diff --git a/src/cmd/compile/internal/big/example_rat_test.go b/src/cmd/compile/internal/big/example_rat_test.go
new file mode 100644
index 0000000..ef06497
--- /dev/null
+++ b/src/cmd/compile/internal/big/example_rat_test.go
@@ -0,0 +1,65 @@
+// Copyright 2015 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.
+
+package big_test
+
+import (
+	"cmd/compile/internal/big"
+	"fmt"
+)
+
+// Use the classic continued fraction for e
+//     e = [1; 0, 1, 1, 2, 1, 1, ... 2n, 1, 1, ...]
+// i.e., for the nth term, use
+//     1          if   n mod 3 != 1
+//  (n-1)/3 * 2   if   n mod 3 == 1
+func recur(n, lim int64) *big.Rat {
+	term := new(big.Rat)
+	if n%3 != 1 {
+		term.SetInt64(1)
+	} else {
+		term.SetInt64((n - 1) / 3 * 2)
+	}
+
+	if n > lim {
+		return term
+	}
+
+	// Directly initialize frac as the fractional
+	// inverse of the result of recur.
+	frac := new(big.Rat).Inv(recur(n+1, lim))
+
+	return term.Add(term, frac)
+}
+
+// This example demonstrates how to use big.Rat to compute the
+// first 15 terms in the sequence of rational convergents for
+// the constant e (base of natural logarithm).
+func Example_eConvergents() {
+	for i := 1; i <= 15; i++ {
+		r := recur(0, int64(i))
+
+		// Print r both as a fraction and as a floating-point number.
+		// Since big.Rat implements fmt.Formatter, we can use %-13s to
+		// get a left-aligned string representation of the fraction.
+		fmt.Printf("%-13s = %s\n", r, r.FloatString(8))
+	}
+
+	// Output:
+	// 2/1           = 2.00000000
+	// 3/1           = 3.00000000
+	// 8/3           = 2.66666667
+	// 11/4          = 2.75000000
+	// 19/7          = 2.71428571
+	// 87/32         = 2.71875000
+	// 106/39        = 2.71794872
+	// 193/71        = 2.71830986
+	// 1264/465      = 2.71827957
+	// 1457/536      = 2.71828358
+	// 2721/1001     = 2.71828172
+	// 23225/8544    = 2.71828184
+	// 25946/9545    = 2.71828182
+	// 49171/18089   = 2.71828183
+	// 517656/190435 = 2.71828183
+}
diff --git a/src/cmd/compile/internal/big/floatmarsh.go b/src/cmd/compile/internal/big/floatmarsh.go
new file mode 100644
index 0000000..44987ee
--- /dev/null
+++ b/src/cmd/compile/internal/big/floatmarsh.go
@@ -0,0 +1,33 @@
+// Copyright 2015 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.
+
+// This file implements encoding/decoding of Floats.
+
+package big
+
+import "fmt"
+
+// MarshalText implements the encoding.TextMarshaler interface.
+// Only the Float value is marshaled (in full precision), other
+// attributes such as precision or accuracy are ignored.
+func (x *Float) MarshalText() (text []byte, err error) {
+	if x == nil {
+		return []byte("<nil>"), nil
+	}
+	var buf []byte
+	return x.Append(buf, 'g', -1), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+// The result is rounded per the precision and rounding mode of z.
+// If z's precision is 0, it is changed to 64 before rounding takes
+// effect.
+func (z *Float) UnmarshalText(text []byte) error {
+	// TODO(gri): get rid of the []byte/string conversion
+	_, _, err := z.Parse(string(text), 0)
+	if err != nil {
+		err = fmt.Errorf("math/big: cannot unmarshal %q into a *big.Float (%v)", text, err)
+	}
+	return err
+}
diff --git a/src/cmd/compile/internal/big/floatmarsh_test.go b/src/cmd/compile/internal/big/floatmarsh_test.go
new file mode 100644
index 0000000..d7ef2fc
--- /dev/null
+++ b/src/cmd/compile/internal/big/floatmarsh_test.go
@@ -0,0 +1,54 @@
+// Copyright 2015 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.
