < len(s) {
+		if asciiSpace[s[i]] == 0 {
+			i++
+			continue
+		}
+		a[na] = s[fieldStart:i:i]
+		na++
+		i++
+		// Skip spaces in between fields.
+		for i < len(s) && asciiSpace[s[i]] != 0 {
+			i++
+		}
+		fieldStart = i
+	}
+	if fieldStart < len(s) { // Last field might end at EOF.
+		a[na] = s[fieldStart:len(s):len(s)]
+	}
+	return a
 }
 
-// FieldsFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
+// FieldsFunc interprets s as a sequence of UTF-8-encoded code points.
 // It splits the slice s at each run of code points c satisfying f(c) and
 // returns a slice of subslices of s. If all code points in s satisfy f(c), or
 // len(s) == 0, an empty slice is returned.
 // FieldsFunc makes no guarantees about the order in which it calls f(c).
 // If f does not return consistent results for a given c, FieldsFunc may crash.
 func FieldsFunc(s []byte, f func(rune) bool) [][]byte {
-	n := 0
-	inField := false
-	for i := 0; i < len(s); {
-		r, size := utf8.DecodeRune(s[i:])
-		wasInField := inField
-		inField = !f(r)
-		if inField && !wasInField {
-			n++
-		}
-		i += size
+	// A span is used to record a slice of s of the form s[start:end].
+	// The start index is inclusive and the end index is exclusive.
+	type span struct {
+		start int
+		end   int
 	}
+	spans := make([]span, 0, 32)
 
-	a := make([][]byte, n)
-	na := 0
-	fieldStart := -1
-	for i := 0; i <= len(s) && na < n; {
-		r, size := utf8.DecodeRune(s[i:])
-		if fieldStart < 0 && size > 0 && !f(r) {
-			fieldStart = i
-			i += size
-			continue
-		}
-		if fieldStart >= 0 && (size == 0 || f(r)) {
-			a[na] = s[fieldStart:i]
-			na++
-			fieldStart = -1
+	// Find the field start and end indices.
+	wasField := false
+	fromIndex := 0
+	for i := 0; i < len(s); {
+		size := 1
+		r := rune(s[i])
+		if r >= utf8.RuneSelf {
+			r, size = utf8.DecodeRune(s[i:])
 		}
-		if size == 0 {
-			break
+		if f(r) {
+			if wasField {
+				spans = append(spans, span{start: fromIndex, end: i})
+				wasField = false
+			}
+		} else {
+			if !wasField {
+				fromIndex = i
+				wasField = true
+			}
 		}
 		i += size
 	}
-	return a[0:na]
+
+	// Last field might end at EOF.
+	if wasField {
+		spans = append(spans, span{fromIndex, len(s)})
+	}
+
+	// Create subslices from recorded field indices.
+	a := make([][]byte, len(spans))
+	for i, span := range spans {
+		a[i] = s[span.start:span.end:span.end]
+	}
+
+	return a
 }
 
 // Join concatenates the elements of s to create a new byte slice. The separator
@@ -349,8 +413,8 @@ func HasSuffix(s, suffix []byte) bool {
 
 // Map returns a copy of the byte slice s with all its characters modified
 // according to the mapping function. If mapping returns a negative value, the character is
-// dropped from the string with no replacement. The characters in s and the
-// output are interpreted as UTF-8-encoded Unicode code points.
+// dropped from the byte slice with no replacement. The characters in s and the
+// output are interpreted as UTF-8-encoded code points.
 func Map(mapping func(r rune) rune, s []byte) []byte {
 	// In the worst case, the slice can grow when mapped, making
 	// things unpleasant. But it's so rare we barge in assuming it's
@@ -408,28 +472,28 @@ func Repeat(b []byte, count int) []byte {
 	return nb
 }
 
-// ToUpper returns a copy of the byte slice s with all Unicode letters mapped to their upper case.
+// ToUpper treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters within it mapped to their upper case.
 func ToUpper(s []byte) []byte { return Map(unicode.ToUpper, s) }
 
-// ToLower returns a copy of the byte slice s with all Unicode letters mapped to their lower case.
+// ToLower treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their lower case.
 func ToLower(s []byte) []byte { return Map(unicode.ToLower, s) }
 
-// ToTitle returns a copy of the byte slice s with all Unicode letters mapped to their title case.
+// ToTitle treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their title case.
 func ToTitle(s []byte) []byte { return Map(unicode.ToTitle, s) }
 
-// ToUpperSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
+// ToUpperSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their
 // upper case, giving priority to the special casing rules.
 func ToUpperSpecial(c unicode.SpecialCase, s []byte) []byte {
 	return Map(func(r rune) rune { return c.ToUpper(r) }, s)
 }
 
-// ToLowerSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
+// ToLowerSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their
 // lower case, giving priority to the special casing rules.
 func ToLowerSpecial(c unicode.SpecialCase, s []byte) []byte {
 	return Map(func(r rune) rune { return c.ToLower(r) }, s)
 }
 
-// ToTitleSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
+// ToTitleSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their
 // title case, giving priority to the special casing rules.
 func ToTitleSpecial(c unicode.SpecialCase, s []byte) []byte {
 	return Map(func(r rune) rune { return c.ToTitle(r) }, s)
@@ -460,8 +524,8 @@ func isSeparator(r rune) bool {
 	return unicode.IsSpace(r)
 }
 
-// Title returns a copy of s with all Unicode letters that begin words
-// mapped to their title case.
+// Title treats s as UTF-8-encoded bytes and returns a copy with all Unicode letters that begin
+// words mapped to their title case.
 //
 // BUG(rsc): The rule Title uses for word boundaries does not handle Unicode punctuation properly.
 func Title(s []byte) []byte {
@@ -481,8 +545,8 @@ func Title(s []byte) []byte {
 		s)
 }
 
-// TrimLeftFunc returns a subslice of s by slicing off all leading UTF-8-encoded
-// Unicode code points c that satisfy f(c).
+// TrimLeftFunc treats s as UTF-8-encoded bytes and returns a subslice of s by slicing off
+// all leading UTF-8-encoded code points c that satisfy f(c).
 func TrimLeftFunc(s []byte, f func(r rune) bool) []byte {
 	i := indexFunc(s, f, false)
 	if i == -1 {
@@ -491,8 +555,8 @@ func TrimLeftFunc(s []byte, f func(r rune) bool) []byte {
 	return s[i:]
 }
 
-// TrimRightFunc returns a subslice of s by slicing off all trailing UTF-8
-// encoded Unicode code points c that satisfy f(c).
+// TrimRightFunc returns a subslice of s by slicing off all trailing
+// UTF-8-encoded code points c that satisfy f(c).
 func TrimRightFunc(s []byte, f func(r rune) bool) []byte {
 	i := lastIndexFunc(s, f, false)
 	if i >= 0 && s[i] >= utf8.RuneSelf {
@@ -505,7 +569,7 @@ func TrimRightFunc(s []byte, f func(r rune) bool) []byte {
 }
 
 // TrimFunc returns a subslice of s by slicing off all leading and trailing
-// UTF-8-encoded Unicode code points c that satisfy f(c).
+// UTF-8-encoded code points c that satisfy f(c).
 func TrimFunc(s []byte, f func(r rune) bool) []byte {
 	return TrimRightFunc(TrimLeftFunc(s, f), f)
 }
@@ -528,14 +592,14 @@ func TrimSuffix(s, suffix []byte) []byte {
 	return s
 }
 
-// IndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
+// IndexFunc interprets s as a sequence of UTF-8-encoded code points.
 // It returns the byte index in s of the first Unicode
 // code point satisfying f(c), or -1 if none do.
 func IndexFunc(s []byte, f func(r rune) bool) int {
 	return indexFunc(s, f, true)
 }
 
-// LastIndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
+// LastIndexFunc interprets s as a sequence of UTF-8-encoded code points.
 // It returns the byte index in s of the last Unicode
 // code point satisfying f(c), or -1 if none do.
 func LastIndexFunc(s []byte, f func(r rune) bool) int {
@@ -626,19 +690,19 @@ func makeCutsetFunc(cutset string) func(r rune) bool {
 }
 
 // Trim returns a subslice of s by slicing off all leading and
-// trailing UTF-8-encoded Unicode code points contained in cutset.
+// trailing UTF-8-encoded code points contained in cutset.
 func Trim(s []byte, cutset string) []byte {
 	return TrimFunc(s, makeCutsetFunc(cutset))
 }
 
 // TrimLeft returns a subslice of s by slicing off all leading
-// UTF-8-encoded Unicode code points contained in cutset.
+// UTF-8-encoded code points contained in cutset.
 func TrimLeft(s []byte, cutset string) []byte {
 	return TrimLeftFunc(s, makeCutsetFunc(cutset))
 }
 
 // TrimRight returns a subslice of s by slicing off all trailing
-// UTF-8-encoded Unicode code points that are contained in cutset.
+// UTF-8-encoded code points that are contained in cutset.
 func TrimRight(s []byte, cutset string) []byte {
 	return TrimRightFunc(s, makeCutsetFunc(cutset))
 }
@@ -649,7 +713,8 @@ func TrimSpace(s []byte) []byte {
 	return TrimFunc(s, unicode.IsSpace)
 }
 