+
+package big
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+var floatVals = []string{
+	"0",
+	"1",
+	"0.1",
+	"2.71828",
+	"1234567890",
+	"3.14e1234",
+	"3.14e-1234",
+	"0.738957395793475734757349579759957975985497e100",
+	"0.73895739579347546656564656573475734957975995797598589749859834759476745986795497e100",
+	"inf",
+	"Inf",
+}
+
+func TestFloatJSONEncoding(t *testing.T) {
+	for _, test := range floatVals {
+		for _, sign := range []string{"", "+", "-"} {
+			for _, prec := range []uint{0, 1, 2, 10, 53, 64, 100, 1000} {
+				x := sign + test
+				var tx Float
+				_, _, err := tx.SetPrec(prec).Parse(x, 0)
+				if err != nil {
+					t.Errorf("parsing of %s (prec = %d) failed (invalid test case): %v", x, prec, err)
+					continue
+				}
+				b, err := json.Marshal(&tx)
+				if err != nil {
+					t.Errorf("marshaling of %v (prec = %d) failed: %v", &tx, prec, err)
+					continue
+				}
+				var rx Float
+				rx.SetPrec(prec)
+				if err := json.Unmarshal(b, &rx); err != nil {
+					t.Errorf("unmarshaling of %v (prec = %d) failed: %v", &tx, prec, err)
+					continue
+				}
+				if rx.Cmp(&tx) != 0 {
+					t.Errorf("JSON encoding of %v (prec = %d) failed: got %v want %v", &tx, prec, &rx, &tx)
+				}
+			}
+		}
+	}
+}
diff --git a/src/cmd/compile/internal/big/intmarsh.go b/src/cmd/compile/internal/big/intmarsh.go
new file mode 100644
index 0000000..4ff57b6
--- /dev/null
+++ b/src/cmd/compile/internal/big/intmarsh.go
@@ -0,0 +1,74 @@
+// Copyright 2015 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.
+
+// This file implements encoding/decoding of Ints.
+
+package big
+
+import "fmt"
+
+// Gob codec version. Permits backward-compatible changes to the encoding.
+const intGobVersion byte = 1
+
+// GobEncode implements the gob.GobEncoder interface.
+func (x *Int) GobEncode() ([]byte, error) {
+	if x == nil {
+		return nil, nil
+	}
+	buf := make([]byte, 1+len(x.abs)*_S) // extra byte for version and sign bit
+	i := x.abs.bytes(buf) - 1            // i >= 0
+	b := intGobVersion << 1              // make space for sign bit
+	if x.neg {
+		b |= 1
+	}
+	buf[i] = b
+	return buf[i:], nil
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+func (z *Int) GobDecode(buf []byte) error {
+	if len(buf) == 0 {
+		// Other side sent a nil or default value.
+		*z = Int{}
+		return nil
+	}
+	b := buf[0]
+	if b>>1 != intGobVersion {
+		return fmt.Errorf("Int.GobDecode: encoding version %d not supported", b>>1)
+	}
+	z.neg = b&1 != 0
+	z.abs = z.abs.setBytes(buf[1:])
+	return nil
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+func (x *Int) MarshalText() (text []byte, err error) {
+	if x == nil {
+		return []byte("<nil>"), nil
+	}
+	return x.abs.itoa(x.neg, 10), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+func (z *Int) UnmarshalText(text []byte) error {
+	// TODO(gri): get rid of the []byte/string conversion
+	if _, ok := z.SetString(string(text), 0); !ok {
+		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Int", text)
+	}
+	return nil
+}
+
+// The JSON marshallers are only here for API backward compatibility
+// (programs that explicitly look for these two methods). JSON works
+// fine with the TextMarshaler only.
+
+// MarshalJSON implements the json.Marshaler interface.
+func (x *Int) MarshalJSON() ([]byte, error) {
+	return x.MarshalText()
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (z *Int) UnmarshalJSON(text []byte) error {
+	return z.UnmarshalText(text)
+}
diff --git a/src/cmd/compile/internal/big/intmarsh_test.go b/src/cmd/compile/internal/big/intmarsh_test.go
new file mode 100644
index 0000000..f82956c
--- /dev/null
+++ b/src/cmd/compile/internal/big/intmarsh_test.go
@@ -0,0 +1,121 @@
+// Copyright 2015 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.
+
+package big
+
+import (
+	"bytes"
+	"encoding/gob"
+	"encoding/json"
+	"encoding/xml"
+	"testing"
+)
+
+var encodingTests = []string{
+	"0",
+	"1",
+	"2",
+	"10",
+	"1000",
+	"1234567890",
+	"298472983472983471903246121093472394872319615612417471234712061",
+}
+
+func TestIntGobEncoding(t *testing.T) {
+	var medium bytes.Buffer
+	enc := gob.NewEncoder(&medium)
+	dec := gob.NewDecoder(&medium)
+	for _, test := range encodingTests {
+		for _, sign := range []string{"", "+", "-"} {
+			x := sign + test
+			medium.Reset() // empty buffer for each test case (in case of failures)
+			var tx Int
+			tx.SetString(x, 10)
+			if err := enc.Encode(&tx); err != nil {
+				t.Errorf("encoding of %s failed: %s", &tx, err)
+				continue
+			}
+			var rx Int
+			if err := dec.Decode(&rx); err != nil {
+				t.Errorf("decoding of %s failed: %s", &tx, err)
+				continue
+			}
+			if rx.Cmp(&tx) != 0 {
+				t.Errorf("transmission of %s failed: got %s want %s", &tx, &rx, &tx)
+			}
+		}
+	}
+}
+
+// Sending a nil Int pointer (inside a slice) on a round trip through gob should yield a zero.