-// Runes returns a slice of runes (Unicode code points) equivalent to s.
+// Runes interprets s as a sequence of UTF-8-encoded code points.
+// It returns a slice of runes (Unicode code points) equivalent to s.
 func Runes(s []byte) []rune {
 	t := make([]rune, utf8.RuneCount(s))
 	i := 0
@@ -758,3 +823,46 @@ func EqualFold(s, t []byte) bool {
 	// One string is empty. Are both?
 	return len(s) == len(t)
 }
+
+func indexRabinKarp(s, sep []byte) int {
+	// Rabin-Karp search
+	hashsep, pow := hashStr(sep)
+	n := len(sep)
+	var h uint32
+	for i := 0; i < n; i++ {
+		h = h*primeRK + uint32(s[i])
+	}
+	if h == hashsep && Equal(s[:n], sep) {
+		return 0
+	}
+	for i := n; i < len(s); {
+		h *= primeRK
+		h += uint32(s[i])
+		h -= pow * uint32(s[i-n])
+		i++
+		if h == hashsep && Equal(s[i-n:i], sep) {
+			return i - n
+		}
+	}
+	return -1
+}
+
+// primeRK is the prime base used in Rabin-Karp algorithm.
+const primeRK = 16777619
+
+// hashStr returns the hash and the appropriate multiplicative
+// factor for use in Rabin-Karp algorithm.
+func hashStr(sep []byte) (uint32, uint32) {
+	hash := uint32(0)
+	for i := 0; i < len(sep); i++ {
+		hash = hash*primeRK + uint32(sep[i])
+	}
+	var pow, sq uint32 = 1, primeRK
+	for i := len(sep); i > 0; i >>= 1 {
+		if i&1 != 0 {
+			pow *= sq
+		}
+		sq *= sq
+	}
+	return hash, pow
+}
diff --git a/libgo/go/bytes/bytes_amd64.go b/libgo/go/bytes/bytes_amd64.go
index d40c744..2fbbbb0 100644
--- a/libgo/go/bytes/bytes_amd64.go
+++ b/libgo/go/bytes/bytes_amd64.go
@@ -77,52 +77,14 @@ func Index(s, sep []byte) int {
 		}
 		return -1
 	}
-	// Rabin-Karp search
-	hashsep, pow := hashStr(sep)
-	var h uint32
-	for i := 0; i < n; i++ {
-		h = h*primeRK + uint32(s[i])
-	}
-	if h == hashsep && Equal(s[:n], sep) {
-		return 0
-	}
-	for i := n; i < len(s); {
-		h *= primeRK
-		h += uint32(s[i])
-		h -= pow * uint32(s[i-n])
-		i++
-		if h == hashsep && Equal(s[i-n:i], sep) {
-			return i - n
-		}
-	}
-	return -1
+	return indexRabinKarp(s, sep)
 }
 
 // Count counts the number of non-overlapping instances of sep in s.
-// If sep is an empty slice, Count returns 1 + the number of Unicode code points in s.
+// If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s.
 func Count(s, sep []byte) int {
 	if len(sep) == 1 && cpu.X86.HasPOPCNT {
 		return countByte(s, sep[0])
 	}
 	return countGeneric(s, sep)
 }
-
-// primeRK is the prime base used in Rabin-Karp algorithm.
-const primeRK = 16777619
-
-// hashStr returns the hash and the appropriate multiplicative
-// factor for use in Rabin-Karp algorithm.
-func hashStr(sep []byte) (uint32, uint32) {
-	hash := uint32(0)
-	for i := 0; i < len(sep); i++ {
-		hash = hash*primeRK + uint32(sep[i])
-	}
-	var pow, sq uint32 = 1, primeRK
-	for i := len(sep); i > 0; i >>= 1 {
-		if i&1 != 0 {
-			pow *= sq
-		}
-		sq *= sq
-	}
-	return hash, pow
-}
diff --git a/libgo/go/bytes/bytes_arm64.go b/libgo/go/bytes/bytes_arm64.go
new file mode 100644
index 0000000..1213b06
--- /dev/null
+++ b/libgo/go/bytes/bytes_arm64.go
@@ -0,0 +1,70 @@
+// 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 ignore
+
+package bytes
+
+func countByte(s []byte, c byte) int // bytes_arm64.s
+
+// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
+func Index(s, sep []byte) int {
+	n := len(sep)
+	switch {
+	case n == 0:
+		return 0
+	case n == 1:
+		return IndexByte(s, sep[0])
+	case n == len(s):
+		if Equal(sep, s) {
+			return 0
+		}
+		return -1
+	case n > len(s):
+		return -1
+	}
+	c := sep[0]
+	i := 0
+	fails := 0
+	t := s[:len(s)-n+1]
+	for i < len(t) {
+		if t[i] != c {
+			o := IndexByte(t[i:], c)
+			if o < 0 {
+				break
+			}
+			i += o
+		}
+		if Equal(s[i:i+n], sep) {
+			return i
+		}
+		i++
+		fails++
+		if fails >= 4+i>>4 && i < len(t) {
+			// Give up on IndexByte, it isn't skipping ahead
+			// far enough to be better than Rabin-Karp.
+			// Experiments (using IndexPeriodic) suggest
+			// the cutover is about 16 byte skips.
+			// TODO: if large prefixes of sep are matching
+			// we should cutover at even larger average skips,
+			// because Equal becomes that much more expensive.
+			// This code does not take that effect into account.
+			j := indexRabinKarp(s[i:], sep)
+			if j < 0 {
+				return -1
+			}
+			return i + j
+		}
+	}
+	return -1
+}
+
+// Count counts the number of non-overlapping instances of sep in s.
+// If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s.
+func Count(s, sep []byte) int {
+	if len(sep) == 1 {
+		return countByte(s, sep[0])
+	}
+	return countGeneric(s, sep)
+}
diff --git a/libgo/go/bytes/bytes_generic.go b/libgo/go/bytes/bytes_generic.go
index 75a9c36..b52d939 100644
--- a/libgo/go/bytes/bytes_generic.go
+++ b/libgo/go/bytes/bytes_generic.go
@@ -2,27 +2,29 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// -build !amd64,!s390x
+// -build !amd64,!s390x,!arm64
 
 package bytes
 
-// TODO: implements short string optimization on non amd64 platforms
-// and get rid of bytes_amd64.go
-
 // Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
 func Index(s, sep []byte) int {
 	n := len(sep)
-	if n == 0 {
+	switch {
+	case n == 0:
 		return 0
-	}
-	if n > len(s) {
+	case n == 1:
+		return IndexByte(s, sep[0])
+	case n == len(s):
+		if Equal(sep, s) {
+			return 0
+		}
+		return -1
+	case n > len(s):
 		return -1
 	}
 	c := sep[0]
-	if n == 1 {
-		return IndexByte(s, c)
-	}
 	i := 0
+	fails := 0
 	t := s[:len(s)-n+1]
 	for i < len(t) {
 		if t[i] != c {
@@ -36,12 +38,28 @@ func Index(s, sep []byte) int {
 			return i
 		}
 		i++
+		fails++
+		if fails >= 4+i>>4 && i < len(t) {
+			// Give up on IndexByte, it isn't skipping ahead
+			// far enough to be better than Rabin-Karp.
+			// Experiments (using IndexPeriodic) suggest
+			// the cutover is about 16 byte skips.
+			// TODO: if large prefixes of sep are matching
+			// we should cutover at even larger average skips,
+			// because Equal becomes that much more expensive.
+			// This code does not take that effect into account.
+			j := indexRabinKarp(s[i:], sep)
+			if j < 0 {
+				return -1
+			}
+			return i + j
+		}
 	}
 	return -1
 }
 
 // Count counts the number of non-overlapping instances of sep in s.
-// If sep is an empty slice, Count returns 1 + the number of Unicode code points in s.
+// If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s.
 func Count(s, sep []byte) int {
 	return countGeneric(s, sep)
 }
diff --git a/libgo/go/bytes/bytes_s390x.go b/libgo/go/bytes/bytes_s390x.go
index 54e013e..0c22848 100644
--- a/libgo/go/bytes/bytes_s390x.go
+++ b/libgo/go/bytes/bytes_s390x.go
@@ -78,49 +78,11 @@ func Index(s, sep []byte) int {
 		}
 		return -1
 	}
-	// Rabin-Karp search
-	hashsep, pow := hashStr(sep)
-	var h uint32
-	for i := 0; i < n; i++ {
-		h = h*primeRK + uint32(s[i])
-	}
-	if h == hashsep && Equal(s[:n], sep) {
-		return 0
-	}
-	for i := n; i < len(s); {
-		h *= primeRK
-		h += uint32(s[i])
-		h -= pow * uint32(s[i-n])
-		i++
-		if h == hashsep && Equal(s[i-n:i], sep) {
-			return i - n
-		}
-	}
-	return -1
+	return indexRabinKarp(s, sep)
 }
 
 // Count counts the number of non-overlapping instances of sep in s.
-// If sep is an empty slice, Count returns 1 + the number of Unicode code points in s.
+// If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s.
 func Count(s, sep []byte) int {
 	return countGeneric(s, sep)
 }
-
-// primeRK is the prime base used in Rabin-Karp algorithm.
-const primeRK = 16777619
-
-// hashStr returns the hash and the appropriate multiplicative
-// factor for use in Rabin-Karp algorithm.
-func hashStr(sep []byte) (uint32, uint32) {
-	hash := uint32(0)
-	for i := 0; i < len(sep); i++ {
-		hash = hash*primeRK + uint32(sep[i])
-	}
-	var pow, sq uint32 = 1, primeRK
-	for i := len(sep); i > 0; i >>= 1 {
-		if i&1 != 0 {
-			pow *= sq
-		}
-		sq *= sq
-	}
-	return hash, pow
-}
diff --git a/libgo/go/bytes/bytes_test.go b/libgo/go/bytes/bytes_test.go
index d571eb3..23fce29 100644
--- a/libgo/go/bytes/bytes_test.go
+++ b/libgo/go/bytes/bytes_test.go
@@ -140,6 +140,9 @@ var indexTests = []BinOpTest{
 	{"barfoobarfooyyyzzzyyyzzzyyyzzzyyyxxxzzzyyy", "x", 33},
 	{"foofyfoobarfoobar", "y", 4},
 	{"oooooooooooooooooooooo", "r", -1},
+	// test fallback to Rabin-Karp.
+	{"oxoxoxoxoxoxoxoxoxoxoxoy", "oy", 22},
+	{"oxoxoxoxoxoxoxoxoxoxoxox", "oy", -1},
 }
 