+// TODO: top-level nils.
+func TestGobEncodingNilIntInSlice(t *testing.T) {
+	buf := new(bytes.Buffer)
+	enc := gob.NewEncoder(buf)
+	dec := gob.NewDecoder(buf)
+
+	var in = make([]*Int, 1)
+	err := enc.Encode(&in)
+	if err != nil {
+		t.Errorf("gob encode failed: %q", err)
+	}
+	var out []*Int
+	err = dec.Decode(&out)
+	if err != nil {
+		t.Fatalf("gob decode failed: %q", err)
+	}
+	if len(out) != 1 {
+		t.Fatalf("wrong len; want 1 got %d", len(out))
+	}
+	var zero Int
+	if out[0].Cmp(&zero) != 0 {
+		t.Fatalf("transmission of (*Int)(nil) failed: got %s want 0", out)
+	}
+}
+
+func TestIntJSONEncoding(t *testing.T) {
+	for _, test := range encodingTests {
+		for _, sign := range []string{"", "+", "-"} {
+			x := sign + test
+			var tx Int
+			tx.SetString(x, 10)
+			b, err := json.Marshal(&tx)
+			if err != nil {
+				t.Errorf("marshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			var rx Int
+			if err := json.Unmarshal(b, &rx); err != nil {
+				t.Errorf("unmarshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			if rx.Cmp(&tx) != 0 {
+				t.Errorf("JSON encoding of %s failed: got %s want %s", &tx, &rx, &tx)
+			}
+		}
+	}
+}
+
+func TestIntXMLEncoding(t *testing.T) {
+	for _, test := range encodingTests {
+		for _, sign := range []string{"", "+", "-"} {
+			x := sign + test
+			var tx Int
+			tx.SetString(x, 0)
+			b, err := xml.Marshal(&tx)
+			if err != nil {
+				t.Errorf("marshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			var rx Int
+			if err := xml.Unmarshal(b, &rx); err != nil {
+				t.Errorf("unmarshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			if rx.Cmp(&tx) != 0 {
+				t.Errorf("XML encoding of %s failed: got %s want %s", &tx, &rx, &tx)
+			}
+		}
+	}
+}
diff --git a/src/cmd/compile/internal/big/ratmarsh.go b/src/cmd/compile/internal/big/ratmarsh.go
new file mode 100644
index 0000000..b82e8d4
--- /dev/null
+++ b/src/cmd/compile/internal/big/ratmarsh.go
@@ -0,0 +1,73 @@
+// Copyright 2015 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.
+
+// This file implements encoding/decoding of Rats.
+
+package big
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
+// Gob codec version. Permits backward-compatible changes to the encoding.
+const ratGobVersion byte = 1
+
+// GobEncode implements the gob.GobEncoder interface.
+func (x *Rat) GobEncode() ([]byte, error) {
+	if x == nil {
+		return nil, nil
+	}
+	buf := make([]byte, 1+4+(len(x.a.abs)+len(x.b.abs))*_S) // extra bytes for version and sign bit (1), and numerator length (4)
+	i := x.b.abs.bytes(buf)
+	j := x.a.abs.bytes(buf[:i])
+	n := i - j
+	if int(uint32(n)) != n {
+		// this should never happen
+		return nil, errors.New("Rat.GobEncode: numerator too large")
+	}
+	binary.BigEndian.PutUint32(buf[j-4:j], uint32(n))
+	j -= 1 + 4
+	b := ratGobVersion << 1 // make space for sign bit
+	if x.a.neg {
+		b |= 1
+	}
+	buf[j] = b
+	return buf[j:], nil
+}
+
+// GobDecode implements the gob.GobDecoder interface.
+func (z *Rat) GobDecode(buf []byte) error {
+	if len(buf) == 0 {
+		// Other side sent a nil or default value.