 var lastIndexTests = []BinOpTest{
@@ -741,6 +744,13 @@ var splittests = []SplitTest{
 func TestSplit(t *testing.T) {
 	for _, tt := range splittests {
 		a := SplitN([]byte(tt.s), []byte(tt.sep), tt.n)
+
+		// Appending to the results should not change future results.
+		var x []byte
+		for _, v := range a {
+			x = append(v, 'z')
+		}
+
 		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
@@ -749,6 +759,11 @@ func TestSplit(t *testing.T) {
 		if tt.n == 0 {
 			continue
 		}
+
+		if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
+			t.Errorf("last appended result was %s; want %s", x, want)
+		}
+
 		s := Join(a, []byte(tt.sep))
 		if string(s) != tt.s {
 			t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
@@ -787,11 +802,23 @@ var splitaftertests = []SplitTest{
 func TestSplitAfter(t *testing.T) {
 	for _, tt := range splitaftertests {
 		a := SplitAfterN([]byte(tt.s), []byte(tt.sep), tt.n)
+
+		// Appending to the results should not change future results.
+		var x []byte
+		for _, v := range a {
+			x = append(v, 'z')
+		}
+
 		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
 			continue
 		}
+
+		if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
+			t.Errorf("last appended result was %s; want %s", x, want)
+		}
+
 		s := Join(a, nil)
 		if string(s) != tt.s {
 			t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
@@ -826,12 +853,29 @@ var fieldstests = []FieldsTest{
 
 func TestFields(t *testing.T) {
 	for _, tt := range fieldstests {
-		a := Fields([]byte(tt.s))
+		b := []byte(tt.s)
+		a := Fields(b)
+
+		// Appending to the results should not change future results.
+		var x []byte
+		for _, v := range a {
+			x = append(v, 'z')
+		}
+
 		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
 			continue
 		}
+
+		if string(b) != tt.s {
+			t.Errorf("slice changed to %s; want %s", string(b), tt.s)
+		}
+		if len(tt.a) > 0 {
+			if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
+				t.Errorf("last appended result was %s; want %s", x, want)
+			}
+		}
 	}
 }
 
@@ -852,11 +896,28 @@ func TestFieldsFunc(t *testing.T) {
 		{"aXXbXXXcX", []string{"a", "b", "c"}},
 	}
 	for _, tt := range fieldsFuncTests {
-		a := FieldsFunc([]byte(tt.s), pred)
+		b := []byte(tt.s)
+		a := FieldsFunc(b, pred)
+
+		// Appending to the results should not change future results.
+		var x []byte
+		for _, v := range a {
+			x = append(v, 'z')
+		}
+
 		result := sliceOfString(a)
 		if !eq(result, tt.a) {
 			t.Errorf("FieldsFunc(%q) = %v, want %v", tt.s, a, tt.a)
 		}
+
+		if string(b) != tt.s {
+			t.Errorf("slice changed to %s; want %s", b, tt.s)
+		}
+		if len(tt.a) > 0 {
+			if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
+				t.Errorf("last appended result was %s; want %s", x, want)
+			}
+		}
 	}
 }
 
@@ -1507,19 +1568,58 @@ var makeFieldsInput = func() []byte {
 	return x
 }
 
-var fieldsInput = makeFieldsInput()
+var makeFieldsInputASCII = func() []byte {
+	x := make([]byte, 1<<20)
+	// Input is ~10% space, rest ASCII non-space.
+	for i := range x {
+		if rand.Intn(10) == 0 {
+			x[i] = ' '
+		} else {
+			x[i] = 'x'
+		}
+	}
+	return x
+}
+
+var bytesdata = []struct {
+	name string
+	data []byte
+}{
+	{"ASCII", makeFieldsInputASCII()},
+	{"Mixed", makeFieldsInput()},
+}
 
 func BenchmarkFields(b *testing.B) {
-	b.SetBytes(int64(len(fieldsInput)))
-	for i := 0; i < b.N; i++ {
-		Fields(fieldsInput)
+	for _, sd := range bytesdata {
+		b.Run(sd.name, func(b *testing.B) {
+			for j := 1 << 4; j <= 1<<20; j <<= 4 {
+				b.Run(fmt.Sprintf("%d", j), func(b *testing.B) {
+					b.ReportAllocs()
+					b.SetBytes(int64(j))
+					data := sd.data[:j]
+					for i := 0; i < b.N; i++ {
+						Fields(data)
+					}
+				})
+			}
+		})
 	}
 }
 
 func BenchmarkFieldsFunc(b *testing.B) {
-	b.SetBytes(int64(len(fieldsInput)))
-	for i := 0; i < b.N; i++ {
-		FieldsFunc(fieldsInput, unicode.IsSpace)
+	for _, sd := range bytesdata {
+		b.Run(sd.name, func(b *testing.B) {
+			for j := 1 << 4; j <= 1<<20; j <<= 4 {
+				b.Run(fmt.Sprintf("%d", j), func(b *testing.B) {
+					b.ReportAllocs()
+					b.SetBytes(int64(j))
+					data := sd.data[:j]
+					for i := 0; i < b.N; i++ {
+						FieldsFunc(data, unicode.IsSpace)
+					}
+				})
+			}
+		})
 	}
 }
 
@@ -1638,3 +1738,18 @@ func BenchmarkTrimASCII(b *testing.B) {
 		}
 	}
 }
+
+func BenchmarkIndexPeriodic(b *testing.B) {
+	key := []byte{1, 1}
+	for _, skip := range [...]int{2, 4, 8, 16, 32, 64} {
+		b.Run(fmt.Sprintf("IndexPeriodic%d", skip), func(b *testing.B) {
+			buf := make([]byte, 1<<16)
+			for i := 0; i < len(buf); i += skip {
+				buf[i] = 1
+			}
+			for i := 0; i < b.N; i++ {
+				Index(buf, key)
+			}
+		})
+	}
+}
diff --git a/libgo/go/bytes/equal_test.go b/libgo/go/bytes/equal_test.go
deleted file mode 100644
index 9fdead8..0000000
--- a/libgo/go/bytes/equal_test.go
+++ /dev/null
@@ -1,47 +0,0 @@
-// Copyright 2013 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 linux
-
-package bytes_test
-
-import (
-	. "bytes"
-	"syscall"
-	"testing"
-	"unsafe"
-)
-
-// This file tests the situation where memeq is checking
-// data very near to a page boundary. We want to make sure
-// equal does not read across the boundary and cause a page
-// fault where it shouldn't.
-
-// This test runs only on linux. The code being tested is
-// not OS-specific, so it does not need to be tested on all
-// operating systems.
-
-func TestEqualNearPageBoundary(t *testing.T) {
-	pagesize := syscall.Getpagesize()
-	b := make([]byte, 4*pagesize)
-	i := pagesize
-	for ; uintptr(unsafe.Pointer(&b[i]))%uintptr(pagesize) != 0; i++ {
-	}
-	syscall.Mprotect(b[i-pagesize:i], 0)
-	syscall.Mprotect(b[i+pagesize:i+2*pagesize], 0)
-	defer syscall.Mprotect(b[i-pagesize:i], syscall.PROT_READ|syscall.PROT_WRITE)
-	defer syscall.Mprotect(b[i+pagesize:i+2*pagesize], syscall.PROT_READ|syscall.PROT_WRITE)
-
-	// both of these should fault
-	//pagesize += int(b[i-1])
-	//pagesize += int(b[i+pagesize])
-
-	for j := 0; j < pagesize; j++ {
-		b[i+j] = 'A'
-	}
-	for j := 0; j <= pagesize; j++ {
-		Equal(b[i:i+j], b[i+pagesize-j:i+pagesize])
-		Equal(b[i+pagesize-j:i+pagesize], b[i:i+j])
-	}
-}
diff --git a/libgo/go/bytes/example_test.go b/libgo/go/bytes/example_test.go
index 9397277..5b7a460 100644
--- a/libgo/go/bytes/example_test.go
+++ b/libgo/go/bytes/example_test.go
@@ -119,6 +119,32 @@ func ExampleContains() {
 	// true
 }
 
+func ExampleContainsAny() {
+	fmt.Println(bytes.ContainsAny([]byte("I like seafood."), "fÄo!"))
+	fmt.Println(bytes.ContainsAny([]byte("I like seafood."), "去是伟大的."))
+	fmt.Println(bytes.ContainsAny([]byte("I like seafood."), ""))
+	fmt.Println(bytes.ContainsAny([]byte(""), ""))
+	// Output:
+	// true
+	// true
+	// false
+	// false
+}
+
+func ExampleContainsRune() {
+	fmt.Println(bytes.ContainsRune([]byte("I like seafood."), 'f'))
+	fmt.Println(bytes.ContainsRune([]byte("I like seafood."), 'ö'))
+	fmt.Println(bytes.ContainsRune([]byte("去是伟大的!"), '大'))
+	fmt.Println(bytes.ContainsRune([]byte("去是伟大的!"), '!'))
+	fmt.Println(bytes.ContainsRune([]byte(""), '@'))
+	// Output:
+	// true
+	// false
+	// true
+	// true
+	// false
+}
+
 func ExampleCount() {
 	fmt.Println(bytes.Count([]byte("cheese"), []byte("e")))
 	fmt.Println(bytes.Count([]byte("five"), []byte(""))) // before & after each rune
@@ -127,6 +153,14 @@ func ExampleCount() {
 	// 5
 }
 