+		*z = Rat{}
+		return nil
+	}
+	b := buf[0]
+	if b>>1 != ratGobVersion {
+		return fmt.Errorf("Rat.GobDecode: encoding version %d not supported", b>>1)
+	}
+	const j = 1 + 4
+	i := j + binary.BigEndian.Uint32(buf[j-4:j])
+	z.a.neg = b&1 != 0
+	z.a.abs = z.a.abs.setBytes(buf[j:i])
+	z.b.abs = z.b.abs.setBytes(buf[i:])
+	return nil
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+func (x *Rat) MarshalText() (text []byte, err error) {
+	// TODO(gri): get rid of the []byte/string conversion
+	return []byte(x.RatString()), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+func (z *Rat) UnmarshalText(text []byte) error {
+	// TODO(gri): get rid of the []byte/string conversion
+	if _, ok := z.SetString(string(text)); !ok {
+		return fmt.Errorf("math/big: cannot unmarshal %q into a *big.Rat", text)
+	}
+	return nil
+}
diff --git a/src/cmd/compile/internal/big/ratmarsh_test.go b/src/cmd/compile/internal/big/ratmarsh_test.go
new file mode 100644
index 0000000..351d109
--- /dev/null
+++ b/src/cmd/compile/internal/big/ratmarsh_test.go
@@ -0,0 +1,125 @@
+// Copyright 2015 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.
+
+package big
+
+import (
+	"bytes"
+	"encoding/gob"
+	"encoding/json"
+	"encoding/xml"
+	"testing"
+)
+
+func TestRatGobEncoding(t *testing.T) {
+	var medium bytes.Buffer
+	enc := gob.NewEncoder(&medium)
+	dec := gob.NewDecoder(&medium)
+	for _, test := range encodingTests {
+		medium.Reset() // empty buffer for each test case (in case of failures)
+		var tx Rat
+		tx.SetString(test + ".14159265")
+		if err := enc.Encode(&tx); err != nil {
+			t.Errorf("encoding of %s failed: %s", &tx, err)
+			continue
+		}
+		var rx Rat
+		if err := dec.Decode(&rx); err != nil {
+			t.Errorf("decoding of %s failed: %s", &tx, err)
+			continue
+		}
+		if rx.Cmp(&tx) != 0 {
+			t.Errorf("transmission of %s failed: got %s want %s", &tx, &rx, &tx)
+		}
+	}
+}
+
+// Sending a nil Rat pointer (inside a slice) on a round trip through gob should yield a zero.
+// TODO: top-level nils.
+func TestGobEncodingNilRatInSlice(t *testing.T) {
+	buf := new(bytes.Buffer)
+	enc := gob.NewEncoder(buf)
+	dec := gob.NewDecoder(buf)
+
+	var in = make([]*Rat, 1)
+	err := enc.Encode(&in)
+	if err != nil {
+		t.Errorf("gob encode failed: %q", err)
+	}
+	var out []*Rat
+	err = dec.Decode(&out)
+	if err != nil {
+		t.Fatalf("gob decode failed: %q", err)
+	}
+	if len(out) != 1 {
+		t.Fatalf("wrong len; want 1 got %d", len(out))
+	}
+	var zero Rat
+	if out[0].Cmp(&zero) != 0 {
+		t.Fatalf("transmission of (*Int)(nil) failed: got %s want 0", out)
+	}
+}
+
+var ratNums = []string{
+	"-141592653589793238462643383279502884197169399375105820974944592307816406286",
+	"-1415926535897932384626433832795028841971",
+	"-141592653589793",
+	"-1",
+	"0",
+	"1",
+	"141592653589793",
+	"1415926535897932384626433832795028841971",
+	"141592653589793238462643383279502884197169399375105820974944592307816406286",
+}
+
+var ratDenoms = []string{
+	"1",
+	"718281828459045",
+	"7182818284590452353602874713526624977572",
+	"718281828459045235360287471352662497757247093699959574966967627724076630353",
+}
+
+func TestRatJSONEncoding(t *testing.T) {
+	for _, num := range ratNums {
+		for _, denom := range ratDenoms {
+			var tx Rat
+			tx.SetString(num + "/" + denom)
+			b, err := json.Marshal(&tx)
+			if err != nil {
+				t.Errorf("marshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			var rx Rat
+			if err := json.Unmarshal(b, &rx); err != nil {
+				t.Errorf("unmarshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			if rx.Cmp(&tx) != 0 {
+				t.Errorf("JSON encoding of %s failed: got %s want %s", &tx, &rx, &tx)
+			}
+		}
+	}
+}
+
+func TestRatXMLEncoding(t *testing.T) {
+	for _, num := range ratNums {
+		for _, denom := range ratDenoms {
+			var tx Rat
+			tx.SetString(num + "/" + denom)
+			b, err := xml.Marshal(&tx)
+			if err != nil {
+				t.Errorf("marshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			var rx Rat
+			if err := xml.Unmarshal(b, &rx); err != nil {
+				t.Errorf("unmarshaling of %s failed: %s", &tx, err)
+				continue
+			}
+			if rx.Cmp(&tx) != 0 {
+				t.Errorf("XML encoding of %s failed: got %s want %s", &tx, &rx, &tx)
+			}
+		}
+	}
+}