+func ExampleEqual() {
+	fmt.Println(bytes.Equal([]byte("Go"), []byte("Go")))
+	fmt.Println(bytes.Equal([]byte("Go"), []byte("C++")))
+	// Output:
+	// true
+	// false
+}
+
 func ExampleEqualFold() {
 	fmt.Println(bytes.EqualFold([]byte("Go"), []byte("go")))
 	// Output: true
@@ -162,6 +196,14 @@ func ExampleIndex() {
 	// -1
 }
 
+func ExampleIndexByte() {
+	fmt.Println(bytes.IndexByte([]byte("chicken"), byte('k')))
+	fmt.Println(bytes.IndexByte([]byte("chicken"), byte('g')))
+	// Output:
+	// 4
+	// -1
+}
+
 func ExampleIndexFunc() {
 	f := func(c rune) bool {
 		return unicode.Is(unicode.Han, c)
@@ -199,6 +241,36 @@ func ExampleLastIndex() {
 	// -1
 }
 
+func ExampleLastIndexAny() {
+	fmt.Println(bytes.LastIndexAny([]byte("go gopher"), "MüQp"))
+	fmt.Println(bytes.LastIndexAny([]byte("go 地鼠"), "地大"))
+	fmt.Println(bytes.LastIndexAny([]byte("go gopher"), "z,!."))
+	// Output:
+	// 5
+	// 3
+	// -1
+}
+
+func ExampleLastIndexByte() {
+	fmt.Println(bytes.LastIndexByte([]byte("go gopher"), byte('g')))
+	fmt.Println(bytes.LastIndexByte([]byte("go gopher"), byte('r')))
+	fmt.Println(bytes.LastIndexByte([]byte("go gopher"), byte('z')))
+	// Output:
+	// 3
+	// 8
+	// -1
+}
+
+func ExampleLastIndexFunc() {
+	fmt.Println(bytes.LastIndexFunc([]byte("go gopher!"), unicode.IsLetter))
+	fmt.Println(bytes.LastIndexFunc([]byte("go gopher!"), unicode.IsPunct))
+	fmt.Println(bytes.LastIndexFunc([]byte("go gopher!"), unicode.IsNumber))
+	// Output:
+	// 8
+	// 9
+	// -1
+}
+
 func ExampleJoin() {
 	s := [][]byte{[]byte("foo"), []byte("bar"), []byte("baz")}
 	fmt.Printf("%s", bytes.Join(s, []byte(", ")))
@@ -218,6 +290,23 @@ func ExampleReplace() {
 	// moo moo moo
 }
 
+func ExampleRunes() {
+	rs := bytes.Runes([]byte("go gopher"))
+	for _, r := range rs {
+		fmt.Printf("%#U\n", r)
+	}
+	// Output:
+	// U+0067 'g'
+	// U+006F 'o'
+	// U+0020 ' '
+	// U+0067 'g'
+	// U+006F 'o'
+	// U+0070 'p'
+	// U+0068 'h'
+	// U+0065 'e'
+	// U+0072 'r'
+}
+
 func ExampleSplit() {
 	fmt.Printf("%q\n", bytes.Split([]byte("a,b,c"), []byte(",")))
 	fmt.Printf("%q\n", bytes.Split([]byte("a man a plan a canal panama"), []byte("a ")))
@@ -267,6 +356,18 @@ func ExampleTrim() {
 	// Output: ["Achtung! Achtung"]
 }
 
+func ExampleTrimFunc() {
+	fmt.Println(string(bytes.TrimFunc([]byte("go-gopher!"), unicode.IsLetter)))
+	fmt.Println(string(bytes.TrimFunc([]byte("\"go-gopher!\""), unicode.IsLetter)))
+	fmt.Println(string(bytes.TrimFunc([]byte("go-gopher!"), unicode.IsPunct)))
+	fmt.Println(string(bytes.TrimFunc([]byte("1234go-gopher!567"), unicode.IsNumber)))
+	// Output:
+	// -gopher!
+	// "go-gopher!"
+	// go-gopher
+	// go-gopher!
+}
+
 func ExampleMap() {
 	rot13 := func(r rune) rune {
 		switch {
@@ -281,11 +382,43 @@ func ExampleMap() {
 	// Output: 'Gjnf oevyyvt naq gur fyvgul tbcure...
 }
 
+func ExampleTrimLeft() {
+	fmt.Print(string(bytes.TrimLeft([]byte("453gopher8257"), "0123456789")))
+	// Output:
+	// gopher8257
+}
+
+func ExampleTrimLeftFunc() {
+	fmt.Println(string(bytes.TrimLeftFunc([]byte("go-gopher"), unicode.IsLetter)))
+	fmt.Println(string(bytes.TrimLeftFunc([]byte("go-gopher!"), unicode.IsPunct)))
+	fmt.Println(string(bytes.TrimLeftFunc([]byte("1234go-gopher!567"), unicode.IsNumber)))
+	// Output:
+	// -gopher
+	// go-gopher!
+	// go-gopher!567
+}
+
 func ExampleTrimSpace() {
 	fmt.Printf("%s", bytes.TrimSpace([]byte(" \t\n a lone gopher \n\t\r\n")))
 	// Output: a lone gopher
 }
 
+func ExampleTrimRight() {
+	fmt.Print(string(bytes.TrimRight([]byte("453gopher8257"), "0123456789")))
+	// Output:
+	// 453gopher
+}
+
+func ExampleTrimRightFunc() {
+	fmt.Println(string(bytes.TrimRightFunc([]byte("go-gopher"), unicode.IsLetter)))
+	fmt.Println(string(bytes.TrimRightFunc([]byte("go-gopher!"), unicode.IsPunct)))
+	fmt.Println(string(bytes.TrimRightFunc([]byte("1234go-gopher!567"), unicode.IsNumber)))
+	// Output:
+	// go-
+	// go-gopher
+	// 1234go-gopher!
+}
+
 func ExampleToUpper() {
 	fmt.Printf("%s", bytes.ToUpper([]byte("Gopher")))
 	// Output: GOPHER
@@ -295,3 +428,11 @@ func ExampleToLower() {
 	fmt.Printf("%s", bytes.ToLower([]byte("Gopher")))
 	// Output: gopher
 }
+
+func ExampleReader_Len() {
+	fmt.Println(bytes.NewReader([]byte("Hi!")).Len())
+	fmt.Println(bytes.NewReader([]byte("こんにちは!")).Len())
+	// Output:
+	// 3
+	// 16
+}
diff --git a/libgo/go/bytes/reader.go b/libgo/go/bytes/reader.go
index 28cfc7a..08464c2 100644
--- a/libgo/go/bytes/reader.go
+++ b/libgo/go/bytes/reader.go
@@ -35,6 +35,7 @@ func (r *Reader) Len() int {
 // to any other method.
 func (r *Reader) Size() int64 { return int64(len(r.s)) }
 
+// Read implements the io.Reader interface.
 func (r *Reader) Read(b []byte) (n int, err error) {
 	if r.i >= int64(len(r.s)) {
 		return 0, io.EOF
@@ -45,6 +46,7 @@ func (r *Reader) Read(b []byte) (n int, err error) {
 	return
 }
 
+// ReadAt implements the io.ReaderAt interface.
 func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
 	// cannot modify state - see io.ReaderAt
 	if off < 0 {
@@ -60,6 +62,7 @@ func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
 	return
 }
 
+// ReadByte implements the io.ByteReader interface.
 func (r *Reader) ReadByte() (byte, error) {
 	r.prevRune = -1
 	if r.i >= int64(len(r.s)) {
@@ -70,6 +73,7 @@ func (r *Reader) ReadByte() (byte, error) {
 	return b, nil
 }
 
+// UnreadByte complements ReadByte in implementing the io.ByteScanner interface.
 func (r *Reader) UnreadByte() error {
 	r.prevRune = -1
 	if r.i <= 0 {
@@ -79,6 +83,7 @@ func (r *Reader) UnreadByte() error {
 	return nil
 }
 
+// ReadRune implements the io.RuneReader interface.
 func (r *Reader) ReadRune() (ch rune, size int, err error) {
 	if r.i >= int64(len(r.s)) {
 		r.prevRune = -1
@@ -94,6 +99,7 @@ func (r *Reader) ReadRune() (ch rune, size int, err error) {
 	return
 }
 
+// UnreadRune complements ReadRune in implementing the io.RuneScanner interface.
 func (r *Reader) UnreadRune() error {
 	if r.prevRune < 0 {
 		return errors.New("bytes.Reader.UnreadRune: previous operation was not ReadRune")
diff --git a/libgo/go/bytes/reader_test.go b/libgo/go/bytes/reader_test.go
index 7b3034d..8806876 100644
--- a/libgo/go/bytes/reader_test.go
+++ b/libgo/go/bytes/reader_test.go
@@ -140,9 +140,9 @@ func TestReaderWriteTo(t *testing.T) {
 	for i := 0; i < 30; i += 3 {
 		var l int
 		if i > 0 {
-			l = len(data) / i
+			l = len(testString) / i
 		}
-		s := data[:l]
+		s := testString[:l]
 		r := NewReader(testBytes[:l])
 		var b Buffer
 		n, err := r.WriteTo(&b)